Copyright	(c) Robbin C.
License	GPLv3
Maintainer	Robbin C.
Stability	unstable
Portability	portable
Safe Haskell	None
Language	Haskell2010

Codec.Archive.Zim.Parser

Contents

Functions
Exceptions
ZIM Header
ZIM Directory Entry
ZIM file format

Description

This is a library for parsing ZIM (http://openzim.org) files. ZIM files contain offline web content (eg, Wikipedia) which can be browsed locally without an Internet connection.

The API is meant to be intuitive for normal use-cases.

To get content for "A/index.htm" from ZIM file "file.zim":

> mimeContent <- "file.zim" `getContent` Url "A/index.htm"
> :t mimeContent
mimeContent :: Maybe (B8.ByteString, BL.ByteString)
> print mimeContent
Just ("text/html", "<html><head>...</html>")

The above will open the file, parse the ZIM header, lookup the MIME type and content of the URL, close the file and return the MIME type and content as a pair. Note that content is a lazy bytestring.

The above operation should suffice for a simple webserver serving a ZIM file. For finer control, it is possible to cache and reuse the file handle and the ZIM header.

> hdl <- openBinaryFile "file.zim" ReadMode
> hdr <- getHeader hdl
> :t hdr
hdr :: ZimHeader
> (hdl, hdr) `getContent` Url "A/index.htm"
Just ("text/html", "<html><head>...</html>")

ZIM files of Wikimedia Foundation (Wikipedia, Wikibooks, etc) can be found at http://ftpmirror.your.org/pub/kiwix/zim.

Below is a full example of a Scotty web server that serves a ZIM file (specified on command line) on localhost port 3000:

{-# LANGUAGE OverloadedStrings #-}

import Control.Monad.IO.Class (liftIO)
import Data.Text.Lazy (toStrict, fromStrict)
import Data.Text.Encoding (decodeUtf8, encodeUtf8)
import System.Environment (getArgs)
import Network.HTTP.Types.Status (status404)
import Web.Scotty
import Codec.Archive.Zim.Parser (getMainPageUrl, getContent, Url(..))

main :: IO ()
main = do
    [fp] <- getArgs
    scotty 3000 $ do
      get "/" (redirectToZimMainPage fp)
      get (regex "^/(./.*)$") (serveZimUrl fp)
      notFound $ text "Invalid URL!"

redirectToZimMainPage :: FilePath -> ActionM ()
redirectToZimMainPage fp = do
    res <- liftIO $ getMainPageUrl fp
    case res of
      Nothing -> do
        status status404
        text "This ZIM file has no main page specified!"
      Just (Url url) -> redirect . fromStrict $ decodeUtf8 url

serveZimUrl :: FilePath -> ActionM ()
serveZimUrl fp = do
    url <- (encodeUtf8 . toStrict) <$> param "1"
    res <- liftIO $ fp `getContent` Url url
    case res of
      Nothing -> do
        liftIO . putStrLn $ "Invalid URL: " ++ show url
        status status404
        text $ "Invalid URL!"
      Just (mimeType, content) -> do
        liftIO . putStrLn $ "Serving: " ++ show url
        setHeader "Content-Type" (fromStrict $ decodeUtf8 mimeType)
        raw content

Feedback and contributions are welcome on http://github.com/robbinch/zim-parser.

Synopsis

Functions

getHeader :: RunZim h => h -> IO ZimHeader Source

getMimeList :: RunZim h => h -> IO MimeList Source

getMainPageUrl :: RunZim h => h -> IO (Maybe Url) Source

Returns URL of main page in ZIM. This URL can be used for redirecting to the actual page.

getCluster :: RunZim h => h -> ClusterNumber -> IO Cluster Source

getBlob :: RunZim h => h -> (ClusterNumber, BlobNumber) -> IO Blob Source

type MimeList = Array Int ByteString Source

List of Mime Types

mkNsTitle :: Char -> ByteString -> Title Source

Construct a Title with a Namespace.

mkNsTitlePrefix :: Char -> ByteString -> TitlePrefix Source

Construct a TitlePrefix with a Namespace.

mkNsUrl :: Char -> ByteString -> Url Source

Construct a Url with a Namespace.

class RunZim h Source

Instances of this class represent a Zim File and are able to perform ZIM operations (getMimeList, getContent, etc). Valid instances include a Handle to a ZIM file, a FilePath to a ZIM file, or a (Handle, ZimHeader) where ZimHeader is parsed previously (so it does not need to be reparsed).

