---
libavcodec/bitstream.h | 475 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 475 insertions(+)
create mode 100644 libavcodec/bitstream.h
diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h
new file mode 100644
index 0000000..8793556
--- /dev/null
+++ b/libavcodec/bitstream.h
@@ -0,0 +1,475 @@
+/*
+ * copyright (c) 2016 Alexandra Hájková
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; 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 "libavutil/common.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/log.h"
+#include "mathops.h"
+#include "vlc.h"
+
+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
+ int size_in_bits;
+} BitstreamContext;
+
+/**
+ * Return number of bits already read.
+ */
+static inline int bitstream_tell(const BitstreamContext *s)
+{
+ return (s->ptr - s->buffer) * 8 - s->bits_left;
+}
+
+static inline void refill_64(BitstreamContext *s)
+{
+ if (av_unlikely(s->ptr >= s->buffer_end || !s->buffer))
+ return;
+
+#ifdef BITSTREAM_READER_LE
+ s->bits = AV_RL64(s->ptr);
+#else
+ s->bits = AV_RB64(s->ptr);
+#endif
+ s->ptr += 8;
+ s->bits_left = 64;
+}
+
+static inline uint64_t get_val(BitstreamContext *s, int n)
+{
+ uint64_t ret;
+
+#ifdef BITSTREAM_READER_LE
+ ret = s->bits & ((UINT64_C(1) << n) - 1);
+ s->bits >>= n;
+#else
+ ret = s->bits >> (64 - n);
+ s->bits <<= n;
+#endif
+ s->bits_left -= n;
+
+ return ret;
+}
+
+/**
+ * Return one bit from the buffer.
+ */
+static inline unsigned int bitstream_read_bit(BitstreamContext *s)
+{
+ if (av_unlikely(!s->bits_left))
+ refill_64(s);
+
+ return (uint8_t)get_val(s, 1);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ */
+static inline uint64_t bitstream_read_63(BitstreamContext *s, int n)
+{
+ uint64_t ret = 0;
+#ifdef BITSTREAM_READER_LE
+ uint64_t left = 0;
+#endif
+
+ if (av_unlikely(!n))
+ return 0;
+
+ if (av_unlikely(n > s->bits_left)) {
+ n -= s->bits_left;
+#ifdef BITSTREAM_READER_LE
+ left = s->bits_left;
+#endif
+ ret = get_val(s, s->bits_left);
+ refill_64(s);
+ }
+
+#ifdef BITSTREAM_READER_LE
+ ret = get_val(s, n) << left | ret;
+#else
+ ret = get_val(s, n) | ret << n;
+#endif
+
+ return ret;
+}
+
+static inline void refill_32(BitstreamContext *s)
+{
+ if (av_unlikely(s->ptr >= s->buffer_end || !s->buffer))
+ return;
+
+#ifdef BITSTREAM_READER_LE
+ s->bits = (uint64_t)AV_RL32(s->ptr) << s->bits_left | s->bits;
+#else
+ s->bits = s->bits | (uint64_t)AV_RB32(s->ptr) << (32 - s->bits_left);
+#endif
+ s->ptr += 4;
+ s->bits_left += 32;
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-32 range.
+ */
+static inline uint32_t bitstream_read_32(BitstreamContext *s, int n)
+{
+ if (av_unlikely(!n))
+ return 0;
+
+ if (av_unlikely(n > s->bits_left)) {
+ refill_32(s);
+ if (av_unlikely(s->bits_left < 32))
+ s->bits_left = n;
+ }
+
+ return get_val(s, n);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ * But do not change the buffer state.
+ */
+static inline unsigned int bitstream_peek_63(BitstreamContext *s, int n)
+{
+ BitstreamContext tmp = *s;
+
+ return bitstream_read_63(&tmp, n);
+}
+
+static inline unsigned int show_val(BitstreamContext *s, int n)
+{
+ int ret;
+
+#ifdef BITSTREAM_READER_LE
+ ret = s->bits & ((UINT64_C(1) << n) - 1);
+#else
+ ret = s->bits >> (64 - n);
+#endif
+
+ return ret;
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-32 range.
+ * But do not change the buffer state.
+ */
+static inline unsigned int bitstream_peek_32(BitstreamContext *s, int n)
+{
+ if (av_unlikely(n > s->bits_left))
+ refill_32(s);
+
+ return show_val(s, n);
+}
+
+static inline void skip_rem(BitstreamContext *s, int n)
+{
+#ifdef BITSTREAM_READER_LE
+ s->bits >>= n;
+#else
+ s->bits <<= n;
+#endif
+ s->bits_left -= n;
+}
+
+/**
+ * Skip n bits in the buffer.
+ */
+static inline void bitstream_skip(BitstreamContext *s, int n)
+{
+ if (n <= s->bits_left)
+ skip_rem(s, n);
+ else {
+ n -= s->bits_left;
+ skip_rem(s, s->bits_left);
+ if (n >= 64) {
+ int skip = n / 8;
+
+ n -= skip * 8;
+ s->ptr += skip;
+ }
+ refill_64(s);
+ if (n)
+ skip_rem(s, n);
+ }
+}
+/**
+ * Read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
+ * If MSB not set it is negative.
+ * @param n length in bits
+ */
+static inline int bitstream_read_xbits(BitstreamContext *s, int n)
+{
+ int sign;
+ int32_t cache;
+
+ cache = bitstream_peek_32(s, 32);
+ sign = ~cache >> 31;
+ bitstream_skip(s, n);
+
+ return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
+}
+
+/**
+ * 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_s32(BitstreamContext *s, int n)
+{
+ return sign_extend(bitstream_read_32(s, n), n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer.
+ * n has to be in the 0-32 range.
