github.com/grailbio/base@v0.0.11/compress/libdeflate/gzip_compress.c (about)

     1  /*
     2   * gzip_compress.c - compress with a gzip wrapper
     3   *
     4   * Originally public domain; changes after 2016-09-07 are copyrighted.
     5   *
     6   * Copyright 2016 Eric Biggers
     7   *
     8   * Permission is hereby granted, free of charge, to any person
     9   * obtaining a copy of this software and associated documentation
    10   * files (the "Software"), to deal in the Software without
    11   * restriction, including without limitation the rights to use,
    12   * copy, modify, merge, publish, distribute, sublicense, and/or sell
    13   * copies of the Software, and to permit persons to whom the
    14   * Software is furnished to do so, subject to the following
    15   * conditions:
    16   *
    17   * The above copyright notice and this permission notice shall be
    18   * included in all copies or substantial portions of the Software.
    19   *
    20   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    21   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
    22   * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    23   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
    24   * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
    25   * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    26   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
    27   * OTHER DEALINGS IN THE SOFTWARE.
    28   */
    29  
    30  #include "deflate_compress.h"
    31  #include "gzip_constants.h"
    32  #include "unaligned.h"
    33  
    34  #include "libdeflate.h"
    35  
    36  LIBDEFLATEAPI size_t
    37  libdeflate_gzip_compress(struct libdeflate_compressor *c,
    38  			 const void *in, size_t in_size,
    39  			 void *out, size_t out_nbytes_avail)
    40  {
    41  	u8 *out_next = out;
    42  	unsigned compression_level;
    43  	u8 xfl;
    44  	size_t deflate_size;
    45  
    46  	if (out_nbytes_avail <= GZIP_MIN_OVERHEAD)
    47  		return 0;
    48  
    49  	/* ID1 */
    50  	*out_next++ = GZIP_ID1;
    51  	/* ID2 */
    52  	*out_next++ = GZIP_ID2;
    53  	/* CM */
    54  	*out_next++ = GZIP_CM_DEFLATE;
    55  	/* FLG */
    56  	*out_next++ = 0;
    57  	/* MTIME */
    58  	put_unaligned_le32(GZIP_MTIME_UNAVAILABLE, out_next);
    59  	out_next += 4;
    60  	/* XFL */
    61  	xfl = 0;
    62  	compression_level = deflate_get_compression_level(c);
    63  	if (compression_level < 2)
    64  		xfl |= GZIP_XFL_FASTEST_COMRESSION;
    65  	else if (compression_level >= 8)
    66  		xfl |= GZIP_XFL_SLOWEST_COMRESSION;
    67  	*out_next++ = xfl;
    68  	/* OS */
    69  	*out_next++ = GZIP_OS_UNKNOWN;	/* OS  */
    70  
    71  	/* Compressed data  */
    72  	deflate_size = libdeflate_deflate_compress(c, in, in_size, out_next,
    73  					out_nbytes_avail - GZIP_MIN_OVERHEAD);
    74  	if (deflate_size == 0)
    75  		return 0;
    76  	out_next += deflate_size;
    77  
    78  	/* CRC32 */
    79  	put_unaligned_le32(libdeflate_crc32(0, in, in_size), out_next);
    80  	out_next += 4;
    81  
    82  	/* ISIZE */
    83  	put_unaligned_le32((u32)in_size, out_next);
    84  	out_next += 4;
    85  
    86  	return out_next - (u8 *)out;
    87  }
    88  
    89  LIBDEFLATEAPI size_t
    90  libdeflate_gzip_compress_bound(struct libdeflate_compressor *c,
    91  			       size_t in_nbytes)
    92  {
    93  	return GZIP_MIN_OVERHEAD +
    94  	       libdeflate_deflate_compress_bound(c, in_nbytes);
    95  }