/*  vcf.c -- VCF/BCF API functions.

    Copyright (C) 2012, 2013 Broad Institute.
    Copyright (C) 2012-2016 Genome Research Ltd.
    Portions copyright (C) 2014 Intel Corporation.

    Author: Heng Li <lh3@sanger.ac.uk>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.  */

#include <config.h>

#include <zlib.h>
#include <stdio.h>
#include <ctype.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include "htslib/kstring.h"
#include "htslib/bgzf.h"
#include "htslib/vcf.h"
#include "htslib/tbx.h"
#include "htslib/hfile.h"
#include "htslib/khash_str2int.h"
#include "hts_internal.h"

#include "htslib/khash.h"
KHASH_MAP_INIT_STR(vdict, bcf_idinfo_t)
typedef khash_t(vdict) vdict_t;

#include "htslib/kseq.h"
KSTREAM_DECLARE(gzFile, gzread)

uint32_t bcf_float_missing    = 0x7F800001;
uint32_t bcf_float_vector_end = 0x7F800002;
uint8_t bcf_type_shift[] = { 0, 0, 1, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
static bcf_idinfo_t bcf_idinfo_def = { .info = { 15, 15, 15 }, .hrec = { NULL, NULL, NULL}, .id = -1 };

static const char *dump_char(char *buffer, char c)
{
    switch (c) {
    case '\n': strcpy(buffer, "\\n"); break;
    case '\r': strcpy(buffer, "\\r"); break;
    case '\t': strcpy(buffer, "\\t"); break;
    case '\'':
    case '\"':
    case '\\':
        sprintf(buffer, "\\%c", c);
        break;
    default:
        if (isprint_c(c)) sprintf(buffer, "%c", c);
        else sprintf(buffer, "\\x%02X", (unsigned char) c);
        break;
    }
    return buffer;
}

/*************************
 *** VCF header parser ***
 *************************/

int bcf_hdr_add_sample(bcf_hdr_t *h, const char *s)
{
    if ( !s ) return 0;

    const char *ss = s;
    while ( !*ss && isspace(*ss) ) ss++;
    if ( !*ss )
    {
        fprintf(stderr,"[E::%s] Empty sample name: trailing spaces/tabs in the header line?\n", __func__);
        abort();
    }

    vdict_t *d = (vdict_t*)h->dict[BCF_DT_SAMPLE];
    int ret;
    char *sdup = strdup(s);
    int k = kh_put(vdict, d, sdup, &ret);
    if (ret) { // absent
        kh_val(d, k) = bcf_idinfo_def;
        kh_val(d, k).id = kh_size(d) - 1;
    } else {
        if (hts_verbose >= 2)
        {
            fprintf(stderr, "[E::%s] Duplicated sample name '%s'\n", __func__, s);
            abort();
        }
        free(sdup);
        return -1;
    }
    int n = kh_size(d);
    h->samples = (char**) realloc(h->samples,sizeof(char*)*n);
    h->samples[n-1] = sdup;
    h->dirty = 1;
    return 0;
}

int bcf_hdr_parse_sample_line(bcf_hdr_t *h, const char *str)
{
    int ret = 0;
    int i = 0;
    const char *p, *q;
    // add samples
    for (p = q = str;; ++q) {
        if (*q != '\t' && *q != 0 && *q != '\n') continue;
        if (++i > 9) {
            char *s = (char*)malloc(q - p + 1);
            strncpy(s, p, q - p);
            s[q - p] = 0;
            if ( bcf_hdr_add_sample(h,s) < 0 ) ret = -1;
            free(s);
        }
        if (*q == 0 || *q == '\n') break;
        p = q + 1;
    }
    bcf_hdr_add_sample(h,NULL);
    return ret;
}

int bcf_hdr_sync(bcf_hdr_t *h)
{
    int i;
    for (i = 0; i < 3; i++)
    {
        vdict_t *d = (vdict_t*)h->dict[i];
        khint_t k;
        if ( h->n[i] < kh_size(d) )
        {
            // this should be true only for i=2, BCF_DT_SAMPLE
            h->n[i] = kh_size(d);
            h->id[i] = (bcf_idpair_t*) realloc(h->id[i], kh_size(d)*sizeof(bcf_idpair_t));
        }
        for (k=kh_begin(d); k<kh_end(d); k++)
        {
            if (!kh_exist(d,k)) continue;
            h->id[i][kh_val(d,k).id].key = kh_key(d,k);
            h->id[i][kh_val(d,k).id].val = &kh_val(d,k);
        }
    }
    h->dirty = 0;
    return 0;
}

void bcf_hrec_destroy(bcf_hrec_t *hrec)
{
    free(hrec->key);
    if ( hrec->value ) free(hrec->value);
    int i;
    for (i=0; i<hrec->nkeys; i++)
    {
        free(hrec->keys[i]);
        free(hrec->vals[i]);
    }
    free(hrec->keys);
    free(hrec->vals);
    free(hrec);
}

// Copies all fields except IDX.
bcf_hrec_t *bcf_hrec_dup(bcf_hrec_t *hrec)
{
    bcf_hrec_t *out = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
    out->type = hrec->type;
    if ( hrec->key ) out->key = strdup(hrec->key);
    if ( hrec->value ) out->value = strdup(hrec->value);
    out->nkeys = hrec->nkeys;
    out->keys = (char**) malloc(sizeof(char*)*hrec->nkeys);
    out->vals = (char**) malloc(sizeof(char*)*hrec->nkeys);
    int i, j = 0;
    for (i=0; i<hrec->nkeys; i++)
    {
        if ( hrec->keys[i] && !strcmp("IDX",hrec->keys[i]) ) continue;
        if ( hrec->keys[i] ) out->keys[j] = strdup(hrec->keys[i]);
        if ( hrec->vals[i] ) out->vals[j] = strdup(hrec->vals[i]);
        j++;
    }
    if ( i!=j ) out->nkeys -= i-j;   // IDX was omitted
    return out;
}

void bcf_hrec_debug(FILE *fp, bcf_hrec_t *hrec)
{
    fprintf(fp, "key=[%s] value=[%s]", hrec->key, hrec->value?hrec->value:"");
    int i;
    for (i=0; i<hrec->nkeys; i++)
        fprintf(fp, "\t[%s]=[%s]", hrec->keys[i],hrec->vals[i]);
    fprintf(fp, "\n");
}

void bcf_header_debug(bcf_hdr_t *hdr)
{
    int i, j;
    for (i=0; i<hdr->nhrec; i++)
    {
        if ( !hdr->hrec[i]->value )
        {
            fprintf(stderr, "##%s=<", hdr->hrec[i]->key);
            fprintf(stderr,"%s=%s", hdr->hrec[i]->keys[0], hdr->hrec[i]->vals[0]);
            for (j=1; j<hdr->hrec[i]->nkeys; j++)
                fprintf(stderr,",%s=%s", hdr->hrec[i]->keys[j], hdr->hrec[i]->vals[j]);
            fprintf(stderr,">\n");
        }
        else
            fprintf(stderr,"##%s=%s\n", hdr->hrec[i]->key,hdr->hrec[i]->value);
    }
}

void bcf_hrec_add_key(bcf_hrec_t *hrec, const char *str, int len)
{
    int n = ++hrec->nkeys;
    hrec->keys = (char**) realloc(hrec->keys, sizeof(char*)*n);
    hrec->vals = (char**) realloc(hrec->vals, sizeof(char*)*n);
    assert( len );
    hrec->keys[n-1] = (char*) malloc((len+1)*sizeof(char));
    memcpy(hrec->keys[n-1],str,len);
    hrec->keys[n-1][len] = 0;
    hrec->vals[n-1] = NULL;
}

void bcf_hrec_set_val(bcf_hrec_t *hrec, int i, const char *str, int len, int is_quoted)
{
    if ( !str ) { hrec->vals[i] = NULL; return; }
    if ( hrec->vals[i] ) free(hrec->vals[i]);
    if ( is_quoted )
    {
        hrec->vals[i] = (char*) malloc((len+3)*sizeof(char));
        hrec->vals[i][0] = '"';
        memcpy(&hrec->vals[i][1],str,len);
        hrec->vals[i][len+1] = '"';
        hrec->vals[i][len+2] = 0;
    }
    else
    {
        hrec->vals[i] = (char*) malloc((len+1)*sizeof(char));
        memcpy(hrec->vals[i],str,len);
        hrec->vals[i][len] = 0;
    }
}

void hrec_add_idx(bcf_hrec_t *hrec, int idx)
{
    int n = ++hrec->nkeys;
    hrec->keys = (char**) realloc(hrec->keys, sizeof(char*)*n);
    hrec->vals = (char**) realloc(hrec->vals, sizeof(char*)*n);
    hrec->keys[n-1] = strdup("IDX");
    kstring_t str = {0,0,0};
    kputw(idx, &str);
    hrec->vals[n-1] = str.s;
}

int bcf_hrec_find_key(bcf_hrec_t *hrec, const char *key)
{
    int i;
    for (i=0; i<hrec->nkeys; i++)
        if ( !strcasecmp(key,hrec->keys[i]) ) return i;
    return -1;
}

static inline int is_escaped(const char *min, const char *str)
{
    int n = 0;
    while ( --str>=min && *str=='\\' ) n++;
    return n%2;
}

bcf_hrec_t *bcf_hdr_parse_line(const bcf_hdr_t *h, const char *line, int *len)
{
    const char *p = line;
    if (p[0] != '#' || p[1] != '#') { *len = 0; return NULL; }
    p += 2;

    const char *q = p;
    while ( *q && *q!='=' ) q++;
    int n = q-p;
    if ( *q!='=' || !n ) { *len = q-line+1; return NULL; } // wrong format

    bcf_hrec_t *hrec = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
    hrec->key = (char*) malloc(sizeof(char)*(n+1));
    memcpy(hrec->key,p,n);
    hrec->key[n] = 0;

    p = ++q;
    if ( *p!='<' ) // generic field, e.g. ##samtoolsVersion=0.1.18-r579
    {
        while ( *q && *q!='\n' ) q++;
        hrec->value = (char*) malloc((q-p+1)*sizeof(char));
        memcpy(hrec->value, p, q-p);
        hrec->value[q-p] = 0;
        *len = q-line+1;
        return hrec;
    }

    // structured line, e.g.
    // ##INFO=<ID=PV1,Number=1,Type=Float,Description="P-value for baseQ bias">
    // ##PEDIGREE=<Name_0=G0-ID,Name_1=G1-ID,Name_3=GN-ID>
    int nopen = 1;
    while ( *q && *q!='\n' && nopen>0 )
    {
        p = ++q;
        while ( *q && *q==' ' ) { p++; q++; }
        // ^[A-Za-z_][0-9A-Za-z_.]*$
        if (p==q && *q && (isalpha(*q) || *q=='_'))
        {
            q++;
            while ( *q && (isalnum(*q) || *q=='_' || *q=='.') ) q++;
        }
        n = q-p;
        int m = 0;
        while ( *q && *q==' ' ) { q++; m++; }
        if ( *q!='=' || !n )
        {
            // wrong format
            while ( *q && *q!='\n' ) q++;
            kstring_t tmp = {0,0,0};
            kputsn(line,q-line,&tmp);
            fprintf(stderr,"Could not parse the header line: \"%s\"\n", tmp.s);
            free(tmp.s);
            *len = q-line+1;
            bcf_hrec_destroy(hrec);
            return NULL;
        }
        bcf_hrec_add_key(hrec, p, q-p-m);
        p = ++q;
        while ( *q && *q==' ' ) { p++; q++; }
        int quoted = *p=='"' ? 1 : 0;
        if ( quoted ) p++, q++;
        while ( *q && *q != '\n' )
        {
            if ( quoted ) { if ( *q=='"' && !is_escaped(p,q) ) break; }
            else
            {
                if ( *q=='<' ) nopen++;
                if ( *q=='>' ) nopen--;
                if ( !nopen ) break;
                if ( *q==',' && nopen==1 ) break;
            }
            q++;
        }
        const char *r = q;
        while ( r > p && r[-1] == ' ' ) r--;
        bcf_hrec_set_val(hrec, hrec->nkeys-1, p, r-p, quoted);
        if ( quoted && *q=='"' ) q++;
        if ( *q=='>' ) { nopen--; q++; }
    }

    // Skip trailing spaces
    while ( *q && *q==' ' ) { q++; }

    *len = q-line+1;
    return hrec;
}

static int bcf_hdr_set_idx(bcf_hdr_t *hdr, int dict_type, const char *tag, bcf_idinfo_t *idinfo)
{
    // If available, preserve existing IDX
    if ( idinfo->id==-1 )
        idinfo->id = hdr->n[dict_type]++;
    else if ( idinfo->id < hdr->n[dict_type] && hdr->id[dict_type][idinfo->id].key )
    {
        fprintf(stderr,"[%s:%d %s] Conflicting IDX=%d lines in the header dictionary, the new tag is %s\n", __FILE__,__LINE__,__FUNCTION__, idinfo->id, tag);
        exit(1);
    }

    if ( idinfo->id >= hdr->n[dict_type] ) hdr->n[dict_type] = idinfo->id+1;
    hts_expand0(bcf_idpair_t,hdr->n[dict_type],hdr->m[dict_type],hdr->id[dict_type]);

    // NB: the next kh_put call can invalidate the idinfo pointer, therefore
    // we leave it unassigned here. It myst be set explicitly in bcf_hdr_sync.
    hdr->id[dict_type][idinfo->id].key = tag;

    return 0;
}

// returns: 1 when hdr needs to be synced, 0 otherwise
int bcf_hdr_register_hrec(bcf_hdr_t *hdr, bcf_hrec_t *hrec)
{
    // contig
    int i,j, ret;
    khint_t k;
    char *str;
    if ( !strcmp(hrec->key, "contig") )
    {
        hrec->type = BCF_HL_CTG;

        // Get the contig ID ($str) and length ($j)
        i = bcf_hrec_find_key(hrec,"length");
        if ( i<0 ) j = 0;
        else if ( sscanf(hrec->vals[i],"%d",&j)!=1 ) return 0;

        i = bcf_hrec_find_key(hrec,"ID");
        if ( i<0 ) return 0;
        str = strdup(hrec->vals[i]);

        // Register in the dictionary
        vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_CTG];
        khint_t k = kh_get(vdict, d, str);
        if ( k != kh_end(d) ) { free(str); return 0; }    // already present
        k = kh_put(vdict, d, str, &ret);

        int idx = bcf_hrec_find_key(hrec,"IDX");
        if ( idx!=-1 )
        {
            char *tmp = hrec->vals[idx];
            idx = strtol(hrec->vals[idx], &tmp, 10);
            if ( *tmp || idx < 0 )
            {
                fprintf(stderr,"[%s:%d %s] Error parsing the IDX tag, skipping.\n", __FILE__,__LINE__,__FUNCTION__);
                return 0;
            }
        }

        kh_val(d, k) = bcf_idinfo_def;
        kh_val(d, k).id = idx;
        kh_val(d, k).info[0] = j;
        kh_val(d, k).hrec[0] = hrec;
        bcf_hdr_set_idx(hdr, BCF_DT_CTG, kh_key(d,k), &kh_val(d,k));
        if ( idx==-1 ) hrec_add_idx(hrec, kh_val(d,k).id);

        return 1;
    }

    if ( !strcmp(hrec->key, "INFO") ) hrec->type = BCF_HL_INFO;
    else if ( !strcmp(hrec->key, "FILTER") ) hrec->type = BCF_HL_FLT;
    else if ( !strcmp(hrec->key, "FORMAT") ) hrec->type = BCF_HL_FMT;
    else if ( hrec->nkeys>0 ) { hrec->type = BCF_HL_STR; return 1; }
    else return 0;

