tor-browser

put_bits.h (11221B)

---

/*
* 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 */