9e052883 |
1 | /* zran.h -- example of zlib/gzip stream indexing and random access |
2 | * Copyright (C) 2005, 2012, 2018 Mark Adler |
3 | * For conditions of distribution and use, see copyright notice in zlib.h |
4 | * Version 1.2 14 Oct 2018 Mark Adler */ |
5 | |
6 | #include <stdio.h> |
7 | #include "zlib.h" |
8 | |
9 | /* Access point list. */ |
10 | struct deflate_index { |
11 | int have; /* number of list entries */ |
12 | int gzip; /* 1 if the index is of a gzip file, 0 if it is of a |
13 | zlib stream */ |
14 | off_t length; /* total length of uncompressed data */ |
15 | void *list; /* allocated list of entries */ |
16 | }; |
17 | |
18 | /* Make one entire pass through a zlib or gzip compressed stream and build an |
19 | index, with access points about every span bytes of uncompressed output. |
20 | gzip files with multiple members are indexed in their entirety. span should |
21 | be chosen to balance the speed of random access against the memory |
22 | requirements of the list, about 32K bytes per access point. The return value |
23 | is the number of access points on success (>= 1), Z_MEM_ERROR for out of |
24 | memory, Z_DATA_ERROR for an error in the input file, or Z_ERRNO for a file |
25 | read error. On success, *built points to the resulting index. */ |
26 | int deflate_index_build(FILE *in, off_t span, struct deflate_index **built); |
27 | |
28 | /* Deallocate an index built by deflate_index_build() */ |
29 | void deflate_index_free(struct deflate_index *index); |
30 | |
31 | /* Use the index to read len bytes from offset into buf. Return bytes read or |
32 | negative for error (Z_DATA_ERROR or Z_MEM_ERROR). If data is requested past |
33 | the end of the uncompressed data, then deflate_index_extract() will return a |
34 | value less than len, indicating how much was actually read into buf. This |
35 | function should not return a data error unless the file was modified since |
36 | the index was generated, since deflate_index_build() validated all of the |
37 | input. deflate_index_extract() will return Z_ERRNO if there is an error on |
38 | reading or seeking the input file. */ |
39 | int deflate_index_extract(FILE *in, struct deflate_index *index, off_t offset, |
40 | unsigned char *buf, int len); |