/*
* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
*
- * This file is part of Libav.
+ * This file is part of FFmpeg.
*
- * Libav is free software; you can redistribute it and/or
+ * FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
- * Libav is distributed in the hope that it will be useful,
+ * FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
- * License along with Libav; if not, write to the Free Software
+ * License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#define AVCODEC_GET_BITS_H
#include <stdint.h>
-#include <stdlib.h>
-#include <assert.h>
-#include "libavutil/bswap.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "mathops.h"
-/* bit input */
-/* buffer, buffer_end and size_in_bits must be present and used by every reader */
+/*
+ * Safe bitstream reading:
+ * optionally, the get_bits API can check to ensure that we
+ * don't read past input buffer boundaries. This is protected
+ * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
+ * then below that with UNCHECKED_BITSTREAM_READER at the per-
+ * decoder level. This means that decoders that check internally
+ * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
+ * overread checks.
+ * Boundary checking causes a minor performance penalty so for
+ * applications that won't want/need this, it can be disabled
+ * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
+ */
+#ifndef UNCHECKED_BITSTREAM_READER
+#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
+#endif
+
typedef struct GetBitContext {
const uint8_t *buffer, *buffer_end;
int index;
int size_in_bits;
+ int size_in_bits_plus8;
} GetBitContext;
#define VLC_TYPE int16_t
SKIP_COUNTER(name, gb, num)
will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
-LAST_SKIP_CACHE(name, gb, num)
- will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
-
LAST_SKIP_BITS(name, gb, num)
- is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
+ like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER
for examples see get_bits, show_bits, skip_bits, get_vlc
*/
# define MIN_CACHE_BITS 25
#endif
-# define OPEN_READER(name, gb) \
+#define OPEN_READER(name, gb) \
unsigned int name##_index = (gb)->index; \
- unsigned int av_unused name##_cache = 0
+ av_unused unsigned int name##_cache
+
+#define CLOSE_READER(name, gb) (gb)->index = name##_index
-# define CLOSE_READER(name, gb) (gb)->index = name##_index
+#ifdef BITSTREAM_READER_LE
-# ifdef ALT_BITSTREAM_READER_LE
# ifdef LONG_BITSTREAM_READER
-# define UPDATE_CACHE(name, gb) \
- name##_cache = AV_RL64((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
+# define UPDATE_CACHE(name, gb) name##_cache = \
+ AV_RL64((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
# else
-# define UPDATE_CACHE(name, gb) \
- name##_cache = AV_RL32((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
+# define UPDATE_CACHE(name, gb) name##_cache = \
+ AV_RL32((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
# endif
-# define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
-# else
+# define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
+
+#else
+
# ifdef LONG_BITSTREAM_READER
-# define UPDATE_CACHE(name, gb) \
- name##_cache = AV_RB64((gb)->buffer+(name##_index >> 3)) >> (32 - (name##_index & 0x07))
+# define UPDATE_CACHE(name, gb) name##_cache = \
+ AV_RB64((gb)->buffer + (name##_index >> 3)) >> (32 - (name##_index & 7))
# else
-# define UPDATE_CACHE(name, gb) \
- name##_cache = AV_RB32((gb)->buffer+(name##_index>>3)) << (name##_index&0x07)
+# define UPDATE_CACHE(name, gb) name##_cache = \
+ AV_RB32((gb)->buffer + (name##_index >> 3)) << (name##_index & 7)
# endif
-# define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
-# endif
+# define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
-// FIXME name?
+#endif
+
+#if UNCHECKED_BITSTREAM_READER
# define SKIP_COUNTER(name, gb, num) name##_index += (num)
+#else
+# define SKIP_COUNTER(name, gb, num) \
+ name##_index = FFMIN((gb)->size_in_bits_plus8, name##_index + (num))
+#endif
-# define SKIP_BITS(name, gb, num) do { \
+#define SKIP_BITS(name, gb, num) do { \
SKIP_CACHE(name, gb, num); \
SKIP_COUNTER(name, gb, num); \
} while (0)
-# define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
-# define LAST_SKIP_CACHE(name, gb, num)
+#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
-# ifdef ALT_BITSTREAM_READER_LE
+#ifdef BITSTREAM_READER_LE
# define SHOW_UBITS(name, gb, num) zero_extend(name##_cache, num)
-
# define SHOW_SBITS(name, gb, num) sign_extend(name##_cache, num)
-# else
+#else
# define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache, num)
-
# define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache, num)
-# endif
+#endif
-# define GET_CACHE(name, gb) ((uint32_t)name##_cache)
+#define GET_CACHE(name, gb) ((uint32_t)name##_cache)
-static inline int get_bits_count(const GetBitContext *s){
+static inline int get_bits_count(const GetBitContext *s)
+{
return s->index;
}
static inline void skip_bits_long(GetBitContext *s, int n){
+#if UNCHECKED_BITSTREAM_READER
s->index += n;
+#else
+ s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
+#endif
}
/**
* read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
* if MSB not set it is negative
* @param n length in bits
- * @author BERO
*/
-static inline int get_xbits(GetBitContext *s, int n){
+static inline int get_xbits(GetBitContext *s, int n)
+{
register int sign;
register int32_t cache;
OPEN_READER(re, s);
return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
}
-static inline int get_sbits(GetBitContext *s, int n){
+static inline int get_sbits(GetBitContext *s, int n)
+{
register int tmp;
OPEN_READER(re, s);
UPDATE_CACHE(re, s);
/**
* Read 1-25 bits.
*/
-static inline unsigned int get_bits(GetBitContext *s, int n){
+static inline unsigned int get_bits(GetBitContext *s, int n)
+{
register int tmp;
OPEN_READER(re, s);
UPDATE_CACHE(re, s);
/**
* Show 1-25 bits.
