/// <summary>Processes a RIFF data sequence.</summary>
/// <param name="reader">The <see cref="SequentialReader"/> from which the data should be read.</param>
/// <param name="handler">The <see cref="IRiffHandler"/> that will coordinate processing and accept read values.</param>
/// <exception cref="RiffProcessingException">An error occurred during the processing of RIFF data that could not be ignored or recovered from.</exception>
/// <exception cref="System.IO.IOException">an error occurred while accessing the required data</exception>
public void ProcessRiff([NotNull] SequentialReader reader, [NotNull] IRiffHandler handler)
{
// RIFF files are always little-endian
reader = reader.WithByteOrder(isMotorolaByteOrder: false);
// PROCESS FILE HEADER
var fileFourCc = reader.GetString(4, Encoding.ASCII);
if (fileFourCc != "RIFF")
{
throw new RiffProcessingException("Invalid RIFF header: " + fileFourCc);
}
// The total size of the chunks that follow plus 4 bytes for the 'WEBP' or 'AVI ' FourCC
int fileSize = reader.GetInt32();
int sizeLeft = fileSize;
string identifier = reader.GetString(4, Encoding.ASCII);
sizeLeft -= 4;
if (!handler.ShouldAcceptRiffIdentifier(identifier))
{
return;
}
ProcessChunks(reader, sizeLeft, handler);
}
/// <summary>Processes a RIFF data sequence.</summary>
/// <param name="reader">The <see cref="SequentialReader"/> from which the data should be read.</param>
/// <param name="handler">The <see cref="IRiffHandler"/> that will coordinate processing and accept read values.</param>
/// <exception cref="RiffProcessingException">An error occurred during the processing of RIFF data that could not be ignored or recovered from.</exception>
/// <exception cref="System.IO.IOException">an error occurred while accessing the required data</exception>
public void ProcessRiff([NotNull] SequentialReader reader, [NotNull] IRiffHandler handler)
{
// RIFF files are always little-endian
reader = reader.WithByteOrder(isMotorolaByteOrder: false);
// PROCESS FILE HEADER
var fileFourCc = reader.GetString(4, Encoding.UTF8);
if (fileFourCc != "RIFF")
{
throw new RiffProcessingException("Invalid RIFF header: " + fileFourCc);
}
// The total size of the chunks that follow plus 4 bytes for the 'WEBP' FourCC
var fileSize = reader.GetInt32();
var sizeLeft = fileSize;
var identifier = reader.GetString(4, Encoding.UTF8);
sizeLeft -= 4;
if (!handler.ShouldAcceptRiffIdentifier(identifier))
{
return;
}
// PROCESS CHUNKS
while (sizeLeft != 0)
{
var chunkFourCc = reader.GetString(4, Encoding.UTF8);
var chunkSize = reader.GetInt32();
sizeLeft -= 8;
// NOTE we fail a negative chunk size here (greater than 0x7FFFFFFF) as we cannot allocate arrays larger than this
if (chunkSize < 0 || sizeLeft < chunkSize)
{
throw new RiffProcessingException("Invalid RIFF chunk size");
}
if (handler.ShouldAcceptChunk(chunkFourCc))
{
// TODO is it feasible to avoid copying the chunk here, and to pass the sequential reader to the handler?
handler.ProcessChunk(chunkFourCc, reader.GetBytes(chunkSize));
}
else
{
reader.Skip(chunkSize);
}
sizeLeft -= chunkSize;
// Skip any padding byte added to keep chunks aligned to even numbers of bytes
if (chunkSize % 2 == 1)
{
reader.GetSByte();
sizeLeft--;
}
}
}