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/******************************************************************************
*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*****************************************************************************
* Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore
*/
/*!
**************************************************************************
* \file ih264d_bitstrm.c
*
* \brief
* Bitstream parsing routines
*
* \date
* 20/11/2002
*
* \author AI
**************************************************************************
*/
#include <stdlib.h>
#include "ih264_typedefs.h"
#include "ih264_macros.h"
#include "ih264_platform_macros.h"
#include "ih264d_bitstrm.h"
#include "ih264d_error_handler.h"
#include "ih264d_debug.h"
#include "ih264d_tables.h"
#include "ih264d_structs.h"
/*!
**************************************************************************
* \if Function name : ih264d_get_bit_h264 \endif
*
* \brief
* Read one bit from the bitstream.
*
* This is a Bitstream processing function. It reads the
* bit currently pointed by the bit pointer in the
* buffer and advances the pointer by one. It returns
* the bit (0 or 1) in the form of an unsigned integer.
*
* \return
* Returns the next bit (0 or 1) in the bitstream.
*
**************************************************************************
*/
UWORD8 ih264d_get_bit_h264(dec_bit_stream_t *ps_stream)
{
UWORD32 u4_code;
GETBIT(u4_code, ps_stream->u4_ofst, ps_stream->pu4_buffer);
return (u4_code);
}
/*!
**************************************************************************
* \if Function name : ih264d_get_bits_h264 \endif
*
* \brief
* Read specified number of bits from the bitstream.
*
* This is a Bitstream processing function. It reads the
* number specified number of bits from the current bit
* position and advances the bit and byte pointers
* appropriately.
*
* \return
* An unsigned 32 bit integer with its least significant bits
* containing the bits in order of their occurence in the bitstream.
*
**************************************************************************
*/
UWORD32 ih264d_get_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits)
{
UWORD32 u4_code = 0;
if(u4_num_bits)
GETBITS(u4_code, ps_bitstrm->u4_ofst, ps_bitstrm->pu4_buffer, u4_num_bits);
return (u4_code);
}
/*!
**************************************************************************
* \if Function name : ih264d_next_bits_h264 \endif
*
* \brief
* Peek specified number of bits from the bitstream.
*
* This is a Bitstream processing function. It gets the
* specified number of bits from the buffer without
* altering the current pointers. It is equivalent to
* next_bits() function in the standard.
*
* \return
* An unsigned 32 bit integer with its least significant bits
* containing the bits in order of their occurence in the bitstream.
**************************************************************************
*/
UWORD32 ih264d_next_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits)
{
UWORD32 u4_word_off = (ps_bitstrm->u4_ofst >> 5);
UWORD32 u4_bit_off = ps_bitstrm->u4_ofst & 0x1F;
UWORD32 *pu4_bitstream = ps_bitstrm->pu4_buffer;
UWORD32 u4_bits = pu4_bitstream[u4_word_off++] << u4_bit_off;
/*************************************************************************/
/* Test if number of bits to be read exceeds the number of bits in the */
/* current word. If yes, read from the next word of the buffer, The bits */
/* from both the words are concatenated to get next 32 bits in 'u4_bits' */
/*************************************************************************/
if(u4_bit_off > (INT_IN_BITS - u4_num_bits))
u4_bits |= (pu4_bitstream[u4_word_off] >> (INT_IN_BITS - u4_bit_off));
return ((u4_bits >> (INT_IN_BITS - u4_num_bits)));
}
/*!
**************************************************************************
* \if Function name : ih264d_flush_bits_h264 \endif
*
* \brief
* Flush specified number of bits from the bitstream.
*
* This function flushes the specified number of bits (marks
* as read) from the buffer.
*
* \return
* A 8 bit unsigned integer with value
* '1' on successful flush
* '0' on failure.
*
**************************************************************************
*/
WORD32 ih264d_flush_bits_h264(dec_bit_stream_t *ps_bitstrm, WORD32 u4_num_bits)
{
ps_bitstrm->u4_ofst += u4_num_bits;
if(ps_bitstrm->u4_ofst > ps_bitstrm->u4_max_ofst)
{
return ERROR_EOB_FLUSHBITS_T;
}
return OK;
}
/*!
**************************************************************************
* \if Function name : ih264d_check_byte_aligned \endif
*
* \brief
* Checks whether the bit ps_bitstrm u4_ofst is at byte boundary.
*
* \param ps_bitstrm : Pointer to bitstream
*
* \return
* Returns 1 if bit ps_bitstrm u4_ofst is at byte alligned position else zero.
**************************************************************************
*/
UWORD8 ih264d_check_byte_aligned(dec_bit_stream_t * ps_bitstrm)
{
if(ps_bitstrm->u4_ofst & 0x07)
return (0);
else
return (1);
}
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