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ffmpeg/libavcodec/put_bits.h

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/*
* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
*
* 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 writer API
*/
#ifndef AVCODEC_PUT_BITS_H
#define AVCODEC_PUT_BITS_H
#include <stdint.h>
#include <stddef.h>
#include "config.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/avassert.h"
#include "libavutil/common.h"
#if ARCH_X86_64
// TODO: Benchmark and optionally enable on other 64-bit architectures.
typedef uint64_t BitBuf;
#define AV_WBBUF AV_WB64
#define AV_WLBUF AV_WL64
#else
typedef uint32_t BitBuf;
#define AV_WBBUF AV_WB32
#define AV_WLBUF AV_WL32
#endif
static const int BUF_BITS = 8 * sizeof(BitBuf);
typedef struct PutBitContext {
BitBuf bit_buf;
int bit_left;
uint8_t *buf, *buf_ptr, *buf_end;
} PutBitContext;
/**
* Initialize the PutBitContext s.
*
* @param buffer the buffer where to put bits
* @param buffer_size the size in bytes of buffer
*/
static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
int buffer_size)
{
if (buffer_size < 0) {
buffer_size = 0;
buffer = NULL;
}
s->buf = buffer;
s->buf_end = s->buf + buffer_size;
s->buf_ptr = s->buf;
s->bit_left = BUF_BITS;
s->bit_buf = 0;
}
/**
* @return the total number of bits written to the bitstream.
*/
static inline int put_bits_count(PutBitContext *s)
{
return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
}
/**
* @return the number of bytes output so far; may only be called
* when the PutBitContext is freshly initialized or flushed.
*/
static inline int put_bytes_output(const PutBitContext *s)
{
av_assert2(s->bit_left == BUF_BITS);
return s->buf_ptr - s->buf;
}
/**
* @param round_up When set, the number of bits written so far will be
* rounded up to the next byte.
* @return the number of bytes output so far.
*/
static inline int put_bytes_count(const PutBitContext *s, int round_up)
{
return s->buf_ptr - s->buf + ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
}
/**
* Rebase the bit writer onto a reallocated buffer.
*
* @param buffer the buffer where to put bits
* @param buffer_size the size in bytes of buffer,
* must be large enough to hold everything written so far
*/
static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
int buffer_size)
{
av_assert0(8*buffer_size >= put_bits_count(s));
s->buf_end = buffer + buffer_size;
s->buf_ptr = buffer + (s->buf_ptr - s->buf);
s->buf = buffer;
}
/**
* @return the number of bits available in the bitstream.
*/
static inline int put_bits_left(PutBitContext* s)
{
return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
}
/**
* @param round_up When set, the number of bits written will be
* rounded up to the next byte.
* @return the number of bytes left.
*/
static inline int put_bytes_left(const PutBitContext *s, int round_up)
{
return s->buf_end - s->buf_ptr - ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
}
/**
* Pad the end of the output stream with zeros.
*/
static inline void flush_put_bits(PutBitContext *s)
{
#ifndef BITSTREAM_WRITER_LE
if (s->bit_left < BUF_BITS)
s->bit_buf <<= s->bit_left;
#endif
while (s->bit_left < BUF_BITS) {
av_assert0(s->buf_ptr < s->buf_end);
#ifdef BITSTREAM_WRITER_LE
*s->buf_ptr++ = s->bit_buf;
s->bit_buf >>= 8;
#else
*s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
s->bit_buf <<= 8;
#endif
s->bit_left += 8;
}
s->bit_left = BUF_BITS;
s->bit_buf = 0;
}
static inline void flush_put_bits_le(PutBitContext *s)
{
while (s->bit_left < BUF_BITS) {
av_assert0(s->buf_ptr < s->buf_end);
*s->buf_ptr++ = s->bit_buf;
s->bit_buf >>= 8;
s->bit_left += 8;
}
s->bit_left = BUF_BITS;
s->bit_buf = 0;
}
#ifdef BITSTREAM_WRITER_LE
#define ff_put_string ff_put_string_unsupported_here
#define ff_copy_bits ff_copy_bits_unsupported_here
#else
/**
* Put the string string in the bitstream.
*
* @param terminate_string 0-terminates the written string if value is 1
*/
void ff_put_string(PutBitContext *pb, const char *string,
int terminate_string);
/**
* Copy the content of src to the bitstream.
*
* @param length the number of bits of src to copy
*/
void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
#endif
static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
{
BitBuf bit_buf;
int bit_left;
bit_buf = s->bit_buf;
bit_left = s->bit_left;
/* XXX: optimize */
#ifdef BITSTREAM_WRITER_LE
bit_buf |= value << (BUF_BITS - bit_left);
if (n >= bit_left) {
if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
AV_WLBUF(s->buf_ptr, bit_buf);
s->buf_ptr += sizeof(BitBuf);
} else {
av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
av_assert2(0);
}
bit_buf = value >> bit_left;
bit_left += BUF_BITS;
}
bit_left -= n;
#else
if (n < bit_left) {
bit_buf = (bit_buf << n) | value;
bit_left -= n;
} else {
bit_buf <<= bit_left;
bit_buf |= value >> (n - bit_left);
if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
AV_WBBUF(s->buf_ptr, bit_buf);
s->buf_ptr += sizeof(BitBuf);
} else {
av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
av_assert2(0);
}
bit_left += BUF_BITS - n;
bit_buf = value;
}
#endif
s->bit_buf = bit_buf;
s->bit_left = bit_left;
}
/**
* Write up to 31 bits into a bitstream.
