github.com/Schaudge/grailbase@v0.0.0-20240223061707-44c758a471c0/compress/libdeflate/zlib_compress.c (about)

     1  /*
     2   * zlib_compress.c - compress with a zlib 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 "unaligned.h"
    32  #include "zlib_constants.h"
    33  
    34  #include "libdeflate.h"
    35  
    36  LIBDEFLATEAPI size_t
    37  libdeflate_zlib_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  	u16 hdr;
    43  	unsigned compression_level;
    44  	unsigned level_hint;
    45  	size_t deflate_size;
    46  
    47  	if (out_nbytes_avail <= ZLIB_MIN_OVERHEAD)
    48  		return 0;
    49  
    50  	/* 2 byte header: CMF and FLG  */
    51  	hdr = (ZLIB_CM_DEFLATE << 8) | (ZLIB_CINFO_32K_WINDOW << 12);
    52  	compression_level = deflate_get_compression_level(c);
    53  	if (compression_level < 2)
    54  		level_hint = ZLIB_FASTEST_COMPRESSION;
    55  	else if (compression_level < 6)
    56  		level_hint = ZLIB_FAST_COMPRESSION;
    57  	else if (compression_level < 8)
    58  		level_hint = ZLIB_DEFAULT_COMPRESSION;
    59  	else
    60  		level_hint = ZLIB_SLOWEST_COMPRESSION;
    61  	hdr |= level_hint << 6;
    62  	hdr |= 31 - (hdr % 31);
    63  
    64  	put_unaligned_be16(hdr, out_next);
    65  	out_next += 2;
    66  
    67  	/* Compressed data  */
    68  	deflate_size = libdeflate_deflate_compress(c, in, in_size, out_next,
    69  					out_nbytes_avail - ZLIB_MIN_OVERHEAD);
    70  	if (deflate_size == 0)
    71  		return 0;
    72  	out_next += deflate_size;
    73  
    74  	/* ADLER32  */
    75  	put_unaligned_be32(libdeflate_adler32(1, in, in_size), out_next);
    76  	out_next += 4;
    77  
    78  	return out_next - (u8 *)out;
    79  }
    80  
    81  LIBDEFLATEAPI size_t
    82  libdeflate_zlib_compress_bound(struct libdeflate_compressor *c,
    83  			       size_t in_nbytes)
    84  {
    85  	return ZLIB_MIN_OVERHEAD +
    86  	       libdeflate_deflate_compress_bound(c, in_nbytes);
    87  }