From 9177970bcac0b0a12894b22586b488dd0c134e26 Mon Sep 17 00:00:00 2001 From: Anton Khirnov Date: Thu, 28 Jan 2021 13:23:23 +0100 Subject: lavc/bitstream: templatize for BE/LE Allows using both BE and LE bitstream readers in the same file. --- libavcodec/bitstream_template.h | 496 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 496 insertions(+) create mode 100644 libavcodec/bitstream_template.h (limited to 'libavcodec/bitstream_template.h') diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h new file mode 100644 index 0000000000..f2c14fc4d3 --- /dev/null +++ b/libavcodec/bitstream_template.h @@ -0,0 +1,496 @@ +/* + * 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_TEMPLATE_LE +# define BS_SUFFIX_LOWER _le +# define BS_SUFFIX_UPPER LE +#else +# define BS_SUFFIX_LOWER _be +# define BS_SUFFIX_UPPER BE +#endif + +#define BS_JOIN(x, y, z) x ## y ## z +#define BS_JOIN3(x, y, z) BS_JOIN(x, y, z) +#define BS_FUNC(x) BS_JOIN3(bits_, x, BS_SUFFIX_LOWER) + +#define BSCTX BS_JOIN3(Bitstream, Context, BS_SUFFIX_UPPER) + +typedef struct BSCTX { + uint64_t bits; // stores bits read from the buffer + const uint8_t *buffer, *buffer_end; + const uint8_t *ptr; // pointer to the position inside a buffer + unsigned bits_valid; // number of bits left in bits field + unsigned size_in_bits; +} BSCTX; + +/** + * @return + * - 0 on successful refill + * - a negative number when bitstream end is hit + * + * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. + */ +static inline int BS_FUNC(priv_refill_64)(BSCTX *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return -1; +#endif + +#ifdef BITSTREAM_TEMPLATE_LE + bc->bits = AV_RL64(bc->ptr); +#else + bc->bits = AV_RB64(bc->ptr); +#endif + bc->ptr += 8; + bc->bits_valid = 64; + + return 0; +} + +/** + * @return + * - 0 on successful refill + * - a negative number when bitstream end is hit + * + * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. + */ +static inline int BS_FUNC(priv_refill_32)(BSCTX *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return -1; +#endif + +#ifdef BITSTREAM_TEMPLATE_LE + bc->bits |= (uint64_t)AV_RL32(bc->ptr) << bc->bits_valid; +#else + bc->bits |= (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_valid); +#endif + bc->ptr += 4; + bc->bits_valid += 32; + + 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 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(init)(BSCTX *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_valid = 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_valid = 0; + bc->bits = 0; + + BS_FUNC(priv_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(init8)(BSCTX *bc, const uint8_t *buffer, + unsigned int byte_size) +{ + if (byte_size > INT_MAX / 8) + return AVERROR_INVALIDDATA; + return BS_FUNC(init)(bc, buffer, byte_size * 8); +} + +/** + * Return number of bits already read. + */ +static inline int BS_FUNC(tell)(const BSCTX *bc) +{ + return (bc->ptr - bc->buffer) * 8 - bc->bits_valid; +} + +/** + * Return buffer size in bits. + */ +static inline int BS_FUNC(size)(const BSCTX *bc) +{ + return bc->size_in_bits; +} + +/** + * Return the number of the bits left in a buffer. + */ +static inline int BS_FUNC(left)(const BSCTX *bc) +{ + return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_valid; +} + +static inline uint64_t BS_FUNC(priv_val_show)(BSCTX *bc, unsigned int n) +{ + av_assert2(n > 0 && n <= 64); + +#ifdef BITSTREAM_TEMPLATE_LE + return bc->bits & (UINT64_MAX >> (64 - n)); +#else + return bc->bits >> (64 - n); +#endif +} + +static inline void BS_FUNC(priv_skip_remaining)(BSCTX *bc, unsigned int n) +{ +#ifdef BITSTREAM_TEMPLATE_LE + bc->bits >>= n; +#else + bc->bits <<= n; +#endif + bc->bits_valid -= n; +} + +static inline uint64_t BS_FUNC(priv_val_get)(BSCTX *bc, unsigned int n) +{ + uint64_t ret; + + av_assert2(n > 0 && n < 64); + + ret = BS_FUNC(priv_val_show)(bc, n); + BS_FUNC(priv_skip_remaining)(bc, n); + + return ret; +} + +/** + * Return one bit from the buffer. + */ +static inline unsigned int BS_FUNC(read_bit)(BSCTX *bc) +{ + if (!bc->bits_valid && BS_FUNC(priv_refill_64)(bc) < 0) + return 0; + + return BS_FUNC(priv_val_get)(bc, 1); +} + +/** + * Return n bits from the buffer, n has to be in the 1-32 range. + * May be faster than bits_read() when n is not a compile-time constant and is + * known to be non-zero; + */ +static inline uint32_t BS_FUNC(read_nz)(BSCTX *bc, unsigned int n) +{ + av_assert2(n > 0 && n <= 32); + + if (n > bc->bits_valid) { + if (BS_FUNC(priv_refill_32)(bc) < 0) + bc->bits_valid = n; + } + + return BS_FUNC(priv_val_get)(bc, n); +} + +/** + * Return n bits from the buffer, n has to be in the 0-32 range. + */ +static inline uint32_t BS_FUNC(read)(BSCTX *bc, unsigned int n) +{ + av_assert2(n <= 32); + + if (!n) + return 0; + + return BS_FUNC(read_nz)(bc, n); +} + +/** + * Return n bits from the buffer, n has to be in the 0-63 range. + */ +static inline uint64_t BS_FUNC(read_63)(BSCTX *bc, unsigned int n) +{ + uint64_t ret = 0; + unsigned left = 0; + + av_assert2(n <= 63); + + if (!n) + return 0; + + if (n > bc->bits_valid) { + left = bc->bits_valid; + n -= left; + + if (left) + ret = BS_FUNC(priv_val_get)(bc, left); + + if (BS_FUNC(priv_refill_64)(bc) < 0) + bc->bits_valid = n; + + } + +#ifdef BITSTREAM_TEMPLATE_LE + ret = BS_FUNC(priv_val_get)(bc, n) << left | ret; +#else + ret = BS_FUNC(priv_val_get)(bc, n) | ret << n; +#endif + + return ret; +} + +/** + * Return n bits from the buffer, n has to be in the 0-64 range. + */ +static inline uint64_t BS_FUNC(read_64)(BSCTX *bc, unsigned int n) +{ + av_assert2(n <= 64); + + if (n == 64) { + uint64_t ret = BS_FUNC(read_63)(bc, 63); +#ifdef BITSTREAM_TEMPLATE_LE + return ret | ((uint64_t)BS_FUNC(read_bit)(bc) << 63); +#else + return (ret << 1) | (uint64_t)BS_FUNC(read_bit)(bc); +#endif + } + return BS_FUNC(read_63)(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(read_signed)(BSCTX *bc, unsigned int n) +{ + return sign_extend(BS_FUNC(read)(bc, n), n); +} + +/** + * Return n bits from the buffer but do not change the buffer state. + * n has to be in the 1-32 range. May + */ +static inline uint32_t BS_FUNC(peek_nz)(BSCTX *bc, unsigned int n) +{ + av_assert2(n > 0 && n <= 32); + + if (n > bc->bits_valid) + BS_FUNC(priv_refill_32)(bc); + + return BS_FUNC(priv_val_show)(bc, n); +} + +/** + * Return n bits from the buffer but do not change the buffer state. + * n has to be in the 0-32 range. + */ +static inline uint32_t BS_FUNC(peek)(BSCTX *bc, unsigned int n) +{ + av_assert2(n <= 32); + + if (!n) + return 0; + + return BS_FUNC(peek_nz)(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(peek_signed)(BSCTX *bc, unsigned int n) +{ + return sign_extend(BS_FUNC(peek)(bc, n), n); +} + +/** + * Skip n bits in the buffer. + */ +static inline void BS_FUNC(skip)(BSCTX *bc, unsigned int n) +{ + if (n < bc->bits_valid) + BS_FUNC(priv_skip_remaining)(bc, n); + else { + n -= bc->bits_valid; + bc->bits = 0; + bc->bits_valid = 0; + + if (n >= 64) { + unsigned int skip = n / 8; + + n -= skip * 8; + bc->ptr += skip; + } + BS_FUNC(priv_refill_64)(bc); + if (n) + BS_FUNC(priv_skip_remaining)(bc, n); + } +} + +/** + * Seek to the given bit position. + */ +static inline void BS_FUNC(seek)(BSCTX *bc, unsigned pos) +{ + bc->ptr = bc->buffer; + bc->bits = 0; + bc->bits_valid = 0; + + BS_FUNC(skip)(bc, pos); +} + +/** + * Skip bits to a byte boundary. + */ +static inline const uint8_t *BS_FUNC(align)(BSCTX *bc) +{ + unsigned int n = -BS_FUNC(tell)(bc) & 7; + if (n) + BS_FUNC(skip)(bc, n); + return bc->buffer + (BS_FUNC(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(read_xbits)(BSCTX *bc, unsigned int n) +{ + int32_t cache = BS_FUNC(peek)(bc, 32); + int sign = ~cache >> 31; + BS_FUNC(priv_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(decode012)(BSCTX *bc) +{ + if (!BS_FUNC(read_bit)(bc)) + return 0; + else + return BS_FUNC(read_bit)(bc) + 1; +} + +/** + * Return decoded truncated unary code for the values 2, 1, 0. + */ +static inline int BS_FUNC(decode210)(BSCTX *bc) +{ + if (BS_FUNC(read_bit)(bc)) + return 0; + else + return 2 - BS_FUNC(read_bit)(bc); +} + +/* Read sign bit and flip the sign of the provided value accordingly. */ +static inline int BS_FUNC(apply_sign)(BSCTX *bc, int val) +{ + int sign = BS_FUNC(read_signed)(bc, 1); + return (val ^ sign) - sign; +} + +static inline int BS_FUNC(skip_1stop_8data)(BSCTX *s) +{ + if (BS_FUNC(left)(s) <= 0) + return AVERROR_INVALIDDATA; + + while (BS_FUNC(read_bit)(s)) { + BS_FUNC(skip)(s, 8); + if (BS_FUNC(left)(s) <= 0) + return AVERROR_INVALIDDATA; + } + + return 0; +} + +/** + * Return the LUT element for the given bitstream configuration. + */ +static inline int BS_FUNC(priv_set_idx)(BSCTX *bc, int code, int *n, + int *nb_bits, const VLCElem *table) +{ + unsigned idx; + + *nb_bits = -*n; + idx = BS_FUNC(peek)(bc, *nb_bits) + code; + *n = table[idx].len; + + return table[idx].sym; +} + +/** + * 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(read_vlc)(BSCTX *bc, const VLCElem *table, + int bits, int max_depth) +{ + int nb_bits; + unsigned idx = BS_FUNC(peek)(bc, bits); + int code = table[idx].sym; + int n = table[idx].len; + + if (max_depth > 1 && n < 0) { + BS_FUNC(priv_skip_remaining)(bc, bits); + code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table); + if (max_depth > 2 && n < 0) { + BS_FUNC(priv_skip_remaining)(bc, nb_bits); + code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table); + } + } + BS_FUNC(priv_skip_remaining)(bc, n); + + return code; +} + +#undef BSCTX +#undef BS_FUNC +#undef BS_JOIN3 +#undef BS_JOIN +#undef BS_SUFFIX_UPPER +#undef BS_SUFFIX_LOWER -- cgit v1.2.1