embdrv/sbc/decoder/srce/bitstream-decode.c

/******************************************************************************
 *
 *  Copyright 2014 The Android Open Source Project
 *  Copyright 2003 - 2004 Open Interface North America, Inc. All rights
 *                        reserved.
 *
 *  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.
 *
 ******************************************************************************/

/*******************************************************************************
  $Revision: #1 $
 ******************************************************************************/

/**
@file
Functions for manipulating input bitstreams.

@ingroup codec_internal
*/

/**
@addtogroup codec_internal
@{
*/

#include "oi_assert.h"
#include "oi_bitstream.h"
#include "oi_stddefs.h"

PRIVATE void OI_BITSTREAM_ReadInit(OI_BITSTREAM* bs, const OI_BYTE* buffer) {
  bs->value = 0;
  bs->ptr.r = buffer;
  bs->bitPtr = 32;
}

PRIVATE uint32_t OI_BITSTREAM_ReadUINT(OI_BITSTREAM* bs, OI_UINT bits) {
  uint32_t result;

  OI_BITSTREAM_READUINT(result, bits, bs->ptr.r, bs->value, bs->bitPtr);

  return result;
}

PRIVATE uint8_t OI_BITSTREAM_ReadUINT4Aligned(OI_BITSTREAM* bs) {
  uint32_t result;

  OI_ASSERT(bs->bitPtr < 16);
  OI_ASSERT(bs->bitPtr % 4 == 0);

  if (bs->bitPtr == 8) {
    result = bs->value << 8;
    bs->bitPtr = 12;
  } else {
    result = bs->value << 12;
    bs->value = (bs->value << 8) | *bs->ptr.r++;
    bs->bitPtr = 8;
  }
  result >>= 28;
  OI_ASSERT(result < (1u << 4));
  return (uint8_t)result;
}

PRIVATE uint8_t OI_BITSTREAM_ReadUINT8Aligned(OI_BITSTREAM* bs) {
  uint32_t result;
  OI_ASSERT(bs->bitPtr == 8);

  result = bs->value >> 16;
  bs->value = (bs->value << 8) | *bs->ptr.r++;

  return (uint8_t)result;
}

/**
@}
*/