/*

    File:       IMAAudioPayload.c

    Contains:   Definition of IMAAudioPayload operations

    Copyright:  © 1997-1999 by Apple Computer, Inc., all rights reserved.

*/

#include "IMAAudioPayload.h"

#include <FixMath.h>

#include <Endian.h>

enum    /* fixed header fields */

{

    __kSampleRateWord           = 0,

    __kSampleRateSize           = 4,

    __kSampleRatePosition       = ( sizeof( UInt16 ) << 3 ) - __kSampleRateSize,

    __kChannelCountWord         = 0,

    __kChannelCountSize         = 3,

    __kChannelCountPosition     = __kSampleRatePosition - __kChannelCountSize,

    __kInterleaveCountWord      = 0,

    __kInterleaveCountSize      = 3,

    __kInterleaveCountPosition  = __kChannelCountPosition - __kInterleaveCountSize,

    __kInterleaveIndexWord      = 0,

    __kInterleaveIndexSize      = __kInterleaveCountSize,

    __kInterleaveIndexPosition  = __kInterleaveCountPosition - __kInterleaveIndexSize,

    __kInterleaveTailWord       = 0,

    __kInterleaveTailSize       = __kInterleaveCountSize,

    __kInterleaveTailPosition   = __kInterleaveIndexPosition - __kInterleaveTailSize

};

static unsigned long    __gSampleRates[] = {

                            8000,

                            11025,

                            16000,

                            22050,

                            24000,

                            32000,

                            44100,

                            48000 };

enum

{

    __kSampleRateCount = sizeof( __gSampleRates ) / sizeof( *__gSampleRates )

};

static

UInt32

__SetBitField(

    UInt16 *    inStorageUnit,

    UInt32      inPosition,

    UInt32      inSize,

    UInt32      inValue )

{

    UInt32  theMask = ( ( 1L << inSize ) - 1 ) << inPosition;

    *inStorageUnit =

        EndianU16_NtoB(

            ( EndianU16_BtoN( *inStorageUnit ) & ( ~theMask ) ) |

            ( theMask & ( inValue << inPosition ) ) );

    return( inValue & ( theMask >> inPosition ) );

}

static

UInt32

__BitField(

    const UInt16 *  inStorageUnit,

    UInt32          inPosition,

    UInt32          inSize )

{

    return( ( EndianU16_BtoN( *inStorageUnit ) >> inPosition ) & ( ( 1L << inSize ) - 1 ) );

}

UInt32

IMAAudioPayloadChannelCountLimit(

    void )

{

    return( 1L << __kChannelCountSize );

}

UInt32

IMAAudioPayloadInterleaveCountLimit(

    void )

{

    return( 1L << __kInterleaveCountSize );

}

IMAAudioPayload *

IMAAudioPayloadInitialize(

    IMAAudioPayload *   inPayload )

{

    UInt32  theCount = sizeof( *inPayload ) / sizeof( *inPayload->itsFixedHeader );

    while( theCount )

    {

        --theCount;

        inPayload->itsFixedHeader[ theCount ] = 0;

    }

    IMAAudioPayloadSetChannelCount( inPayload, 1 );

    IMAAudioPayloadSetSampleRate( inPayload, 0 );

    IMAAudioPayloadSetInterleaving( inPayload, 1, 0 );

    return( inPayload );

}

UInt32

IMAAudioPayloadSetChannelCount(

    IMAAudioPayload *   inPayload,

    UInt32              inChannelCount )

{

    UInt32  theResult;

    theResult =

        __SetBitField(

            &inPayload->itsFixedHeader[ __kChannelCountWord ], __kChannelCountPosition,

            __kChannelCountSize, inChannelCount - 1 ) + 1;

    return( theResult );

}

UnsignedFixed

IMAAudioPayloadSetSampleRate(

    IMAAudioPayload *   inPayload,

    UnsignedFixed       inSampleRate )

{

    UnsignedFixed   theResult;