* Use put_bits32 to write 32 bits.
*/
static inline void put_bits(PutBitContext *s, int n, BitBuf value)
{
av_assert2(n <= 31 && value < (1UL << n));
put_bits_no_assert(s, n, value);
}
static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
{
BitBuf bit_buf;
int bit_left;
av_assert2(n <= 31 && value < (1UL << n));
bit_buf = s->bit_buf;
bit_left = s->bit_left;
bit_buf |= value << (BUF_BITS - bit_left);
if (n >= bit_left) {
if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
AV_WLBUF(s->buf_ptr, bit_buf);
s->buf_ptr += sizeof(BitBuf);
} else {
av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
av_assert2(0);
}
bit_buf = value >> bit_left;
bit_left += BUF_BITS;
}
bit_left -= n;
s->bit_buf = bit_buf;
s->bit_left = bit_left;
}
static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
{
av_assert2(n >= 0 && n <= 31);
put_bits(pb, n, av_zero_extend(value, n));
}
/**
* Write exactly 32 bits into a bitstream.
*/
static void av_unused put_bits32(PutBitContext *s, uint32_t value)
{
BitBuf bit_buf;
int bit_left;
if (BUF_BITS > 32) {
put_bits_no_assert(s, 32, value);
return;
}
bit_buf = s->bit_buf;
bit_left = s->bit_left;
#ifdef BITSTREAM_WRITER_LE
bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
AV_WLBUF(s->buf_ptr, bit_buf);
s->buf_ptr += sizeof(BitBuf);
} else {
av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
av_assert2(0);
}
bit_buf = (uint64_t)value >> bit_left;
#else
bit_buf = (uint64_t)bit_buf << bit_left;
bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
AV_WBBUF(s->buf_ptr, bit_buf);
s->buf_ptr += sizeof(BitBuf);
} else {
av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
av_assert2(0);
}
bit_buf = value;
#endif
s->bit_buf = bit_buf;
s->bit_left = bit_left;
}
/**
* Write up to 64 bits into a bitstream.
*/
static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
{
av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
if (n < 32)
put_bits(s, n, value);
else if (n == 32)
put_bits32(s, value);
else if (n < 64) {
uint32_t lo = value & 0xffffffff;
uint32_t hi = value >> 32;
#ifdef BITSTREAM_WRITER_LE
put_bits32(s, lo);
put_bits(s, n - 32, hi);
#else
put_bits(s, n - 32, hi);
put_bits32(s, lo);
#endif
} else {
uint32_t lo = value & 0xffffffff;
uint32_t hi = value >> 32;
#ifdef BITSTREAM_WRITER_LE
put_bits32(s, lo);
put_bits32(s, hi);
#else
put_bits32(s, hi);
put_bits32(s, lo);
#endif
}
}
static inline void put_sbits63(PutBitContext *pb, int n, int64_t value)
{
av_assert2(n >= 0 && n < 64);
put_bits64(pb, n, (uint64_t)(value) & (~(UINT64_MAX << n)));
}
/**
* Return the pointer to the byte where the bitstream writer will put
* the next bit.
*/
static inline uint8_t *put_bits_ptr(PutBitContext *s)
{
return s->buf_ptr;
}
/**
* Skip the given number of bytes.
* PutBitContext must be flushed & aligned to a byte boundary before calling this.
*/
static inline void skip_put_bytes(PutBitContext *s, int n)
{
av_assert2((put_bits_count(s) & 7) == 0);
av_assert2(s->bit_left == BUF_BITS);
av_assert0(n <= s->buf_end - s->buf_ptr);
s->buf_ptr += n;
}
/**
* Skip the given number of bits.
* Must only be used if the actual values in the bitstream do not matter.
* If n is < 0 the behavior is undefined.
*/
static inline void skip_put_bits(PutBitContext *s, int n)
{
unsigned bits = BUF_BITS - s->bit_left + n;
s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
}
/**
* Change the end of the buffer.
*
* @param size the new size in bytes of the buffer where to put bits
*/
static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
{
av_assert0(size <= INT_MAX/8 - BUF_BITS);
s->buf_end = s->buf + size;
}
/**
* Pad the bitstream with zeros up to the next byte boundary.
*/
static inline void align_put_bits(PutBitContext *s)
{
put_bits(s, s->bit_left & 7, 0);
}
#undef AV_WBBUF
#undef AV_WLBUF
#endif /* AVCODEC_PUT_BITS_H */
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