/* * 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 "libavutil/intreadwrite.h" #include "libavutil/avassert.h" typedef struct PutBitContext { uint32_t bit_buf; int bit_left; uint8_t *buf, *buf_ptr, *buf_end; int size_in_bits; } 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->size_in_bits = 8 * buffer_size; s->buf = buffer; s->buf_end = s->buf + buffer_size; s->buf_ptr = s->buf; s->bit_left = 32; s->bit_buf = 0; } /** * 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 larger than the previous size */ static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size) { av_assert0(8*buffer_size > s->size_in_bits); s->buf_end = buffer + buffer_size; s->buf_ptr = buffer + (s->buf_ptr - s->buf); s->buf = buffer; s->size_in_bits = 8 * buffer_size; } /** * @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 + 32 - s->bit_left; } /** * @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 - 32 + s->bit_left; } /** * 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 < 32) s->bit_buf <<= s->bit_left; #endif while (s->bit_left < 32) { 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 >> 24; s->bit_buf <<= 8; #endif s->bit_left += 8; } s->bit_left = 32; s->bit_buf = 0; } #ifdef BITSTREAM_WRITER_LE #define avpriv_align_put_bits align_put_bits_unsupported_here #define avpriv_put_string ff_put_string_unsupported_here #define avpriv_copy_bits avpriv_copy_bits_unsupported_here #else /** * Pad the bitstream with zeros up to the next byte boundary. */ void avpriv_align_put_bits(PutBitContext *s); /** * Put the string string in the bitstream. * * @param terminate_string 0-terminates the written string if value is 1 */ void avpriv_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 avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length); #endif /** * Write up to 31 bits into a bitstream. * Use put_bits32 to write 32 bits. */ static inline void put_bits(PutBitContext *s, int n, unsigned int value) { unsigned int bit_buf; int bit_left; av_assert2(n <= 31 && value < (1U << n)); bit_buf = s->bit_buf; bit_left = s->bit_left; /* XXX: optimize */ #ifdef BITSTREAM_WRITER_LE bit_buf |= value << (32 - bit_left); if (n >= bit_left) { if (3 < s->buf_end - s->buf_ptr) { AV_WL32(s->buf_ptr, bit_buf); s->buf_ptr += 4; } 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 += 32; } 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 (3 < s->buf_end - s->buf_ptr) { AV_WB32(s->buf_ptr, bit_buf); s->buf_ptr += 4; } else { av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n"); av_assert2(0); } bit_left += 32 - n; bit_buf = value; } #endif 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_mod_uintp2(value, n)); } /** * Write exactly 32 bits into a bitstream. */ static void av_unused put_bits32(PutBitContext *s, uint32_t value) { int lo = value & 0xffff; int hi = value >> 16; #ifdef BITSTREAM_WRITER_LE put_bits(s, 16, lo); put_bits(s, 16, hi); #else put_bits(s, 16, hi); put_bits(s, 16, lo); #endif } /** * 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 == 32); 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) { s->bit_left -= n; s->buf_ptr -= 4 * (s->bit_left >> 5); s->bit_left &= 31; } /** * 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 - 32); s->buf_end = s->buf + size; s->size_in_bits = 8*size; } #endif /* AVCODEC_PUT_BITS_H */