blob: 5925d68e35390d2b78fb34a7a6b1234c221d22dd [file] [log] [blame]
/*
* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
/*
* arith_routins.c
*
* This C file contains a function for finalizing the bitstream
* after arithmetic coding.
*
*/
#include "arith_routins.h"
/****************************************************************************
* WebRtcIsacfix_EncTerminate(...)
*
* Final call to the arithmetic coder for an encoder call. This function
* terminates and return byte stream.
*
* Input:
* - streamData : in-/output struct containing bitstream
*
* Return value : number of bytes in the stream
*/
int16_t WebRtcIsacfix_EncTerminate(Bitstr_enc *streamData)
{
uint16_t *streamPtr;
uint16_t negCarry;
/* point to the right place in the stream buffer */
streamPtr = streamData->stream + streamData->stream_index;
/* find minimum length (determined by current interval width) */
if ( streamData->W_upper > 0x01FFFFFF )
{
streamData->streamval += 0x01000000;
/* if result is less than the added value we must take care of the carry */
if (streamData->streamval < 0x01000000)
{
/* propagate carry */
if (streamData->full == 0) {
/* Add value to current value */
negCarry = *streamPtr;
negCarry += 0x0100;
*streamPtr = negCarry;
/* if value is too big, propagate carry to next byte, and so on */
while (!(negCarry))
{
negCarry = *--streamPtr;
negCarry++;
*streamPtr = negCarry;
}
} else {
/* propagate carry by adding one to the previous byte in the
* stream if that byte is 0xFFFF we need to propagate the carry
* furhter back in the stream */
while ( !(++(*--streamPtr)) );
}
/* put pointer back to the old value */
streamPtr = streamData->stream + streamData->stream_index;
}
/* write remaining data to bitstream, if "full == 0" first byte has data */
if (streamData->full == 0) {
*streamPtr++ += (uint16_t)(streamData->streamval >> 24);
streamData->full = 1;
} else {
*streamPtr = (uint16_t)((streamData->streamval >> 24) << 8);
streamData->full = 0;
}
}
else
{
streamData->streamval += 0x00010000;
/* if result is less than the added value we must take care of the carry */
if (streamData->streamval < 0x00010000)
{
/* propagate carry */
if (streamData->full == 0) {
/* Add value to current value */
negCarry = *streamPtr;
negCarry += 0x0100;
*streamPtr = negCarry;
/* if value to big, propagate carry to next byte, and so on */
while (!(negCarry))
{
negCarry = *--streamPtr;
negCarry++;
*streamPtr = negCarry;
}
} else {
/* Add carry to previous byte */
while ( !(++(*--streamPtr)) );
}
/* put pointer back to the old value */
streamPtr = streamData->stream + streamData->stream_index;
}
/* write remaining data (2 bytes) to bitstream */
if (streamData->full) {
*streamPtr++ = (uint16_t)(streamData->streamval >> 16);
} else {
*streamPtr++ |= (uint16_t)(streamData->streamval >> 24);
*streamPtr = (uint16_t)(streamData->streamval >> 8) & 0xFF00;
}
}
/* calculate stream length in bytes */
return (((streamPtr - streamData->stream)<<1) + !(streamData->full));
}