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