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Diffstat (limited to 'libavcodec/bitstream_template.h')
| -rw-r--r-- | libavcodec/bitstream_template.h | 392 |
1 files changed, 392 insertions, 0 deletions
diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h new file mode 100644 index 0000000000..14a420139c --- /dev/null +++ b/libavcodec/bitstream_template.h @@ -0,0 +1,392 @@ +/* + * Copyright (c) 2016 Alexandra Hájková + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifdef BITSTREAM_LE +# define BS_SUFFIX le +#else +# define BS_SUFFIX be +#endif + +#define BS_JOIN(x, y) x ## _ ## y +#define BS_FUNC2(x, y) BS_JOIN(x, y) +#define BS_FUNC(x) BS_FUNC2(x, BS_SUFFIX) + +static inline void BS_FUNC(refill_64)(BitstreamContext *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return; +#endif + +#ifdef BITSTREAM_LE + bc->bits = AV_RL64(bc->ptr); +#else + bc->bits = AV_RB64(bc->ptr); +#endif + bc->ptr += 8; + bc->bits_left = 64; +} + +static inline void BS_FUNC(refill_32)(BitstreamContext *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return; +#endif + +#ifdef BITSTREAM_LE + bc->bits = (uint64_t)AV_RL32(bc->ptr) << bc->bits_left | bc->bits; +#else + bc->bits = bc->bits | (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_left); +#endif + bc->ptr += 4; + bc->bits_left += 32; +} + +/** + * Initialize BitstreamContext. + * @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 bits 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 BS_FUNC(bitstream_init)(BitstreamContext *bc, const uint8_t *buffer, + unsigned int bit_size) +{ + unsigned int buffer_size; + + if (bit_size > INT_MAX - 7 || !buffer) { + bc->buffer = NULL; + bc->ptr = NULL; + bc->bits_left = 0; + return AVERROR_INVALIDDATA; + } + + buffer_size = (bit_size + 7) >> 3; + + bc->buffer = buffer; + bc->buffer_end = buffer + buffer_size; + bc->ptr = bc->buffer; + bc->size_in_bits = bit_size; + bc->bits_left = 0; + bc->bits = 0; + + BS_FUNC(refill_64)(bc); + + return 0; +} + +/** + * Initialize BitstreamContext. + * @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 bits at once and could read over the end + * @param byte_size the size of the buffer in bytes + * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow + */ +static inline int BS_FUNC(bitstream_init8)(BitstreamContext *bc, const uint8_t *buffer, + unsigned int byte_size) +{ + if (byte_size > INT_MAX / 8) + return AVERROR_INVALIDDATA; + return BS_FUNC(bitstream_init)(bc, buffer, byte_size * 8); +} + +static inline uint64_t BS_FUNC(get_val)(BitstreamContext *bc, unsigned int n) +{ + uint64_t ret; + +#ifdef BITSTREAM_LE + ret = bc->bits & ((UINT64_C(1) << n) - 1); + bc->bits >>= n; +#else + ret = bc->bits >> (64 - n); + bc->bits <<= n; +#endif + bc->bits_left -= n; + + return ret; +} + +/** + * Return one bit from the buffer. + */ +static inline unsigned int BS_FUNC(bitstream_read_bit)(BitstreamContext *bc) +{ + if (!bc->bits_left) + BS_FUNC(refill_64)(bc); + + return BS_FUNC(get_val)(bc, 1); +} + +/** + * Return n bits from the buffer, n has to be in the 0-63 range. + */ +static inline uint64_t BS_FUNC(bitstream_read_63)(BitstreamContext *bc, unsigned int n) +{ + uint64_t ret = 0; +#ifdef BITSTREAM_LE + uint64_t left = 0; +#endif + + if (!n) + return 0; + + if (n > bc->bits_left) { + n -= bc->bits_left; +#ifdef BITSTREAM_LE + left = bc->bits_left; +#endif + ret = BS_FUNC(get_val)(bc, bc->bits_left); + BS_FUNC(refill_64)(bc); + } + +#ifdef BITSTREAM_LE + ret = get_val_le(bc, n) << left | ret; +#else + ret = get_val_be(bc, n) | ret << n; +#endif + + return ret; +} + +/** + * Return n bits from the buffer, n has to be in the 0-32 range. + */ +static inline uint32_t BS_FUNC(bitstream_read)(BitstreamContext *bc, unsigned int n) +{ + if (!n) + return 0; + + if (n > bc->bits_left) { + BS_FUNC(refill_32)(bc); + if (bc->bits_left < 32) + bc->bits_left = n; + } + + return BS_FUNC(get_val)(bc, n); +} + +/** + * Return n bits from the buffer as a signed integer. + * n has to be in the 0-32 range. + */ +static inline int32_t BS_FUNC(bitstream_read_signed)(BitstreamContext *bc, unsigned int n) +{ + return sign_extend(BS_FUNC(bitstream_read)(bc, n), n); +} + +static inline unsigned int BS_FUNC(show_val)(BitstreamContext *bc, unsigned