0b33310cd0
bits_*_signed(0) will currently invoke an undefined shift by 8 * sizeof(int). Add bits_*_signed_nz() that only works for n>0, analogous to bits_read_nz(). Add an explicit check for n=0 in bits_*_signed(). Found-by: James Almer
529 lines
13 KiB
C
529 lines
13 KiB
C
/*
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* Copyright (c) 2016 Alexandra Hájková
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifdef BITSTREAM_TEMPLATE_LE
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# define BS_SUFFIX_LOWER _le
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# define BS_SUFFIX_UPPER LE
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#else
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# define BS_SUFFIX_LOWER _be
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# define BS_SUFFIX_UPPER BE
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#endif
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#define BS_JOIN(x, y, z) x ## y ## z
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#define BS_JOIN3(x, y, z) BS_JOIN(x, y, z)
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#define BS_FUNC(x) BS_JOIN3(bits_, x, BS_SUFFIX_LOWER)
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#define BSCTX BS_JOIN3(Bitstream, Context, BS_SUFFIX_UPPER)
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typedef struct BSCTX {
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uint64_t bits; // stores bits read from the buffer
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const uint8_t *buffer, *buffer_end;
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const uint8_t *ptr; // pointer to the position inside a buffer
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unsigned bits_valid; // number of bits left in bits field
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unsigned size_in_bits;
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} BSCTX;
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/**
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* @return
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* - 0 on successful refill
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* - a negative number when bitstream end is hit
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*
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* Always succeeds when UNCHECKED_BITSTREAM_READER is enabled.
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*/
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static inline int BS_FUNC(priv_refill_64)(BSCTX *bc)
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{
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#if !UNCHECKED_BITSTREAM_READER
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if (bc->ptr >= bc->buffer_end)
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return -1;
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#endif
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#ifdef BITSTREAM_TEMPLATE_LE
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bc->bits = AV_RL64(bc->ptr);
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#else
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bc->bits = AV_RB64(bc->ptr);
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#endif
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bc->ptr += 8;
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bc->bits_valid = 64;
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return 0;
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}
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/**
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* @return
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* - 0 on successful refill
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* - a negative number when bitstream end is hit
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*
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* Always succeeds when UNCHECKED_BITSTREAM_READER is enabled.
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*/
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static inline int BS_FUNC(priv_refill_32)(BSCTX *bc)
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{
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#if !UNCHECKED_BITSTREAM_READER
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if (bc->ptr >= bc->buffer_end)
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return -1;
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#endif
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#ifdef BITSTREAM_TEMPLATE_LE
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bc->bits |= (uint64_t)AV_RL32(bc->ptr) << bc->bits_valid;
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#else
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bc->bits |= (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_valid);
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#endif
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bc->ptr += 4;
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bc->bits_valid += 32;
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return 0;
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}
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/**
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* Initialize BitstreamContext.
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
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* larger than the actual read bits because some optimized bitstream
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* readers read 32 or 64 bits at once and could read over the end
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* @param bit_size the size of the buffer in bits
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
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*/
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static inline int BS_FUNC(init)(BSCTX *bc, const uint8_t *buffer,
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unsigned int bit_size)
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{
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unsigned int buffer_size;
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if (bit_size > INT_MAX - 7 || !buffer) {
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bc->buffer = NULL;
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bc->ptr = NULL;
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bc->bits_valid = 0;
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return AVERROR_INVALIDDATA;
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}
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buffer_size = (bit_size + 7) >> 3;
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bc->buffer = buffer;
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bc->buffer_end = buffer + buffer_size;
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bc->ptr = bc->buffer;
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bc->size_in_bits = bit_size;
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bc->bits_valid = 0;
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bc->bits = 0;
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BS_FUNC(priv_refill_64)(bc);
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return 0;
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}
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/**
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* Initialize BitstreamContext.
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
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* larger than the actual read bits because some optimized bitstream
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* readers read 32 or 64 bits at once and could read over the end
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* @param byte_size the size of the buffer in bytes
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow
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*/
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static inline int BS_FUNC(init8)(BSCTX *bc, const uint8_t *buffer,
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unsigned int byte_size)
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{
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if (byte_size > INT_MAX / 8)
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return AVERROR_INVALIDDATA;
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return BS_FUNC(init)(bc, buffer, byte_size * 8);
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}
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/**
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* Return number of bits already read.
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*/
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static inline int BS_FUNC(tell)(const BSCTX *bc)
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{
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return (bc->ptr - bc->buffer) * 8 - bc->bits_valid;
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}
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/**
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* Return buffer size in bits.
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*/
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static inline int BS_FUNC(size)(const BSCTX *bc)
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{
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return bc->size_in_bits;
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}
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/**
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* Return the number of the bits left in a buffer.
