/** \file bitstream.h Bitstream structures and inline functions. */
-#define AV_RB32(x) ((((const uint8_t*)(x))[0] << 24) | \
- (((const uint8_t*)(x))[1] << 16) | \
- (((const uint8_t*)(x))[2] << 8) | \
- ((const uint8_t*)(x))[3])
-
-# define NEG_SSR32(a,s) ((( int32_t)(a))>>(32-(s)))
-# define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
-
-/**
- * Structure for bistream I/O.
- *
- * The buffer, buffer_end and size_in_bits fields must be present and are used
- * by every reader.
- */
+/** Structure for bistream I/O. */
struct getbit_context {
- const uint8_t *buffer, *buffer_end;
+ /* Start of the internal buffer. */
+ const uint8_t *buffer;
+ /* End of the internal buffer. */
+ const uint8_t *buffer_end;
+ /** Bit counter. */
int index;
- int size_in_bits;
};
#define VLC_TYPE int16_t
+/** A variable length code table. */
struct vlc {
+ /** Number of bits of the table. */
int bits;
- VLC_TYPE(*table)[2]; ///< code, bits
- int table_size, table_allocated;
+ /** The code and the bits table. */
+ VLC_TYPE(*table)[2];
+ /** The size of the table. */
+ int table_size;
+ /** Amount of memory allocated so far. */
+ int table_allocated;
};
-#define MIN_CACHE_BITS 25
-
-/** Load \a gb into local variables. */
-#define OPEN_READER(name, gb)\
- int name##_index= (gb)->index;\
- int name##_cache= 0;\
-
-/** Store local vars in gb. */
-#define CLOSE_READER(name, gb)\
- (gb)->index= name##_index;\
-
-/**
- * Refill the internal cache from the bitstream.
- *
- * After this call at least MIN_CACHE_BITS will be available.
- */
-#define UPDATE_CACHE(name, gb)\
- name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer) \
- + (name##_index >> 3) ) << (name##_index & 0x07);\
-
-/**
- * Remove the next num bits from the cache.
- *
- * SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER).
- */
-#define SKIP_CACHE(name, gb, num)\
- name##_cache <<= (num);
-
-/**
- * Increment the internal bit counter.
- *
- * \sa SKIP_CACHE, SKIP_BITS.
- */
-#define SKIP_COUNTER(name, gb, num)\
- name##_index += (num);\
-
-/**
- * Skip over the next num bits.
- *
- * This is equivalent to SKIP_CACHE; SKIP_COUNTER.
- */
-#define SKIP_BITS(name, gb, num)\
- {\
- SKIP_CACHE(name, gb, num)\
- SKIP_COUNTER(name, gb, num)\
- }\
-
-/** This is equivalent to SKIP_LAST_CACHE; SKIP_COUNTER. */
-#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
-
-/** Return the next num bits. */
-#define SHOW_UBITS(name, gb, num)\
- NEG_USR32(name##_cache, num)
-
-static inline int get_bits_count(struct getbit_context *s)
-{
- return s->index;
-}
-
-static inline void skip_bits_long(struct getbit_context *s, int n)
-{
- s->index += n;
-}
-
-/**
- * reads 1-17 bits.
- * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
- */
-static inline unsigned int get_bits(struct getbit_context *s, int n)
+static inline uint32_t show_bits(struct getbit_context *gbc, int num)
{
- register int tmp;
- OPEN_READER(re, s)
- UPDATE_CACHE(re, s)
- tmp = SHOW_UBITS(re, s, n);
- LAST_SKIP_BITS(re, s, n)
- CLOSE_READER(re, s)
- return tmp;
+ int idx = gbc->index;
+ const uint8_t *p = gbc->buffer + (idx >> 3);
+ uint32_t x = ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+ return (x << (idx & 7)) >> (32 - num);
}
-/**
- * Show 1-17 bits.
- *
- * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2
- * reader can't.
