1 /*
2 * libid3tag - ID3 tag manipulation library
3 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
20 */
21
22 # ifdef HAVE_CONFIG_H
23 # include "config.h"
24 # endif
25
26 # include "global.h"
27
28 # include <stdlib.h>
29 # include <zlib.h>
30
31 # include "id3tag.h"
32 # include "util.h"
33
34 /*
35 * NAME: util->unsynchronise()
36 * DESCRIPTION: perform (in-place) unsynchronisation
37 */
id3_util_unsynchronise(id3_byte_t * data,id3_length_t length)38 id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
39 {
40 id3_length_t bytes = 0, count;
41 id3_byte_t *end = data + length;
42 id3_byte_t const *ptr;
43
44 if (length == 0)
45 return 0;
46
47 for (ptr = data; ptr < end - 1; ++ptr) {
48 if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
49 ++bytes;
50 }
51
52 if (bytes) {
53 ptr = end;
54 end += bytes;
55
56 *--end = *--ptr;
57
58 for (count = bytes; count; *--end = *--ptr) {
59 if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0)) {
60 *--end = 0x00;
61 --count;
62 }
63 }
64 }
65
66 return length + bytes;
67 }
68
69 /*
70 * NAME: util->deunsynchronise()
71 * DESCRIPTION: undo unsynchronisation (in-place)
72 */
id3_util_deunsynchronise(id3_byte_t * data,id3_length_t length)73 id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
74 {
75 id3_byte_t const *old, *end = data + length;
76 id3_byte_t *new;
77
78 if (length == 0)
79 return 0;
80
81 for (old = new = data; old < end - 1; ++old) {
82 *new++ = *old;
83 if (old[0] == 0xff && old[1] == 0x00)
84 ++old;
85 }
86
87 *new++ = *old;
88
89 return new - data;
90 }
91
92 /*
93 * NAME: util->compress()
94 * DESCRIPTION: perform zlib deflate method compression
95 */
id3_util_compress(id3_byte_t const * data,id3_length_t length,id3_length_t * newlength)96 id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
97 id3_length_t *newlength)
98 {
99 id3_byte_t *compressed;
100
101 *newlength = length + 12;
102 *newlength += *newlength / 1000;
103
104 compressed = malloc(*newlength);
105 if (compressed) {
106 if (compress2(compressed, newlength, data, length,
107 Z_BEST_COMPRESSION) != Z_OK ||
108 *newlength >= length) {
109 free(compressed);
110 compressed = 0;
111 }
112 else {
113 id3_byte_t *resized;
114
115 resized = realloc(compressed, *newlength ? *newlength : 1);
116 if (resized)
117 compressed = resized;
118 }
119 }
120
121 return compressed;
122 }
123
124 /*
125 * NAME: util->decompress()
126 * DESCRIPTION: undo zlib deflate method compression
127 */
id3_util_decompress(id3_byte_t const * data,id3_length_t length,id3_length_t newlength)128 id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
129 id3_length_t newlength)
130 {
131 id3_byte_t *decompressed;
132
133 decompressed = malloc(newlength ? newlength : 1);
134 if (decompressed) {
135 id3_length_t size;
136
137 size = newlength;
138
139 if (uncompress(decompressed, &size, data, length) != Z_OK ||
140 size != newlength) {
141 free(decompressed);
142 decompressed = 0;
143 }
144 }
145
146 return decompressed;
147 }
148