*/
-static inline unsigned int show_bits(GetBitContext *s, int n){
+static inline unsigned int show_bits(GetBitContext *s, int n)
+{
register int tmp;
OPEN_READER(re, s);
UPDATE_CACHE(re, s);
return tmp;
}
-static inline void skip_bits(GetBitContext *s, int n){
- //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
+static inline void skip_bits(GetBitContext *s, int n)
+{
OPEN_READER(re, s);
UPDATE_CACHE(re, s);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
}
-static inline unsigned int get_bits1(GetBitContext *s){
+static inline unsigned int get_bits1(GetBitContext *s)
+{
unsigned int index = s->index;
uint8_t result = s->buffer[index>>3];
-#ifdef ALT_BITSTREAM_READER_LE
+#ifdef BITSTREAM_READER_LE
result >>= index & 7;
result &= 1;
#else
result <<= index & 7;
result >>= 8 - 1;
#endif
- index++;
+#if !UNCHECKED_BITSTREAM_READER
+ if (s->index < s->size_in_bits_plus8)
+#endif
+ index++;
s->index = index;
return result;
}
-static inline unsigned int show_bits1(GetBitContext *s){
+static inline unsigned int show_bits1(GetBitContext *s)
+{
return show_bits(s, 1);
}
-static inline void skip_bits1(GetBitContext *s){
+static inline void skip_bits1(GetBitContext *s)
+{
skip_bits(s, 1);
}
/**
* Read 0-32 bits.
*/
-static inline unsigned int get_bits_long(GetBitContext *s, int n){
- if (n <= MIN_CACHE_BITS) return get_bits(s, n);
+static inline unsigned int get_bits_long(GetBitContext *s, int n)
+{
+ if (n <= MIN_CACHE_BITS)
+ return get_bits(s, n);
else {
-#ifdef ALT_BITSTREAM_READER_LE
+#ifdef BITSTREAM_READER_LE
int ret = get_bits(s, 16);
return ret | (get_bits(s, n-16) << 16);
#else
/**
* Read 0-32 bits as a signed integer.
*/
-static inline int get_sbits_long(GetBitContext *s, int n) {
+static inline int get_sbits_long(GetBitContext *s, int n)
+{
return sign_extend(get_bits_long(s, n), n);
}
/**
* Show 0-32 bits.
*/
-static inline unsigned int show_bits_long(GetBitContext *s, int n){
- if (n <= MIN_CACHE_BITS) return show_bits(s, n);
+static inline unsigned int show_bits_long(GetBitContext *s, int n)
+{
+ if (n <= MIN_CACHE_BITS)
+ return show_bits(s, n);
else {
GetBitContext gb = *s;
return get_bits_long(&gb, n);
* @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger than the actual read bits
* because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
* @param bit_size the size of the buffer in bits
- *
- * While GetBitContext stores the buffer size, for performance reasons you are
- * responsible for checking for the buffer end yourself (take advantage of the padding)!
*/
-static inline void init_get_bits(GetBitContext *s,
- const uint8_t *buffer, int bit_size)
+static inline void init_get_bits(GetBitContext *s, const uint8_t *buffer,
+ int bit_size)
{
int buffer_size = (bit_size+7)>>3;
if (buffer_size < 0 || bit_size < 0) {
s->buffer = buffer;
s->size_in_bits = bit_size;
+ s->size_in_bits_plus8 = bit_size + 8;
s->buffer_end = buffer + buffer_size;
s->index = 0;
}
* If the vlc code is invalid and max_depth>1, then the number of bits removed
* is undefined.
*/
-#define GET_VLC(code, name, gb, table, bits, max_depth) do { \
+#define GET_VLC(code, name, gb, table, bits, max_depth) \
+ do { \
int n, nb_bits; \
unsigned int index; \
\
SKIP_BITS(name, gb, n); \
} while (0)
-#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) do { \
+#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) \
+ do { \
int n, nb_bits; \
unsigned int index; \
\
/**
- * Parse a vlc code, faster than get_vlc().
+ * Parse a vlc code.
* @param bits is the number of bits which will be read at once, must be
* identical to nb_bits in init_vlc()
* @param max_depth is the number of times bits bits must be read to completely
* = (max_vlc_length + bits - 1) / bits
*/
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
- int bits, int max_depth)
+ int bits, int max_depth)
{
int code;
return code;
}
-static inline int decode012(GetBitContext *gb){
+static inline int decode012(GetBitContext *gb)
+{
int n;
n = get_bits1(gb);
if (n == 0)
return get_bits1(gb) + 1;
}
-static inline int decode210(GetBitContext *gb){
+static inline int decode210(GetBitContext *gb)
+{
if (get_bits1(gb))
return 0;
else
//#define TRACE
#ifdef TRACE
-static inline void print_bin(int bits, int n){
+static inline void print_bin(int bits, int n)
+{
int i;
for (i = n-1; i >= 0; i--) {
}
static inline int get_bits_trace(GetBitContext *s, int n, char *file,
- const char *func, int line){
+ const char *func, int line)
+{
int r = get_bits(s, n);
print_bin(r, n);
}
static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
int bits, int max_depth, char *file,
- const char *func, int line){
+ const char *func, int line)
+{
int show = show_bits(s, 24);
int pos = get_bits_count(s);
int r = get_vlc2(s, table, bits, max_depth);
return r;
}
static inline int get_xbits_trace(GetBitContext *s, int n, char *file,
- const char *func, int line){
+ const char *func, int line)
+{
int show = show_bits(s, n);
int r = get_xbits(s, n);
projects / ffmpeg / blobdiff