| 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); |