X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=bitstream.h;h=98937e89f2b98f126007d795f8070c0b33508598;hp=07c65389081d9b4b979c5c556dc5e1a9d4ce75f1;hb=79a88784e0819c1bbe9de8d39a0e05997c8211f6;hpb=96d3bb449fbff0bee733fb311c23247c32a13ca1 diff --git a/bitstream.h b/bitstream.h index 07c65389..98937e89 100644 --- a/bitstream.h +++ b/bitstream.h @@ -3,199 +3,96 @@ * * copyright (c) 2004 Michael Niedermayer * - * Licensed under the GNU Lesser General Public License. - * For licencing details see COPYING.LIB. + * Licensed under the GNU Lesser General Public License, see file COPYING.LIB. */ /** \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_USR32(a,s) (((uint32_t)(a))>>(32-(s))) - /** Structure for bistream I/O. */ struct getbit_context { - /* Start of the internal buffer. */ + /** Start of the internal buffer. */ const uint8_t *buffer; - /* End of the internal buffer. */ - const uint8_t *buffer_end; + /** Length of buffer in bits (always a multiple of 8). */ + uint32_t num_bits; /** Bit counter. */ int index; }; -#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. */ + int16_t (*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( ((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) +static inline uint32_t show_bits(struct getbit_context *gbc, int num) { - return s->index; + int idx = gbc->index; + const char *p; + uint32_t x; + + assert(idx + num <= gbc->num_bits); + p = (const char *)gbc->buffer + (idx >> 3); + x = read_u32_be(p); + 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); - LAST_SKIP_BITS(re, s, n) - CLOSE_READER(re, s) - return tmp; + return gbc->index; } -/** - * Show 1-17 bits. - */ -static inline unsigned int show_bits(struct getbit_context *s, int n) +static inline void skip_bits(struct getbit_context *gbc, int n) { - register int tmp; - OPEN_READER(re, s) - UPDATE_CACHE(re, s) - tmp = SHOW_UBITS(re, s, n); - return tmp; + assert(gbc->index + n <= gbc->num_bits); + gbc->index += n; } -static inline void skip_bits(struct getbit_context *s, int n) +static inline unsigned int get_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) + unsigned int ret = show_bits(gbc, n); /* checks n */ + skip_bits(gbc, n); + return ret; } -static inline unsigned int get_bits1(struct getbit_context *s) +/* 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 = s->index; - uint8_t result = s->buffer[idx >> 3]; - - result <<= (idx & 0x07); - result >>= 8 - 1; - idx++; - s->index = idx; - return result; + int idx; + uint8_t tmp, mask; + + assert(gbc->index < gbc->num_bits); + idx = gbc->index++; + 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 gbc The structure to initialize. + * \param buffer The bitstream buffer. + * \param size The size of the buffer in bytes. * - * \param bit_size The size of the buffer in bits. + * The bitstream buffer 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. */ -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->buffer_end = buffer + buffer_size; - s->index = 0; + gbc->buffer = buffer; + gbc->num_bits = size * 8; + 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); - -/** - * - * 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)\ -} +int get_vlc(struct getbit_context *gbc, const struct vlc *vlc);