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
libdeflate_gzip_compress(struct libdeflate_compressor * c,const void * in,size_t in_size,void * out,size_t out_nbytes_avail)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
libdeflate_gzip_compress_bound(struct libdeflate_compressor * c,size_t in_nbytes)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 }
96