    // INFO/FILTER/FORMAT
    char *id = NULL;
    int type = -1, num = -1, var = -1, idx = -1;
    for (i=0; i<hrec->nkeys; i++)
    {
        if ( !strcmp(hrec->keys[i], "ID") ) id = hrec->vals[i];
        else if ( !strcmp(hrec->keys[i], "IDX") )
        {
            char *tmp = hrec->vals[i];
            idx = strtol(hrec->vals[i], &tmp, 10);
            if ( *tmp || idx < 0 )
            {
                fprintf(stderr,"[%s:%d %s] Error parsing the IDX tag, skipping.\n", __FILE__,__LINE__,__FUNCTION__);
                return 0;
            }
        }
        else if ( !strcmp(hrec->keys[i], "Type") )
        {
            if ( !strcmp(hrec->vals[i], "Integer") ) type = BCF_HT_INT;
            else if ( !strcmp(hrec->vals[i], "Float") ) type = BCF_HT_REAL;
            else if ( !strcmp(hrec->vals[i], "String") ) type = BCF_HT_STR;
            else if ( !strcmp(hrec->vals[i], "Character") ) type = BCF_HT_STR;
            else if ( !strcmp(hrec->vals[i], "Flag") ) type = BCF_HT_FLAG;
            else
            {
                if (hts_verbose >= 2) fprintf(stderr, "[E::%s] The type \"%s\" is not supported, assuming \"String\"\n", __func__, hrec->vals[i]);
                type = BCF_HT_STR;
            }
        }
        else if ( !strcmp(hrec->keys[i], "Number") )
        {
            if ( !strcmp(hrec->vals[i],"A") ) var = BCF_VL_A;
            else if ( !strcmp(hrec->vals[i],"R") ) var = BCF_VL_R;
            else if ( !strcmp(hrec->vals[i],"G") ) var = BCF_VL_G;
            else if ( !strcmp(hrec->vals[i],".") ) var = BCF_VL_VAR;
            else
            {
                sscanf(hrec->vals[i],"%d",&num);
                var = BCF_VL_FIXED;
            }
            if (var != BCF_VL_FIXED) num = 0xfffff;
        }
    }
    uint32_t info = (uint32_t)num<<12 | var<<8 | type<<4 | hrec->type;

    if ( !id ) return 0;
    str = strdup(id);

    vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_ID];
    k = kh_get(vdict, d, str);
    if ( k != kh_end(d) ) 
    {
        // already present
        free(str);
        if ( kh_val(d, k).hrec[info&0xf] ) return 0;
        kh_val(d, k).info[info&0xf] = info;
        kh_val(d, k).hrec[info&0xf] = hrec;
        if ( idx==-1 ) hrec_add_idx(hrec, kh_val(d, k).id);
        return 1;
    }
    k = kh_put(vdict, d, str, &ret);
    kh_val(d, k) = bcf_idinfo_def;
    kh_val(d, k).info[info&0xf] = info;
    kh_val(d, k).hrec[info&0xf] = hrec;
    kh_val(d, k).id = idx;
    bcf_hdr_set_idx(hdr, BCF_DT_ID, kh_key(d,k), &kh_val(d,k));
    if ( idx==-1 ) hrec_add_idx(hrec, kh_val(d,k).id);

    return 1;
}

int bcf_hdr_add_hrec(bcf_hdr_t *hdr, bcf_hrec_t *hrec)
{
    if ( !hrec ) return 0;

    hrec->type = BCF_HL_GEN;
    if ( !bcf_hdr_register_hrec(hdr,hrec) )
    {
        // If one of the hashed field, then it is already present
        if ( hrec->type != BCF_HL_GEN )
        {
            bcf_hrec_destroy(hrec);
            return 0;
        }

        // Is one of the generic fields and already present?
        int i;
        for (i=0; i<hdr->nhrec; i++)
        {
            if ( hdr->hrec[i]->type!=BCF_HL_GEN ) continue;
            if ( !strcmp(hdr->hrec[i]->key,hrec->key) && !strcmp(hrec->key,"fileformat") ) break;
            if ( !strcmp(hdr->hrec[i]->key,hrec->key) && !strcmp(hdr->hrec[i]->value,hrec->value) ) break;
        }
        if ( i<hdr->nhrec )
        {
            bcf_hrec_destroy(hrec);
            return 0;
        }
    }

    // New record, needs to be added
    int n = ++hdr->nhrec;
    hdr->hrec = (bcf_hrec_t**) realloc(hdr->hrec, n*sizeof(bcf_hrec_t*));
    hdr->hrec[n-1] = hrec;
    hdr->dirty = 1;

    return hrec->type==BCF_HL_GEN ? 0 : 1;
}

/*
 *  Note that while querying of FLT,INFO,FMT,CTG lines is fast (the keys are hashed),
 *  the STR,GEN lines are searched for linearly in a linked list of all header lines.
 *  This may become a problem for VCFs with huge headers, we might need to build a
 *  dictionary for these lines as well.
 */
bcf_hrec_t *bcf_hdr_get_hrec(const bcf_hdr_t *hdr, int type, const char *key, const char *value, const char *str_class)
{
    int i;
    if ( type==BCF_HL_GEN )
    {
        for (i=0; i<hdr->nhrec; i++)
        {
            if ( hdr->hrec[i]->type!=type ) continue;
            if ( strcmp(hdr->hrec[i]->key,key) ) continue;
            if ( !value || !strcmp(hdr->hrec[i]->value,value) ) return hdr->hrec[i];
        }
        return NULL;
    }
    else if ( type==BCF_HL_STR )
    {
        for (i=0; i<hdr->nhrec; i++)
        {
            if ( hdr->hrec[i]->type!=type ) continue;
            if ( strcmp(hdr->hrec[i]->key,str_class) ) continue;
            int j = bcf_hrec_find_key(hdr->hrec[i],key);
            if ( j>=0 && !strcmp(hdr->hrec[i]->vals[j],value) ) return hdr->hrec[i];
        }
        return NULL;
    }
    vdict_t *d = type==BCF_HL_CTG ? (vdict_t*)hdr->dict[BCF_DT_CTG] : (vdict_t*)hdr->dict[BCF_DT_ID];
    khint_t k = kh_get(vdict, d, value);
    if ( k == kh_end(d) ) return NULL;
    return kh_val(d, k).hrec[type==BCF_HL_CTG?0:type];
}

void bcf_hdr_check_sanity(bcf_hdr_t *hdr)
{
    static int PL_warned = 0, GL_warned = 0;

    if ( !PL_warned )
    {
        int id = bcf_hdr_id2int(hdr, BCF_DT_ID, "PL");
        if ( bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) && bcf_hdr_id2length(hdr,BCF_HL_FMT,id)!=BCF_VL_G )
        {
            if (hts_verbose >= 2) fprintf(stderr,"[W::%s] PL should be declared as Number=G\n", __func__);
            PL_warned = 1;
        }
    }
    if ( !GL_warned )
    {
        int id = bcf_hdr_id2int(hdr, BCF_DT_ID, "GL");
        if ( bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) && bcf_hdr_id2length(hdr,BCF_HL_FMT,id)!=BCF_VL_G )
        {
            if (hts_verbose >= 2) fprintf(stderr,"[W::%s] GL should be declared as Number=G\n", __func__);
            GL_warned = 1;
        }
    }
}

int bcf_hdr_parse(bcf_hdr_t *hdr, char *htxt)
{
    int len, needs_sync = 0;
    char *p = htxt;

    // Check sanity: "fileformat" string must come as first
    bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr,p,&len);
    if ( !hrec || !hrec->key || strcasecmp(hrec->key,"fileformat") )
        fprintf(stderr, "[W::%s] The first line should be ##fileformat; is the VCF/BCF header broken?\n", __func__);
    needs_sync += bcf_hdr_add_hrec(hdr, hrec);

    // The filter PASS must appear first in the dictionary
    hrec = bcf_hdr_parse_line(hdr,"##FILTER=<ID=PASS,Description=\"All filters passed\">",&len);
    needs_sync += bcf_hdr_add_hrec(hdr, hrec);

    // Parse the whole header
    while ( (hrec=bcf_hdr_parse_line(hdr,p,&len)) )
    {
        needs_sync += bcf_hdr_add_hrec(hdr, hrec);
        p += len;
    }
    int ret = bcf_hdr_parse_sample_line(hdr,p);
    bcf_hdr_sync(hdr);
    bcf_hdr_check_sanity(hdr);
    return ret;
}

int bcf_hdr_append(bcf_hdr_t *hdr, const char *line)
{
    int len;
    bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr, (char*) line, &len);
    if ( !hrec ) return -1;
    bcf_hdr_add_hrec(hdr, hrec);
    return 0;
}

void bcf_hdr_remove(bcf_hdr_t *hdr, int type, const char *key)
{
    int i = 0;
    bcf_hrec_t *hrec;
    if ( !key )
    {
        while ( i<hdr->nhrec )
        {
            if ( hdr->hrec[i]->type!=type ) { i++; continue; }
            hrec = hdr->hrec[i];

            if ( type==BCF_HL_FLT || type==BCF_HL_INFO || type==BCF_HL_FMT || type== BCF_HL_CTG )
            {
                int j = bcf_hrec_find_key(hdr->hrec[i], "ID");
                if ( j>0 )
                {
                    vdict_t *d = type==BCF_HL_CTG ? (vdict_t*)hdr->dict[BCF_DT_CTG] : (vdict_t*)hdr->dict[BCF_DT_ID];
                    khint_t k = kh_get(vdict, d, hdr->hrec[i]->vals[j]);
                    kh_val(d, k).hrec[type==BCF_HL_CTG?0:type] = NULL;
                }
            }

            hdr->dirty = 1;
            hdr->nhrec--;
            if ( i < hdr->nhrec )
                memmove(&hdr->hrec[i],&hdr->hrec[i+1],(hdr->nhrec-i)*sizeof(bcf_hrec_t*));
            bcf_hrec_destroy(hrec);
        }
        return;
    }
    while (1)
    {
        if ( type==BCF_HL_FLT || type==BCF_HL_INFO || type==BCF_HL_FMT || type== BCF_HL_CTG )
        {
            hrec = bcf_hdr_get_hrec(hdr, type, "ID", key, NULL);
            if ( !hrec ) return;

            for (i=0; i<hdr->nhrec; i++)
                if ( hdr->hrec[i]==hrec ) break;
            assert( i<hdr->nhrec );

            vdict_t *d = type==BCF_HL_CTG ? (vdict_t*)hdr->dict[BCF_DT_CTG] : (vdict_t*)hdr->dict[BCF_DT_ID];
            khint_t k = kh_get(vdict, d, key);
            kh_val(d, k).hrec[type==BCF_HL_CTG?0:type] = NULL;
        }
        else
        {
            for (i=0; i<hdr->nhrec; i++)
            {
                if ( hdr->hrec[i]->type!=type ) continue;
                if ( type==BCF_HL_GEN )
                {
                    if ( !strcmp(hdr->hrec[i]->key,key) ) break;
                }
                else
                {
                    // not all structured lines have ID, we could be more sophisticated as in bcf_hdr_get_hrec()
                    int j = bcf_hrec_find_key(hdr->hrec[i], "ID");
                    if ( j>=0 && !strcmp(hdr->hrec[i]->vals[j],key) ) break;
                }
            }
            if ( i==hdr->nhrec ) return;
            hrec = hdr->hrec[i];
        }

        hdr->nhrec--;
        if ( i < hdr->nhrec )
            memmove(&hdr->hrec[i],&hdr->hrec[i+1],(hdr->nhrec-i)*sizeof(bcf_hrec_t*));
        bcf_hrec_destroy(hrec);
        hdr->dirty = 1;
    }
}

int bcf_hdr_printf(bcf_hdr_t *hdr, const char *fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    int n = vsnprintf(NULL, 0, fmt, ap) + 2;
    va_end(ap);

    char *line = (char*)malloc(n);
    va_start(ap, fmt);
    vsnprintf(line, n, fmt, ap);
    va_end(ap);

    int ret = bcf_hdr_append(hdr, line);

    free(line);
    return ret;
}


/**********************
 *** BCF header I/O ***
 **********************/

const char *bcf_hdr_get_version(const bcf_hdr_t *hdr)
{
    bcf_hrec_t *hrec = bcf_hdr_get_hrec(hdr, BCF_HL_GEN, "fileformat", NULL, NULL);
    if ( !hrec )
    {
        fprintf(stderr,"No version string found, assuming VCFv4.2\n");
        return "VCFv4.2";
    }
    return hrec->value;
}

void bcf_hdr_set_version(bcf_hdr_t *hdr, const char *version)
{
    bcf_hrec_t *hrec = bcf_hdr_get_hrec(hdr, BCF_HL_GEN, "fileformat", NULL, NULL);
    if ( !hrec )
    {
        int len;
        kstring_t str = {0,0,0};
        ksprintf(&str,"##fileformat=%s", version);
        hrec = bcf_hdr_parse_line(hdr, str.s, &len);
        free(str.s);
    }
    else
    {
        free(hrec->value);
        hrec->value = strdup(version);
    }
    hdr->dirty = 1;
}

bcf_hdr_t *bcf_hdr_init(const char *mode)
{
    int i;
    bcf_hdr_t *h;
    h = (bcf_hdr_t*)calloc(1, sizeof(bcf_hdr_t));
    if (!h) return NULL;
    for (i = 0; i < 3; ++i)
        if ((h->dict[i] = kh_init(vdict)) == NULL) goto fail;
    if ( strchr(mode,'w') )
    {
        bcf_hdr_append(h, "##fileformat=VCFv4.2");
        // The filter PASS must appear first in the dictionary
        bcf_hdr_append(h, "##FILTER=<ID=PASS,Description=\"All filters passed\">");
    }
    return h;

 fail:
    for (i = 0; i < 3; ++i)
        kh_destroy(vdict, h->dict[i]);
    free(h);
    return NULL;
}

void bcf_hdr_destroy(bcf_hdr_t *h)
{
    int i;
    khint_t k;
    for (i = 0; i < 3; ++i) {
        vdict_t *d = (vdict_t*)h->dict[i];
        if (d == 0) continue;
        for (k = kh_begin(d); k != kh_end(d); ++k)
            if (kh_exist(d, k)) free((char*)kh_key(d, k));
        kh_destroy(vdict, d);
        free(h->id[i]);
    }
    for (i=0; i<h->nhrec; i++)
        bcf_hrec_destroy(h->hrec[i]);
    if (h->nhrec) free(h->hrec);
    if (h->samples) free(h->samples);
    free(h->keep_samples);
    free(h->transl[0]); free(h->transl[1]);
    free(h->mem.s);
    free(h);
}

bcf_hdr_t *bcf_hdr_read(htsFile *hfp)
{
    if (hfp->format.format == vcf)
        return vcf_hdr_read(hfp);

    BGZF *fp = hfp->fp.bgzf;
    uint8_t magic[5];
    bcf_hdr_t *h;
    h = bcf_hdr_init("r");
    if (!h) {
        fprintf(stderr, "[E::%s] failed to allocate bcf header\n", __func__);
        return NULL;
    }
    if (bgzf_read(fp, magic, 5) != 5)
    {
        fprintf(stderr,"[%s:%d %s] Failed to read the header (reading BCF in text mode?)\n", __FILE__,__LINE__,__FUNCTION__);
        bcf_hdr_destroy(h);
        return NULL;
    }
    if (strncmp((char*)magic, "BCF\2\2", 5) != 0)
    {
        if (!strncmp((char*)magic, "BCF", 3))
            fprintf(stderr,"[%s:%d %s] invalid BCF2 magic string: only BCFv2.2 is supported.\n", __FILE__,__LINE__,__FUNCTION__);
        else if (hts_verbose >= 2)
            fprintf(stderr, "[E::%s] invalid BCF2 magic string\n", __func__);
        bcf_hdr_destroy(h);
        return NULL;
    }
    int hlen;
    char *htxt = NULL;
    if (bgzf_read(fp, &hlen, 4) != 4) goto fail;
    htxt = (char*)malloc(hlen);
    if (!htxt) goto fail;
    if (bgzf_read(fp, htxt, hlen) != hlen) goto fail;
    bcf_hdr_parse(h, htxt);  // FIXME: Does this return anything meaningful?
    free(htxt);
    return h;
 fail:
    if (hts_verbose >= 2) {
        fprintf(stderr, "[E::%s] failed to read BCF header\n", __func__);
    }
    free(htxt);
    bcf_hdr_destroy(h);
    return NULL;
}

int bcf_hdr_write(htsFile *hfp, bcf_hdr_t *h)
{
    if ( h->dirty ) bcf_hdr_sync(h);
    if (hfp->format.format == vcf || hfp->format.format == text_format)
        return vcf_hdr_write(hfp, h);

    int hlen;
    char *htxt = bcf_hdr_fmt_text(h, 1, &hlen);
    hlen++; // include the \0 byte

    BGZF *fp = hfp->fp.bgzf;
    if ( bgzf_write(fp, "BCF\2\2", 5) !=5 ) return -1;
    if ( bgzf_write(fp, &hlen, 4) !=4 ) return -1;
    if ( bgzf_write(fp, htxt, hlen) != hlen ) return -1;

    free(htxt);
    return 0;
}

/********************
 *** BCF site I/O ***
 ********************/

bcf1_t *bcf_init()
{
    bcf1_t *v;
    v = (bcf1_t*)calloc(1, sizeof(bcf1_t));
    return v;
}

void bcf_clear(bcf1_t *v)
{
    int i;
    for (i=0; i<v->d.m_info; i++)
    {
        if ( v->d.info[i].vptr_free )
        {
            free(v->d.info[i].vptr - v->d.info[i].vptr_off);
            v->d.info[i].vptr_free = 0;
        }
    }
    for (i=0; i<v->d.m_fmt; i++)
    {
        if ( v->d.fmt[i].p_free )
        {
            free(v->d.fmt[i].p - v->d.fmt[i].p_off);
            v->d.fmt[i].p_free = 0;
        }
    }
    v->rid = v->pos = v->rlen = v->unpacked = 0;
    bcf_float_set_missing(v->qual);
    v->n_info = v->n_allele = v->n_fmt = v->n_sample = 0;
    v->shared.l = v->indiv.l = 0;
    v->d.var_type = -1;
    v->d.shared_dirty = 0;
    v->d.indiv_dirty  = 0;
    v->d.n_flt = 0;
    v->errcode = 0;
    if (v->d.m_als) v->d.als[0] = 0;
    if (v->d.m_id) v->d.id[0] = 0;
}

void bcf_empty(bcf1_t *v)
{
    bcf_clear1(v);
    free(v->d.id);
    free(v->d.als);
    free(v->d.allele); free(v->d.flt); free(v->d.info); free(v->d.fmt);
    if (v->d.var ) free(v->d.var);
    free(v->shared.s); free(v->indiv.s);
}

void bcf_destroy(bcf1_t *v)
{
    bcf_empty1(v);
    free(v);
}

static inline int bcf_read1_core(BGZF *fp, bcf1_t *v)
{
    uint32_t x[8];
    int ret;
    if ((ret = bgzf_read(fp, x, 32)) != 32) {
        if (ret == 0) return -1;
        return -2;
    }
    bcf_clear1(v);
    x[0] -= 24; // to exclude six 32-bit integers
    ks_resize(&v->shared, x[0]);
    ks_resize(&v->indiv, x[1]);
    memcpy(v, x + 2, 16);
    v->n_allele = x[6]>>16; v->n_info = x[6]&0xffff;
    v->n_fmt = x[7]>>24; v->n_sample = x[7]&0xffffff;
    v->shared.l = x[0], v->indiv.l = x[1];
    // silent fix of broken BCFs produced by earlier versions of bcf_subset, prior to and including bd6ed8b4
    if ( (!v->indiv.l || !v->n_sample) && v->n_fmt ) v->n_fmt = 0;

    if (bgzf_read(fp, v->shared.s, v->shared.l) != v->shared.l) return -1;
    if (bgzf_read(fp, v->indiv.s, v->indiv.l) != v->indiv.l) return -1;
    return 0;
}