Minimal complete definition

runZim

Instances

RunZim Handle Source
RunZim FilePath Source
RunZim (Handle, ZimHeader) Source

class ZimGetDE k where Source

Methods

getDE :: RunZim h => h -> k -> IO ZimDirEnt Source

Instances

ZimGetDE TitleIndex Source
ZimGetDE UrlIndex Source

class ZimSearchDE k where Source

Methods

searchDE :: RunZim h => h -> k -> IO [(Int, ZimDirEnt)] Source

Search for a Directory Entry on a RunZim. When searching for a:

Url: Returns either 0 (not found) or 1 element.
Title: Returns either 0 (not found) or 1 element.
TitlePrefix: Returns either 0 (not found) or 2 elements corresponding to lower and upper bound of titles containing the prefix.

Instances

ZimSearchDE TitlePrefix Source
ZimSearchDE Title Source
ZimSearchDE Url Source

class ZimGetContent k where Source

Methods

getContent :: RunZim h => h -> k -> IO (Maybe (ByteString, ByteString)) Source

Get (MIME type, Content). Note that Content is lazy.

Exceptions

data ZimException Source

Other than the below, ErrorCall can be thrown by LZMA library if there is a problem with decompression.

Constructors

ZimInvalidMagic	ZIM file has invalid magic number (anything other than 72173914).
ZimParseError String	There is an error in parsing.
ZimIncompleteInput	There is insufficient bytes required to parse.
ZimInvalidIndex Int	The given index (URL, title or cluster) is out of bounds for this ZIM file.

Instances

Show ZimException Source
Exception ZimException Source

ZIM Header

data ZimHeader Source

See http://www.openzim.org/wiki/ZIM_file_format#Header for more details.

Constructors

ZimHeader

Fields

zimMagicNumber :: Int: Magic Number of file (somewhat superfluous as getZimHeader will throw an exception if magic number is anything other than 72173914)
zimVersion :: Int: Version of ZIM header
zimUuid :: ByteString: UUID of file
zimArticleCount :: Int: Number of articles
zimClusterCount :: Int: Number of clusters
zimUrlPtrPos :: Integer: Position of sorted URL pointers
zimTitlePtrPos :: Integer: Position of sorted Title pointers
zimClusterPtrPos :: Integer: Position of Cluster pointers
zimMimeListPos :: Integer: Position of MIME list
zimMainPage :: Maybe Int: Index of main page
zimLayoutPage :: Maybe Int: Index of layout page
zimChecksumPos :: Integer: Position of MD5 checksum

Instances

Eq ZimHeader Source
Show ZimHeader Source
RunZim (Handle, ZimHeader) Source

ZIM Directory Entry

data ZimDirEntType Source

There are 4 types of directory entries. Most content in a ZIM file are usually ZimArticleEntry or ZimRedirectEntry.

Constructors

ZimArticleEntry
ZimRedirectEntry
ZimLinkTarget
ZimDeletedEntry

Instances

Eq ZimDirEntType Source
Show ZimDirEntType Source

data ZimDirEnt Source

See http://www.openzim.org/wiki/ZIM_file_format#Directory_Entries for more details.

Constructors

ZimDirEnt

Fields

zimDeType :: ZimDirEntType: Type of this Directory Entry
zimDeMimeType :: Int: Index into MIME list given by getZimMimeList
zimDeParameterLen :: Int: Parameter Length
zimDeNamespace :: Char: Namespace
zimDeRevision :: Int: Revision
zimDeRedirectIndex :: Maybe Int: Redirect Index (only applicable for ZimRedirectEntry)
zimDeClusterNumber :: Maybe Int: Content is stored in this Cluster Number (only applicable for ZimArticleEntry)
zimDeBlobNumber :: Maybe Int: Content is stored in this Blob Number (only applicable for ZimArticleEntry)
zimDeUrl :: ByteString: URL
zimDeTitle :: ByteString: Title

