[FFmpeg-devel] [PATCH v4 4/4] lavc/get_bits: add a compat wrapper for the cached bitstream reader
Anton Khirnov
anton at khirnov.net
Sat Oct 22 13:32:57 EEST 2022
Use that instead of the merged version.
---
libavcodec/get_bits.h | 309 +++++++++---------------------------------
1 file changed, 62 insertions(+), 247 deletions(-)
diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 992765dc92..a50469b427 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -1,6 +1,5 @@
/*
* Copyright (c) 2004 Michael Niedermayer <michaelni at gmx.at>
- * Copyright (c) 2016 Alexandra Hájková
*
* This file is part of FFmpeg.
*
@@ -58,12 +57,55 @@
#define CACHED_BITSTREAM_READER 0
#endif
-typedef struct GetBitContext {
- const uint8_t *buffer, *buffer_end;
#if CACHED_BITSTREAM_READER
- uint64_t cache;
- unsigned bits_left;
+
+// we always want the LE implementation, to provide get_bits_le()
+#define BITSTREAM_LE
+
+#ifndef BITSTREAM_READER_LE
+# define BITSTREAM_BE
+# define BITSTREAM_DEFAULT_BE
#endif
+
+#include "bitstream.h"
+
+#undef BITSTREAM_LE
+#undef BITSTREAM_BE
+#undef BITSTREAM_DEFAULT_BE
+
+typedef BitstreamContext GetBitContext;
+
+#define get_bits_count bits_tell
+#define get_bits_left bits_left
+#define skip_bits_long bits_skip
+#define skip_bits bits_skip
+#define get_bits bits_read_nz
+#define get_bitsz bits_read
+#define get_bits_long bits_read
+#define get_bits1 bits_read_bit
+#define get_bits64 bits_read_64
+#define get_xbits bits_read_xbits
+#define get_sbits bits_read_signed
+#define get_sbits_long bits_read_signed
+#define show_bits bits_peek
+#define show_bits_long bits_peek
+#define init_get_bits bits_init
+#define init_get_bits8 bits_init8
+#define align_get_bits bits_align
+#define get_vlc2 bits_read_vlc
+
+#define init_get_bits8_le(s, buffer, byte_size) bits_init8_le((BitstreamContextLE*)s, buffer, byte_size)
+#define get_bits_le(s, n) bits_read_le((BitstreamContextLE*)s, n)
+
+#define show_bits1(s) bits_peek(s, 1)
+#define skip_bits1(s) bits_skip(s, 1)
+
+#define skip_1stop_8data_bits bits_skip_1stop_8data
+
+#else // CACHED_BITSTREAM_READER
+
+typedef struct GetBitContext {
+ const uint8_t *buffer, *buffer_end;
int index;
int size_in_bits;
int size_in_bits_plus8;
@@ -120,16 +162,12 @@ static inline unsigned int show_bits(GetBitContext *s, int n);
* For examples see get_bits, show_bits, skip_bits, get_vlc.
*/
-#if CACHED_BITSTREAM_READER
-# define MIN_CACHE_BITS 64
-#elif defined LONG_BITSTREAM_READER
+#if defined LONG_BITSTREAM_READER
# define MIN_CACHE_BITS 32
#else
# define MIN_CACHE_BITS 25
#endif
-#if !CACHED_BITSTREAM_READER
-
#define OPEN_READER_NOSIZE(name, gb) \
unsigned int name ## _index = (gb)->index; \
unsigned int av_unused name ## _cache
@@ -214,73 +252,12 @@ static inline unsigned int show_bits(GetBitContext *s, int n);
#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
-#endif
static inline int get_bits_count(const GetBitContext *s)
{
-#if CACHED_BITSTREAM_READER
- return s->index - s->bits_left;
-#else
return s->index;
-#endif
-}
-
-#if CACHED_BITSTREAM_READER
-static inline void refill_32(GetBitContext *s, int is_le)
-{
-#if !UNCHECKED_BITSTREAM_READER
- if (s->index >> 3 >= s->buffer_end - s->buffer)
- return;
-#endif
-
- if (is_le)
- s->cache = (uint64_t)AV_RL32(s->buffer + (s->index >> 3)) << s->bits_left | s->cache;
- else
- s->cache = s->cache | (uint64_t)AV_RB32(s->buffer + (s->index >> 3)) << (32 - s->bits_left);
- s->index += 32;
- s->bits_left += 32;
-}
-
-static inline void refill_64(GetBitContext *s, int is_le)
-{
-#if !UNCHECKED_BITSTREAM_READER
- if (s->index >> 3 >= s->buffer_end - s->buffer)
- return;
-#endif
-
- if (is_le)
- s->cache = AV_RL64(s->buffer + (s->index >> 3));
- else
- s->cache = AV_RB64(s->buffer + (s->index >> 3));
- s->index += 64;
- s->bits_left = 64;
}
-static inline uint64_t get_val(GetBitContext *s, unsigned n, int is_le)
-{
- uint64_t ret;
- av_assert2(n>0 && n<=63);
- if (is_le) {
- ret = s->cache & ((UINT64_C(1) << n) - 1);
- s->cache >>= n;
- } else {
- ret = s->cache >> (64 - n);
- s->cache <<= n;
- }
- s->bits_left -= n;
- return ret;
-}
-
-static inline unsigned show_val(const GetBitContext *s, unsigned n)
-{
-#ifdef BITSTREAM_READER_LE
- return s->cache & ((UINT64_C(1) << n) - 1);
-#else
- return s->cache >> (64 - n);
-#endif
-}
-#endif
-
/**
* Skips the specified number of bits.
