text: /*
     Source File : InputAscii85DecodeStream.cpp
  
  
     Copyright 2011 Gal Kahana PDFWriter
  
     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.
  
  
  */
  #include "InputAscii85DecodeStream.h"
  
  #include <string.h>
  
  #include <algorithm>
  
  using namespace IOBasicTypes;
  
  InputAscii85DecodeStream::InputAscii85DecodeStream(void)
  {
  	mSourceStream = NULL;
  }
  
  InputAscii85DecodeStream::~InputAscii85DecodeStream(void)
  {
  	if(mSourceStream)
  		delete mSourceStream;
  }
  
  InputAscii85DecodeStream::InputAscii85DecodeStream(IByteReader* inSourceReader)
  {
  	Assign(inSourceReader);
  }
  
  void InputAscii85DecodeStream::Assign(IByteReader* inSourceReader)
  {
  	mSourceStream = inSourceReader;
  	mHitEnd = false;
  
  	mReadBufferSize = 0;
  	mReadBufferIndex = 0;
  }
  
  bool InputAscii85DecodeStream::NotEnded()
  {
  	return mSourceStream && ((!mHitEnd && mSourceStream->NotEnded()) || mReadBufferIndex < mReadBufferSize);
  }
  
  LongBufferSizeType InputAscii85DecodeStream::Read(IOBasicTypes::Byte* inBuffer,LongBufferSizeType inBufferSize)
  {
  	LongBufferSizeType mCurrentIndex = 0;
  
  
  	if(NotEnded() && mReadBufferSize == 0) // read buffer, in any case (don't like 0 size memcpys)
  		ReadNextBuffer();
  
  
  	while(NotEnded() && mCurrentIndex < inBufferSize)
  	{
  		// copy what's in the buffer
  		int sizeToCopy = std::min<int>(mReadBufferSize-mReadBufferIndex,(int)(inBufferSize-mCurrentIndex));
  		memcpy(inBuffer + mCurrentIndex,mBuffer + mReadBufferIndex ,sizeToCopy);
  
  		mReadBufferIndex+=sizeToCopy;
  		mCurrentIndex+=sizeToCopy;
  
  		// now read the next batch (even if buffer is satisfied...so we'll have for next read)
  		if(mReadBufferIndex == mReadBufferSize)
  			ReadNextBuffer();
  	}
  
  	return mCurrentIndex;
  }
  
  void InputAscii85DecodeStream::ReadNextBuffer()
  {
  	Byte buffer[5];
  	int readIndex = 0;
  	Byte aByte;
  
  	while(readIndex < 5 && mSourceStream->NotEnded())
  	{
  		mSourceStream->Read(&aByte,1);
  
  		if(33 <= aByte && aByte<= 117)
  		{
  			buffer[readIndex] = aByte;
  			++readIndex;
  		}
  		else if(aByte == 122)
  		{
  			// z - special case
  			buffer[readIndex] = aByte;
  			++readIndex;
  			break;
  		}
  		else if(aByte == 126)
  		{
  			// EOD marker
  			mSourceStream->Read(&aByte,1);
  			if(aByte == 62)
  			{
  				mHitEnd = true;
  				break;
  			}
  		}
  		// else, continue to next character, skipping space and invalid
  
  	}
  
  	// if there's anything to encode
  	if(readIndex > 0)
  	{
  		if(buffer[0] == 122)
  		{
  			// special case Z
  			mBuffer[0] = mBuffer[1] = mBuffer[2] = mBuffer[3] = 0;
  			mReadBufferIndex = 0;
  			mReadBufferSize = 4;
  		}
  		else
  		{
  			unsigned long encodedValue = 0;
  
  			int i=0;
  			for(;i <readIndex;++i)
  				encodedValue = encodedValue * 85 + buffer[i] - 33;
  			for(;i<5;++i)
  				encodedValue= encodedValue * 85 + 117 -33;
  
  			for(int j=0;j < 4;++j)
  			{
  				mBuffer[3-j] = encodedValue & 0xFF;
  				encodedValue = encodedValue>>8;
  			}
  			mReadBufferIndex = 0;
  			mReadBufferSize = readIndex-1;
  		}
  
  	}
  }
  