- */
-static inline unsigned int show_bits(struct getbit_context *s, int n)
+static inline int get_bits_count(struct getbit_context *gbc)
{
- register int tmp;
- OPEN_READER(re, s)
- UPDATE_CACHE(re, s)
- tmp = SHOW_UBITS(re, s, n);
-// CLOSE_READER(re, s)
- return tmp;
+ return gbc->index;
}
-static inline void skip_bits(struct getbit_context *s, int n)
+static inline void skip_bits(struct getbit_context *gbc, int n)
{
- /* gcc seems to optimize this to s->index+=n for the ALT_READER :)) */
- OPEN_READER(re, s)
- UPDATE_CACHE(re, s)
- LAST_SKIP_BITS(re, s, n)
- CLOSE_READER(re, s)
+ gbc->index += n;
}
-static inline unsigned int get_bits1(struct getbit_context *s)
+static inline unsigned int get_bits(struct getbit_context *gbc, int n)
{
- int idx = s->index;
- uint8_t result = s->buffer[idx >> 3];
-
- result <<= (idx & 0x07);
- result >>= 8 - 1;
- idx++;
- s->index = idx;
- return result;
+ unsigned int ret = show_bits(gbc, n);
+ skip_bits(gbc, n);
+ return ret;
}
-/**
- * reads 0-32 bits.
- */
-static inline unsigned int get_bits_long(struct getbit_context *s, int n)
+/* This is rather hot, we can do better than get_bits(gbc, 1). */
+static inline unsigned int get_bit(struct getbit_context *gbc)
{
- if (n <= 17)
- return get_bits(s, n);
- else {
- int ret = get_bits(s, 16) << (n - 16);
- return ret | get_bits(s, n - 16);
- }
+ int idx = gbc->index++;
+ uint8_t tmp = gbc->buffer[idx >> 3], mask = (1 << (7 - (idx & 7)));
+ return !!(tmp & mask);
}
/**
* Initialize a getbit_context structure.
*
- * \param buffer The bitstream buffer. It must be FF_INPUT_BUFFER_PADDING_SIZE
- * bytes larger then the actual read bits * because some optimized bitstream
- * readers read 32 or 64 bit at once and could read over the end.
+ * \param buffer The bitstream buffer. It must be 4 bytes larger then the
+ * actual read bits because the bitstream reader might read 32 bits at once and
+ * could read over the end.
*
- * \param bit_size The size of the buffer in bits.
+ * \param bit_size The size of the buffer in bytes.
*/
-static inline void init_get_bits(struct getbit_context *s,
- const uint8_t * buffer, int bit_size)
+static inline void init_get_bits(struct getbit_context *gbc,
+ const uint8_t *buffer, int size)
{
- int buffer_size = (bit_size + 7) >> 3;
- if (buffer_size < 0 || bit_size < 0) {
- buffer_size = bit_size = 0;
- buffer = NULL;
- }
- s->buffer = buffer;
- s->size_in_bits = bit_size;
- s->buffer_end = buffer + buffer_size;
- s->index = 0;
+ gbc->buffer = buffer;
+ gbc->buffer_end = buffer + size;
+ gbc->index = 0;
}
-int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
- const void *bits, int bits_wrap, int bits_size,
- const void *codes, int codes_wrap, int codes_size);
-
+void init_vlc(struct vlc *vlc, int nb_bits, int nb_codes, const void *bits,
+ const void *codes, int codes_size);
void free_vlc(struct vlc *vlc);
+int get_vlc(struct getbit_context *gbc, VLC_TYPE(*table)[2], int bits,
+ int max_depth);
-/**
- *
- * if the vlc code is invalid and max_depth=1 than no bits will be removed
- * if the vlc code is invalid and max_depth>1 than the number of bits removed
- * is undefined
- */
-#define GET_VLC(code, name, gb, table, bits, max_depth)\
-{\
- int n, index, nb_bits;\
-\
- index= SHOW_UBITS(name, gb, bits);\
- code = table[index][0];\
- n = table[index][1];\
-\
- if(max_depth > 1 && n < 0){\
- LAST_SKIP_BITS(name, gb, bits)\
- UPDATE_CACHE(name, gb)\
-\
- nb_bits = -n;\
-\
- index= SHOW_UBITS(name, gb, nb_bits) + code;\
- code = table[index][0];\
- n = table[index][1];\
- if(max_depth > 2 && n < 0){\
- LAST_SKIP_BITS(name, gb, nb_bits)\
- UPDATE_CACHE(name, gb)\
-\
- nb_bits = -n;\
-\
- index= SHOW_UBITS(name, gb, nb_bits) + code;\
- code = table[index][0];\
- n = table[index][1];\
- }\
- }\
- SKIP_BITS(name, gb, n)\
-}
projects / paraslash.git / blobdiff