Method doWriteMetadata

src/pngimage.cpp:497–687

}  // PngImage::writeMetadata

void PngImage::doWriteMetadata(BasicIo& outIo) {
  if (!io_->isopen())
    throw Error(ErrorCode::kerInputDataReadFailed);
  if (!outIo.isopen())
    throw Error(ErrorCode::kerImageWriteFailed);

#ifdef EXIV2_DEBUG_MESSAGES
  std::cout << "Exiv2::PngImage::doWriteMetadata: Writing PNG file " << io_->path() << "\n";
  std::cout << "Exiv2::PngImage::doWriteMetadata: tmp file created " << outIo.path() << "\n";
#endif

  if (!isPngType(*io_, true)) {
    throw Error(ErrorCode::kerNoImageInInputData);
  }

  // Write PNG Signature.
  if (outIo.write(pngSignature, 8) != 8)
    throw Error(ErrorCode::kerImageWriteFailed);

  DataBuf cheaderBuf(8);  // Chunk header : 4 bytes (data size) + 4 bytes (chunk type).

  while (!io_->eof()) {
    // Read chunk header.
    size_t bufRead = io_->read(cheaderBuf.data(), 8);
    if (io_->error())
      throw Error(ErrorCode::kerFailedToReadImageData);
    if (bufRead != 8)
      throw Error(ErrorCode::kerInputDataReadFailed);

    // Decode chunk data length.

    uint32_t dataOffset = cheaderBuf.read_uint32(0, Exiv2::bigEndian);
    if (dataOffset > 0x7FFFFFFF)
      throw Exiv2::Error(ErrorCode::kerFailedToReadImageData);

    // Read whole chunk : Chunk header + Chunk data (not fixed size - can be null) + CRC (4 bytes).

    DataBuf chunkBuf(8 + dataOffset + 4);                   // Chunk header (8 bytes) + Chunk data + CRC (4 bytes).
    std::copy_n(cheaderBuf.begin(), 8, chunkBuf.begin());   // Copy header.
    bufRead = io_->read(chunkBuf.data(8), dataOffset + 4);  // Extract chunk data + CRC
    if (io_->error())
      throw Error(ErrorCode::kerFailedToReadImageData);
    if (bufRead != dataOffset + 4)
      throw Error(ErrorCode::kerInputDataReadFailed);

    char szChunk[5];
    memcpy(szChunk, cheaderBuf.c_data(4), 4);
    szChunk[4] = 0;

    if (!strcmp(szChunk, "IEND")) {
      // Last chunk found: we write it and done.
#ifdef EXIV2_DEBUG_MESSAGES
      std::cout << "Exiv2::PngImage::doWriteMetadata: Write IEND chunk (length: " << dataOffset << ")\n";
#endif
      if (outIo.write(chunkBuf.data(), chunkBuf.size()) != chunkBuf.size())
        throw Error(ErrorCode::kerImageWriteFailed);
      return;
    }