| #ifndef AVCODEC_GET_BITS_H |
| #define AVCODEC_GET_BITS_H |
| |
| #include <linux/kernel.h> |
| #include <linux/types.h> |
| #include "common.h" |
| |
| /* |
| * 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". |
| */ |
| |
| struct get_bits_context { |
| const u8 *buffer; |
| const u8 *buffer_end; |
| int index; |
| int size_in_bits; |
| int size_in_bits_plus8; |
| }; |
| |
| /* Bitstream reader API docs: |
| * name |
| * arbitrary name which is used as prefix for the internal variables |
| * |
| * gb |
| * struct get_bits_context |
| * |
| * OPEN_READER(name, gb) |
| * load gb into local variables |
| * |
| * CLOSE_READER(name, gb) |
| * store local vars in gb |
| * |
| * UPDATE_CACHE(name, gb) |
| * Refill the internal cache from the bitstream. |
| * After this call at least MIN_CACHE_BITS will be available. |
| * |
| * GET_CACHE(name, gb) |
| * Will output the contents of the internal cache, |
| * next bit is MSB of 32 or 64 bits (FIXME 64 bits). |
| * |
| * SHOW_UBITS(name, gb, num) |
| * Will return the next num bits. |
| * |
| * SHOW_SBITS(name, gb, num) |
| * Will return the next num bits and do sign extension. |
| * |
| * SKIP_BITS(name, gb, num) |
| * Will skip over the next num bits. |
| * Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER. |
| * |
| * SKIP_CACHE(name, gb, num) |
| * Will remove the next num bits from the cache (note SKIP_COUNTER |
| * MUST be called before UPDATE_CACHE / CLOSE_READER). |
| * |
| * SKIP_COUNTER(name, gb, num) |
| * Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS). |
| * |
| * LAST_SKIP_BITS(name, gb, num) |
| * Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER. |
| * |
| * BITS_LEFT(name, gb) |
| * Return the number of bits left |
| * |
| * For examples see get_bits, show_bits, skip_bits, get_vlc. |
| */ |
| |
| #define OPEN_READER_NOSIZE(name, gb) \ |
| u32 name ## _index = (gb)->index; \ |
| u32 name ## _cache |
| |
| #define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb) |
| #define BITS_AVAILABLE(name, gb) 1 |
| |
| #define CLOSE_READER(name, gb) (gb)->index = name ## _index |
| |
| #define UPDATE_CACHE_LE(name, gb) name ##_cache = \ |
| AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7) |
| |
| #define UPDATE_CACHE_BE(name, gb) name ## _cache = \ |
| AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7) |
| |
| #define SKIP_COUNTER(name, gb, num) name ## _index += (num) |
| |
| #define BITS_LEFT(name, gb) ((int)((gb)->size_in_bits - name ## _index)) |
| |
| #define SKIP_BITS(name, gb, num) \ |
| do { \ |
| SKIP_CACHE(name, gb, num); \ |
| SKIP_COUNTER(name, gb, num); \ |
| } while (0) |
| |
| #define GET_CACHE(name, gb) ((u32) name ## _cache) |
| |
| #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num) |
| |
| #define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num) |
| #define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num) |
| |
| #define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num) |
| #define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num) |
| |
| #ifdef BITSTREAM_READER_LE |
| #define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb) |
| #define SKIP_CACHE(name, gb, num) name ## _cache >>= (num) |
| |
| #define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num) |
| #define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num) |
