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
libdeflate_zlib_compress(struct libdeflate_compressor * c,const void * in,size_t in_size,void * out,size_t out_nbytes_avail)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
libdeflate_zlib_compress_bound(struct libdeflate_compressor * c,size_t in_nbytes)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 }
88