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ImfRleCompressor.cpp

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2002, 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 RleCompressor
//
//-----------------------------------------------------------------------------

#include <ImfRleCompressor.h>
#include "Iex.h"

namespace Imf {
namespace {

const int MIN_RUN_LENGTH = 3;
const int MAX_RUN_LENGTH = 127;


//
// Compress an array of bytes, using run-length encoding,
// and return the length of the compressed data.
//

int
rleCompress (int inLength, const char in[], signed char out[])
{
    const char *inEnd = in + inLength;
    const char *runStart = in;
    const char *runEnd = in + 1;
    signed char *outWrite = out;

    while (runStart < inEnd)
    {
      while (runEnd < inEnd &&
             *runStart == *runEnd &&
             runEnd - runStart - 1 < MAX_RUN_LENGTH)
      {
          ++runEnd;
      }

      if (runEnd - runStart >= MIN_RUN_LENGTH)
      {
          //
          // Compressable run
          //

          *outWrite++ = (runEnd - runStart) - 1;
          *outWrite++ = *(signed char *) runStart;
          runStart = runEnd;
      }
      else
      {
          //
          // Uncompressable run
          //

          while (runEnd < inEnd &&
               ((runEnd + 1 >= inEnd ||
                 *runEnd != *(runEnd + 1)) ||
                (runEnd + 2 >= inEnd ||
                 *(runEnd + 1) != *(runEnd + 2))) &&
               runEnd - runStart < MAX_RUN_LENGTH)
          {
            ++runEnd;
          }

          *outWrite++ = runStart - runEnd;

          while (runStart < runEnd)
          {
            *outWrite++ = *(signed char *) (runStart++);
          }
      }

      ++runEnd;
    }

    return outWrite - out;
}


//
// Uncompress an array of bytes compressed with rleCompress().
// Returns the length of the oncompressed data, or 0 if the
// length of the uncompressed data would be more than maxLength.
//

int
rleUncompress (int inLength, int maxLength, const signed char in[], char out[])
{
    char *outStart = out;

    while (inLength > 0)
    {
      if (*in < 0)
      {
          int count = -((int)*in++);
          inLength -= count + 1;

          if (0 > (maxLength -= count))
            return 0;

          while (count-- > 0)
            *out++ = *(char *) (in++);
      }
      else
      {
          int count = *in++;
          inLength -= 2;

          if (0 > (maxLength -= count + 1))
            return 0;

          while (count-- >= 0)
            *out++ = *(char *) in;

          in++;
      }
    }

    return out - outStart;
}

} // namespace


RleCompressor::RleCompressor (const Header &hdr, int maxScanLineSize):
    Compressor (hdr),
    _maxScanLineSize (maxScanLineSize),
    _tmpBuffer (0),
    _outBuffer (0)
{
    _tmpBuffer = new char [maxScanLineSize];
    _outBuffer = new char [maxScanLineSize * 3 / 2];
}


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


int
RleCompressor::numScanLines () const
{
    //
    // This compressor compresses individual scan lines.
    //

    return 1;
}


int
RleCompressor::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;
      }
    }

    //
    // Run-length encode the data.
    //

    outPtr = _outBuffer;
    return rleCompress (inSize, _tmpBuffer, (signed char *) _outBuffer);
}


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

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

    //
    // Decode the run-length encoded data
    //

    int outSize;

    if (0 == (outSize = rleUncompress (inSize, _maxScanLineSize,
                               (const signed char *) inPtr,
                               _tmpBuffer)))
    {
      throw Iex::InputExc ("Data decoding (rle) 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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