84 lines
2.6 KiB
C
84 lines
2.6 KiB
C
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/*
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* zlib_compress.c - compress with a zlib wrapper
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*
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* Copyright 2016 Eric Biggers
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "deflate_compress.h"
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#include "zlib_constants.h"
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#include "adler32.h"
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LIBDEFLATEAPI size_t
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libdeflate_zlib_compress(struct libdeflate_compressor *c,
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const void *in, size_t in_nbytes,
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void *out, size_t out_nbytes_avail)
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{
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u8 *out_next = out;
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u16 hdr;
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unsigned compression_level;
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unsigned level_hint;
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size_t deflate_size;
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if (out_nbytes_avail <= ZLIB_MIN_OVERHEAD)
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return 0;
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/* 2 byte header: CMF and FLG */
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hdr = (ZLIB_CM_DEFLATE << 8) | (ZLIB_CINFO_32K_WINDOW << 12);
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compression_level = libdeflate_get_compression_level(c);
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if (compression_level < 2)
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level_hint = ZLIB_FASTEST_COMPRESSION;
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else if (compression_level < 6)
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level_hint = ZLIB_FAST_COMPRESSION;
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else if (compression_level < 8)
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level_hint = ZLIB_DEFAULT_COMPRESSION;
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else
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level_hint = ZLIB_SLOWEST_COMPRESSION;
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hdr |= level_hint << 6;
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hdr |= 31 - (hdr % 31);
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put_unaligned_be16(hdr, out_next);
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out_next += 2;
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/* Compressed data */
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deflate_size = libdeflate_deflate_compress(c, in, in_nbytes, out_next,
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out_nbytes_avail - ZLIB_MIN_OVERHEAD);
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if (deflate_size == 0)
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return 0;
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out_next += deflate_size;
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/* ADLER32 */
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put_unaligned_be32(libdeflate_adler32(1, in, in_nbytes), out_next);
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out_next += 4;
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return out_next - (u8 *)out;
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}
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/*LIBDEFLATEAPI*/ static size_t
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libdeflate_zlib_compress_bound(struct libdeflate_compressor *c,
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size_t in_nbytes)
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{
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return ZLIB_MIN_OVERHEAD +
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libdeflate_deflate_compress_bound(c, in_nbytes);
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}
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