1*6881a400Schristos /* zran.h -- example of zlib/gzip stream indexing and random access 2*6881a400Schristos * Copyright (C) 2005, 2012, 2018 Mark Adler 3*6881a400Schristos * For conditions of distribution and use, see copyright notice in zlib.h 4*6881a400Schristos * Version 1.2 14 Oct 2018 Mark Adler */ 5*6881a400Schristos 6*6881a400Schristos #include <stdio.h> 7*6881a400Schristos #include "zlib.h" 8*6881a400Schristos 9*6881a400Schristos /* Access point list. */ 10*6881a400Schristos struct deflate_index { 11*6881a400Schristos int have; /* number of list entries */ 12*6881a400Schristos int gzip; /* 1 if the index is of a gzip file, 0 if it is of a 13*6881a400Schristos zlib stream */ 14*6881a400Schristos off_t length; /* total length of uncompressed data */ 15*6881a400Schristos void *list; /* allocated list of entries */ 16*6881a400Schristos }; 17*6881a400Schristos 18*6881a400Schristos /* Make one entire pass through a zlib or gzip compressed stream and build an 19*6881a400Schristos index, with access points about every span bytes of uncompressed output. 20*6881a400Schristos gzip files with multiple members are indexed in their entirety. span should 21*6881a400Schristos be chosen to balance the speed of random access against the memory 22*6881a400Schristos requirements of the list, about 32K bytes per access point. The return value 23*6881a400Schristos is the number of access points on success (>= 1), Z_MEM_ERROR for out of 24*6881a400Schristos memory, Z_DATA_ERROR for an error in the input file, or Z_ERRNO for a file 25*6881a400Schristos read error. On success, *built points to the resulting index. */ 26*6881a400Schristos int deflate_index_build(FILE *in, off_t span, struct deflate_index **built); 27*6881a400Schristos 28*6881a400Schristos /* Deallocate an index built by deflate_index_build() */ 29*6881a400Schristos void deflate_index_free(struct deflate_index *index); 30*6881a400Schristos 31*6881a400Schristos /* Use the index to read len bytes from offset into buf. Return bytes read or 32*6881a400Schristos negative for error (Z_DATA_ERROR or Z_MEM_ERROR). If data is requested past 33*6881a400Schristos the end of the uncompressed data, then deflate_index_extract() will return a 34*6881a400Schristos value less than len, indicating how much was actually read into buf. This 35*6881a400Schristos function should not return a data error unless the file was modified since 36*6881a400Schristos the index was generated, since deflate_index_build() validated all of the 37*6881a400Schristos input. deflate_index_extract() will return Z_ERRNO if there is an error on 38*6881a400Schristos reading or seeking the input file. */ 39*6881a400Schristos int deflate_index_extract(FILE *in, struct deflate_index *index, off_t offset, 40*6881a400Schristos unsigned char *buf, int len); 41