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CAAudioChannelLayout.cpp

/*    Copyright:  © Copyright 2005 Apple Computer, Inc. All rights reserved.

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*/
/*=============================================================================
      CAAudioChannelLayout.cpp

=============================================================================*/

//=============================================================================
//    Includes
//=============================================================================

//    Self Include
#include "CAAudioChannelLayout.h"
#include <stdlib.h>
#include <string.h>

//=============================================================================
//    CAAudioChannelLayout
//=============================================================================

AudioChannelLayout*     CAAudioChannelLayout::Create(UInt32 inNumberChannelDescriptions)
{
      UInt32 theSize = CalculateByteSize(inNumberChannelDescriptions);
      AudioChannelLayout* theAnswer = static_cast<AudioChannelLayout*>(calloc(1, theSize));
      if(theAnswer != NULL)
      {
            SetAllToUnknown(*theAnswer, inNumberChannelDescriptions);
      }
      return theAnswer;
}

void  CAAudioChannelLayout::Destroy(AudioChannelLayout* inChannelLayout)
{
      free(inChannelLayout);
}

void  CAAudioChannelLayout::SetAllToUnknown(AudioChannelLayout& outChannelLayout, UInt32 inNumberChannelDescriptions)
{
      outChannelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_UseChannelDescriptions;
      outChannelLayout.mChannelBitmap = 0;
      outChannelLayout.mNumberChannelDescriptions = inNumberChannelDescriptions;
      for(UInt32 theChannelIndex = 0; theChannelIndex < inNumberChannelDescriptions; ++theChannelIndex)
      {
            outChannelLayout.mChannelDescriptions[theChannelIndex].mChannelLabel = kAudioChannelLabel_Unknown;
            outChannelLayout.mChannelDescriptions[theChannelIndex].mChannelFlags = 0;
            outChannelLayout.mChannelDescriptions[theChannelIndex].mCoordinates[0] = 0;
            outChannelLayout.mChannelDescriptions[theChannelIndex].mCoordinates[1] = 0;
            outChannelLayout.mChannelDescriptions[theChannelIndex].mCoordinates[2] = 0;
      }
}

bool  operator== (const AudioChannelLayout &x, const AudioChannelLayout &y)
{
      // compare based on the number of channel descriptions present
      // (this may be too strict a comparison if all you care about are matching layout tags)
      UInt32 theSize1 = CAAudioChannelLayout::CalculateByteSize(x.mNumberChannelDescriptions);
      UInt32 theSize2 = CAAudioChannelLayout::CalculateByteSize(y.mNumberChannelDescriptions);
      
      if (theSize1 != theSize2)
            return false;
            
      return !memcmp (&x, &y, theSize1);
}

// counting the one bits in a word
inline UInt32 CountOnes(UInt32 x)
{
      // secret magic algorithm for counting bits in a word.
      UInt32 t;
      x = x - ((x >> 1) & 0x55555555);
      t = ((x >> 2) & 0x33333333);
      x = (x & 0x33333333) + t;
      x = (x + (x >> 4)) & 0x0F0F0F0F;
      x = x + (x << 8);
      x = x + (x << 16);
      return x >> 24;
}

UInt32      CAAudioChannelLayout::NumberChannels (const AudioChannelLayout& inLayout)
{
      if (inLayout.mChannelLayoutTag == kAudioChannelLayoutTag_UseChannelDescriptions)
            return inLayout.mNumberChannelDescriptions;
      
      if (inLayout.mChannelLayoutTag == kAudioChannelLayoutTag_UseChannelBitmap)
            return CountOnes (inLayout.mChannelBitmap);

      return AudioChannelLayoutTag_GetNumberOfChannels(inLayout.mChannelLayoutTag);
}

void  CAShowAudioChannelLayout (FILE* file, const AudioChannelLayout *layout)
{
      fprintf (file, "\tTag=0x%lX, ", layout->mChannelLayoutTag);
      if (layout->mChannelLayoutTag == kAudioChannelLayoutTag_UseChannelBitmap)
            fprintf (file, "Using Bitmap:0x%lX\n", layout->mChannelBitmap);
      else {
            fprintf (file, "Num Chan Descs=%ld\n", layout->mNumberChannelDescriptions);
            const AudioChannelDescription *desc = layout->mChannelDescriptions;
            for (unsigned int i = 0; i < layout->mNumberChannelDescriptions; ++i, ++desc) {
                  fprintf (file, "\t\tLabel=%ld, Flags=0x%lX, ", desc->mChannelLabel, desc->mChannelFlags);
                  fprintf (file, "[az=%f,el=%f,dist=%f]\n", desc->mCoordinates[0], desc->mCoordinates[1], desc->mCoordinates[2]);
            }
      }
}

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