/** \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])
-
/** Structure for bistream I/O. */
struct getbit_context {
/* Start of the internal buffer. */
#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;
};
-/** 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.
- */
-#define UPDATE_CACHE(name, gb)\
- name##_cache= AV_RB32( ((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.
- */
-#define SKIP_COUNTER(name, gb, num)\
- name##_index += (num);\
-
-/** Return the next num bits. */
-#define SHOW_UBITS(name, gb, num) \
- (((uint32_t)(name##_cache)) >> (32 - (num)))
-
-static inline int get_bits_count(struct getbit_context *s)
+static inline uint32_t show_bits(struct getbit_context *gbc, int num)
{
- return s->index;
+ 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);
}
-/**
- * Read 1-17 bits.
- */
-static inline unsigned int get_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);
- SKIP_COUNTER(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)
{
- s->index += n;
+ 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];
+ unsigned int ret = show_bits(gbc, n);
+ skip_bits(gbc, n);
+ return ret;
+}
- result <<= (idx & 0x07);
- result >>= 8 - 1;
- idx++;
- s->index = idx;
- return result;
+/* This is rather hot, we can do better than get_bits(gbc, 1). */
+static inline unsigned int get_bit(struct getbit_context *gbc)
+{
+ 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 bytes.
*/
-static inline void init_get_bits(struct getbit_context *s,
+static inline void init_get_bits(struct getbit_context *gbc,
const uint8_t *buffer, int size)
{
- s->buffer = buffer;
- s->buffer_end = buffer + size;
- s->index = 0;
+ gbc->buffer = buffer;
+ gbc->buffer_end = buffer + size;
+ gbc->index = 0;
}
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);
-/**
- * Parse a vlc code.
- *
- * \param bits The number of bits which will be read at once, must be
- * identical to nb_bits in init_vlc()
- *
- * \param max_depth The number of times bits bits must be read to completely
- * read the longest vlc code = (max_vlc_length + bits - 1) / bits.
- */
-static inline int get_vlc(struct getbit_context *gb, VLC_TYPE(*table)[2],
- int bits, int max_depth)
-{
- int n, idx, nb_bits, code;
-
- OPEN_READER(re, gb)
- UPDATE_CACHE(re, gb)
- idx = SHOW_UBITS(re, gb, bits);
- code = table[idx][0];
- n = table[idx][1];
- if (max_depth > 1 && n < 0) {
- SKIP_COUNTER(re, gb, bits)
- UPDATE_CACHE(re, gb)
- nb_bits = -n;
- idx = SHOW_UBITS(re, gb, nb_bits) + code;
- code = table[idx][0];
- n = table[idx][1];
- if (max_depth > 2 && n < 0) {
- SKIP_COUNTER(re, gb, nb_bits)
- UPDATE_CACHE(re, gb)
- nb_bits = -n;
- idx = SHOW_UBITS(re, gb, nb_bits) + code;
- code = table[idx][0];
- n = table[idx][1];
- }
- }
- SKIP_CACHE(re, gb, n)
- SKIP_COUNTER(re, gb, n)
- CLOSE_READER(re, gb)
- return code;
-}
projects / paraslash.git / blobdiff