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*/
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static inline int BS_FUNC(left)(const BSCTX *bc)
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{
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return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_valid;
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}
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static inline uint64_t BS_FUNC(priv_val_show)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n > 0 && n <= 64);
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#ifdef BITSTREAM_TEMPLATE_LE
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return bc->bits & (UINT64_MAX >> (64 - n));
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#else
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return bc->bits >> (64 - n);
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#endif
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}
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static inline void BS_FUNC(priv_skip_remaining)(BSCTX *bc, unsigned int n)
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{
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#ifdef BITSTREAM_TEMPLATE_LE
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bc->bits >>= n;
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#else
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bc->bits <<= n;
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#endif
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bc->bits_valid -= n;
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}
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static inline uint64_t BS_FUNC(priv_val_get)(BSCTX *bc, unsigned int n)
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{
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uint64_t ret;
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av_assert2(n > 0 && n < 64);
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ret = BS_FUNC(priv_val_show)(bc, n);
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BS_FUNC(priv_skip_remaining)(bc, n);
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return ret;
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}
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/**
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* Return one bit from the buffer.
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*/
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static inline unsigned int BS_FUNC(read_bit)(BSCTX *bc)
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{
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if (!bc->bits_valid && BS_FUNC(priv_refill_64)(bc) < 0)
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return 0;
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return BS_FUNC(priv_val_get)(bc, 1);
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}
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/**
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* Return n bits from the buffer, n has to be in the 1-32 range.
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* May be faster than bits_read() when n is not a compile-time constant and is
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* known to be non-zero;
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*/
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static inline uint32_t BS_FUNC(read_nz)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n > 0 && n <= 32);
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if (n > bc->bits_valid) {
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if (BS_FUNC(priv_refill_32)(bc) < 0)
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bc->bits_valid = n;
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}
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return BS_FUNC(priv_val_get)(bc, n);
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}
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/**
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* Return n bits from the buffer, n has to be in the 0-32 range.
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*/
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static inline uint32_t BS_FUNC(read)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n <= 32);
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if (!n)
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return 0;
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return BS_FUNC(read_nz)(bc, n);
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}
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/**
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* Return n bits from the buffer, n has to be in the 0-63 range.
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*/
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static inline uint64_t BS_FUNC(read_63)(BSCTX *bc, unsigned int n)
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{
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uint64_t ret = 0;
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unsigned left = 0;
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av_assert2(n <= 63);
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if (!n)
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return 0;
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if (n > bc->bits_valid) {
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left = bc->bits_valid;
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n -= left;
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if (left)
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ret = BS_FUNC(priv_val_get)(bc, left);
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if (BS_FUNC(priv_refill_64)(bc) < 0)
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bc->bits_valid = n;
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}
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#ifdef BITSTREAM_TEMPLATE_LE
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ret = BS_FUNC(priv_val_get)(bc, n) << left | ret;
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#else
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ret = BS_FUNC(priv_val_get)(bc, n) | ret << n;
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#endif
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return ret;
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}
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/**
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* Return n bits from the buffer, n has to be in the 0-64 range.
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*/
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static inline uint64_t BS_FUNC(read_64)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n <= 64);
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if (n == 64) {
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uint64_t ret = BS_FUNC(read_63)(bc, 63);
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#ifdef BITSTREAM_TEMPLATE_LE
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return ret | ((uint64_t)BS_FUNC(read_bit)(bc) << 63);
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#else
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return (ret << 1) | (uint64_t)BS_FUNC(read_bit)(bc);
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#endif
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}
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return BS_FUNC(read_63)(bc, n);
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}
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/**
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* Return n bits from the buffer as a signed integer, n has to be in the 1-32
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* range. May be faster than bits_read_signed() when n is not a compile-time
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* constant and is known to be non-zero;
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*/
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static inline int32_t BS_FUNC(read_signed_nz)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n > 0 && n <= 32);
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return sign_extend(BS_FUNC(read_nz)(bc, n), n);
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}
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/**
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* Return n bits from the buffer as a signed integer.
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* n has to be in the 0-32 range.
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*/
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static inline int32_t BS_FUNC(read_signed)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n <= 32);
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if (!n)
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return 0;
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return BS_FUNC(read_signed_nz)(bc, n);
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}
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/**
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* Return n bits from the buffer but do not change the buffer state.
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* n has to be in the 1-32 range. May
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*/
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static inline uint32_t BS_FUNC(peek_nz)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n > 0 && n <= 32);
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if (n > bc->bits_valid)
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BS_FUNC(priv_refill_32)(bc);
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return BS_FUNC(priv_val_show)(bc, n);
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}
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/**
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* Return n bits from the buffer but do not change the buffer state.
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* n has to be in the 0-32 range.
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*/
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static inline uint32_t BS_FUNC(peek)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n <= 32);
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if (!n)
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return 0;
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return BS_FUNC(peek_nz)(bc, n);
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}
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/**
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* Return n bits from the buffer as a signed integer, do not change the buffer
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* state. n has to be in the 1-32 range. May be faster than bits_peek_signed()
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* when n is not a compile-time constant and is known to be non-zero;
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*/
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static inline int BS_FUNC(peek_signed_nz)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n > 0 && n <= 32);
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return sign_extend(BS_FUNC(peek_nz)(bc, n), n);
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}
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/**
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* Return n bits from the buffer as a signed integer,
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* do not change the buffer state.
