Libav
lzo.c
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1 /*
2  * LZO 1x decompression
3  * Copyright (c) 2006 Reimar Doeffinger
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include <string.h>
23 
24 #include "avutil.h"
25 #include "common.h"
26 #include "intreadwrite.h"
27 #include "lzo.h"
28 
30 #define OUTBUF_PADDED 1
31 
32 #define INBUF_PADDED 1
33 
34 typedef struct LZOContext {
35  const uint8_t *in, *in_end;
37  int error;
38 } LZOContext;
39 
44 static inline int get_byte(LZOContext *c)
45 {
46  if (c->in < c->in_end)
47  return *c->in++;
49  return 1;
50 }
51 
52 #ifdef INBUF_PADDED
53 #define GETB(c) (*(c).in++)
54 #else
55 #define GETB(c) get_byte(&(c))
56 #endif
57 
64 static inline int get_len(LZOContext *c, int x, int mask)
65 {
66  int cnt = x & mask;
67  if (!cnt) {
68  while (!(x = get_byte(c)))
69  cnt += 255;
70  cnt += mask + x;
71  }
72  return cnt;
73 }
74 
79 static inline void copy(LZOContext *c, int cnt)
80 {
81  register const uint8_t *src = c->in;
82  register uint8_t *dst = c->out;
83  if (cnt > c->in_end - src) {
84  cnt = FFMAX(c->in_end - src, 0);
86  }
87  if (cnt > c->out_end - dst) {
88  cnt = FFMAX(c->out_end - dst, 0);
90  }
91 #if defined(INBUF_PADDED) && defined(OUTBUF_PADDED)
92  AV_COPY32U(dst, src);
93  src += 4;
94  dst += 4;
95  cnt -= 4;
96  if (cnt > 0)
97 #endif
98  memcpy(dst, src, cnt);
99  c->in = src + cnt;
100  c->out = dst + cnt;
101 }
102 
111 static inline void copy_backptr(LZOContext *c, int back, int cnt)
112 {
113  register uint8_t *dst = c->out;
114  if (dst - c->out_start < back) {
116  return;
117  }
118  if (cnt > c->out_end - dst) {
119  cnt = FFMAX(c->out_end - dst, 0);
121  }
122  av_memcpy_backptr(dst, back, cnt);
123  c->out = dst + cnt;
124 }
125 
126 int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen)
127 {
128  int state = 0;
129  int x;
130  LZOContext c;
131  if (!*outlen || !*inlen) {
132  int res = 0;
133  if (!*outlen)
134  res |= AV_LZO_OUTPUT_FULL;
135  if (!*inlen)
136  res |= AV_LZO_INPUT_DEPLETED;
137  return res;
138  }
139  c.in = in;
140  c.in_end = (const uint8_t *)in + *inlen;
141  c.out = c.out_start = out;
142  c.out_end = (uint8_t *)out + *outlen;
143  c.error = 0;
144  x = GETB(c);
145  if (x > 17) {
146  copy(&c, x - 17);
147  x = GETB(c);
148  if (x < 16)
149  c.error |= AV_LZO_ERROR;
150  }
151  if (c.in > c.in_end)
153  while (!c.error) {
154  int cnt, back;
155  if (x > 15) {
156  if (x > 63) {
157  cnt = (x >> 5) - 1;
158  back = (GETB(c) << 3) + ((x >> 2) & 7) + 1;
159  } else if (x > 31) {
160  cnt = get_len(&c, x, 31);
161  x = GETB(c);
162  back = (GETB(c) << 6) + (x >> 2) + 1;
163  } else {
164  cnt = get_len(&c, x, 7);
165  back = (1 << 14) + ((x & 8) << 11);
166  x = GETB(c);
167  back += (GETB(c) << 6) + (x >> 2);
168  if (back == (1 << 14)) {
169  if (cnt != 1)
170  c.error |= AV_LZO_ERROR;
171  break;
172  }
173  }
174  } else if (!state) {
175  cnt = get_len(&c, x, 15);
176  copy(&c, cnt + 3);
177  x = GETB(c);
178  if (x > 15)
179  continue;
180  cnt = 1;
181  back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1;
182  } else {
183  cnt = 0;
184  back = (GETB(c) << 2) + (x >> 2) + 1;
185  }
186  copy_backptr(&c, back, cnt + 2);
187  state =
188  cnt = x & 3;
189  copy(&c, cnt);
190  x = GETB(c);
191  }
192  *inlen = c.in_end - c.in;
193  if (c.in > c.in_end)
194  *inlen = 0;
195  *outlen = c.out_end - c.out;
196  return c.error;
197 }