| #else |
| #define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb) |
| #define SKIP_CACHE(name, gb, num) name ## _cache <<= (num) |
| |
| #define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num) |
| #define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num) |
| #endif |
| |
| static inline const int sign_extend(int val, u32 bits) |
| { |
| u32 shift = 8 * sizeof(int) - bits; |
| |
| union { u32 u; int s; } v = { (u32) val << shift }; |
| return v.s >> shift; |
| } |
| |
| static inline u32 zero_extend(u32 val, u32 bits) |
| { |
| return (val << ((8 * sizeof(int)) - bits)) >> ((8 * sizeof(int)) - bits); |
| } |
| |
| static inline int get_bits_count(const struct get_bits_context *s) |
| { |
| return s->index; |
| } |
| |
| /** |
| * Skips the specified number of bits. |
| * @param n the number of bits to skip, |
| * For the UNCHECKED_BITSTREAM_READER this must not cause the distance |
| * from the start to overflow int. Staying within the bitstream + padding |
| * is sufficient, too. |
| */ |
| static inline void skip_bits_long(struct get_bits_context *s, int n) |
| { |
| s->index += n; |
| } |
| |
| /** |
| * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB). |
| * if MSB not set it is negative |
| * @param n length in bits |
| */ |
| static inline int get_xbits(struct get_bits_context *s, int n) |
| { |
| register int sign; |
| register int cache; |
| |
| OPEN_READER(re, s); |
| UPDATE_CACHE(re, s); |
| cache = GET_CACHE(re, s); |
| sign = ~cache >> 31; |
| LAST_SKIP_BITS(re, s, n); |
| CLOSE_READER(re, s); |
| |
| return (NEG_USR32(sign ^ cache, n) ^ sign) - sign; |
| } |
| |
| |
| static inline int get_xbits_le(struct get_bits_context *s, int n) |
| { |
| register int sign; |
| register int cache; |
| |
| OPEN_READER(re, s); |
| UPDATE_CACHE_LE(re, s); |
| cache = GET_CACHE(re, s); |
| sign = sign_extend(~cache, n) >> 31; |
| LAST_SKIP_BITS(re, s, n); |
| CLOSE_READER(re, s); |
| |
| return (zero_extend(sign ^ cache, n) ^ sign) - sign; |
| } |
| |
| static inline int get_sbits(struct get_bits_context *s, int n) |
| { |
| register int tmp; |
| |
| OPEN_READER(re, s); |
| UPDATE_CACHE(re, s); |
| tmp = SHOW_SBITS(re, s, n); |
| LAST_SKIP_BITS(re, s, n); |
| CLOSE_READER(re, s); |
| |
| return tmp; |
| } |
| |
| /** |
| * Read 1-25 bits. |
| */ |
| static inline u32 get_bits(struct get_bits_context *s, int n) |
| { |
| register u32 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; |
| } |
| |
| /** |
| * Read 0-25 bits. |
| */ |
| static inline int get_bitsz(struct get_bits_context *s, int n) |
| { |
| return n ? get_bits(s, n) : 0; |
| } |
| |
| static inline u32 get_bits_le(struct get_bits_context *s, int n) |
| { |
| register int tmp; |
| |
| OPEN_READER(re, s); |
| UPDATE_CACHE_LE(re, s); |
| tmp = SHOW_UBITS_LE(re, s, n); |
| LAST_SKIP_BITS(re, s, n); |
| CLOSE_READER(re, s); |
| |
| return tmp; |
| } |
| |
| /** |
| * Show 1-25 bits. |
| */ |
| static inline u32 show_bits(struct get_bits_context *s, int n) |
| { |
| register u32 tmp; |
| |
| OPEN_READER_NOSIZE(re, s); |
| UPDATE_CACHE(re, s); |
| tmp = SHOW_UBITS(re, s, n); |
| |
| return tmp; |
| } |
| |
| static inline void skip_bits(struct get_bits_context *s, int n) |
| { |
| u32 re_index = s->index; |
| LAST_SKIP_BITS(re, s, n); |