#define bit_array_size(n) ((n)/8+1)
#define bit_array_set(a,i)   ((a)[(i)/8] |=   1 << ((i)%8))
#define bit_array_clear(a,i) ((a)[(i)/8] &= ~(1 << ((i)%8)))
#define bit_array_test(a,i)  ((a)[(i)/8] &   (1 << ((i)%8)))

static inline uint8_t *bcf_unpack_fmt_core1(uint8_t *ptr, int n_sample, bcf_fmt_t *fmt);
int bcf_subset_format(const bcf_hdr_t *hdr, bcf1_t *rec)
{
    if ( !hdr->keep_samples ) return 0;
    if ( !bcf_hdr_nsamples(hdr) )
    {
        rec->indiv.l = rec->n_sample = 0;
        return 0;
    }

    int i, j;
    uint8_t *ptr = (uint8_t*)rec->indiv.s, *dst = NULL, *src;
    bcf_dec_t *dec = &rec->d;
    hts_expand(bcf_fmt_t, rec->n_fmt, dec->m_fmt, dec->fmt);
    for (i=0; i<dec->m_fmt; ++i) dec->fmt[i].p_free = 0;

    for (i=0; i<rec->n_fmt; i++)
    {
        ptr = bcf_unpack_fmt_core1(ptr, rec->n_sample, &dec->fmt[i]);
        src = dec->fmt[i].p - dec->fmt[i].size;
        if ( dst )
        {
            memmove(dec->fmt[i-1].p + dec->fmt[i-1].p_len, dec->fmt[i].p - dec->fmt[i].p_off, dec->fmt[i].p_off);
            dec->fmt[i].p = dec->fmt[i-1].p + dec->fmt[i-1].p_len + dec->fmt[i].p_off;
        }
        dst = dec->fmt[i].p;
        for (j=0; j<hdr->nsamples_ori; j++)
        {
            src += dec->fmt[i].size;
            if ( !bit_array_test(hdr->keep_samples,j) ) continue;
            memmove(dst, src, dec->fmt[i].size);
            dst += dec->fmt[i].size;
        }
        rec->indiv.l -= dec->fmt[i].p_len - (dst - dec->fmt[i].p);
        dec->fmt[i].p_len = dst - dec->fmt[i].p;
    }
    rec->unpacked |= BCF_UN_FMT;

    rec->n_sample = bcf_hdr_nsamples(hdr);
    return 0;
}

int bcf_read(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
{
    if (fp->format.format == vcf) return vcf_read(fp,h,v);
    int ret = bcf_read1_core(fp->fp.bgzf, v);
    if ( ret!=0 || !h->keep_samples ) return ret;
    return bcf_subset_format(h,v);
}

int bcf_readrec(BGZF *fp, void *null, void *vv, int *tid, int *beg, int *end)
{
    bcf1_t *v = (bcf1_t *) vv;
    int ret;
    if ((ret = bcf_read1_core(fp, v)) >= 0)
        *tid = v->rid, *beg = v->pos, *end = v->pos + v->rlen;
    return ret;
}

static inline void bcf1_sync_id(bcf1_t *line, kstring_t *str)
{
    // single typed string
    if ( line->d.id && strcmp(line->d.id, ".") ) bcf_enc_vchar(str, strlen(line->d.id), line->d.id);
    else bcf_enc_size(str, 0, BCF_BT_CHAR);
}
static inline void bcf1_sync_alleles(bcf1_t *line, kstring_t *str)
{
    // list of typed strings
    int i;
    for (i=0; i<line->n_allele; i++)
        bcf_enc_vchar(str, strlen(line->d.allele[i]), line->d.allele[i]);
    if ( !line->rlen && line->n_allele ) line->rlen = strlen(line->d.allele[0]);
}
static inline void bcf1_sync_filter(bcf1_t *line, kstring_t *str)
{
    // typed vector of integers
    if ( line->d.n_flt ) bcf_enc_vint(str, line->d.n_flt, line->d.flt, -1);
    else bcf_enc_vint(str, 0, 0, -1);
}

static inline void bcf1_sync_info(bcf1_t *line, kstring_t *str)
{
    // pairs of typed vectors
    int i, irm = -1;
    for (i=0; i<line->n_info; i++)
    {
        bcf_info_t *info = &line->d.info[i];
        if ( !info->vptr )
        {
            // marked for removal
            if ( irm < 0 ) irm = i;
            continue;
        }
        kputsn_(info->vptr - info->vptr_off, info->vptr_len + info->vptr_off, str);
        if ( irm >=0 )
        {
            bcf_info_t tmp = line->d.info[irm]; line->d.info[irm] = line->d.info[i]; line->d.info[i] = tmp;
            while ( irm<=i && line->d.info[irm].vptr ) irm++;
        }
    }
    if ( irm>=0 ) line->n_info = irm;
}

static int bcf1_sync(bcf1_t *line)
{
    char *shared_ori = line->shared.s;
    size_t prev_len;

    kstring_t tmp = {0,0,0};
    if ( !line->shared.l )
    {
        // New line created via API, BCF data blocks do not exist. Get it ready for BCF output
        tmp = line->shared;
        bcf1_sync_id(line, &tmp);
        line->unpack_size[0] = tmp.l; prev_len = tmp.l;

        bcf1_sync_alleles(line, &tmp);
        line->unpack_size[1] = tmp.l - prev_len; prev_len = tmp.l;

        bcf1_sync_filter(line, &tmp);
        line->unpack_size[2] = tmp.l - prev_len;

        bcf1_sync_info(line, &tmp);
        line->shared = tmp;
    }
    else if ( line->d.shared_dirty )
    {
        // The line was edited, update the BCF data block.
        
        if ( !(line->unpacked & BCF_UN_STR) ) bcf_unpack(line,BCF_UN_STR);
        
        // ptr_ori points to the original unchanged BCF data.
        uint8_t *ptr_ori = (uint8_t *) line->shared.s;

        // ID: single typed string
        if ( line->d.shared_dirty & BCF1_DIRTY_ID )
            bcf1_sync_id(line, &tmp);
        else
            kputsn_(ptr_ori, line->unpack_size[0], &tmp);
        ptr_ori += line->unpack_size[0];
        line->unpack_size[0] = tmp.l; prev_len = tmp.l;

        // REF+ALT: list of typed strings
        if ( line->d.shared_dirty & BCF1_DIRTY_ALS )
            bcf1_sync_alleles(line, &tmp);
        else
        {
            kputsn_(ptr_ori, line->unpack_size[1], &tmp);
            if ( !line->rlen && line->n_allele ) line->rlen = strlen(line->d.allele[0]);
        }
        ptr_ori += line->unpack_size[1];
        line->unpack_size[1] = tmp.l - prev_len; prev_len = tmp.l;

        if ( line->unpacked & BCF_UN_FLT )
        {
            // FILTER: typed vector of integers
            if ( line->d.shared_dirty & BCF1_DIRTY_FLT )
                bcf1_sync_filter(line, &tmp);
            else if ( line->d.n_flt )
                kputsn_(ptr_ori, line->unpack_size[2], &tmp);
            else
                bcf_enc_vint(&tmp, 0, 0, -1);
            ptr_ori += line->unpack_size[2];
            line->unpack_size[2] = tmp.l - prev_len;

            if ( line->unpacked & BCF_UN_INFO )
            {
                // INFO: pairs of typed vectors
                if ( line->d.shared_dirty & BCF1_DIRTY_INF )
                {
                    bcf1_sync_info(line, &tmp);
                    ptr_ori = (uint8_t*)line->shared.s + line->shared.l;
                }
            }
        }

        int size = line->shared.l - (size_t)ptr_ori + (size_t)line->shared.s;
        if ( size ) kputsn_(ptr_ori, size, &tmp);

        free(line->shared.s);
        line->shared = tmp;
    }
    if ( line->shared.s != shared_ori && line->unpacked & BCF_UN_INFO )
    {
        // Reallocated line->shared.s block invalidated line->d.info[].vptr pointers
        size_t off_new = line->unpack_size[0] + line->unpack_size[1] + line->unpack_size[2];
        int i;
        for (i=0; i<line->n_info; i++)
        {
            uint8_t *vptr_free = line->d.info[i].vptr_free ? line->d.info[i].vptr - line->d.info[i].vptr_off : NULL;
            line->d.info[i].vptr = (uint8_t*) line->shared.s + off_new + line->d.info[i].vptr_off;
            off_new += line->d.info[i].vptr_len + line->d.info[i].vptr_off;
            if ( vptr_free )
            {
                free(vptr_free);
                line->d.info[i].vptr_free = 0;
            }
        }
    }

    if ( line->n_sample && line->n_fmt && (!line->indiv.l || line->d.indiv_dirty) )
    {
        // The genotype fields changed or are not present
        tmp.l = tmp.m = 0; tmp.s = NULL;
        int i, irm = -1;
        for (i=0; i<line->n_fmt; i++)
        {
            bcf_fmt_t *fmt = &line->d.fmt[i];
            if ( !fmt->p )
            {
                // marked for removal
                if ( irm < 0 ) irm = i;
                continue;
            }
            kputsn_(fmt->p - fmt->p_off, fmt->p_len + fmt->p_off, &tmp);
            if ( irm >=0 )
            {
                bcf_fmt_t tfmt = line->d.fmt[irm]; line->d.fmt[irm] = line->d.fmt[i]; line->d.fmt[i] = tfmt;
                while ( irm<=i && line->d.fmt[irm].p ) irm++;
            }

        }
        if ( irm>=0 ) line->n_fmt = irm;
        free(line->indiv.s);
        line->indiv = tmp;

        // Reallocated line->indiv.s block invalidated line->d.fmt[].p pointers
        size_t off_new = 0;
        for (i=0; i<line->n_fmt; i++)
        {
            uint8_t *p_free = line->d.fmt[i].p_free ? line->d.fmt[i].p - line->d.fmt[i].p_off : NULL;
            line->d.fmt[i].p = (uint8_t*) line->indiv.s + off_new + line->d.fmt[i].p_off;
            off_new += line->d.fmt[i].p_len + line->d.fmt[i].p_off;
            if ( p_free )
            {
                free(p_free);
                line->d.fmt[i].p_free = 0;
            }
        }
    }
    if ( !line->n_sample ) line->n_fmt = 0;
    line->d.shared_dirty = line->d.indiv_dirty = 0;
    return 0;
}

bcf1_t *bcf_copy(bcf1_t *dst, bcf1_t *src)
{
    bcf1_sync(src);

    bcf_clear(dst);
    dst->rid  = src->rid;
    dst->pos  = src->pos;
    dst->rlen = src->rlen;
    dst->qual = src->qual;
    dst->n_info = src->n_info; dst->n_allele = src->n_allele;
    dst->n_fmt = src->n_fmt; dst->n_sample = src->n_sample;

    dst->shared.m = dst->shared.l = src->shared.l;
    dst->shared.s = (char*) malloc(dst->shared.l);
    memcpy(dst->shared.s,src->shared.s,dst->shared.l);

    dst->indiv.m = dst->indiv.l = src->indiv.l;
    dst->indiv.s = (char*) malloc(dst->indiv.l);
    memcpy(dst->indiv.s,src->indiv.s,dst->indiv.l);

    return dst;
}
bcf1_t *bcf_dup(bcf1_t *src)
{
    bcf1_t *out = bcf_init1();
    return bcf_copy(out, src);
}

int bcf_write(htsFile *hfp, bcf_hdr_t *h, bcf1_t *v)
{
    if ( h->dirty ) bcf_hdr_sync(h);
    if ( bcf_hdr_nsamples(h)!=v->n_sample )
    {
        fprintf(stderr,"[%s:%d %s] Broken VCF record, the number of columns at %s:%d does not match the number of samples (%d vs %d).\n",
                __FILE__,__LINE__,__FUNCTION__,bcf_seqname(h,v),v->pos+1, v->n_sample,bcf_hdr_nsamples(h));
        return -1;
    }

    if ( hfp->format.format == vcf || hfp->format.format == text_format )
        return vcf_write(hfp,h,v);

    if ( v->errcode )
    {
        // vcf_parse1() encountered a new contig or tag, undeclared in the
        // header.  At this point, the header must have been printed,
        // proceeding would lead to a broken BCF file. Errors must be checked
        // and cleared by the caller before we can proceed.
        fprintf(stderr,"[%s:%d %s] Unchecked error (%d), exiting.\n", __FILE__,__LINE__,__FUNCTION__,v->errcode);
        exit(1);
    }
    bcf1_sync(v);   // check if the BCF record was modified

    BGZF *fp = hfp->fp.bgzf;
    uint32_t x[8];
    x[0] = v->shared.l + 24; // to include six 32-bit integers
    x[1] = v->indiv.l;
    memcpy(x + 2, v, 16);
    x[6] = (uint32_t)v->n_allele<<16 | v->n_info;
    x[7] = (uint32_t)v->n_fmt<<24 | v->n_sample;
    if ( bgzf_write(fp, x, 32) != 32 ) return -1;
    if ( bgzf_write(fp, v->shared.s, v->shared.l) != v->shared.l ) return -1;
    if ( bgzf_write(fp, v->indiv.s, v->indiv.l) != v->indiv.l ) return -1;
    return 0;
}

/**********************
 *** VCF header I/O ***
 **********************/

bcf_hdr_t *vcf_hdr_read(htsFile *fp)
{
    kstring_t txt, *s = &fp->line;
    bcf_hdr_t *h;
    h = bcf_hdr_init("r");
    if (!h) {
        fprintf(stderr, "[E::%s] failed to allocate bcf header\n", __func__);
        return NULL;
    }
    txt.l = txt.m = 0; txt.s = 0;
    while (hts_getline(fp, KS_SEP_LINE, s) >= 0) {
        if (s->l == 0) continue;
        if (s->s[0] != '#') {
            if (hts_verbose >= 2)
                fprintf(stderr, "[E::%s] no sample line\n", __func__);
            free(txt.s);
            bcf_hdr_destroy(h);
            return NULL;
        }
        if (s->s[1] != '#' && fp->fn_aux) { // insert contigs here
            int dret;
            gzFile f;
            kstream_t *ks;
            kstring_t tmp;
            tmp.l = tmp.m = 0; tmp.s = 0;
            f = gzopen(fp->fn_aux, "r");
            ks = ks_init(f);
            while (ks_getuntil(ks, 0, &tmp, &dret) >= 0) {
                int c;
                kputs("##contig=<ID=", &txt); kputs(tmp.s, &txt);
                ks_getuntil(ks, 0, &tmp, &dret);
                kputs(",length=", &txt); kputw(atol(tmp.s), &txt);
                kputsn(">\n", 2, &txt);
                if (dret != '\n')
                    while ((c = ks_getc(ks)) != '\n' && c != -1); // skip the rest of the line
            }
            free(tmp.s);
            ks_destroy(ks);
            gzclose(f);
        }
        kputsn(s->s, s->l, &txt);
        kputc('\n', &txt);
        if (s->s[1] != '#') break;
    }
    if ( !txt.s )
    {
        fprintf(stderr,"[%s:%d %s] Could not read the header\n", __FILE__,__LINE__,__FUNCTION__);
        return NULL;
    }
    bcf_hdr_parse(h, txt.s);