    UInt32          theRateCode = __kSampleRateCount;

    do

    {

        --theRateCode;

    }

    while( theRateCode  &&  inSampleRate < Long2Fix( __gSampleRates[ theRateCode ] ) );

    theRateCode =

        __SetBitField(

            &inPayload->itsFixedHeader[ __kSampleRateWord ], __kSampleRatePosition,

            __kSampleRateSize, theRateCode );

    if( theRateCode < __kSampleRateCount )

        theResult = Long2Fix( __gSampleRates[ theRateCode ] );

    else

        theResult = 0;

    return( theResult );

}

UInt32

IMAAudioPayloadSetInterleaving(

    IMAAudioPayload *   inPayload,

    UInt32              inInterleaveCount,

    UInt32              inInterleaveGroupFrameCount )

{

    UInt32  theResult;

    theResult =

        __SetBitField(

            &inPayload->itsFixedHeader[ __kInterleaveCountWord ],

            __kInterleaveCountPosition, __kInterleaveCountSize,

            inInterleaveCount - 1 ) + 1;

    __SetBitField(

        &inPayload->itsFixedHeader[ __kInterleaveIndexWord ], __kInterleaveIndexPosition,

        __kInterleaveIndexSize, 0 );

    __SetBitField(

        &inPayload->itsFixedHeader[ __kInterleaveTailWord ], __kInterleaveTailPosition,

        __kInterleaveTailSize, ( inInterleaveGroupFrameCount - 1 ) % theResult );

    return( theResult );

}

UInt32

IMAAudioPayloadIncrementInterleaveIndex(

    IMAAudioPayload *   inPayload )

{

    UInt32  theResult;

    theResult =

        __BitField(

            &inPayload->itsFixedHeader[ __kInterleaveIndexWord ],

            __kInterleaveIndexPosition, __kInterleaveIndexSize );

    theResult =

        __SetBitField(

            &inPayload->itsFixedHeader[ __kInterleaveIndexWord ],

            __kInterleaveIndexPosition, __kInterleaveIndexSize,

            ( theResult + 1 ) % IMAAudioPayloadInterleaveCount( inPayload ) );

    return( theResult );

}

UInt32

IMAAudioPayloadChannelCount(

    const IMAAudioPayload *     inPayload )

{

    return(

        __BitField(

            &inPayload->itsFixedHeader[ __kChannelCountWord ],

            __kChannelCountPosition, __kChannelCountSize ) + 1 );

}

UnsignedFixed

IMAAudioPayloadSampleRate(

    const IMAAudioPayload *     inPayload )

{

    UnsignedFixed   theResult;

    UInt32          theRateCode;

    theRateCode =

        __BitField(

            &inPayload->itsFixedHeader[ __kSampleRateWord ],

            __kSampleRatePosition, __kSampleRateSize );

    if( theRateCode < __kSampleRateCount )

        theResult = Long2Fix( __gSampleRates[ theRateCode ] );

    else

        theResult = 0;

    return( theResult );

}

UInt32

IMAAudioPayloadInterleaveCount(

    const IMAAudioPayload *     inPayload )

{

    return(

        __BitField(

            &inPayload->itsFixedHeader[ __kInterleaveCountWord ],

            __kInterleaveCountPosition, __kInterleaveCountSize ) + 1 );

}

UInt32

IMAAudioPayloadInterleaveIndex(

    const IMAAudioPayload *     inPayload )

{

    return(

        __BitField(

            &inPayload->itsFixedHeader[ __kInterleaveIndexWord ],

            __kInterleaveIndexPosition, __kInterleaveIndexSize ) );

}

UInt32

IMAAudioPayloadInterleaveTail(

    const IMAAudioPayload *     inPayload )

{

    return(

        __BitField(

            &inPayload->itsFixedHeader[ __kInterleaveTailWord ],

            __kInterleaveTailPosition, __kInterleaveTailSize ) );

}