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ImfZipCompressor.cpp

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2004, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// *       Neither the name of Industrial Light & Magic nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
///////////////////////////////////////////////////////////////////////////



//-----------------------------------------------------------------------------
//
//    class ZipCompressor
//
//-----------------------------------------------------------------------------

#include <ImfZipCompressor.h>
#include "Iex.h"
#include <zlib.h>

namespace Imf {


ZipCompressor::ZipCompressor
    (const Header &hdr,
     int maxScanLineSize,
     int numScanLines)
:
    Compressor (hdr),
    _maxScanLineSize (maxScanLineSize),
    _numScanLines (numScanLines),
    _tmpBuffer (0),
    _outBuffer (0)
{
    _tmpBuffer =
      new char [maxScanLineSize * numScanLines];

    _outBuffer =
      new char [int (ceil (maxScanLineSize * numScanLines * 1.01)) + 100];
}


ZipCompressor::~ZipCompressor ()
{
    delete [] _tmpBuffer;
    delete [] _outBuffer;
}


int
ZipCompressor::numScanLines () const
{
    return _numScanLines;
}


int
ZipCompressor::compress (const char *inPtr,
                   int inSize,
                   int minY,
                   const char *&outPtr)
{
    //
    // Special case - empty input buffer
    //

    if (inSize == 0)
    {
      outPtr = _outBuffer;
      return 0;
    }

    //
    // Reorder the pixel data.
    //

    {
      char *t1 = _tmpBuffer;
      char *t2 = _tmpBuffer + (inSize + 1) / 2;
      const char *stop = inPtr + inSize;

      while (true)
      {
          if (inPtr < stop)
            *(t1++) = *(inPtr++);
          else
            break;

          if (inPtr < stop)
            *(t2++) = *(inPtr++);
          else
            break;
      }
    }

    //
    // Predictor.
    //

    {
      unsigned char *t = (unsigned char *) _tmpBuffer + 1;
      unsigned char *stop = (unsigned char *) _tmpBuffer + inSize;
      int p = t[-1];

      while (t < stop)
      {
          int d = int (t[0]) - p + (128 + 256);
          p = t[0];
          t[0] = d;
          ++t;
      }
    }

    //
    // Compress the data using zlib
    //

    uLongf outSize = int(ceil(inSize * 1.01)) + 100;

    if (Z_OK != ::compress ((Bytef *)_outBuffer, &outSize,
                      (const Bytef *) _tmpBuffer, inSize))
    {
      throw Iex::BaseExc ("Data compression (zlib) failed.");
    }

    outPtr = _outBuffer;
    return outSize;
}


int
ZipCompressor::uncompress (const char *inPtr,
                     int inSize,
                     int minY,
                     const char *&outPtr)
{
    //
    // Special case - empty input buffer
    //

    if (inSize == 0)
    {
      outPtr = _outBuffer;
      return 0;
    }

    //
    // Decompress the data using zlib
    //

    uLongf outSize = _maxScanLineSize * _numScanLines;

    if (Z_OK != ::uncompress ((Bytef *)_tmpBuffer, &outSize,
                        (const Bytef *) inPtr, inSize))
    {
      throw Iex::InputExc ("Data decompression (zlib) failed.");
    }

    //
    // Predictor.
    //

    {
      unsigned char *t = (unsigned char *) _tmpBuffer + 1;
      unsigned char *stop = (unsigned char *) _tmpBuffer + outSize;

      while (t < stop)
      {
          int d = int (t[-1]) + int (t[0]) - 128;
          t[0] = d;
          ++t;
      }
    }

    //
    // Reorder the pixel data.
    //

    {
      const char *t1 = _tmpBuffer;
      const char *t2 = _tmpBuffer + (outSize + 1) / 2;
      char *s = _outBuffer;
      char *stop = s + outSize;

      while (true)
      {
          if (s < stop)
            *(s++) = *(t1++);
          else
            break;

          if (s < stop)
            *(s++) = *(t2++);
          else
            break;
      }
    }

    outPtr = _outBuffer;
    return outSize;
}


} // namespace Imf

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