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/*
* gzip_compress.c - compress with a gzip wrapper
*
* Originally public domain; changes after 2016-09-07 are copyrighted.
*
* Copyright 2016 Eric Biggers
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "deflate_compress.h"
#include "gzip_constants.h"
#include "unaligned.h"
#include "libdeflate.h"
LIBDEFLATEEXPORT size_t LIBDEFLATEAPI
libdeflate_gzip_compress(struct libdeflate_compressor *c,
const void *in, size_t in_nbytes,
void *out, size_t out_nbytes_avail)
{
u8 *out_next = out;
unsigned compression_level;
u8 xfl;
size_t deflate_size;
if (out_nbytes_avail <= GZIP_MIN_OVERHEAD)
return 0;
/* ID1 */
*out_next++ = GZIP_ID1;
/* ID2 */
*out_next++ = GZIP_ID2;
/* CM */
*out_next++ = GZIP_CM_DEFLATE;
/* FLG */
*out_next++ = 0;
/* MTIME */
put_unaligned_le32(GZIP_MTIME_UNAVAILABLE, out_next);
out_next += 4;
/* XFL */
xfl = 0;
compression_level = deflate_get_compression_level(c);
if (compression_level < 2)
xfl |= GZIP_XFL_FASTEST_COMPRESSION;
else if (compression_level >= 8)
xfl |= GZIP_XFL_SLOWEST_COMPRESSION;
*out_next++ = xfl;
/* OS */
*out_next++ = GZIP_OS_UNKNOWN; /* OS */
/* Compressed data */
deflate_size = libdeflate_deflate_compress(c, in, in_nbytes, out_next,
out_nbytes_avail - GZIP_MIN_OVERHEAD);
if (deflate_size == 0)
return 0;
out_next += deflate_size;
/* CRC32 */
put_unaligned_le32(libdeflate_crc32(0, in, in_nbytes), out_next);
out_next += 4;
/* ISIZE */
put_unaligned_le32((u32)in_nbytes, out_next);
out_next += 4;
return out_next - (u8 *)out;
}
LIBDEFLATEEXPORT size_t LIBDEFLATEAPI
libdeflate_gzip_compress_bound(struct libdeflate_compressor *c,
size_t in_nbytes)
{
return GZIP_MIN_OVERHEAD +
libdeflate_deflate_compress_bound(c, in_nbytes);
}
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