    // check tabix index, are all contigs listed in the header? add the missing ones
    tbx_t *idx = tbx_index_load(fp->fn);
    if ( idx )
    {
        int i, n, need_sync = 0;
        const char **names = tbx_seqnames(idx, &n);
        for (i=0; i<n; i++)
        {
            bcf_hrec_t *hrec = bcf_hdr_get_hrec(h, BCF_HL_CTG, "ID", (char*) names[i], NULL);
            if ( hrec ) continue;
            hrec = (bcf_hrec_t*) calloc(1,sizeof(bcf_hrec_t));
            hrec->key = strdup("contig");
            bcf_hrec_add_key(hrec, "ID", strlen("ID"));
            bcf_hrec_set_val(hrec, hrec->nkeys-1, (char*) names[i], strlen(names[i]), 0);
            bcf_hdr_add_hrec(h, hrec);
            need_sync = 1;
        }
        free(names);
        tbx_destroy(idx);
        if ( need_sync )
            bcf_hdr_sync(h);
    }
    free(txt.s);
    return h;
}

int bcf_hdr_set(bcf_hdr_t *hdr, const char *fname)
{
    int i, n;
    char **lines = hts_readlines(fname, &n);
    if ( !lines ) return 1;
    for (i=0; i<n-1; i++)
    {
        int k;
        bcf_hrec_t *hrec = bcf_hdr_parse_line(hdr,lines[i],&k);
        if ( hrec ) bcf_hdr_add_hrec(hdr, hrec);
        free(lines[i]);
    }
    bcf_hdr_parse_sample_line(hdr,lines[n-1]);
    free(lines[n-1]);
    free(lines);
    bcf_hdr_sync(hdr);
    return 0;
}

static void _bcf_hrec_format(const bcf_hrec_t *hrec, int is_bcf, kstring_t *str)
{
    if ( !hrec->value )
    {
        int j, nout = 0;
        ksprintf(str, "##%s=<", hrec->key);
        for (j=0; j<hrec->nkeys; j++)
        {
            // do not output IDX if output is VCF
            if ( !is_bcf && !strcmp("IDX",hrec->keys[j]) ) continue;
            if ( nout ) kputc(',',str);
            ksprintf(str,"%s=%s", hrec->keys[j], hrec->vals[j]);
            nout++;
        }
        ksprintf(str,">\n");
    }
    else
        ksprintf(str,"##%s=%s\n", hrec->key,hrec->value);
}

void bcf_hrec_format(const bcf_hrec_t *hrec, kstring_t *str)
{
    _bcf_hrec_format(hrec,0,str);
}
char *bcf_hdr_fmt_text(const bcf_hdr_t *hdr, int is_bcf, int *len)
{
    int i;
    kstring_t txt = {0,0,0};
    for (i=0; i<hdr->nhrec; i++)
        _bcf_hrec_format(hdr->hrec[i], is_bcf, &txt);

    ksprintf(&txt,"#CHROM\tPOS\tID\tREF\tALT\tQUAL\tFILTER\tINFO");
    if ( bcf_hdr_nsamples(hdr) )
    {
        ksprintf(&txt,"\tFORMAT");
        for (i=0; i<bcf_hdr_nsamples(hdr); i++)
            ksprintf(&txt,"\t%s", hdr->samples[i]);
    }
    ksprintf(&txt,"\n");

    if ( len ) *len = txt.l;
    return txt.s;
}

const char **bcf_hdr_seqnames(const bcf_hdr_t *h, int *n)
{
    vdict_t *d = (vdict_t*)h->dict[BCF_DT_CTG];
    int tid, m = kh_size(d);
    const char **names = (const char**) calloc(m,sizeof(const char*));
    khint_t k;
    for (k=kh_begin(d); k<kh_end(d); k++)
    {
        if ( !kh_exist(d,k) ) continue;
        tid = kh_val(d,k).id;
        assert( tid<m );
        names[tid] = kh_key(d,k);
    }
    // sanity check: there should be no gaps
    for (tid=0; tid<m; tid++)
        assert(names[tid]);
    *n = m;
    return names;
}

int vcf_hdr_write(htsFile *fp, const bcf_hdr_t *h)
{
    int hlen;
    char *htxt = bcf_hdr_fmt_text(h, 0, &hlen);
    while (hlen && htxt[hlen-1] == 0) --hlen; // kill trailing zeros
    int ret;
    if ( fp->format.compression!=no_compression )
        ret = bgzf_write(fp->fp.bgzf, htxt, hlen);
    else
        ret = hwrite(fp->fp.hfile, htxt, hlen);
    free(htxt);
    return ret<0 ? -1 : 0;
}

/***********************
 *** Typed value I/O ***
 ***********************/

void bcf_enc_vint(kstring_t *s, int n, int32_t *a, int wsize)
{
    int32_t max = INT32_MIN + 1, min = INT32_MAX;
    int i;
    if (n == 0) bcf_enc_size(s, 0, BCF_BT_NULL);
    else if (n == 1) bcf_enc_int1(s, a[0]);
    else {
        if (wsize <= 0) wsize = n;
        for (i = 0; i < n; ++i) {
            if (a[i] == bcf_int32_missing || a[i] == bcf_int32_vector_end ) continue;
            if (max < a[i]) max = a[i];
            if (min > a[i]) min = a[i];
        }
        if (max <= INT8_MAX && min > bcf_int8_vector_end) {
            bcf_enc_size(s, wsize, BCF_BT_INT8);
            for (i = 0; i < n; ++i)
                if ( a[i]==bcf_int32_vector_end ) kputc(bcf_int8_vector_end, s);
                else if ( a[i]==bcf_int32_missing ) kputc(bcf_int8_missing, s);
                else kputc(a[i], s);
        } else if (max <= INT16_MAX && min > bcf_int16_vector_end) {
            bcf_enc_size(s, wsize, BCF_BT_INT16);
            for (i = 0; i < n; ++i)
            {
                int16_t x;
                if ( a[i]==bcf_int32_vector_end ) x = bcf_int16_vector_end;
                else if ( a[i]==bcf_int32_missing ) x = bcf_int16_missing;
                else x = a[i];
                kputsn((char*)&x, 2, s);
            }
        } else {
            bcf_enc_size(s, wsize, BCF_BT_INT32);
            for (i = 0; i < n; ++i) {
                int32_t x = a[i];
                kputsn((char*)&x, 4, s);
            }
        }
    }
}

void bcf_enc_vfloat(kstring_t *s, int n, float *a)
{
    bcf_enc_size(s, n, BCF_BT_FLOAT);
    kputsn((char*)a, n << 2, s);
}

void bcf_enc_vchar(kstring_t *s, int l, const char *a)
{
    bcf_enc_size(s, l, BCF_BT_CHAR);
    kputsn(a, l, s);
}

void bcf_fmt_array(kstring_t *s, int n, int type, void *data)
{
    int j = 0;
    if (n == 0) {
        kputc('.', s);
        return;
    }
    if (type == BCF_BT_CHAR)
    {
        char *p = (char*)data;
        for (j = 0; j < n && *p; ++j, ++p)
        {
            if ( *p==bcf_str_missing ) kputc('.', s);
            else kputc(*p, s);
        }
    }
    else
    {
        #define BRANCH(type_t, is_missing, is_vector_end, kprint) { \
            type_t *p = (type_t *) data; \
            for (j=0; j<n; j++) \
            { \
                if ( is_vector_end ) break; \
                if ( j ) kputc(',', s); \
                if ( is_missing ) kputc('.', s); \
                else kprint; \
            } \
        }
        switch (type) {
            case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  kputw(p[j], s)); break;
            case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, kputw(p[j], s)); break;
            case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, kputw(p[j], s)); break;
            case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), ksprintf(s, "%g", p[j])); break;
            default: fprintf(stderr,"todo: type %d\n", type); exit(1); break;
        }
        #undef BRANCH
    }
}

uint8_t *bcf_fmt_sized_array(kstring_t *s, uint8_t *ptr)
{
    int x, type;
    x = bcf_dec_size(ptr, &ptr, &type);
    bcf_fmt_array(s, x, type, ptr);
    return ptr + (x << bcf_type_shift[type]);
}

/********************
 *** VCF site I/O ***
 ********************/

typedef struct {
    int key, max_m, size, offset;
    uint64_t is_gt:1, max_g:31, max_l:32;
    uint32_t y;
    uint8_t *buf;
} fmt_aux_t;

static inline void align_mem(kstring_t *s)
{
    if (s->l&7) {
        uint64_t zero = 0;
        int l = ((s->l + 7)>>3<<3) - s->l;
        kputsn((char*)&zero, l, s);
    }
}

// p,q is the start and the end of the FORMAT field
#define MAX_N_FMT 255   /* Limited by size of bcf1_t n_fmt field */
static int vcf_parse_format(kstring_t *s, const bcf_hdr_t *h, bcf1_t *v, char *p, char *q)
{
    if ( !bcf_hdr_nsamples(h) ) return 0;

    char *r, *t;
    int j, l, m, g;
    khint_t k;
    ks_tokaux_t aux1;
    vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
    kstring_t *mem = (kstring_t*)&h->mem;
    fmt_aux_t fmt[MAX_N_FMT];
    mem->l = 0;

    char *end = s->s + s->l;
    if ( q>=end )
    {
        fprintf(stderr,"[%s:%d %s] Error: FORMAT column with no sample columns starting at %s:%d\n", __FILE__,__LINE__,__FUNCTION__,s->s,v->pos+1);
        return -1;
    }

    // get format information from the dictionary
    v->n_fmt = 0;
    for (j = 0, t = kstrtok(p, ":", &aux1); t; t = kstrtok(0, 0, &aux1), ++j) {
        if (j >= MAX_N_FMT) {
            v->errcode |= BCF_ERR_LIMITS;
            fprintf(stderr,"[E::%s] Error: FORMAT column at %s:%d lists more identifiers than htslib can handle.\n", __func__, bcf_seqname(h,v), v->pos+1);
            return -1;
        }

        *(char*)aux1.p = 0;
        k = kh_get(vdict, d, t);
        if (k == kh_end(d) || kh_val(d, k).info[BCF_HL_FMT] == 15) {
            if (hts_verbose >= 2) fprintf(stderr, "[W::%s] FORMAT '%s' is not defined in the header, assuming Type=String\n", __func__, t);
            kstring_t tmp = {0,0,0};
            int l;
            ksprintf(&tmp, "##FORMAT=<ID=%s,Number=1,Type=String,Description=\"Dummy\">", t);
            bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
            free(tmp.s);
            if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
            k = kh_get(vdict, d, t);
            v->errcode = BCF_ERR_TAG_UNDEF;
            if (k == kh_end(d)) {
                fprintf(stderr, "[E::%s] Could not add dummy header for FORMAT '%s'\n", __func__, t);
                v->errcode |= BCF_ERR_TAG_INVALID;
                return -1;
            }
        }
        fmt[j].max_l = fmt[j].max_m = fmt[j].max_g = 0;
        fmt[j].key = kh_val(d, k).id;
        fmt[j].is_gt = !strcmp(t, "GT");
        fmt[j].y = h->id[0][fmt[j].key].val->info[BCF_HL_FMT];
        v->n_fmt++;
    }
    // compute max
    int n_sample_ori = -1;
    r = q + 1;  // r: position in the format string
    l = 0, m = g = 1, v->n_sample = 0;  // m: max vector size, l: max field len, g: max number of alleles
    while ( r<end )
    {
        // can we skip some samples?
        if ( h->keep_samples )
        {
            n_sample_ori++;
            if ( !bit_array_test(h->keep_samples,n_sample_ori) )
            {
                while ( *r!='\t' && r<end ) r++;
                if ( *r=='\t' ) { *r = 0; r++; }
                continue;
            }
        }

        // collect fmt stats: max vector size, length, number of alleles
        j = 0;  // j-th format field
        for (;;)
        {
            if ( *r == '\t' ) *r = 0;
            if ( *r == ':' || !*r )  // end of field or end of sample
            {
                if (fmt[j].max_m < m) fmt[j].max_m = m;
                if (fmt[j].max_l < l) fmt[j].max_l = l;
                if (fmt[j].is_gt && fmt[j].max_g < g) fmt[j].max_g = g;
                l = 0, m = g = 1;
                if ( *r==':' ) 
                {
                    j++;
                    if ( j>=v->n_fmt ) 
                    { 
                        fprintf(stderr,"Incorrect number of FORMAT fields at %s:%d\n", h->id[BCF_DT_CTG][v->rid].key,v->pos+1);
                        exit(1); 
                    }
                }
                else break;
            }
            else if ( *r== ',' ) m++;
            else if ( fmt[j].is_gt && (*r == '|' || *r == '/') ) g++;
            if ( r>=end ) break;
            r++; l++;
        }
        v->n_sample++;
        if ( v->n_sample == bcf_hdr_nsamples(h) ) break;
        r++;
    }

    // allocate memory for arrays
    for (j = 0; j < v->n_fmt; ++j) {
        fmt_aux_t *f = &fmt[j];
        if ( !f->max_m ) f->max_m = 1;  // omitted trailing format field
        if ((f->y>>4&0xf) == BCF_HT_STR) {
            f->size = f->is_gt? f->max_g << 2 : f->max_l;
        } else if ((f->y>>4&0xf) == BCF_HT_REAL || (f->y>>4&0xf) == BCF_HT_INT) {
            f->size = f->max_m << 2;
        } else
        {
            fprintf(stderr, "[E::%s] the format type %d currently not supported\n", __func__, f->y>>4&0xf);
            abort(); // I do not know how to do with Flag in the genotype fields
        }
        align_mem(mem);
        f->offset = mem->l;
        ks_resize(mem, mem->l + v->n_sample * f->size);
        mem->l += v->n_sample * f->size;
    }
    for (j = 0; j < v->n_fmt; ++j)
        fmt[j].buf = (uint8_t*)mem->s + fmt[j].offset;
    // fill the sample fields; at beginning of the loop, t points to the first char of a format
    n_sample_ori = -1;
    t = q + 1; m = 0;   // m: sample id
    while ( t<end )
    {
        // can we skip some samples?
        if ( h->keep_samples )
        {
            n_sample_ori++;
            if ( !bit_array_test(h->keep_samples,n_sample_ori) )
            {
                while ( *t && t<end ) t++;
                t++;
                continue;
            }
        }
        if ( m == bcf_hdr_nsamples(h) ) break;

        j = 0; // j-th format field, m-th sample
        while ( t < end )
        {
            fmt_aux_t *z = &fmt[j++];
            if ((z->y>>4&0xf) == BCF_HT_STR) {
                if (z->is_gt) { // genotypes
                    int32_t is_phased = 0, *x = (int32_t*)(z->buf + z->size * m);
                    for (l = 0;; ++t) {
                        if (*t == '.') ++t, x[l++] = is_phased;
                        else x[l++] = (strtol(t, &t, 10) + 1) << 1 | is_phased;
#if THOROUGH_SANITY_CHECKS
                        assert( 0 );    // success of strtol,strtod not checked
#endif
                        is_phased = (*t == '|');
                        if (*t != '|' && *t != '/') break;
                    }
                    if ( !l ) x[l++] = 0;   // An empty field, insert missing value
                    for (; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
                } else {
                    char *x = (char*)z->buf + z->size * m;
                    for (r = t, l = 0; *t != ':' && *t; ++t) x[l++] = *t;
                    for (; l < z->size; ++l) x[l] = 0;
                }
            } else if ((z->y>>4&0xf) == BCF_HT_INT) {
                int32_t *x = (int32_t*)(z->buf + z->size * m);
                for (l = 0;; ++t) {
                    if (*t == '.') x[l++] = bcf_int32_missing, ++t; // ++t to skip "."
                    else x[l++] = strtol(t, &t, 10);
                    if (*t != ',') break;
                }
                if ( !l ) x[l++] = bcf_int32_missing;
                for (; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
            } else if ((z->y>>4&0xf) == BCF_HT_REAL) {
                float *x = (float*)(z->buf + z->size * m);
                for (l = 0;; ++t) {
                    if (*t == '.' && !isdigit(t[1])) bcf_float_set_missing(x[l++]), ++t; // ++t to skip "."
                    else x[l++] = strtod(t, &t);
                    if (*t != ',') break;
                }
                if ( !l ) bcf_float_set_missing(x[l++]);    // An empty field, insert missing value
                for (; l < z->size>>2; ++l) bcf_float_set_vector_end(x[l]);
            } else abort();

            if (*t == '\0') {
                break;
            }
            else if (*t == ':') {
                t++;
            }
            else {
                char buffer[8];
                fprintf(stderr,"[E::%s] Invalid character '%s' in '%s' FORMAT field at %s:%d\n", __FUNCTION__, dump_char(buffer, *t), h->id[BCF_DT_ID][z->key].key, bcf_seqname(h,v), v->pos+1);
                v->errcode |= BCF_ERR_CHAR;
                return -1;
            }
        }

        for (; j < v->n_fmt; ++j) { // fill end-of-vector values
            fmt_aux_t *z = &fmt[j];
            if ((z->y>>4&0xf) == BCF_HT_STR) {
                if (z->is_gt) {
                    int32_t *x = (int32_t*)(z->buf + z->size * m);
                    if (z->size) x[0] = bcf_int32_missing;
                    for (l = 1; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
                } else {
                    char *x = (char*)z->buf + z->size * m;
                    if ( z->size ) x[0] = '.';
                    for (l = 1; l < z->size; ++l) x[l] = 0;
                }
            } else if ((z->y>>4&0xf) == BCF_HT_INT) {
                int32_t *x = (int32_t*)(z->buf + z->size * m);
                x[0] = bcf_int32_missing;
                for (l = 1; l < z->size>>2; ++l) x[l] = bcf_int32_vector_end;
            } else if ((z->y>>4&0xf) == BCF_HT_REAL) {
                float *x = (float*)(z->buf + z->size * m);
                bcf_float_set_missing(x[0]);
                for (l = 1; l < z->size>>2; ++l) bcf_float_set_vector_end(x[l]);
            }
        }

        m++; t++;
    }

    // write individual genotype information
    kstring_t *str = &v->indiv;
    int i;
    if (v->n_sample > 0) {
        for (i = 0; i < v->n_fmt; ++i) {
            fmt_aux_t *z = &fmt[i];
            bcf_enc_int1(str, z->key);
            if ((z->y>>4&0xf) == BCF_HT_STR && !z->is_gt) {
                bcf_enc_size(str, z->size, BCF_BT_CHAR);
                kputsn((char*)z->buf, z->size * v->n_sample, str);
            } else if ((z->y>>4&0xf) == BCF_HT_INT || z->is_gt) {
                bcf_enc_vint(str, (z->size>>2) * v->n_sample, (int32_t*)z->buf, z->size>>2);
            } else {
                bcf_enc_size(str, z->size>>2, BCF_BT_FLOAT);
                kputsn((char*)z->buf, z->size * v->n_sample, str);
            }
        }
    }

    if ( v->n_sample!=bcf_hdr_nsamples(h) )
    {
        fprintf(stderr,"[%s:%d %s] Number of columns at %s:%d does not match the number of samples (%d vs %d).\n",
                __FILE__,__LINE__,__FUNCTION__,bcf_seqname(h,v),v->pos+1, v->n_sample,bcf_hdr_nsamples(h));
        v->errcode |= BCF_ERR_NCOLS;
        return -1;
    }
    if ( v->indiv.l > 0xffffffff )
    {
        fprintf(stderr,"[%s:%d %s] The FORMAT at %s:%d is too long...\n",
                __FILE__,__LINE__,__FUNCTION__,bcf_seqname(h,v),v->pos+1);
        v->errcode |= BCF_ERR_LIMITS;