+ * Do not change the buffer state.
+ */
+static inline int bitstream_peek_s(BitstreamContext *s, int n)
+{
+ return sign_extend(bitstream_peek_32(s, n), n);
+}
+
+/**
+ * Return marker bit.
+ * Print a message msg if it is missing.
+ */
+static inline int bitstream_check_marker(BitstreamContext *s, const char *msg)
+{
+ int bit = bitstream_read_bit(s);
+ if (!bit)
+ av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
+
+ return bit;
+}
+
+/**
+ * Seek to the given bit position.
+ */
+static inline void bitstream_seek(BitstreamContext *s, unsigned pos)
+{
+ s->ptr = s->buffer;;
+ s->bits = 0;
+ s->bits_left = 0;
+
+ bitstream_skip(s, pos);
+}
+
+/**
+ * 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 bit 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 *s, const uint8_t *buffer,
int bit_size)
+{
+ int buffer_size;
+ int ret = 0;
+
+ if (bit_size > INT_MAX - 7 || bit_size < 0 || !buffer) {
+ buffer = s->buffer = s->ptr = NULL;
+ s->bits_left = 0;
+ return AVERROR_INVALIDDATA;
+ }
+
+ buffer_size = (bit_size + 7) >> 3;
+
+ s->buffer = buffer;
+ s->buffer_end = buffer + buffer_size;
+ s->ptr = s->buffer;
+ s->size_in_bits = bit_size;
+ s->bits_left = 0;
+ s->bits = 0;
+
+ refill_64(s);
+
+ return ret;
+}
+
+/**
+ * Return buffer size in bits.
+ */
+static inline int bitstream_tell_size(BitstreamContext *s)
+{
+ return s->size_in_bits;
+}
+
+/**
+ * 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 bit 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 *s, const uint8_t *buffer,
+ int byte_size)
+{
+ if (byte_size > INT_MAX / 8)
+ return AVERROR_INVALIDDATA;
+ return bitstream_init(s, buffer, byte_size * 8);
+}
+
+/* Skip bits to a byte boundary */
+static inline const uint8_t *bitstream_align(BitstreamContext *s)
+{
+ int n = -bitstream_tell(s) & 7;
+ if (n)
+ bitstream_skip(s, n);
+ return s->buffer + (bitstream_tell(s) >> 3);
+}
+
+
+/**
+ * Return the LUT element for the given bitstream configuration.
+ */
+static int set_idx(BitstreamContext *s, int code, int *n, int *nb_bits,
VLC_TYPE (*table)[2])
+{
+ unsigned int idx;
+
+ *nb_bits = -*n;
+ idx = bitstream_peek_32(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
+ * 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 av_always_inline int bitstream_read_vlc(BitstreamContext *s, VLC_TYPE
(*table)[2],
+ int bits, int max_depth)
+{
+ int code, n, nb_bits;
+ unsigned int idx;
+
+ idx = bitstream_peek_32(s, bits);
+ code = table[idx][0];
+ n = table[idx][1];
+
+ if (max_depth > 1 && n < 0) {
+
+ bitstream_skip(s, bits);
+ code = set_idx(s, code, &n, &nb_bits, table);
+ if (max_depth > 2 && n < 0) {
+ bitstream_skip(s, nb_bits);
+ code = set_idx(s, code, &n, &nb_bits, table);
+ }
+ }
+ bitstream_skip(s, n);
+
+ return code;
+}
+
+#define BITSTREAM_RL_VLC(level, run, bb, table, bits, max_depth) \
+ do { \
+ int n, nb_bits; \
+ unsigned int index; \
+ \
+ index = bitstream_peek_32(bb, bits); \
+ level = table[index].level; \
+ n = table[index].len; \
+ \
+ if (max_depth > 1 && n < 0) { \
+ bitstream_skip(bb, bits); \
+ \
+ nb_bits = -n; \
+ \
+ index = bitstream_peek_32(bb, nb_bits) + level; \
+ level = table[index].level; \
+ n = table[index].len; \
+ if (max_depth > 2 && n < 0) { \
+ bitstream_skip(bb, nb_bits); \
+ nb_bits = -n; \
+ \
+ index = bitstream_peek_32(bb, nb_bits) + level; \
+ level = table[index].level; \
+ n = table[index].len; \
+ } \
+ } \
+ run = table[index].run; \
+ bitstream_skip(bb, n); \
+ } while (0)
+
+/**
+ * Return decoded truncated unary code for the values 0, 1, 2.
+ */
+static inline int bitstream_decode012(BitstreamContext *bb)
+{
+ int n;
+ n = bitstream_read_bit(bb);
+ if (n == 0)
+ return 0;
+ else
+ return bitstream_read_bit(bb) + 1;
+}
+
+/**
+ * Return decoded truncated unary code for the values 2, 1, 0.
+ */
+static inline int bitstream_decode210(BitstreamContext *bb)
+{
+ if (bitstream_read_bit(bb))
+ return 0;
+ else
+ return 2 - bitstream_read_bit(bb);
+}
+
+/**
+ * Return the number of the bits left in a buffer.
+ */
+static inline int bitstream_bits_left(BitstreamContext *bb)
+{
+ int ret;
+
+ ret = (bb->buffer - bb->ptr) * 8 + bb->size_in_bits + bb->bits_left;
+ return ret;
+}
+
+static inline void print_bin(int bits, int n)
+{
+ int i;
+
+ for (i = n - 1; i >= 0; i--)
+ av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
+ for (i = n; i < 24; i++)
+ av_log(NULL, AV_LOG_DEBUG, " ");
+}
+
+#endif /* AVCODEC_BITSTREAM_H */
--
2.1.4
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