* @param n the number of bits to skip,
@@ -290,28 +267,12 @@ static inline unsigned show_val(const GetBitContext *s, unsigned n)
*/
static inline void skip_bits_long(GetBitContext *s, int n)
{
-#if CACHED_BITSTREAM_READER
- skip_bits(s, n);
-#else
#if UNCHECKED_BITSTREAM_READER
s->index += n;
#else
s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
#endif
-#endif
-}
-
-#if CACHED_BITSTREAM_READER
-static inline void skip_remaining(GetBitContext *s, unsigned n)
-{
-#ifdef BITSTREAM_READER_LE
- s->cache >>= n;
-#else
- s->cache <<= n;
-#endif
- s->bits_left -= n;
}
-#endif
/**
* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
@@ -320,13 +281,6 @@ static inline void skip_remaining(GetBitContext *s, unsigned n)
*/
static inline int get_xbits(GetBitContext *s, int n)
{
-#if CACHED_BITSTREAM_READER
- int32_t cache = show_bits(s, 32);
- int sign = ~cache >> 31;
- skip_remaining(s, n);
-
- return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
-#else
register int sign;
register int32_t cache;
OPEN_READER(re, s);
@@ -337,10 +291,8 @@ static inline int get_xbits(GetBitContext *s, int n)
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
-#endif
}
-#if !CACHED_BITSTREAM_READER
static inline int get_xbits_le(GetBitContext *s, int n)
{
register int sign;
@@ -354,22 +306,16 @@ static inline int get_xbits_le(GetBitContext *s, int n)
CLOSE_READER(re, s);
return (zero_extend(sign ^ cache, n) ^ sign) - sign;
}
-#endif
static inline int get_sbits(GetBitContext *s, int n)
{
register int tmp;
-#if CACHED_BITSTREAM_READER
- av_assert2(n>0 && n<=25);
- tmp = sign_extend(get_bits(s, n), n);
-#else
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_SBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
-#endif
return tmp;
}
@@ -379,32 +325,12 @@ static inline int get_sbits(GetBitContext *s, int n)
static inline unsigned int get_bits(GetBitContext *s, int n)
{
register unsigned int tmp;
-#if CACHED_BITSTREAM_READER
-
- av_assert2(n>0 && n<=32);
- if (n > s->bits_left) {
-#ifdef BITSTREAM_READER_LE
- refill_32(s, 1);
-#else
- refill_32(s, 0);
-#endif
- if (s->bits_left < 32)
- s->bits_left = n;
- }
-
-#ifdef BITSTREAM_READER_LE
- tmp = get_val(s, n, 1);
-#else
- tmp = get_val(s, n, 0);
-#endif
-#else
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
-#endif
av_assert2(tmp < UINT64_C(1) << n);
return tmp;
}
@@ -419,16 +345,6 @@ static av_always_inline int get_bitsz(GetBitContext *s, int n)
static inline unsigned int get_bits_le(GetBitContext *s, int n)
{
-#if CACHED_BITSTREAM_READER
- av_assert2(n>0 && n<=32);
- if (n > s->bits_left) {
- refill_32(s, 1);
- if (s->bits_left < 32)
- s->bits_left = n;
- }
-
- return get_val(s, n, 1);
-#else
register int tmp;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
@@ -437,7 +353,6 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return tmp;
-#endif
}
/**
@@ -446,71 +361,22 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
static inline unsigned int show_bits(GetBitContext *s, int n)
{
register unsigned int tmp;
-#if CACHED_BITSTREAM_READER
- if (n > s->bits_left)
-#ifdef BITSTREAM_READER_LE
- refill_32(s, 1);
-#else
- refill_32(s, 0);
-#endif
-
- tmp = show_val(s, n);
-#else
OPEN_READER_NOSIZE(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
-#endif
return tmp;
}
static inline void skip_bits(GetBitContext *s, int n)
{
-#if CACHED_BITSTREAM_READER
- if (n < s->bits_left)
- skip_remaining(s, n);
- else {
- n -= s->bits_left;
- s->cache = 0;
- s->bits_left = 0;
-
- if (n >= 64) {
- unsigned skip = (n / 8) * 8;
-
- n -= skip;
- s->index += skip;
- }
-#ifdef BITSTREAM_READER_LE
- refill_64(s, 1);
-#else
- refill_64(s, 0);
-#endif
- if (n)
- skip_remaining(s, n);
- }
-#else
OPEN_READER(re, s);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
-#endif
}
static inline unsigned int get_bits1(GetBitContext *s)
{
-#if CACHED_BITSTREAM_READER
- if (!s->bits_left)
-#ifdef BITSTREAM_READER_LE
- refill_64(s, 1);