        // Error recovery: return -1 if this is a critical error or 0 if we want to ignore the FORMAT and proceed
        v->n_fmt = 0;
        return -1;
    }

    return 0;
}

int vcf_parse(kstring_t *s, const bcf_hdr_t *h, bcf1_t *v)
{
    int i = 0;
    char *p, *q, *r, *t;
    kstring_t *str;
    khint_t k;
    ks_tokaux_t aux;

    bcf_clear1(v);
    str = &v->shared;
    memset(&aux, 0, sizeof(ks_tokaux_t));
    for (p = kstrtok(s->s, "\t", &aux), i = 0; p; p = kstrtok(0, 0, &aux), ++i) {
        q = (char*)aux.p;
        *q = 0;
        if (i == 0) { // CHROM
            vdict_t *d = (vdict_t*)h->dict[BCF_DT_CTG];
            k = kh_get(vdict, d, p);
            if (k == kh_end(d))
            {
                // Simple error recovery for chromosomes not defined in the header. It will not help when VCF header has
                // been already printed, but will enable tools like vcfcheck to proceed.
                if (hts_verbose >= 2) fprintf(stderr, "[W::%s] contig '%s' is not defined in the header. (Quick workaround: index the file with tabix.)\n", __func__, p);
                kstring_t tmp = {0,0,0};
                int l;
                ksprintf(&tmp, "##contig=<ID=%s>", p);
                bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
                free(tmp.s);
                if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
                k = kh_get(vdict, d, p);
                v->errcode = BCF_ERR_CTG_UNDEF;
                if (k == kh_end(d)) {
                    fprintf(stderr, "[E::%s] Could not add dummy header for contig '%s'\n", __func__, p);
                    v->errcode |= BCF_ERR_CTG_INVALID;
                    return -1;
                }
            }
            v->rid = kh_val(d, k).id;
        } else if (i == 1) { // POS
            v->pos = atoi(p) - 1;
        } else if (i == 2) { // ID
            if (strcmp(p, ".")) bcf_enc_vchar(str, q - p, p);
            else bcf_enc_size(str, 0, BCF_BT_CHAR);
        } else if (i == 3) { // REF
            bcf_enc_vchar(str, q - p, p);
            v->n_allele = 1, v->rlen = q - p;
        } else if (i == 4) { // ALT
            if (strcmp(p, ".")) {
                for (r = t = p;; ++r) {
                    if (*r == ',' || *r == 0) {
                        bcf_enc_vchar(str, r - t, t);
                        t = r + 1;
                        ++v->n_allele;
                    }
                    if (r == q) break;
                }
            }
        } else if (i == 5) { // QUAL
            if (strcmp(p, ".")) v->qual = atof(p);
            else memcpy(&v->qual, &bcf_float_missing, 4);
            if ( v->max_unpack && !(v->max_unpack>>1) ) return 0; // BCF_UN_STR
        } else if (i == 6) { // FILTER
            if (strcmp(p, ".")) {
                int32_t *a;
                int n_flt = 1, i;
                ks_tokaux_t aux1;
                vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
                // count the number of filters
                if (*(q-1) == ';') *(q-1) = 0;
                for (r = p; *r; ++r)
                    if (*r == ';') ++n_flt;
                a = (int32_t*)alloca(n_flt * sizeof(int32_t));
                // add filters
                for (t = kstrtok(p, ";", &aux1), i = 0; t; t = kstrtok(0, 0, &aux1)) {
                    *(char*)aux1.p = 0;
                    k = kh_get(vdict, d, t);
                    if (k == kh_end(d))
                    {
                        // Simple error recovery for FILTERs not defined in the header. It will not help when VCF header has
                        // been already printed, but will enable tools like vcfcheck to proceed.
                        if (hts_verbose >= 2) fprintf(stderr, "[W::%s] FILTER '%s' is not defined in the header\n", __func__, t);
                        kstring_t tmp = {0,0,0};
                        int l;
                        ksprintf(&tmp, "##FILTER=<ID=%s,Description=\"Dummy\">", t);
                        bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
                        free(tmp.s);
                        if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
                        k = kh_get(vdict, d, t);
                        v->errcode = BCF_ERR_TAG_UNDEF;
                        if (k == kh_end(d)) {
                            fprintf(stderr, "[E::%s] Could not add dummy header for FILTER '%s'\n", __func__, t);
                            v->errcode |= BCF_ERR_TAG_INVALID;
                            return -1;
                        }
                    }
                    a[i++] = kh_val(d, k).id;
                }
                n_flt = i;
                bcf_enc_vint(str, n_flt, a, -1);
            } else bcf_enc_vint(str, 0, 0, -1);
            if ( v->max_unpack && !(v->max_unpack>>2) ) return 0;    // BCF_UN_FLT
        } else if (i == 7) { // INFO
            char *key;
            vdict_t *d = (vdict_t*)h->dict[BCF_DT_ID];
            v->n_info = 0;
            if (strcmp(p, ".")) {
                if (*(q-1) == ';') *(q-1) = 0;
                for (r = key = p;; ++r) {
                    int c;
                    char *val, *end;
                    if (*r != ';' && *r != '=' && *r != 0) continue;
                    val = end = 0;
                    c = *r; *r = 0;
                    if (c == '=') {
                        val = r + 1;
                        for (end = val; *end != ';' && *end != 0; ++end);
                        c = *end; *end = 0;
                    } else end = r;
                    if ( !*key ) { if (c==0) break; r = end; key = r + 1; continue; }  // faulty VCF, ";;" in the INFO
                    k = kh_get(vdict, d, key);
                    if (k == kh_end(d) || kh_val(d, k).info[BCF_HL_INFO] == 15)
                    {
                        if (hts_verbose >= 2) fprintf(stderr, "[W::%s] INFO '%s' is not defined in the header, assuming Type=String\n", __func__, key);
                        kstring_t tmp = {0,0,0};
                        int l;
                        ksprintf(&tmp, "##INFO=<ID=%s,Number=1,Type=String,Description=\"Dummy\">", key);
                        bcf_hrec_t *hrec = bcf_hdr_parse_line(h,tmp.s,&l);
                        free(tmp.s);
                        if ( bcf_hdr_add_hrec((bcf_hdr_t*)h, hrec) ) bcf_hdr_sync((bcf_hdr_t*)h);
                        k = kh_get(vdict, d, key);
                        v->errcode = BCF_ERR_TAG_UNDEF;
                        if (k == kh_end(d)) {
                            fprintf(stderr, "[E::%s] Could not add dummy header for INFO '%s'\n", __func__, key);
                            v->errcode |= BCF_ERR_TAG_INVALID;
                            return -1;
                        }
                    }
                    uint32_t y = kh_val(d, k).info[BCF_HL_INFO];
                    ++v->n_info;
                    bcf_enc_int1(str, kh_val(d, k).id);
                    if (val == 0) {
                        bcf_enc_size(str, 0, BCF_BT_NULL);
                    } else if ((y>>4&0xf) == BCF_HT_FLAG || (y>>4&0xf) == BCF_HT_STR) { // if Flag has a value, treat it as a string
                        bcf_enc_vchar(str, end - val, val);
                    } else { // int/float value/array
                        int i, n_val;
                        char *t, *te;
                        for (t = val, n_val = 1; *t; ++t) // count the number of values
                            if (*t == ',') ++n_val;
                        if ((y>>4&0xf) == BCF_HT_INT) {
                            int32_t *z;
                            z = (int32_t*)alloca(n_val * sizeof(int32_t));
                            for (i = 0, t = val; i < n_val; ++i, ++t)
                            {
                                z[i] = strtol(t, &te, 10);
                                if ( te==t ) // conversion failed
                                {
                                    z[i] = bcf_int32_missing;
                                    while ( *te && *te!=',' ) te++;
                                }
                                t = te;
                            }
                            bcf_enc_vint(str, n_val, z, -1);
                            if (strcmp(key, "END") == 0) v->rlen = z[0] - v->pos;
                        } else if ((y>>4&0xf) == BCF_HT_REAL) {
                            float *z;
                            z = (float*)alloca(n_val * sizeof(float));
                            for (i = 0, t = val; i < n_val; ++i, ++t)
                            {
                                z[i] = strtod(t, &te);
                                if ( te==t ) // conversion failed
                                {
                                    bcf_float_set_missing(z[i]);
                                    while ( *te && *te!=',' ) te++;
                                }
                                t = te;
                            }
                            bcf_enc_vfloat(str, n_val, z);
                        }
                    }
                    if (c == 0) break;
                    r = end;
                    key = r + 1;
                }
            }
            if ( v->max_unpack && !(v->max_unpack>>3) ) return 0;
        } else if (i == 8) // FORMAT
            return vcf_parse_format(s, h, v, p, q);
    }
    return 0;
}

int vcf_read(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
{
    int ret;
    ret = hts_getline(fp, KS_SEP_LINE, &fp->line);
    if (ret < 0) return -1;
    return vcf_parse1(&fp->line, h, v);
}

static inline uint8_t *bcf_unpack_fmt_core1(uint8_t *ptr, int n_sample, bcf_fmt_t *fmt)
{
    uint8_t *ptr_start = ptr;
    fmt->id = bcf_dec_typed_int1(ptr, &ptr);
    fmt->n = bcf_dec_size(ptr, &ptr, &fmt->type);
    fmt->size = fmt->n << bcf_type_shift[fmt->type];
    fmt->p = ptr;
    fmt->p_off  = ptr - ptr_start;
    fmt->p_free = 0;
    ptr += n_sample * fmt->size;
    fmt->p_len = ptr - fmt->p;
    return ptr;
}

static inline uint8_t *bcf_unpack_info_core1(uint8_t *ptr, bcf_info_t *info)
{
    uint8_t *ptr_start = ptr;
    info->key = bcf_dec_typed_int1(ptr, &ptr);
    info->len = bcf_dec_size(ptr, &ptr, &info->type);
    info->vptr = ptr;
    info->vptr_off  = ptr - ptr_start;
    info->vptr_free = 0;
    info->v1.i = 0;
    if (info->len == 1) {
        if (info->type == BCF_BT_INT8 || info->type == BCF_BT_CHAR) info->v1.i = *(int8_t*)ptr;
        else if (info->type == BCF_BT_INT32) info->v1.i = *(int32_t*)ptr;
        else if (info->type == BCF_BT_FLOAT) info->v1.f = *(float*)ptr;
        else if (info->type == BCF_BT_INT16) info->v1.i = *(int16_t*)ptr;
    }
    ptr += info->len << bcf_type_shift[info->type];
    info->vptr_len = ptr - info->vptr;
    return ptr;
}

int bcf_unpack(bcf1_t *b, int which)
{
    if ( !b->shared.l ) return 0; // Building a new BCF record from scratch
    uint8_t *ptr = (uint8_t*)b->shared.s, *ptr_ori;
    int *offset, i;
    bcf_dec_t *d = &b->d;
    if (which & BCF_UN_FLT) which |= BCF_UN_STR;
    if (which & BCF_UN_INFO) which |= BCF_UN_SHR;
    if ((which&BCF_UN_STR) && !(b->unpacked&BCF_UN_STR))
    {
        kstring_t tmp;

        // ID
        tmp.l = 0; tmp.s = d->id; tmp.m = d->m_id;
        ptr_ori = ptr;
        ptr = bcf_fmt_sized_array(&tmp, ptr);
        b->unpack_size[0] = ptr - ptr_ori;
        kputc('\0', &tmp);
        d->id = tmp.s; d->m_id = tmp.m;

        // REF and ALT are in a single block (d->als) and d->alleles are pointers into this block
        tmp.l = 0; tmp.s = d->als; tmp.m = d->m_als;
        offset = (int*)alloca(b->n_allele * sizeof(int));
        ptr_ori = ptr;
        for (i = 0; i < b->n_allele; ++i) {
            offset[i] = tmp.l;
            ptr = bcf_fmt_sized_array(&tmp, ptr);
            kputc('\0', &tmp);
        }
        b->unpack_size[1] = ptr - ptr_ori;
        d->als = tmp.s; d->m_als = tmp.m;

        hts_expand(char*, b->n_allele, d->m_allele, d->allele); // NM: hts_expand() is a macro
        for (i = 0; i < b->n_allele; ++i)
            d->allele[i] = d->als + offset[i];
        b->unpacked |= BCF_UN_STR;
    }
    if ((which&BCF_UN_FLT) && !(b->unpacked&BCF_UN_FLT)) { // FILTER
        ptr = (uint8_t*)b->shared.s + b->unpack_size[0] + b->unpack_size[1];
        ptr_ori = ptr;
        if (*ptr>>4) {
            int type;
            d->n_flt = bcf_dec_size(ptr, &ptr, &type);
            hts_expand(int, d->n_flt, d->m_flt, d->flt);
            for (i = 0; i < d->n_flt; ++i)
                d->flt[i] = bcf_dec_int1(ptr, type, &ptr);
        } else ++ptr, d->n_flt = 0;
        b->unpack_size[2] = ptr - ptr_ori;
        b->unpacked |= BCF_UN_FLT;
    }
    if ((which&BCF_UN_INFO) && !(b->unpacked&BCF_UN_INFO)) { // INFO
        ptr = (uint8_t*)b->shared.s + b->unpack_size[0] + b->unpack_size[1] + b->unpack_size[2];
        hts_expand(bcf_info_t, b->n_info, d->m_info, d->info);
        for (i = 0; i < d->m_info; ++i) d->info[i].vptr_free = 0;
        for (i = 0; i < b->n_info; ++i)
            ptr = bcf_unpack_info_core1(ptr, &d->info[i]);
        b->unpacked |= BCF_UN_INFO;
    }
    if ((which&BCF_UN_FMT) && b->n_sample && !(b->unpacked&BCF_UN_FMT)) { // FORMAT
        ptr = (uint8_t*)b->indiv.s;
        hts_expand(bcf_fmt_t, b->n_fmt, d->m_fmt, d->fmt);
        for (i = 0; i < d->m_fmt; ++i) d->fmt[i].p_free = 0;
        for (i = 0; i < b->n_fmt; ++i)
            ptr = bcf_unpack_fmt_core1(ptr, b->n_sample, &d->fmt[i]);
        b->unpacked |= BCF_UN_FMT;
    }
    return 0;
}