Instances

Eq ZimDirEnt Source
Show ZimDirEnt Source
ZimGetContent ZimDirEnt Source
ZimGetContent (MimeList, ZimDirEnt) Source

newtype UrlIndex Source

Wrapper for URL index

Constructors

UrlIndex Int

Instances

Eq UrlIndex Source
Ord UrlIndex Source
Show UrlIndex Source
ZimGetContent UrlIndex Source
ZimGetDE UrlIndex Source
ZimGetContent (MimeList, UrlIndex) Source

newtype TitleIndex Source

Wrapper for Title index

Constructors

TitleIndex Int

Instances

Eq TitleIndex Source
Ord TitleIndex Source
Show TitleIndex Source
ZimGetContent TitleIndex Source
ZimGetDE TitleIndex Source
ZimGetContent (MimeList, TitleIndex) Source

newtype ClusterNumber Source

Wrapper for Cluster number

Constructors

ClusterNumber Int

Instances

Eq ClusterNumber Source
Ord ClusterNumber Source
Show ClusterNumber Source

newtype BlobNumber Source

Wrapper for Blob number

Constructors

BlobNumber Int

Instances

Eq BlobNumber Source
Ord BlobNumber Source
Show BlobNumber Source

newtype Cluster Source

Wrapper for Cluster

Constructors

Cluster
Fields unCluster :: ByteString

newtype Blob Source

Wrapper for Blob

Constructors

Blob
Fields unBlob :: ByteString

newtype Url Source

Wrapper for Url

Constructors

Url ByteString

Instances

Eq Url Source
Ord Url Source
Show Url Source
ZimSearchDE Url Source
ZimGetContent Url Source
ZimGetContent (MimeList, Url) Source

data Title Source

Wrapper for Title

Instances

Eq Title Source
Ord Title Source
Show Title Source
ZimSearchDE Title Source
ZimGetContent Title Source
ZimGetContent (MimeList, Title) Source

data TitlePrefix Source

Wrapper for Title Prefix

Instances

Eq TitlePrefix Source
Ord TitlePrefix Source
Show TitlePrefix Source
ZimSearchDE TitlePrefix Source

ZIM file format

Following is a short summary of the ZIM file format. The authoritative reference is at http://www.openzim.org/wiki/ZIM_file_format.

1. ZIM header

This is an 80-byte header (see ZimHeader). Among other things, it contains file offsets to the below.

2. List of MIME types

This is a sequence of null-terminated strings (eg. text/html, text/javascript). The last string is zero length, so the end always consists of 2 consecutive null bytes.

3. List of URLs

This is a sequence of 8-byte file offsets, each pointing to a directory entry. This list is sorted by the directory entries' URL.

getZimDirEntByUrlIndex looks up this table to return a directory entry.

4. List of Titles

This is a sequence of 4-byte indices, each pointing to a URL above (which in turn point to a directory entry). This list is sorted by the directory entries' Title.

getZimDirEntByTitleIndex uses this table to return a directory entry.

5. Directory Entries

This is a sequence of Directory Entries (see ZimDirEnt). The first 2 bytes determine the type of this entry, which also determine the length. Contents include:

a. MIME type

This 2-byte field means:

0xffff: This directory entry is a ZimRedirectEntry.
0xfffe: This directory entry is a ZimLinkTarget.
0xfffd: This directory entry is a ZimDeletedEntry.
any other value: This directory entry is a ZimArticleEntry and this index into the MIME list from above determines its MIME type.

b. Namespace

This single character determines the directory entry's namespace. (eg. A for articles, I for images, etc.) The comprehensive list is at http://www.openzim.org/wiki/ZIM_file_format#Namespaces.

c. Cluster and Blob number

Only for ZimArticleEntry, this is the directory entry's Cluster and Blob number. The Cluster number is a 4-byte index into the list of Clusters below. The Blob number refers to a block inside the (decompressed) cluster. Together, they provide the content of this directory entry.

d. URL and Title

These 2 null-terminated strings represent the URL and Title of this directory entry respectively. If the Title is empty, it is taken to be the same as the URL.

6. List of Clusters

This is a list of 8-byte file offsets, each pointing to a cluster in the file. The end of a cluster is also the start of the next cluster. Therefore, the length of a cluster is the difference between the adjacent offsets. For the last cluster, the end is the Checksum file offset, as the Checksum is always the last 16 bytes of a ZIM file.

a. Compression Type

The first byte of the cluster determines if it is uncompressed (eg. PNG image) or compressed with LZMA (eg. HTML).

0 or 1: No compression
4: Compressed with LZMA

b. List of Blobs

This is a list of 4-byte offsets, each pointing inside this cluster. The end of a blob is also the start of the next blob. Therefore, the length of a blob is the difference between the adjacent offsets. The last offset points to the end of the data area so there is always one more offset than blobs.