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-rw-r--r--libavcodec/bitstream.h490
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diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
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+/*
+ * 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
+ */
+
+/**
+ * @file
+ * bitstream reader API header.
+ */
+
+#ifndef AVCODEC_BITSTREAM_H
+#define AVCODEC_BITSTREAM_H
+
+#include <stdint.h>
+
+#include "config.h"
+
+#include "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/log.h"
+
+#include "mathops.h"
+#include "vlc.h"
+
+#ifndef UNCHECKED_BITSTREAM_READER
+#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
+#endif
+
+typedef struct BitstreamContext {
+ 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_left; // number of bits left in bits field
+ unsigned size_in_bits;
+} BitstreamContext;
+
+static inline void refill_64(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+ if (bc->ptr >= bc->buffer_end)
+ return;
+#endif
+
+#ifdef BITSTREAM_READER_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 refill_32(BitstreamContext *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+ if (bc->ptr >= bc->buffer_end)
+ return;
+#endif
+
+#ifdef BITSTREAM_READER_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 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;
+
+ 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 bitstream_init8(BitstreamContext *bc, const uint8_t *buffer,
+ unsigned int byte_size)
+{
+ if (byte_size > INT_MAX / 8)
+ return AVERROR_INVALIDDATA;
+ return bitstream_init(bc, buffer, byte_size * 8);
+}
+
+/**
+ * Return number of bits already read.
+ */
+static inline int bitstream_tell(const BitstreamContext *bc)
+{
+ return (bc->ptr - bc->buffer) * 8 - bc->bits_left;
+}
+
+/**
+ * Return buffer size in bits.
+ */
+static inline int bitstream_tell_size(const BitstreamContext *bc)
+{
+ return bc->size_in_bits;
+}
+
+/**
+ * Return the number of the bits left in a buffer.
+ */
+static inline int bitstream_bits_left(const BitstreamContext *bc)
+{
+ return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_left;
+}
+
+static inline uint64_t get_val(BitstreamContext *bc, unsigned int n)
+{
+ uint64_t ret;
+
+#ifdef BITSTREAM_READER_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 bitstream_read_bit(BitstreamContext *bc)
+{
+ if (!bc->bits_left)
+ refill_64(bc);
+
+ return get_val(bc, 1);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ */
+static inline uint64_t bitstream_read_63(BitstreamContext *bc, unsigned int n)
+{
+ uint64_t ret = 0;
+#ifdef BITSTREAM_READER_LE
+ uint64_t left = 0;
+#endif
+
+ if (!n)
+ return 0;
+
+ if (n > bc->bits_left) {
+ n -= bc->bits_left;
+#ifdef BITSTREAM_READER_LE
+ left = bc->bits_left;
+#endif
+ ret = get_val(bc, bc->bits_left);
+ refill_64(bc);
+ }
+
+#ifdef BITSTREAM_READER_LE
+ ret = get_val(bc, n) << left | ret;
+#else
+ ret = get_val(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 bitstream_read(BitstreamContext *bc, unsigned int n)
+{
+ if (!n)
+ return 0;
+
+ if (n > bc->bits_left) {
+ refill_32(bc);
+ if (bc->bits_left < 32)
+ bc->bits_left = n;
+ }
+
+ return 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 bitstream_read_signed(BitstreamContext *bc, unsigned int n)
+{
+ return sign_extend(bitstream_read(bc, n), n);
+}
+
+static inline unsigned int show_val(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_READER_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 bitstream_peek(BitstreamContext *bc, unsigned int n)
+{
+ if (n > bc->bits_left)
+ refill_32(bc);
+
+ return 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 bitstream_peek_signed(BitstreamContext *bc, unsigned int n)
+{
+ return sign_extend(bitstream_peek(bc, n), n);
+}
+
+static inline void skip_remaining(BitstreamContext *bc, unsigned int n)
+{
+#ifdef BITSTREAM_READER_LE
+ bc->bits >>= n;
+#else
+ bc->bits <<= n;
+#endif
+ bc->bits_left -= n;
+}
+
+/**
+ * Skip n bits in the buffer.
+ */
+static inline void bitstream_skip(BitstreamContext *bc, unsigned int n)
+{
+ if (n < bc->bits_left)
+ 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;
+ }
+ refill_64(bc);
+ if (n)
+ skip_remaining(bc, n);
+ }
+}
+
+/**
+ * Seek to the given bit position.
+ */
+static inline void bitstream_seek(BitstreamContext *bc, unsigned pos)
+{
+ bc->ptr = bc->buffer;
+ bc->bits = 0;
+ bc->bits_left = 0;
+
+ bitstream_skip(bc, pos);
+}
+
+/**
+ * Skip bits to a byte boundary.