int vcf_format(const bcf_hdr_t *h, const bcf1_t *v, kstring_t *s)
{
    int i;
    bcf_unpack((bcf1_t*)v, BCF_UN_ALL);
    kputs(h->id[BCF_DT_CTG][v->rid].key, s); // CHROM
    kputc('\t', s); kputw(v->pos + 1, s); // POS
    kputc('\t', s); kputs(v->d.id ? v->d.id : ".", s); // ID
    kputc('\t', s); // REF
    if (v->n_allele > 0) kputs(v->d.allele[0], s);
    else kputc('.', s);
    kputc('\t', s); // ALT
    if (v->n_allele > 1) {
        for (i = 1; i < v->n_allele; ++i) {
            if (i > 1) kputc(',', s);
            kputs(v->d.allele[i], s);
        }
    } else kputc('.', s);
    kputc('\t', s); // QUAL
    if ( bcf_float_is_missing(v->qual) ) kputc('.', s); // QUAL
    else ksprintf(s, "%g", v->qual);
    kputc('\t', s); // FILTER
    if (v->d.n_flt) {
        for (i = 0; i < v->d.n_flt; ++i) {
            if (i) kputc(';', s);
            kputs(h->id[BCF_DT_ID][v->d.flt[i]].key, s);
        }
    } else kputc('.', s);
    kputc('\t', s); // INFO
    if (v->n_info) {
        int first = 1;
        for (i = 0; i < v->n_info; ++i) {
            bcf_info_t *z = &v->d.info[i];
            if ( !z->vptr ) continue;
            if ( !first ) kputc(';', s);
            first = 0;
            kputs(h->id[BCF_DT_ID][z->key].key, s);
            if (z->len <= 0) continue;
            kputc('=', s);
            if (z->len == 1) 
            {
                switch (z->type) 
                {
                    case BCF_BT_INT8:  if ( z->v1.i==bcf_int8_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
                    case BCF_BT_INT16: if ( z->v1.i==bcf_int16_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
                    case BCF_BT_INT32: if ( z->v1.i==bcf_int32_missing ) kputc('.', s); else kputw(z->v1.i, s); break;
                    case BCF_BT_FLOAT: if ( bcf_float_is_missing(z->v1.f) ) kputc('.', s); else ksprintf(s, "%g", z->v1.f); break;
                    case BCF_BT_CHAR:  kputc(z->v1.i, s); break;
                    default: fprintf(stderr,"todo: type %d\n", z->type); exit(1); break;
                }
            }
            else bcf_fmt_array(s, z->len, z->type, z->vptr);
        }
        if ( first ) kputc('.', s);
    } else kputc('.', s);
    // FORMAT and individual information
    if (v->n_sample)
    {
        int i,j;
        if ( v->n_fmt)
        {
            int gt_i = -1;
            bcf_fmt_t *fmt = v->d.fmt;
            int first = 1;
            for (i = 0; i < (int)v->n_fmt; ++i) {
                if ( !fmt[i].p ) continue;
                kputc(!first ? ':' : '\t', s); first = 0;
                if ( fmt[i].id<0 ) //!bcf_hdr_idinfo_exists(h,BCF_HL_FMT,fmt[i].id) )
                {
                    fprintf(stderr, "[E::%s] invalid BCF, the FORMAT tag id=%d not present in the header.\n", __func__, fmt[i].id);
                    abort();
                }
                kputs(h->id[BCF_DT_ID][fmt[i].id].key, s);
                if (strcmp(h->id[BCF_DT_ID][fmt[i].id].key, "GT") == 0) gt_i = i;
            }
            if ( first ) kputs("\t.", s);
            for (j = 0; j < v->n_sample; ++j) {
                kputc('\t', s);
                first = 1;
                for (i = 0; i < (int)v->n_fmt; ++i) {
                    bcf_fmt_t *f = &fmt[i];
                    if ( !f->p ) continue;
                    if (!first) kputc(':', s);
                    first = 0;
                    if (gt_i == i)
                        bcf_format_gt(f,j,s);
                    else
                        bcf_fmt_array(s, f->n, f->type, f->p + j * f->size);
                }
                if ( first ) kputc('.', s);
            }
        }
        else
            for (j=0; j<=v->n_sample; j++)
                kputs("\t.", s);
    }
    kputc('\n', s);
    return 0;
}

int vcf_write_line(htsFile *fp, kstring_t *line)
{
    int ret;
    if ( line->s[line->l-1]!='\n' ) kputc('\n',line);
    if ( fp->format.compression!=no_compression )
        ret = bgzf_write(fp->fp.bgzf, line->s, line->l);
    else
        ret = hwrite(fp->fp.hfile, line->s, line->l);
    return ret==line->l ? 0 : -1;
}

int vcf_write(htsFile *fp, const bcf_hdr_t *h, bcf1_t *v)
{
    int ret;
    fp->line.l = 0;
    vcf_format1(h, v, &fp->line);
    if ( fp->format.compression!=no_compression )
        ret = bgzf_write(fp->fp.bgzf, fp->line.s, fp->line.l);
    else
        ret = hwrite(fp->fp.hfile, fp->line.s, fp->line.l);
    return ret==fp->line.l ? 0 : -1;
}

/************************
 * Data access routines *
 ************************/

int bcf_hdr_id2int(const bcf_hdr_t *h, int which, const char *id)
{
    khint_t k;
    vdict_t *d = (vdict_t*)h->dict[which];
    k = kh_get(vdict, d, id);
    return k == kh_end(d)? -1 : kh_val(d, k).id;
}


/********************
 *** BCF indexing ***
 ********************/

hts_idx_t *bcf_index(htsFile *fp, int min_shift)
{
    int n_lvls, i;
    bcf1_t *b;
    hts_idx_t *idx;
    bcf_hdr_t *h;
    int64_t max_len = 0, s;
    h = bcf_hdr_read(fp);
    if ( !h ) return NULL;
    int nids = 0;
    for (i = 0; i < h->n[BCF_DT_CTG]; ++i)
    {
        if ( !h->id[BCF_DT_CTG][i].val ) continue;
        if ( max_len < h->id[BCF_DT_CTG][i].val->info[0] ) max_len = h->id[BCF_DT_CTG][i].val->info[0];
        nids++;
    }
    if ( !max_len ) max_len = ((int64_t)1<<31) - 1;  // In case contig line is broken.
    max_len += 256;
    for (n_lvls = 0, s = 1<<min_shift; max_len > s; ++n_lvls, s <<= 3);
    idx = hts_idx_init(nids, HTS_FMT_CSI, bgzf_tell(fp->fp.bgzf), min_shift, n_lvls);
    b = bcf_init1();
    while (bcf_read1(fp,h, b) >= 0) {
        int ret;
        ret = hts_idx_push(idx, b->rid, b->pos, b->pos + b->rlen, bgzf_tell(fp->fp.bgzf), 1);
        if (ret < 0)
        {
            bcf_destroy1(b);
            hts_idx_destroy(idx);
            return NULL;
        }
    }
    hts_idx_finish(idx, bgzf_tell(fp->fp.bgzf));
    bcf_destroy1(b);
    bcf_hdr_destroy(h);
    return idx;
}

hts_idx_t *bcf_index_load2(const char *fn, const char *fnidx)
{
    return fnidx? hts_idx_load2(fn, fnidx) : bcf_index_load(fn);
}

int bcf_index_build2(const char *fn, const char *fnidx, int min_shift)
{
    htsFile *fp;
    hts_idx_t *idx;
    int ret;
    if ((fp = hts_open(fn, "rb")) == 0) return -1;
    if ( fp->format.compression!=bgzf ) { hts_close(fp); return -1; }
    idx = bcf_index(fp, min_shift);
    hts_close(fp);
    if ( !idx ) return -1;
    ret = hts_idx_save_as(idx, fn, fnidx, HTS_FMT_CSI);
    hts_idx_destroy(idx);
    return ret;
}

int bcf_index_build(const char *fn, int min_shift)
{
    return bcf_index_build2(fn, NULL, min_shift);
}

/*****************
 *** Utilities ***
 *****************/

int bcf_hdr_combine(bcf_hdr_t *dst, const bcf_hdr_t *src)
{
    int i, ndst_ori = dst->nhrec, need_sync = 0, ret = 0;
    for (i=0; i<src->nhrec; i++)
    {
        if ( src->hrec[i]->type==BCF_HL_GEN && src->hrec[i]->value )
        {
            int j;
            for (j=0; j<ndst_ori; j++)
            {
                if ( dst->hrec[j]->type!=BCF_HL_GEN ) continue;

                // Checking only the key part of generic lines, otherwise
                // the VCFs are too verbose. Should we perhaps add a flag
                // to bcf_hdr_combine() and make this optional?
                if ( !strcmp(src->hrec[i]->key,dst->hrec[j]->key) ) break;
            }
            if ( j>=ndst_ori )
                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
        }
        else if ( src->hrec[i]->type==BCF_HL_STR )
        {
            // NB: we are ignoring fields without ID
            int j = bcf_hrec_find_key(src->hrec[i],"ID");
            if ( j>=0 )
            {
                bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], src->hrec[i]->key);
                if ( !rec )
                    need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
            }
        }
        else
        {
            int j = bcf_hrec_find_key(src->hrec[i],"ID");
            assert( j>=0 ); // this should always be true for valid VCFs

            bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], NULL);
            if ( !rec )
                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
            else if ( src->hrec[i]->type==BCF_HL_INFO || src->hrec[i]->type==BCF_HL_FMT )
            {
                // Check that both records are of the same type. The bcf_hdr_id2length
                // macro cannot be used here because dst header is not synced yet.
                vdict_t *d_src = (vdict_t*)src->dict[BCF_DT_ID];
                vdict_t *d_dst = (vdict_t*)dst->dict[BCF_DT_ID];
                khint_t k_src  = kh_get(vdict, d_src, src->hrec[i]->vals[0]);
                khint_t k_dst  = kh_get(vdict, d_dst, src->hrec[i]->vals[0]);
                if ( (kh_val(d_src,k_src).info[rec->type]>>8 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>8 & 0xf) )
                {
                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different lengths\n", src->hrec[i]->vals[0]);
                    ret |= 1;
                }
                if ( (kh_val(d_src,k_src).info[rec->type]>>4 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>4 & 0xf) )
                {
                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different types\n", src->hrec[i]->vals[0]);
                    ret |= 1;
                }
            }
        }
    }
    if ( need_sync ) bcf_hdr_sync(dst);
    return ret;
}

bcf_hdr_t *bcf_hdr_merge(bcf_hdr_t *dst, const bcf_hdr_t *src)
{
    if ( !dst )
    {
        // this will effectively strip existing IDX attributes from src to become dst
        dst = bcf_hdr_init("r");
        char *htxt = bcf_hdr_fmt_text(src, 0, NULL);
        bcf_hdr_parse(dst, htxt);
        free(htxt);
        return dst;
    }

    int i, ndst_ori = dst->nhrec, need_sync = 0, ret = 0;
    for (i=0; i<src->nhrec; i++)
    {
        if ( src->hrec[i]->type==BCF_HL_GEN && src->hrec[i]->value )
        {
            int j;
            for (j=0; j<ndst_ori; j++)
            {
                if ( dst->hrec[j]->type!=BCF_HL_GEN ) continue;

                // Checking only the key part of generic lines, otherwise
                // the VCFs are too verbose. Should we perhaps add a flag
                // to bcf_hdr_combine() and make this optional?
                if ( !strcmp(src->hrec[i]->key,dst->hrec[j]->key) ) break;
            }
            if ( j>=ndst_ori )
                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
        }
        else if ( src->hrec[i]->type==BCF_HL_STR )
        {
            // NB: we are ignoring fields without ID
            int j = bcf_hrec_find_key(src->hrec[i],"ID");
            if ( j>=0 )
            {
                bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], src->hrec[i]->key);
                if ( !rec )
                    need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
            }
        }
        else
        {
            int j = bcf_hrec_find_key(src->hrec[i],"ID");
            assert( j>=0 ); // this should always be true for valid VCFs

            bcf_hrec_t *rec = bcf_hdr_get_hrec(dst, src->hrec[i]->type, "ID", src->hrec[i]->vals[j], NULL);
            if ( !rec )
                need_sync += bcf_hdr_add_hrec(dst, bcf_hrec_dup(src->hrec[i]));
            else if ( src->hrec[i]->type==BCF_HL_INFO || src->hrec[i]->type==BCF_HL_FMT )
            {
                // Check that both records are of the same type. The bcf_hdr_id2length
                // macro cannot be used here because dst header is not synced yet.
                vdict_t *d_src = (vdict_t*)src->dict[BCF_DT_ID];
                vdict_t *d_dst = (vdict_t*)dst->dict[BCF_DT_ID];
                khint_t k_src  = kh_get(vdict, d_src, src->hrec[i]->vals[0]);
                khint_t k_dst  = kh_get(vdict, d_dst, src->hrec[i]->vals[0]);
                if ( (kh_val(d_src,k_src).info[rec->type]>>8 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>8 & 0xf) )
                {
                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different lengths\n", src->hrec[i]->vals[0]);
                    ret |= 1;
                }
                if ( (kh_val(d_src,k_src).info[rec->type]>>4 & 0xf) != (kh_val(d_dst,k_dst).info[rec->type]>>4 & 0xf) )
                {
                    fprintf(stderr,"Warning: trying to combine \"%s\" tag definitions of different types\n", src->hrec[i]->vals[0]);
                    ret |= 1;
                }
            }
        }
    }
    if ( need_sync ) bcf_hdr_sync(dst);
    return dst;
}
int bcf_translate(const bcf_hdr_t *dst_hdr, bcf_hdr_t *src_hdr, bcf1_t *line)
{
    int i;
    if ( line->errcode )
    {
        fprintf(stderr,"[%s:%d %s] Unchecked error (%d), exiting.\n", __FILE__,__LINE__,__FUNCTION__,line->errcode);
        exit(1);
    }
    if ( src_hdr->ntransl==-1 ) return 0;    // no need to translate, all tags have the same id
    if ( !src_hdr->ntransl )  // called for the first time, see what needs translating
    {
        int dict;
        for (dict=0; dict<2; dict++)    // BCF_DT_ID and BCF_DT_CTG
        {
            src_hdr->transl[dict] = (int*) malloc(src_hdr->n[dict]*sizeof(int));
            for (i=0; i<src_hdr->n[dict]; i++)
            {
                if ( !src_hdr->id[dict][i].key ) // gap left after removed BCF header lines
                {
                    src_hdr->transl[dict][i] = -1;
                    continue;
                }
                src_hdr->transl[dict][i] = bcf_hdr_id2int(dst_hdr,dict,src_hdr->id[dict][i].key);
                if ( src_hdr->transl[dict][i]!=-1 && i!=src_hdr->transl[dict][i] ) src_hdr->ntransl++;
            }
        }
        if ( !src_hdr->ntransl )
        {
            free(src_hdr->transl[0]); src_hdr->transl[0] = NULL;
            free(src_hdr->transl[1]); src_hdr->transl[1] = NULL;
            src_hdr->ntransl = -1;
        }
        if ( src_hdr->ntransl==-1 ) return 0;
    }
    bcf_unpack(line,BCF_UN_ALL);

    // CHROM
    if ( src_hdr->transl[BCF_DT_CTG][line->rid] >=0 ) line->rid = src_hdr->transl[BCF_DT_CTG][line->rid];

    // FILTER
    for (i=0; i<line->d.n_flt; i++)
    {
        int src_id = line->d.flt[i];
        if ( src_hdr->transl[BCF_DT_ID][src_id] >=0 )
            line->d.flt[i] = src_hdr->transl[BCF_DT_ID][src_id];
        line->d.shared_dirty |= BCF1_DIRTY_FLT;
    }

    // INFO
    for (i=0; i<line->n_info; i++)
    {
        int src_id = line->d.info[i].key;
        int dst_id = src_hdr->transl[BCF_DT_ID][src_id];
        if ( dst_id<0 ) continue;
        int src_size = src_id>>7 ? ( src_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
        int dst_size = dst_id>>7 ? ( dst_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
        if ( src_size==dst_size )   // can overwrite
        {
            line->d.info[i].key = dst_id;
            uint8_t *vptr = line->d.info[i].vptr - line->d.info[i].vptr_off;
            if ( dst_size==BCF_BT_INT8 ) { vptr[1] = (uint8_t)dst_id; }
            else if ( dst_size==BCF_BT_INT16 ) { *(uint16_t*)vptr = (uint16_t)dst_id; }
            else { *(uint32_t*)vptr = (uint32_t)dst_id; }
        }
        else    // must realloc
        {
            bcf_info_t *info = &line->d.info[i];
            assert( !info->vptr_free );
            kstring_t str = {0,0,0};
            bcf_enc_int1(&str, dst_id);
            bcf_enc_size(&str, info->len,info->type);
            info->vptr_off = str.l;
            kputsn((char*)info->vptr, info->vptr_len, &str);
            info->vptr = (uint8_t*)str.s + info->vptr_off;
            info->vptr_free = 1;
            info->key = dst_id;
            line->d.shared_dirty |= BCF1_DIRTY_INF;
        }
    }