-#else
- refill_64(s, 0);
-#endif
-
-#ifdef BITSTREAM_READER_LE
- return get_val(s, 1, 1);
-#else
- return get_val(s, 1, 0);
-#endif
-#else
unsigned int index = s->index;
uint8_t result = s->buffer[index >> 3];
#ifdef BITSTREAM_READER_LE
@@ -527,7 +393,6 @@ static inline unsigned int get_bits1(GetBitContext *s)
s->index = index;
return result;
-#endif
}
static inline unsigned int show_bits1(GetBitContext *s)
@@ -548,10 +413,6 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
av_assert2(n>=0 && n<=32);
if (!n) {
return 0;
-#if CACHED_BITSTREAM_READER
- }
- return get_bits(s, n);
-#else
} else if (n <= MIN_CACHE_BITS) {
return get_bits(s, n);
} else {
@@ -563,7 +424,6 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
return ret | get_bits(s, n - 16);
#endif
}
-#endif
}
/**
@@ -609,8 +469,17 @@ static inline unsigned int show_bits_long(GetBitContext *s, int n)
}
}
-static inline int init_get_bits_xe(GetBitContext *s, const uint8_t *buffer,
- int bit_size, int is_le)
+
+/**
+ * Initialize GetBitContext.
+ * @param buffer bitstream buffer, must be AV_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
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
+ */
+static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
+ int bit_size)
{
int buffer_size;
int ret = 0;
@@ -629,33 +498,9 @@ static inline int init_get_bits_xe(GetBitContext *s, const uint8_t *buffer,
s->buffer_end = buffer + buffer_size;
s->index = 0;
-#if CACHED_BITSTREAM_READER
- s->cache = 0;
- s->bits_left = 0;
- refill_64(s, is_le);
-#endif
-
return ret;
}
-/**
- * Initialize GetBitContext.
- * @param buffer bitstream buffer, must be AV_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
- * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
- */
-static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
- int bit_size)
-{
-#ifdef BITSTREAM_READER_LE
- return init_get_bits_xe(s, buffer, bit_size, 1);
-#else
- return init_get_bits_xe(s, buffer, bit_size, 0);
-#endif
-}
-
/**
* Initialize GetBitContext.
* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
@@ -677,7 +522,7 @@ static inline int init_get_bits8_le(GetBitContext *s, const uint8_t *buffer,
{
if (byte_size > INT_MAX / 8 || byte_size < 0)
byte_size = -1;
- return init_get_bits_xe(s, buffer, byte_size * 8, 1);
+ return init_get_bits(s, buffer, byte_size * 8);
}
static inline const uint8_t *align_get_bits(GetBitContext *s)
@@ -762,19 +607,6 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
SKIP_BITS(name, gb, n); \
} while (0)
-/* Return the LUT element for the given bitstream configuration. */
-static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
- const VLCElem *table)
-{
- unsigned idx;
-
- *nb_bits = -*n;
- idx = show_bits(s, *nb_bits) + code;
- *n = table[idx].len;
-
- return table[idx].sym;
-}
-
/**
* Parse a vlc code.
* @param bits is the number of bits which will be read at once, must be
@@ -787,24 +619,6 @@ static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
static av_always_inline int get_vlc2(GetBitContext *s, const VLCElem *table,
int bits, int max_depth)
{
-#if CACHED_BITSTREAM_READER
- int nb_bits;
- unsigned idx = show_bits(s, bits);
- int code = table[idx].sym;
- int n = table[idx].len;
-
- if (max_depth > 1 && n < 0) {
- skip_remaining(s, bits);
- code = set_idx(s, code, &n, &nb_bits, table);
- if (max_depth > 2 && n < 0) {
- skip_remaining(s, nb_bits);
- code = set_idx(s, code, &n, &nb_bits, table);
- }
- }
- skip_remaining(s, n);
-
- return code;
-#else
int code;
OPEN_READER(re, s);
@@ -815,7 +629,6 @@ static av_always_inline int get_vlc2(GetBitContext *s, const VLCElem *table,
CLOSE_READER(re, s);
return code;
-#endif
}
static inline int decode012(GetBitContext *gb)
@@ -855,4 +668,6 @@ static inline int skip_1stop_8data_bits(GetBitContext *gb)
return 0;
}
+#endif // CACHED_BITSTREAM_READER
+
#endif /* AVCODEC_GET_BITS_H */
--
2.35.1
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