BufferedStreamReader.cpp

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/**********************************************************************
 
  Audacity: A Digital Audio Editor
 
  BufferedStreamReader.cpp
 
  Dmitry Vedenko
 
**********************************************************************/
 
#include "BufferedStreamReader.h"
 
#include <algorithm>
#include <memory>
#include <cstring>
 
BufferedStreamReader::BufferedStreamReader(size_t bufferSize)
    : mBufferSize(std::max(bufferSize, RequiredAlignment))
{
   mBufferData.resize(mBufferSize + RequiredAlignment);
 
   auto ptr = static_cast<void*>(mBufferData.data());
   auto space = mBufferData.size();
 
   std::align(RequiredAlignment, mBufferSize, ptr, space);
 
   mBufferStart = static_cast<uint8_t*>(ptr);
}
 
size_t BufferedStreamReader::Read(void* buffer, size_t maxBytes)
{
   size_t bytesWritten = 0;
 
   while (maxBytes > 0)
   {
      if (mCurrentBytes == mCurrentIndex)
      {
         if (!HandleUnderflow())
            return bytesWritten;
      }
 
      const size_t availableBytes = mCurrentBytes - mCurrentIndex;
      const size_t bytesToRead = std::min(maxBytes, availableBytes);
 
      std::memcpy(static_cast<uint8_t*>(buffer) + bytesWritten, mBufferStart + mCurrentIndex, bytesToRead);
 
      maxBytes -= bytesToRead;
      bytesWritten += bytesToRead;
      mCurrentIndex += bytesToRead;
   }
 
   return bytesWritten;
}
 
bool BufferedStreamReader::Eof() const
{
   return mCurrentBytes == mCurrentIndex && !HasMoreData();
}
 
int BufferedStreamReader::GetC()
{
   uint8_t value = 0;
 
   if (ReadValue(value))
      return value;
 
   return -1;
}
 
bool BufferedStreamReader::HandleUnderflow()
{
   if (!HasMoreData())
      return false;
 
   mCurrentBytes = ReadData(mBufferStart, mBufferSize);
   mCurrentIndex = 0;
 
   return true;
}