    // FORMAT
    for (i=0; i<line->n_fmt; i++)
    {
        int src_id = line->d.fmt[i].id;
        int dst_id = src_hdr->transl[BCF_DT_ID][src_id];
        if ( dst_id<0 ) continue;
        int src_size = src_id>>7 ? ( src_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
        int dst_size = dst_id>>7 ? ( dst_id>>15 ? BCF_BT_INT32 : BCF_BT_INT16) : BCF_BT_INT8;
        if ( src_size==dst_size )   // can overwrite
        {
            line->d.fmt[i].id = dst_id;
            uint8_t *p = line->d.fmt[i].p - line->d.fmt[i].p_off;    // pointer to the vector size (4bits) and BT type (4bits)
            if ( dst_size==BCF_BT_INT8 ) { p[1] = dst_id; }
            else if ( dst_size==BCF_BT_INT16 ) { uint8_t *x = (uint8_t*) &dst_id; p[1] = x[0]; p[2] = x[1]; }
            else { uint8_t *x = (uint8_t*) &dst_id; p[1] = x[0]; p[2] = x[1]; p[3] = x[2]; p[4] = x[3]; }
        }
        else    // must realloc
        {
            bcf_fmt_t *fmt = &line->d.fmt[i];
            assert( !fmt->p_free );
            kstring_t str = {0,0,0};
            bcf_enc_int1(&str, dst_id);
            bcf_enc_size(&str, fmt->n, fmt->type);
            fmt->p_off = str.l;
            kputsn((char*)fmt->p, fmt->p_len, &str);
            fmt->p = (uint8_t*)str.s + fmt->p_off;
            fmt->p_free = 1;
            fmt->id = dst_id;
            line->d.indiv_dirty = 1;
        }
    }
    return 0;
}

bcf_hdr_t *bcf_hdr_dup(const bcf_hdr_t *hdr)
{
    bcf_hdr_t *hout = bcf_hdr_init("r");
    char *htxt = bcf_hdr_fmt_text(hdr, 1, NULL);
    if (!hout) {
        fprintf(stderr, "[E::%s] failed to allocate bcf header\n", __func__);
        free(htxt);
        return NULL;
    }
    bcf_hdr_parse(hout, htxt);
    free(htxt);
    return hout;
}

bcf_hdr_t *bcf_hdr_subset(const bcf_hdr_t *h0, int n, char *const* samples, int *imap)
{
    int hlen;
    void *names_hash = khash_str2int_init();
    char *htxt = bcf_hdr_fmt_text(h0, 1, &hlen);
    kstring_t str;
    bcf_hdr_t *h;
    str.l = str.m = 0; str.s = 0;
    h = bcf_hdr_init("w");
    if (!h) {
        fprintf(stderr, "[E::%s] failed to allocate bcf header\n", __func__);
        free(htxt);
        return NULL;
    }
    bcf_hdr_set_version(h,bcf_hdr_get_version(h0));
    int j;
    for (j=0; j<n; j++) imap[j] = -1;
    if ( bcf_hdr_nsamples(h0) > 0) {
        char *p;
        int i = 0, end = n? 8 : 7;
        while ((p = strstr(htxt, "#CHROM\t")) != 0)
            if (p > htxt && *(p-1) == '\n') break;
        while ((p = strchr(p, '\t')) != 0 && i < end) ++i, ++p;
        if (i != end) {
            free(h); free(str.s);
            return 0; // malformated header
        }
        kputsn(htxt, p - htxt, &str);
        for (i = 0; i < n; ++i) {
            if ( khash_str2int_has_key(names_hash,samples[i]) )
            {
                fprintf(stderr,"[E::bcf_hdr_subset] Duplicate sample name \"%s\".\n", samples[i]);
                free(str.s);
                free(htxt);
                khash_str2int_destroy(names_hash);
                bcf_hdr_destroy(h);
                return NULL;
            }
            imap[i] = bcf_hdr_id2int(h0, BCF_DT_SAMPLE, samples[i]);
            if (imap[i] < 0) continue;
            kputc('\t', &str);
            kputs(samples[i], &str);
            khash_str2int_inc(names_hash,samples[i]);
        }
    } else kputsn(htxt, hlen, &str);
    while (str.l && (!str.s[str.l-1] || str.s[str.l-1]=='\n') ) str.l--; // kill trailing zeros and newlines
    kputc('\n',&str);
    bcf_hdr_parse(h, str.s);
    free(str.s);
    free(htxt);
    khash_str2int_destroy(names_hash);
    return h;
}

int bcf_hdr_set_samples(bcf_hdr_t *hdr, const char *samples, int is_file)
{
    if ( samples && !strcmp("-",samples) ) return 0;            // keep all samples

    hdr->nsamples_ori = bcf_hdr_nsamples(hdr);
    if ( !samples ) { bcf_hdr_nsamples(hdr) = 0; return 0; }    // exclude all samples

    int i, narr = bit_array_size(bcf_hdr_nsamples(hdr));
    hdr->keep_samples = (uint8_t*) calloc(narr,1);
    if ( samples[0]=='^' )
        for (i=0; i<bcf_hdr_nsamples(hdr); i++) bit_array_set(hdr->keep_samples,i);

    int idx, n, ret = 0;
    char **smpls = hts_readlist(samples[0]=='^'?samples+1:samples, is_file, &n);
    if ( !smpls ) return -1;
    for (i=0; i<n; i++)
    {
        idx = bcf_hdr_id2int(hdr,BCF_DT_SAMPLE,smpls[i]);
        if ( idx<0 )
        {
            if ( !ret ) ret = i+1;
            continue;
        }
        assert( idx<bcf_hdr_nsamples(hdr) );
        if (  samples[0]=='^' )
            bit_array_clear(hdr->keep_samples, idx);
        else
            bit_array_set(hdr->keep_samples, idx);
    }
    for (i=0; i<n; i++) free(smpls[i]);
    free(smpls);

    bcf_hdr_nsamples(hdr) = 0;
    for (i=0; i<hdr->nsamples_ori; i++)
        if ( bit_array_test(hdr->keep_samples,i) ) bcf_hdr_nsamples(hdr)++;
    if ( !bcf_hdr_nsamples(hdr) ) { free(hdr->keep_samples); hdr->keep_samples=NULL; }
    else
    {
        char **samples = (char**) malloc(sizeof(char*)*bcf_hdr_nsamples(hdr));
        idx = 0;
        for (i=0; i<hdr->nsamples_ori; i++)
            if ( bit_array_test(hdr->keep_samples,i) ) samples[idx++] = strdup(hdr->samples[i]);
        free(hdr->samples);
        hdr->samples = samples;

        // delete original samples from the dictionary
        vdict_t *d = (vdict_t*)hdr->dict[BCF_DT_SAMPLE];
        int k;
        for (k = kh_begin(d); k != kh_end(d); ++k)
            if (kh_exist(d, k)) free((char*)kh_key(d, k));
        kh_destroy(vdict, d);

        // add the subset back
        hdr->dict[BCF_DT_SAMPLE] = d = kh_init(vdict);
        for (i=0; i<bcf_hdr_nsamples(hdr); i++)
        {
            int ignore, k = kh_put(vdict, d, hdr->samples[i], &ignore);
            kh_val(d, k) = bcf_idinfo_def;
            kh_val(d, k).id = kh_size(d) - 1;
        }
        bcf_hdr_sync(hdr);
    }

    return ret;
}

int bcf_subset(const bcf_hdr_t *h, bcf1_t *v, int n, int *imap)
{
    kstring_t ind;
    ind.s = 0; ind.l = ind.m = 0;
    if (n) {
        bcf_fmt_t *fmt;
        int i, j;
        fmt = (bcf_fmt_t*)alloca(v->n_fmt * sizeof(bcf_fmt_t));
        uint8_t *ptr = (uint8_t*)v->indiv.s;
        for (i = 0; i < v->n_fmt; ++i)
            ptr = bcf_unpack_fmt_core1(ptr, v->n_sample, &fmt[i]);
        for (i = 0; i < (int)v->n_fmt; ++i) {
            bcf_fmt_t *f = &fmt[i];
            bcf_enc_int1(&ind, f->id);
            bcf_enc_size(&ind, f->n, f->type);
            for (j = 0; j < n; ++j)
                if (imap[j] >= 0) kputsn((char*)(f->p + imap[j] * f->size), f->size, &ind);
        }
        for (i = j = 0; j < n; ++j) if (imap[j] >= 0) ++i;
        v->n_sample = i;
    } else v->n_sample = 0;
    if ( !v->n_sample ) v->n_fmt = 0;
    free(v->indiv.s);
    v->indiv = ind;
    v->unpacked &= ~BCF_UN_FMT;    // only BCF is ready for output, VCF will need to unpack again
    return 0;
}

int bcf_is_snp(bcf1_t *v)
{
    int i;
    bcf_unpack(v, BCF_UN_STR);
    for (i = 0; i < v->n_allele; ++i)
    {
        if ( v->d.allele[i][1]==0 ) continue;

        // mpileup's <X> allele, see also below. This is not completely satisfactory,
        // a general library is here narrowly tailored to fit samtools.
        if ( v->d.allele[i][0]=='<' && v->d.allele[i][1]=='X' && v->d.allele[i][2]=='>' ) continue;
        if ( v->d.allele[i][0]=='<' && v->d.allele[i][1]=='*' && v->d.allele[i][2]=='>' ) continue;

        break;
    }
    return i == v->n_allele;
}

static void bcf_set_variant_type(const char *ref, const char *alt, variant_t *var)
{
    // The most frequent case
    if ( !ref[1] && !alt[1] )
    {
        if ( *alt == '.' || *ref==*alt ) { var->n = 0; var->type = VCF_REF; return; }
        if ( *alt == 'X' ) { var->n = 0; var->type = VCF_REF; return; }  // mpileup's X allele shouldn't be treated as variant
        if ( *alt == '*' ) { var->n = 0; var->type = VCF_REF; return; } 
        var->n = 1; var->type = VCF_SNP; return;
    }
    if ( alt[0]=='<' )
    {
        if ( alt[1]=='X' && alt[2]=='>' ) { var->n = 0; var->type = VCF_REF; return; }  // mpileup's X allele shouldn't be treated as variant
        if ( alt[1]=='*' && alt[2]=='>' ) { var->n = 0; var->type = VCF_REF; return; }
        var->type = VCF_OTHER;
        return;
    }

    const char *r = ref, *a = alt;
    while (*r && *a && toupper(*r)==toupper(*a) ) { r++; a++; }     // unfortunately, matching REF,ALT case is not guaranteed

    if ( *a && !*r )
    {
        while ( *a ) a++;
        var->n = (a-alt)-(r-ref); var->type = VCF_INDEL; return;
    }
    else if ( *r && !*a )
    {
        while ( *r ) r++;
        var->n = (a-alt)-(r-ref); var->type = VCF_INDEL; return;
    }
    else if ( !*r && !*a )
    {
        var->n = 0; var->type = VCF_REF; return;
    }

    const char *re = r, *ae = a;
    while ( re[1] ) re++;
    while ( ae[1] ) ae++;
    while ( re>r && ae>a && toupper(*re)==toupper(*ae) ) { re--; ae--; }
    if ( ae==a )
    {
        if ( re==r ) { var->n = 1; var->type = VCF_SNP; return; }
        var->n = -(re-r);
        if ( toupper(*re)==toupper(*ae) ) { var->type = VCF_INDEL; return; }
        var->type = VCF_OTHER; return;
    }
    else if ( re==r )
    {
        var->n = ae-a;
        if ( toupper(*re)==toupper(*ae) ) { var->type = VCF_INDEL; return; }
        var->type = VCF_OTHER; return;
    }

    var->type = ( re-r == ae-a ) ? VCF_MNP : VCF_OTHER;
    var->n = ( re-r > ae-a ) ? -(re-r+1) : ae-a+1;

    // should do also complex events, SVs, etc...
}

static void bcf_set_variant_types(bcf1_t *b)
{
    if ( !(b->unpacked & BCF_UN_STR) ) bcf_unpack(b, BCF_UN_STR);
    bcf_dec_t *d = &b->d;
    if ( d->n_var < b->n_allele )
    {
        d->var = (variant_t *) realloc(d->var, sizeof(variant_t)*b->n_allele);
        d->n_var = b->n_allele;
    }
    int i;
    b->d.var_type = 0;
    for (i=1; i<b->n_allele; i++)
    {
        bcf_set_variant_type(d->allele[0],d->allele[i], &d->var[i]);
        b->d.var_type |= d->var[i].type;
        //fprintf(stderr,"[set_variant_type] %d   %s %s -> %d %d .. %d\n", b->pos+1,d->allele[0],d->allele[i],d->var[i].type,d->var[i].n, b->d.var_type);
    }
}

int bcf_get_variant_types(bcf1_t *rec)
{
    if ( rec->d.var_type==-1 ) bcf_set_variant_types(rec);
    return rec->d.var_type;
}
int bcf_get_variant_type(bcf1_t *rec, int ith_allele)
{
    if ( rec->d.var_type==-1 ) bcf_set_variant_types(rec);
    return rec->d.var[ith_allele].type;
}

int bcf_update_info(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const void *values, int n, int type)
{
    // Is the field already present?
    int i, inf_id = bcf_hdr_id2int(hdr,BCF_DT_ID,key);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,inf_id) ) return -1;    // No such INFO field in the header
    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);

    for (i=0; i<line->n_info; i++)
        if ( inf_id==line->d.info[i].key ) break;
    bcf_info_t *inf = i==line->n_info ? NULL : &line->d.info[i];

    if ( !n || (type==BCF_HT_STR && !values) )
    {
        if ( n==0 && !strcmp("END",key) )
            line->rlen = line->n_allele ? strlen(line->d.allele[0]) : 0;
        if ( inf )
        {
            // Mark the tag for removal, free existing memory if necessary
            if ( inf->vptr_free )
            {
                free(inf->vptr - inf->vptr_off);
                inf->vptr_free = 0;
            }
            line->d.shared_dirty |= BCF1_DIRTY_INF;
            inf->vptr = NULL;
        }
        return 0;
    }

    // Encode the values and determine the size required to accommodate the values
    kstring_t str = {0,0,0};
    bcf_enc_int1(&str, inf_id);
    if ( type==BCF_HT_INT )
        bcf_enc_vint(&str, n, (int32_t*)values, -1);
    else if ( type==BCF_HT_REAL )
        bcf_enc_vfloat(&str, n, (float*)values);
    else if ( type==BCF_HT_FLAG || type==BCF_HT_STR )
    {
        if ( values==NULL )
            bcf_enc_size(&str, 0, BCF_BT_NULL);
        else
            bcf_enc_vchar(&str, strlen((char*)values), (char*)values);
    }
    else
    {
        fprintf(stderr, "[E::%s] the type %d not implemented yet\n", __func__, type);
        abort();
    }

    // Is the INFO tag already present
    if ( inf )
    {
        // Is it big enough to accommodate new block?
        if ( str.l <= inf->vptr_len + inf->vptr_off )
        {
            if ( str.l != inf->vptr_len + inf->vptr_off ) line->d.shared_dirty |= BCF1_DIRTY_INF;
            uint8_t *ptr = inf->vptr - inf->vptr_off;
            memcpy(ptr, str.s, str.l);
            free(str.s);
            int vptr_free = inf->vptr_free;
            bcf_unpack_info_core1(ptr, inf);
            inf->vptr_free = vptr_free;
        }
        else
        {
            assert( !inf->vptr_free );  // fix the caller or improve here: this has been modified before
            bcf_unpack_info_core1((uint8_t*)str.s, inf);
            inf->vptr_free = 1;
            line->d.shared_dirty |= BCF1_DIRTY_INF;
        }
    }
    else
    {
        // The tag is not present, create new one
        line->n_info++;
        hts_expand0(bcf_info_t, line->n_info, line->d.m_info , line->d.info);
        inf = &line->d.info[line->n_info-1];
        bcf_unpack_info_core1((uint8_t*)str.s, inf);
        inf->vptr_free = 1;
        line->d.shared_dirty |= BCF1_DIRTY_INF;
    }
    line->unpacked |= BCF_UN_INFO;

    if ( n==1 && !strcmp("END",key) ) line->rlen = ((int32_t*)values)[0] - line->pos;
    return 0;
}

int bcf_update_format_string(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const char **values, int n)
{
    if ( !n )
        return bcf_update_format(hdr,line,key,NULL,0,BCF_HT_STR);

    int i, max_len = 0;
    for (i=0; i<n; i++)
    {
        int len = strlen(values[i]);
        if ( len > max_len ) max_len = len;
    }
    char *out = (char*) malloc(max_len*n);
    if ( !out ) return -2;
    for (i=0; i<n; i++)
    {
        char *dst = out+i*max_len;
        const char *src = values[i];
        int j = 0;
        while ( src[j] ) { dst[j] = src[j]; j++; }
        for (; j<max_len; j++) dst[j] = 0;
    }
    int ret = bcf_update_format(hdr,line,key,out,max_len*n,BCF_HT_STR);
    free(out);
    return ret;
}

int bcf_update_format(const bcf_hdr_t *hdr, bcf1_t *line, const char *key, const void *values, int n, int type)
{
    // Is the field already present?
    int i, fmt_id = bcf_hdr_id2int(hdr,BCF_DT_ID,key);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,fmt_id) )
    {
        if ( !n ) return 0;
        return -1;  // the key not present in the header
    }

    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);

    for (i=0; i<line->n_fmt; i++)
        if ( line->d.fmt[i].id==fmt_id ) break;
    bcf_fmt_t *fmt = i==line->n_fmt ? NULL : &line->d.fmt[i];

    if ( !n )
    {
        if ( fmt )
        {
            // Mark the tag for removal, free existing memory if necessary
            if ( fmt->p_free )
            {
                free(fmt->p - fmt->p_off);
                fmt->p_free = 0;
            }
            line->d.indiv_dirty = 1;
            fmt->p = NULL;
        }
        return 0;
    }

    line->n_sample = bcf_hdr_nsamples(hdr);
    int nps = n / line->n_sample;  // number of values per sample
    assert( nps && nps*line->n_sample==n );     // must be divisible by n_sample

    // Encode the values and determine the size required to accommodate the values
    kstring_t str = {0,0,0};
    bcf_enc_int1(&str, fmt_id);
    if ( type==BCF_HT_INT )
        bcf_enc_vint(&str, n, (int32_t*)values, nps);
    else if ( type==BCF_HT_REAL )
    {
        bcf_enc_size(&str, nps, BCF_BT_FLOAT);
        kputsn((char*)values, nps*line->n_sample*sizeof(float), &str);
    }
    else if ( type==BCF_HT_STR )
    {
        bcf_enc_size(&str, nps, BCF_BT_CHAR);
        kputsn((char*)values, nps*line->n_sample, &str);
    }
    else
    {
        fprintf(stderr, "[E::%s] the type %d not implemented yet\n", __func__, type);
        abort();
    }

    if ( !fmt )
    {
        // Not present, new format field
        line->n_fmt++;
        hts_expand0(bcf_fmt_t, line->n_fmt, line->d.m_fmt, line->d.fmt);