| CLOSE_READER(re, s); |
| } |
| |
| static inline u32 get_bits1(struct get_bits_context *s) |
| { |
| u32 index = s->index; |
| u8 result = s->buffer[index >> 3]; |
| |
| #ifdef BITSTREAM_READER_LE |
| result >>= index & 7; |
| result &= 1; |
| #else |
| result <<= index & 7; |
| result >>= 8 - 1; |
| #endif |
| |
| index++; |
| s->index = index; |
| |
| return result; |
| } |
| |
| static inline u32 show_bits1(struct get_bits_context *s) |
| { |
| return show_bits(s, 1); |
| } |
| |
| static inline void skip_bits1(struct get_bits_context *s) |
| { |
| skip_bits(s, 1); |
| } |
| |
| /** |
| * Read 0-32 bits. |
| */ |
| static inline u32 get_bits_long(struct get_bits_context *s, int n) |
| { |
| if (!n) { |
| return 0; |
| } else if (n <= MIN_CACHE_BITS) { |
| return get_bits(s, n); |
| } else { |
| #ifdef BITSTREAM_READER_LE |
| u32 ret = get_bits(s, 16); |
| return ret | (get_bits(s, n - 16) << 16); |
| #else |
| u32 ret = get_bits(s, 16) << (n - 16); |
| return ret | get_bits(s, n - 16); |
| #endif |
| } |
| } |
| |
| /** |
| * Read 0-64 bits. |
| */ |
| static inline u64 get_bits64(struct get_bits_context *s, int n) |
| { |
| if (n <= 32) { |
| return get_bits_long(s, n); |
| } else { |
| #ifdef BITSTREAM_READER_LE |
| u64 ret = get_bits_long(s, 32); |
| return ret | (u64) get_bits_long(s, n - 32) << 32; |
| #else |
| u64 ret = (u64) get_bits_long(s, n - 32) << 32; |
| return ret | get_bits_long(s, 32); |
| #endif |
| } |
| } |
| |
| /** |
| * Read 0-32 bits as a signed integer. |
| */ |
| static inline int get_sbits_long(struct get_bits_context *s, int n) |
| { |
| if (!n) |
| return 0; |
| |
| return sign_extend(get_bits_long(s, n), n); |
| } |
| |
| /** |
| * Show 0-32 bits. |
| */ |
| static inline u32 show_bits_long(struct get_bits_context *s, int n) |
| { |
| if (n <= MIN_CACHE_BITS) { |
| return show_bits(s, n); |
| } else { |
| struct get_bits_context gb = *s; |
| |
| return get_bits_long(&gb, n); |
| } |
| } |
| |
| static inline int check_marker(struct get_bits_context *s, const char *msg) |
| { |
| int bit = get_bits1(s); |
| |
| if (!bit) |
| pr_err("Marker bit missing at %d of %d %s\n", |
| get_bits_count(s) - 1, s->size_in_bits, msg); |
| return bit; |
| } |
| |
| static inline int init_get_bits_xe(struct get_bits_context *s, |
| const u8 *buffer, int bit_size, int is_le) |
| { |
| int buffer_size; |
| int ret = 0; |
| |
| if (bit_size >= INT_MAX - FFMAX(7, AV_INPUT_BUFFER_PADDING_SIZE * 8) || |
| bit_size < 0 || !buffer) { |
| bit_size = 0; |
| buffer = NULL; |
| ret = -1; |
| } |
| |
| buffer_size = (bit_size + 7) >> 3; |
| |
| 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; |
| |
| return ret; |
| } |
| |
| /** |
| * Initialize struct get_bits_context. |
| * @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, -1 if the buffer_size would overflow. |
| */ |
| static inline int init_get_bits(struct get_bits_context *s, |
| const u8 *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 struct get_bits_context. |
| * @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 byte_size the size of the buffer in bytes |
| * @return 0 on success, -1 if the buffer_size would overflow. |
| */ |
| static inline int init_get_bits8(struct get_bits_context *s, |
| const u8 *buffer, int byte_size) |
| { |
| if (byte_size > INT_MAX / 8 || byte_size < 0) |