int n) +{ +#ifdef BITSTREAM_LE + return bc->bits & ((UINT64_C(1) << n) - 1); +#else + return bc->bits >> (64 - n); +#endif +} + +/** + * Return n bits from the buffer but do not change the buffer state. + * n has to be in the 0-32 range. + */ +static inline unsigned int BS_FUNC(bitstream_peek)(BitstreamContext *bc, unsigned int n) +{ + if (n > bc->bits_left) + BS_FUNC(refill_32)(bc); + + return BS_FUNC(show_val)(bc, n); +} + +/** + * Return n bits from the buffer as a signed integer, + * do not change the buffer state. + * n has to be in the 0-32 range. + */ +static inline int BS_FUNC(bitstream_peek_signed)(BitstreamContext *bc, unsigned int n) +{ + return sign_extend(BS_FUNC(bitstream_peek)(bc, n), n); +} + +static inline void BS_FUNC(skip_remaining)(BitstreamContext *bc, unsigned int n) +{ +#ifdef BITSTREAM_LE + bc->bits >>= n; +#else + bc->bits <<= n; +#endif + bc->bits_left -= n; +} + +/** + * Skip n bits in the buffer. + */ +static inline void BS_FUNC(bitstream_skip)(BitstreamContext *bc, unsigned int n) +{ + if (n < bc->bits_left) + BS_FUNC(skip_remaining)(bc, n); + else { + n -= bc->bits_left; + bc->bits = 0; + bc->bits_left = 0; + + if (n >= 64) { + unsigned int skip = n / 8; + + n -= skip * 8; + bc->ptr += skip; + } + BS_FUNC(refill_64)(bc); + if (n) + BS_FUNC(skip_remaining)(bc, n); + } +} + +/** + * Seek to the given bit position. + */ +static inline void BS_FUNC(bitstream_seek)(BitstreamContext *bc, unsigned pos) +{ + bc->ptr = bc->buffer; + bc->bits = 0; + bc->bits_left = 0; + + BS_FUNC(bitstream_skip)(bc, pos); +} + +/** + * Skip bits to a byte boundary. + */ +static inline const uint8_t *BS_FUNC(bitstream_align)(BitstreamContext *bc) +{ + unsigned int n = -bitstream_tell(bc) & 7; + if (n) + BS_FUNC(bitstream_skip)(bc, n); + return bc->buffer + (bitstream_tell(bc) >> 3); +} + +/** + * 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 BS_FUNC(bitstream_read_xbits)(BitstreamContext *bc, unsigned int n) +{ + int32_t cache = BS_FUNC(bitstream_peek)(bc, 32); + int sign = ~cache >> 31; + BS_FUNC(skip_remaining)(bc, n); + + return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign; +} + +/** + * Return decoded truncated unary code for the values 0, 1, 2. + */ +static inline int BS_FUNC(bitstream_decode012)(BitstreamContext *bc) +{ + if (!BS_FUNC(bitstream_read_bit)(bc)) + return 0; + else + return BS_FUNC(bitstream_read_bit)(bc) + 1; +} + +/** + * Return decoded truncated unary code for the values 2, 1, 0. + */ +static inline int BS_FUNC(bitstream_decode210)(BitstreamContext *bc) +{ + if (BS_FUNC(bitstream_read_bit)(bc)) + return 0; + else + return 2 - BS_FUNC(bitstream_read_bit)(bc); +} + +/* Read sign bit and flip the sign of the provided value accordingly. */ +static inline int BS_FUNC(bitstream_apply_sign)(BitstreamContext *bc, int val) +{ + int sign = BS_FUNC(bitstream_read_signed)(bc, 1); + return (val ^ sign) - sign; +} + +static inline int BS_FUNC(bitstream_skip_1stop_8data)(BitstreamContext *s) +{ + if (bitstream_bits_left(s) <= 0) + return AVERROR_INVALIDDATA; + + while (BS_FUNC(bitstream_read)(s, 1)) { + BS_FUNC(bitstream_skip)(s, 8); + if (bitstream_bits_left(s) <= 0) + return AVERROR_INVALIDDATA; + } + + return 0; +} + +/** + * Return the LUT element for the given bitstream configuration. + */ +static inline int BS_FUNC(set_idx)(BitstreamContext *bc, int code, int *n, int *nb_bits, + VLC_TYPE (*table)[2]) +{ + unsigned idx; + + *nb_bits = -*n; + idx = BS_FUNC(bitstream_peek)(bc, *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 + * 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. + */ +static inline int BS_FUNC(bitstream_read_vlc)(BitstreamContext *bc, VLC_TYPE (*table)[2], + int bits, int max_depth) +{ + int nb_bits; + unsigned idx = BS_FUNC(bitstream_peek)(bc, bits); + int code = table[idx][0]; + int n = table[idx][1]; + + if (max_depth > 1 && n < 0) { + BS_FUNC(skip_remaining)(bc, bits); + code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table); + if (max_depth > 2 && n < 0) { + BS_FUNC(skip_remaining)(bc, nb_bits); + code = BS_FUNC(set_idx)(bc, code, &n, &nb_bits, table); + } + } + BS_FUNC(skip_remaining)(bc, n); + + return code; +} + +#undef BS_FUNC +#undef BS_FUNC2 +#undef BS_JOIN +#undef BS_SUFFIX |