        // Special case: VCF specification requires that GT is always first
        if ( line->n_fmt > 1 && key[0]=='G' && key[1]=='T' && !key[2] )
        {
            for (i=line->n_fmt-1; i>0; i--)
                line->d.fmt[i] = line->d.fmt[i-1];
            fmt = &line->d.fmt[0];
        }
        else
            fmt = &line->d.fmt[line->n_fmt-1];
        bcf_unpack_fmt_core1((uint8_t*)str.s, line->n_sample, fmt);
        line->d.indiv_dirty = 1;
        fmt->p_free = 1;
    }
    else
    {
        // The tag is already present, check if it is big enough to accomodate the new block
        if ( str.l <= fmt->p_len + fmt->p_off )
        {
            // good, the block is big enough
            if ( str.l != fmt->p_len + fmt->p_off ) line->d.indiv_dirty = 1;
            uint8_t *ptr = fmt->p - fmt->p_off;
            memcpy(ptr, str.s, str.l);
            free(str.s);
            int p_free = fmt->p_free;
            bcf_unpack_fmt_core1(ptr, line->n_sample, fmt);
            fmt->p_free = p_free;
        }
        else
        {
            assert( !fmt->p_free );  // fix the caller or improve here: this has been modified before
            bcf_unpack_fmt_core1((uint8_t*)str.s, line->n_sample, fmt);
            fmt->p_free = 1;
            line->d.indiv_dirty = 1;
        }
    }
    line->unpacked |= BCF_UN_FMT;
    return 0;
}


int bcf_update_filter(const bcf_hdr_t *hdr, bcf1_t *line, int *flt_ids, int n)
{
    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
    line->d.shared_dirty |= BCF1_DIRTY_FLT;
    line->d.n_flt = n;
    if ( !n ) return 0;
    hts_expand(int, line->d.n_flt, line->d.m_flt, line->d.flt);
    int i;
    for (i=0; i<n; i++)
        line->d.flt[i] = flt_ids[i];
    return 0;
}

int bcf_add_filter(const bcf_hdr_t *hdr, bcf1_t *line, int flt_id)
{
    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
    int i;
    for (i=0; i<line->d.n_flt; i++)
        if ( flt_id==line->d.flt[i] ) break;
    if ( i<line->d.n_flt ) return 0;    // this filter is already set
    line->d.shared_dirty |= BCF1_DIRTY_FLT;
    if ( flt_id==0 )    // set to PASS
        line->d.n_flt = 1;
    else if ( line->d.n_flt==1 && line->d.flt[0]==0 )
        line->d.n_flt = 1;
    else
        line->d.n_flt++;
    hts_expand(int, line->d.n_flt, line->d.m_flt, line->d.flt);
    line->d.flt[line->d.n_flt-1] = flt_id;
    return 1;
}
int bcf_remove_filter(const bcf_hdr_t *hdr, bcf1_t *line, int flt_id, int pass)
{
    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
    int i;
    for (i=0; i<line->d.n_flt; i++)
        if ( flt_id==line->d.flt[i] ) break;
    if ( i==line->d.n_flt ) return 0;   // the filter is not present
    line->d.shared_dirty |= BCF1_DIRTY_FLT;
    if ( i!=line->d.n_flt-1 ) memmove(line->d.flt+i,line->d.flt+i+1,(line->d.n_flt-i-1)*sizeof(*line->d.flt));
    line->d.n_flt--;
    if ( !line->d.n_flt && pass ) bcf_add_filter(hdr,line,0);
    return 0;
}

int bcf_has_filter(const bcf_hdr_t *hdr, bcf1_t *line, char *filter)
{
    if ( filter[0]=='.' && !filter[1] ) filter = "PASS";
    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, filter);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FLT,id) ) return -1;  // not defined in the header

    if ( !(line->unpacked & BCF_UN_FLT) ) bcf_unpack(line, BCF_UN_FLT);
    if ( id==0 && !line->d.n_flt) return 1; // PASS

    int i;
    for (i=0; i<line->d.n_flt; i++)
        if ( line->d.flt[i]==id ) return 1;
    return 0;
}

static inline int _bcf1_sync_alleles(const bcf_hdr_t *hdr, bcf1_t *line, int nals)
{
    line->d.shared_dirty |= BCF1_DIRTY_ALS;

    line->n_allele = nals;
    hts_expand(char*, line->n_allele, line->d.m_allele, line->d.allele);

    char *als = line->d.als;
    int n = 0;
    while (n<nals)
    {
        line->d.allele[n] = als;
        while ( *als ) als++;
        als++;
        n++;
    }

    // Update REF length
    bcf_info_t *end_info = bcf_get_info(hdr,line,"END");
    line->rlen = end_info ? end_info->v1.i : strlen(line->d.allele[0]);

    return 0;
}
int bcf_update_alleles(const bcf_hdr_t *hdr, bcf1_t *line, const char **alleles, int nals)
{
    kstring_t tmp = {0,0,0};
    char *free_old = NULL;

    // If the supplied alleles are not pointers to line->d.als, the existing block can be reused.
    int i;
    for (i=0; i<nals; i++)
        if ( alleles[i]>=line->d.als && alleles[i]<line->d.als+line->d.m_als ) break;
    if ( i==nals )
    {
        // all alleles point elsewhere, reuse the existing block
        tmp.l = 0; tmp.s = line->d.als; tmp.m = line->d.m_als;
    }
    else
        free_old = line->d.als;

    for (i=0; i<nals; i++)
    {
        kputs(alleles[i], &tmp);
        kputc(0, &tmp);
    }
    line->d.als = tmp.s; line->d.m_als = tmp.m;
    free(free_old);
    return _bcf1_sync_alleles(hdr,line,nals);
}

int bcf_update_alleles_str(const bcf_hdr_t *hdr, bcf1_t *line, const char *alleles_string)
{
    kstring_t tmp;
    tmp.l = 0; tmp.s = line->d.als; tmp.m = line->d.m_als;
    kputs(alleles_string, &tmp);
    line->d.als = tmp.s; line->d.m_als = tmp.m;

    int nals = 1;
    char *t = line->d.als;
    while (*t)
    {
        if ( *t==',' ) { *t = 0; nals++; }
        t++;
    }
    return _bcf1_sync_alleles(hdr, line, nals);
}

int bcf_update_id(const bcf_hdr_t *hdr, bcf1_t *line, const char *id)
{
    kstring_t tmp;
    tmp.l = 0; tmp.s = line->d.id; tmp.m = line->d.m_id;
    if ( id )
        kputs(id, &tmp);
    else
        kputs(".", &tmp);
    line->d.id = tmp.s; line->d.m_id = tmp.m;
    line->d.shared_dirty |= BCF1_DIRTY_ID;
    return 0;
}

int bcf_add_id(const bcf_hdr_t *hdr, bcf1_t *line, const char *id)
{
    if ( !id ) return 0;

    kstring_t tmp;
    tmp.l = 0; tmp.s = line->d.id; tmp.m = line->d.m_id;

    int len = strlen(id);
    char *dst = line->d.id;
    while ( *dst && (dst=strstr(dst,id)) )
    {
        if ( dst[len]!=0 && dst[len]!=';' ) dst++;              // a prefix, not a match
        else if ( dst==line->d.id || dst[-1]==';' ) return 0;   // already present
        dst++;  // a suffix, not a match
    }
    if ( line->d.id && (line->d.id[0]!='.' || line->d.id[1]) )
    {
        tmp.l = strlen(line->d.id);
        kputc(';',&tmp);
    }
    kputs(id,&tmp);

    line->d.id = tmp.s; line->d.m_id = tmp.m;
    line->d.shared_dirty |= BCF1_DIRTY_ID;
    return 0;

}

bcf_fmt_t *bcf_get_fmt(const bcf_hdr_t *hdr, bcf1_t *line, const char *key)
{
    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, key);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,id) ) return NULL;   // no such FMT field in the header
    return bcf_get_fmt_id(line, id);
}

bcf_info_t *bcf_get_info(const bcf_hdr_t *hdr, bcf1_t *line, const char *key)
{
    int id = bcf_hdr_id2int(hdr, BCF_DT_ID, key);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,id) ) return NULL;   // no such INFO field in the header
    return bcf_get_info_id(line, id);
}

bcf_fmt_t *bcf_get_fmt_id(bcf1_t *line, const int id) 
{
    int i;
    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);
    for (i=0; i<line->n_fmt; i++)
    {
        if ( line->d.fmt[i].id==id ) return &line->d.fmt[i];
    }
    return NULL;
}

bcf_info_t *bcf_get_info_id(bcf1_t *line, const int id) 
{
    int i;
    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);
    for (i=0; i<line->n_info; i++)
    {
        if ( line->d.info[i].key==id ) return &line->d.info[i];
    }
    return NULL;
}


int bcf_get_info_values(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, void **dst, int *ndst, int type)
{
    int i,j, tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_INFO,tag_id) ) return -1;    // no such INFO field in the header
    if ( bcf_hdr_id2type(hdr,BCF_HL_INFO,tag_id)!=type ) return -2;     // expected different type

    if ( !(line->unpacked & BCF_UN_INFO) ) bcf_unpack(line, BCF_UN_INFO);

    for (i=0; i<line->n_info; i++)
        if ( line->d.info[i].key==tag_id ) break;
    if ( i==line->n_info ) return ( type==BCF_HT_FLAG ) ? 0 : -3;       // the tag is not present in this record
    if ( type==BCF_HT_FLAG ) return 1;

    bcf_info_t *info = &line->d.info[i];
    if ( !info->vptr ) return -3;           // the tag was marked for removal
    if ( type==BCF_HT_STR )
    {
        if ( *ndst < info->len+1 )
        {
            *ndst = info->len + 1;
            *dst  = realloc(*dst, *ndst);
        }
        memcpy(*dst,info->vptr,info->len);
        ((uint8_t*)*dst)[info->len] = 0;
        return info->len;
    }

    // Make sure the buffer is big enough
    int size1 = type==BCF_HT_INT ? sizeof(int32_t) : sizeof(float);
    if ( *ndst < info->len )
    {
        *ndst = info->len;
        *dst  = realloc(*dst, *ndst * size1);
    }

    if ( info->len == 1 )
    {
        if ( info->type==BCF_BT_FLOAT ) *((float*)*dst) = info->v1.f;
        else 
        {
            #define BRANCH(type_t, missing) { \
                if ( info->v1.i==missing ) *((int32_t*)*dst) = bcf_int32_missing; \
                else *((int32_t*)*dst) = info->v1.i; \
            }
            switch (info->type)
            {
                case BCF_BT_INT8:  BRANCH(int8_t,  bcf_int8_missing ); break;
                case BCF_BT_INT16: BRANCH(int16_t, bcf_int16_missing); break;
                case BCF_BT_INT32: BRANCH(int32_t, bcf_int32_missing); break;
            }
            #undef BRANCH
        }
        return 1;
    }

    #define BRANCH(type_t, is_missing, is_vector_end, set_missing, out_type_t) { \
        out_type_t *tmp = (out_type_t *) *dst; \
        type_t *p = (type_t *) info->vptr; \
        for (j=0; j<info->len; j++) \
        { \
            if ( is_vector_end ) return j; \
            if ( is_missing ) set_missing; \
            else *tmp = p[j]; \
            tmp++; \
        } \
        return j; \
    }
    switch (info->type) {
        case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  *tmp=bcf_int32_missing, int32_t); break;
        case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, *tmp=bcf_int32_missing, int32_t); break;
        case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, *tmp=bcf_int32_missing, int32_t); break;
        case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), bcf_float_set_missing(*tmp), float); break;
        default: fprintf(stderr,"TODO: %s:%d .. info->type=%d\n", __FILE__,__LINE__, info->type); exit(1);
    }
    #undef BRANCH
    return -4;  // this can never happen
}

int bcf_get_format_string(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, char ***dst, int *ndst)
{
    int i,tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,tag_id) ) return -1;    // no such FORMAT field in the header
    if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=BCF_HT_STR ) return -2;     // expected different type

    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);

    for (i=0; i<line->n_fmt; i++)
        if ( line->d.fmt[i].id==tag_id ) break;
    if ( i==line->n_fmt ) return -3;                               // the tag is not present in this record
    bcf_fmt_t *fmt = &line->d.fmt[i];
    if ( !fmt->p ) return -3;                                      // the tag was marked for removal

    int nsmpl = bcf_hdr_nsamples(hdr);
    if ( !*dst )
    {
        *dst = (char**) malloc(sizeof(char*)*nsmpl);
        if ( !*dst ) return -4;     // could not alloc
        (*dst)[0] = NULL;
    }
    int n = (fmt->n+1)*nsmpl;
    if ( *ndst < n )
    {
        (*dst)[0] = realloc((*dst)[0], n);
        if ( !(*dst)[0] ) return -4;    // could not alloc
        *ndst = n;
    }
    for (i=0; i<nsmpl; i++)
    {
        uint8_t *src = fmt->p + i*fmt->n;
        uint8_t *tmp = (uint8_t*)(*dst)[0] + i*(fmt->n+1);
        memcpy(tmp,src,fmt->n);
        tmp[fmt->n] = 0;
        (*dst)[i] = (char*) tmp;
    }
    return n;
}

int bcf_get_format_values(const bcf_hdr_t *hdr, bcf1_t *line, const char *tag, void **dst, int *ndst, int type)
{
    int i,j, tag_id = bcf_hdr_id2int(hdr, BCF_DT_ID, tag);
    if ( !bcf_hdr_idinfo_exists(hdr,BCF_HL_FMT,tag_id) ) return -1;    // no such FORMAT field in the header
    if ( tag[0]=='G' && tag[1]=='T' && tag[2]==0 )
    {
        // Ugly: GT field is considered to be a string by the VCF header but BCF represents it as INT.
        if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=BCF_HT_STR ) return -2;
    }
    else if ( bcf_hdr_id2type(hdr,BCF_HL_FMT,tag_id)!=type ) return -2;     // expected different type

    if ( !(line->unpacked & BCF_UN_FMT) ) bcf_unpack(line, BCF_UN_FMT);

    for (i=0; i<line->n_fmt; i++)
        if ( line->d.fmt[i].id==tag_id ) break;
    if ( i==line->n_fmt ) return -3;                               // the tag is not present in this record
    bcf_fmt_t *fmt = &line->d.fmt[i];
    if ( !fmt->p ) return -3;                                      // the tag was marked for removal

    if ( type==BCF_HT_STR )
    {
        int n = fmt->n*bcf_hdr_nsamples(hdr);
        if ( *ndst < n )
        {
            *dst  = realloc(*dst, n);
            if ( !*dst ) return -4;     // could not alloc
            *ndst = n;
        }
        memcpy(*dst,fmt->p,n);
        return n;
    }

    // Make sure the buffer is big enough
    int nsmpl = bcf_hdr_nsamples(hdr);
    int size1 = type==BCF_HT_INT ? sizeof(int32_t) : sizeof(float);
    if ( *ndst < fmt->n*nsmpl )
    {
        *ndst = fmt->n*nsmpl;
        *dst  = realloc(*dst, *ndst*size1);
        if ( !dst ) return -4;     // could not alloc
    }

    #define BRANCH(type_t, is_missing, is_vector_end, set_missing, set_vector_end, out_type_t) { \
        out_type_t *tmp = (out_type_t *) *dst; \
        type_t *p = (type_t*) fmt->p; \
        for (i=0; i<nsmpl; i++) \
        { \
            for (j=0; j<fmt->n; j++) \
            { \
                if ( is_missing ) set_missing; \
                else if ( is_vector_end ) { set_vector_end; break; } \
                else *tmp = p[j]; \
                tmp++; \
            } \
            for (; j<fmt->n; j++) { set_vector_end; tmp++; } \
            p = (type_t *)((char *)p + fmt->size); \
        } \
    }
    switch (fmt->type) {
        case BCF_BT_INT8:  BRANCH(int8_t,  p[j]==bcf_int8_missing,  p[j]==bcf_int8_vector_end,  *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
        case BCF_BT_INT16: BRANCH(int16_t, p[j]==bcf_int16_missing, p[j]==bcf_int16_vector_end, *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
        case BCF_BT_INT32: BRANCH(int32_t, p[j]==bcf_int32_missing, p[j]==bcf_int32_vector_end, *tmp=bcf_int32_missing, *tmp=bcf_int32_vector_end, int32_t); break;
        case BCF_BT_FLOAT: BRANCH(float,   bcf_float_is_missing(p[j]), bcf_float_is_vector_end(p[j]), bcf_float_set_missing(*tmp), bcf_float_set_vector_end(*tmp), float); break;
        default: fprintf(stderr,"TODO: %s:%d .. fmt->type=%d\n", __FILE__,__LINE__, fmt->type); exit(1);
    }
    #undef BRANCH
    return nsmpl*fmt->n;
}