| byte_size = -1; |
| return init_get_bits(s, buffer, byte_size * 8); |
| } |
| |
| static inline int init_get_bits8_le(struct get_bits_context *s, |
| const u8 *buffer, int byte_size) |
| { |
| if (byte_size > INT_MAX / 8 || byte_size < 0) |
| byte_size = -1; |
| return init_get_bits_xe(s, buffer, byte_size * 8, 1); |
| } |
| |
| static inline const u8 *align_get_bits(struct get_bits_context *s) |
| { |
| int n = -get_bits_count(s) & 7; |
| |
| if (n) |
| skip_bits(s, n); |
| return s->buffer + (s->index >> 3); |
| } |
| |
| /** |
| * If the vlc code is invalid and max_depth=1, then no bits will be removed. |
| * 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 { \ |
| int n, nb_bits; \ |
| u32 index; \ |
| \ |
| 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); \ |
| } while (0) |
| |
| #define GET_RL_VLC(level, run, name, gb, table, bits, \ |
| max_depth, need_update) \ |
| do { \ |
| int n, nb_bits; \ |
| u32 index; \ |
| \ |
| index = SHOW_UBITS(name, gb, bits); \ |
| level = table[index].level; \ |
| n = table[index].len; \ |
| \ |
| if (max_depth > 1 && n < 0) { \ |
| SKIP_BITS(name, gb, bits); \ |
| if (need_update) { \ |
| UPDATE_CACHE(name, gb); \ |
| } \ |
| \ |
| nb_bits = -n; \ |
| \ |
| index = SHOW_UBITS(name, gb, nb_bits) + level; \ |
| level = table[index].level; \ |
| n = table[index].len; \ |
| if (max_depth > 2 && n < 0) { \ |
| LAST_SKIP_BITS(name, gb, nb_bits); \ |
| if (need_update) { \ |
| UPDATE_CACHE(name, gb); \ |
| } \ |
| nb_bits = -n; \ |
| \ |
| index = SHOW_UBITS(name, gb, nb_bits) + level; \ |
| level = table[index].level; \ |
| n = table[index].len; \ |
| } \ |
| } \ |
| run = table[index].run; \ |
| SKIP_BITS(name, gb, n); \ |
| } while (0) |
| |
| /* Return the LUT element for the given bitstream configuration. */ |
| static inline int set_idx(struct get_bits_context *s, |
| int code, int *n, int *nb_bits, int (*table)[2]) |
| { |
| u32 idx; |
| |
| *nb_bits = -*n; |
| idx = show_bits(s, *nb_bits) + code; |
| *n = table[idx][1]; |
| |
| return table[idx][0]; |
| } |
| |
| /** |
| * 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 |
| * read the longest vlc code |
| * = (max_vlc_length + bits - 1) / bits |
| * @returns the code parsed or -1 if no vlc matches |
| */ |
| static inline int get_vlc2(struct get_bits_context *s, |
| int (*table)[2], int bits, int max_depth) |
| { |
| int code; |
| |
| OPEN_READER(re, s); |
| UPDATE_CACHE(re, s); |
| |
| GET_VLC(code, re, s, table, bits, max_depth); |
| |
| CLOSE_READER(re, s); |
| |
| return code; |
| } |
| |
| static inline int decode012(struct get_bits_context *gb) |
| { |
| int n; |
| |
| n = get_bits1(gb); |
| if (n == 0) |
| return 0; |
| else |
| return get_bits1(gb) + 1; |
| } |
| |
| static inline int decode210(struct get_bits_context *gb) |
| { |
| if (get_bits1(gb)) |
| return 0; |
| else |
| return 2 - get_bits1(gb); |
| } |
| |
| static inline int get_bits_left(struct get_bits_context *gb) |
| { |
| return gb->size_in_bits - get_bits_count(gb); |
| } |
| |
| static inline int skip_1stop_8data_bits(struct get_bits_context *gb) |
| { |
| if (get_bits_left(gb) <= 0) |
| return -1; |
| |
| while (get_bits1(gb)) { |
| skip_bits(gb, 8); |
| if (get_bits_left(gb) <= 0) |
| return -1; |
| } |
| |
| return 0; |
| } |
| |
| #endif /* AVCODEC_GET_BITS_H */ |
| |