module Runtime.Prim.Text
export value
 makeTextLit    : [r1: Region]. Addr# -> Ptr# r1 Obj
 takeTextLit    : [r1: Region]. Ptr# r1 Obj -> Addr#
 sizeOfTextLit  : [r1: Region]. Ptr# r1 Obj -> Nat#
 indexTextLit   : [r1: Region]. Ptr# r1 Obj -> Nat# -> Word8#

import value 
 -- Objects with raw, non-pointer data.
 allocRaw       : [r1: Region]. Tag# -> Nat# -> Ptr# r1 Obj
 payloadRaw     : [r1: Region]. Ptr# r1 Obj  -> Ptr# r1 Word8#
 payloadSizeRaw : [r1: Region]. Ptr# r1 Obj  -> Nat#

with letrec


-- | Make a boxed text literal from a pointer to a null terminated
--   sequence of bytes.
--
--   We first take the length of the string for bounds checks during
--   indexing and store the pointer and length together in the object.
--
--   typedef struct
--   {   uint32_t  tagFormat;   // Constructor tag and format field.
--       uint32_t  size         // Size of this boxed object in bytes.
--       uint32_t  length;      // Length of the string literal in bytes.
--       uint8_t*  ptr;         // Pointer to null terminated string data.
--   } TextLit;
--
makeTextLit [r1: Region] (addrString: Addr#): Ptr# r1 Obj
 = do
        len     = sizeOfString 0# addrString
        obj     = allocRaw (truncate# 0#) (add# 4# (size# [Addr#]))
        payload = takePtr# (payloadRaw obj)
        write# [Word32#] payload 0# (truncate# len)
        write# [Addr#]   payload 4# addrString
        obj


-- | Take the pointer from a text literal.
takeTextLit [r1: Region] (obj: Ptr# r1 Obj): Addr#
 = do   
        payload = takePtr# (payloadRaw obj)
        read# [Addr#] payload 4#


-- | Get the size of a text literal, in bytes.
sizeOfTextLit [r1: Region] (obj: Ptr# r1 Obj): Nat#
 = do
        payload = takePtr# (payloadRaw obj)
        promote# (read# [Word32#] payload 0#)


-- | Get a single byte of a text literal.
indexTextLit [r1: Region] (obj: Ptr# r1 Obj) (ix: Nat#): Word8#
 = do   
        charPtr = takeTextLit obj
        size    = sizeOfTextLit obj

        char    = peekBounded# (makePtr# charPtr) ix size
        char


-- | Get the size of a null-terminated array of characters, in bytes.
sizeOfString (i: Nat#) (str: Addr#): Nat#
 = do
        x       = promote# (read# [Word8#] str i)
        case x of
         0#     -> i
         _      -> sizeOfString (add# i 1#) str