+ */
+static inline const uint8_t *bitstream_align(BitstreamContext *bc)
+{
+ unsigned int n = -bitstream_tell(bc) & 7;
+ if (n)
+ 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 bitstream_read_xbits(BitstreamContext *bc, unsigned int n)
+{
+ int32_t cache = bitstream_peek(bc, 32);
+ int sign = ~cache >> 31;
+ 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 bitstream_decode012(BitstreamContext *bc)
+{
+ if (!bitstream_read_bit(bc))
+ return 0;
+ else
+ return bitstream_read_bit(bc) + 1;
+}
+
+/**
+ * Return decoded truncated unary code for the values 2, 1, 0.
+ */
+static inline int bitstream_decode210(BitstreamContext *bc)
+{
+ if (bitstream_read_bit(bc))
+ return 0;
+ else
+ return 2 - bitstream_read_bit(bc);
+}
+
+/* Read sign bit and flip the sign of the provided value accordingly. */
+static inline int bitstream_apply_sign(BitstreamContext *bc, int val)
+{
+ int sign = bitstream_read_signed(bc, 1);
+ return (val ^ sign) - sign;
+}
+
+static inline int bitstream_skip_1stop_8data(BitstreamContext *s)
+{
+ if (bitstream_bits_left(s) <= 0)
+ return AVERROR_INVALIDDATA;
+
+ while (bitstream_read(s, 1)) {
+ bitstream_skip(s, 8);
+ if (bitstream_bits_left(s) <= 0)
+ return AVERROR_INVALIDDATA;
+ }
+
+ return 0;
+}
+
+/* Unwind the cache so a refill_32 can fill it again. */
+static inline void bitstream_unwind(BitstreamContext *bc)
+{
+ int unwind = 4;
+ int unwind_bits = unwind * 8;
+
+ if (bc->bits_left < unwind_bits)
+ return;
+
+ bc->bits >>= unwind_bits;
+ bc->bits <<= unwind_bits;
+ bc->bits_left -= unwind_bits;
+ bc->ptr -= unwind;
+}
+
+/* Unget up to 32 bits. */
+static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
+ size_t amount)
+{
+ size_t cache_size = sizeof(bc->bits) * 8;
+
+ if (bc->bits_left + amount > cache_size)
+ bitstream_unwind(bc);
+
+ bc->bits = (bc->bits >> amount) | (value << (cache_size - amount));
+ bc->bits_left += amount;
+}
+
+/**
+ * Return the LUT element for the given bitstream configuration.
+ */
+static inline int set_idx(BitstreamContext *bc, int code, int *n, int *nb_bits,
+ VLC_TYPE (*table)[2])
+{
+ unsigned idx;
+
+ *nb_bits = -*n;
+ idx = 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 bitstream_read_vlc(BitstreamContext *bc, VLC_TYPE (*table)[2],
+ int bits, int max_depth)
+{
+ int nb_bits;
+ unsigned idx = bitstream_peek(bc, bits);
+ int code = table[idx][0];
+ int n = table[idx][1];
+
+ if (max_depth > 1 && n < 0) {
+ skip_remaining(bc, bits);
+ code = set_idx(bc, code, &n, &nb_bits, table);
+ if (max_depth > 2 && n < 0) {
+ skip_remaining(bc, nb_bits);
+ code = set_idx(bc, code, &n, &nb_bits, table);
+ }
+ }
+ skip_remaining(bc, n);
+
+ return code;
+}
+
+#define BITSTREAM_RL_VLC(level, run, bc, table, bits, max_depth) \
+ do { \
+ int n, nb_bits; \
+ unsigned int index = bitstream_peek(bc, bits); \
+ level = table[index].level; \
+ n = table[index].len; \
+ \
+ if (max_depth > 1 && n < 0) { \
+ bitstream_skip(bc, bits); \
+ \
+ nb_bits = -n; \
+ \
+ index = bitstream_peek(bc, nb_bits) + level; \
+ level = table[index].level; \
+ n = table[index].len; \
+ if (max_depth > 2 && n < 0) { \
+ bitstream_skip(bc, nb_bits); \
+ nb_bits = -n; \
+ \
+ index = bitstream_peek(bc, nb_bits) + level; \
+ level = table[index].level; \
+ n = table[index].len; \
+ } \
+ } \
+ run = table[index].run; \
+ bitstream_skip(bc, n); \
+ } while (0)
+
+#endif /* AVCODEC_BITSTREAM_H */
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