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* n has to be in the 0-32 range.
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*/
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static inline int BS_FUNC(peek_signed)(BSCTX *bc, unsigned int n)
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{
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av_assert2(n <= 32);
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if (!n)
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return 0;
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return BS_FUNC(peek_signed_nz)(bc, n);
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}
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/**
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* Skip n bits in the buffer.
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*/
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static inline void BS_FUNC(skip)(BSCTX *bc, unsigned int n)
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{
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if (n < bc->bits_valid)
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BS_FUNC(priv_skip_remaining)(bc, n);
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else {
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n -= bc->bits_valid;
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bc->bits = 0;
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bc->bits_valid = 0;
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if (n >= 64) {
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unsigned int skip = n / 8;
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n -= skip * 8;
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bc->ptr += skip;
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}
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BS_FUNC(priv_refill_64)(bc);
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if (n)
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BS_FUNC(priv_skip_remaining)(bc, n);
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}
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}
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/**
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* Seek to the given bit position.
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*/
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static inline void BS_FUNC(seek)(BSCTX *bc, unsigned pos)
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{
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bc->ptr = bc->buffer;
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bc->bits = 0;
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bc->bits_valid = 0;
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BS_FUNC(skip)(bc, pos);
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}
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/**
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* Skip bits to a byte boundary.
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*/
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static inline const uint8_t *BS_FUNC(align)(BSCTX *bc)
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{
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unsigned int n = -BS_FUNC(tell)(bc) & 7;
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if (n)
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BS_FUNC(skip)(bc, n);
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return bc->buffer + (BS_FUNC(tell)(bc) >> 3);
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}
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/**
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* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
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* If MSB not set it is negative.
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* @param n length in bits
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*/
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static inline int BS_FUNC(read_xbits)(BSCTX *bc, unsigned int n)
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{
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int32_t cache = BS_FUNC(peek)(bc, 32);
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int sign = ~cache >> 31;
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BS_FUNC(priv_skip_remaining)(bc, n);
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return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
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}
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/**
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* Return decoded truncated unary code for the values 0, 1, 2.
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*/
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static inline int BS_FUNC(decode012)(BSCTX *bc)
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{
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if (!BS_FUNC(read_bit)(bc))
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return 0;
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else
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return BS_FUNC(read_bit)(bc) + 1;
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}
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/**
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* Return decoded truncated unary code for the values 2, 1, 0.
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*/
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static inline int BS_FUNC(decode210)(BSCTX *bc)
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{
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if (BS_FUNC(read_bit)(bc))
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return 0;
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else
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return 2 - BS_FUNC(read_bit)(bc);
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}
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/* Read sign bit and flip the sign of the provided value accordingly. */
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static inline int BS_FUNC(apply_sign)(BSCTX *bc, int val)
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{
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int sign = BS_FUNC(read_signed)(bc, 1);
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return (val ^ sign) - sign;
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}
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static inline int BS_FUNC(skip_1stop_8data)(BSCTX *s)
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{
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if (BS_FUNC(left)(s) <= 0)
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return AVERROR_INVALIDDATA;
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while (BS_FUNC(read_bit)(s)) {
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BS_FUNC(skip)(s, 8);
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if (BS_FUNC(left)(s) <= 0)
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return AVERROR_INVALIDDATA;
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}
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return 0;
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}
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/**
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* Return the LUT element for the given bitstream configuration.
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*/
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static inline int BS_FUNC(priv_set_idx)(BSCTX *bc, int code, int *n,
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int *nb_bits, const VLCElem *table)
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{
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unsigned idx;
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*nb_bits = -*n;
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idx = BS_FUNC(peek)(bc, *nb_bits) + code;
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*n = table[idx].len;
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return table[idx].sym;
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}
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/**
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* Parse a vlc code.
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* @param bits is the number of bits which will be read at once, must be
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* identical to nb_bits in init_vlc()
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* @param max_depth is the number of times bits bits must be read to completely
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* read the longest vlc code
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* = (max_vlc_length + bits - 1) / bits
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* If the vlc code is invalid and max_depth=1, then no bits will be removed.
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* If the vlc code is invalid and max_depth>1, then the number of bits removed
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* is undefined.
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*/
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static inline int BS_FUNC(read_vlc)(BSCTX *bc, const VLCElem *table,
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int bits, int max_depth)
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{
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int nb_bits;
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unsigned idx = BS_FUNC(peek)(bc, bits);
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int code = table[idx].sym;
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int n = table[idx].len;
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if (max_depth > 1 && n < 0) {
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BS_FUNC(priv_skip_remaining)(bc, bits);
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code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
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if (max_depth > 2 && n < 0) {
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BS_FUNC(priv_skip_remaining)(bc, nb_bits);
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code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
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}
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}
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BS_FUNC(priv_skip_remaining)(bc, n);
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return code;
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}
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#undef BSCTX
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#undef BS_FUNC
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#undef BS_JOIN3
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#undef BS_JOIN
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#undef BS_SUFFIX_UPPER
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#undef BS_SUFFIX_LOWER
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