codecs_v2/audio/aac/dec/src/buf_getbits.cpp

/* ------------------------------------------------------------------
 * Copyright (C) 2008 PacketVideo
 *
 * 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.
 * -------------------------------------------------------------------
 */
/*
------------------------------------------------------------------------------



 Filename: buf_getbits.c

     Date: 07/22/2003

------------------------------------------------------------------------------
 REVISION HISTORY


 Description:

------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Arguments:   hBitBuf Handle to Bitbuffer
              n       Number of bits to read

 Return:      bits


------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

            Reads n bits from Bitbuffer

------------------------------------------------------------------------------
 REQUIREMENTS


------------------------------------------------------------------------------
 REFERENCES

SC 29 Software Copyright Licencing Disclaimer:

This software module was originally developed by
  Coding Technologies

and edited by
  -

in the course of development of the ISO/IEC 13818-7 and ISO/IEC 14496-3
standards for reference purposes and its performance may not have been
optimized. This software module is an implementation of one or more tools as
specified by the ISO/IEC 13818-7 and ISO/IEC 14496-3 standards.
ISO/IEC gives users free license to this software module or modifications
thereof for use in products claiming conformance to audiovisual and
image-coding related ITU Recommendations and/or ISO/IEC International
Standards. ISO/IEC gives users the same free license to this software module or
modifications thereof for research purposes and further ISO/IEC standardisation.
Those intending to use this software module in products are advised that its
use may infringe existing patents. ISO/IEC have no liability for use of this
software module or modifications thereof. Copyright is not released for
products that do not conform to audiovisual and image-coding related ITU
Recommendations and/or ISO/IEC International Standards.
The original developer retains full right to modify and use the code for its
own purpose, assign or donate the code to a third party and to inhibit third
parties from using the code for products that do not conform to audiovisual and
image-coding related ITU Recommendations and/or ISO/IEC International Standards.
This copyright notice must be included in all copies or derivative works.
Copyright (c) ISO/IEC 2002.

------------------------------------------------------------------------------
 PSEUDO-CODE

------------------------------------------------------------------------------
*/


/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/

#ifdef AAC_PLUS

#include    "buf_getbits.h"

/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/


/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; EXTERNAL FUNCTION REFERENCES
; Declare functions defined elsewhere and referenced in this module
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/

UInt32 buf_getbits(BIT_BUFFER * hBitBuf, Int32 n)
{

    /* read bits from MSB side */
    if (hBitBuf->buffered_bits <= 16)
    {
        hBitBuf->buffer_word    = (hBitBuf->buffer_word << 16) | (*(hBitBuf->char_ptr++) << 8);
        hBitBuf->buffer_word   |= *(hBitBuf->char_ptr++);
        hBitBuf->buffered_bits += 16;
    }

    hBitBuf->buffered_bits -= n;
    hBitBuf->nrBitsRead    += n;

    return ((hBitBuf->buffer_word >> hBitBuf->buffered_bits) & ((1 << n) - 1));

}


UInt32 buf_get_1bit(BIT_BUFFER * hBitBuf)
{

    /* read bits from MSB side */
    if (hBitBuf->buffered_bits <= 16)
    {
        hBitBuf->buffer_word    = (hBitBuf->buffer_word << 16) | (*(hBitBuf->char_ptr++) << 8);
        hBitBuf->buffer_word   |= *(hBitBuf->char_ptr++);
        hBitBuf->buffered_bits += 16;
    }

    hBitBuf->buffered_bits--;
    hBitBuf->nrBitsRead++;

    return ((hBitBuf->buffer_word >> hBitBuf->buffered_bits) & 1);

}

#endif