/// <summary> Called after setting data, before writing to os </summary>
int ComputeCrc()
{
Zlib.CRC32 crcengine = PngHelperInternal.GetCRC();
crcengine.Reset();
crcengine.Update(IdBytes, 0, 4);
if (Len > 0)
{
crcengine.Update(Data, 0, Len);
}
return((int)crcengine.GetValue());
}
/// <summary>
/// Constructor must be called just after reading length and id of first IDAT
/// chunk
/// </summary>
public PngIDatChunkInputStream(System.IO.Stream iStream, int lenFirstChunk, long offset_0)
{
this.idLastChunk = new byte[4];
this.toReadThisChunk = 0;
this.ended = false;
this.foundChunksInfo = new System.Collections.Generic.List <IdatChunkInfo>();
this.offset = offset_0;
checkCrc = true;
inputStream = iStream;
crcEngine = new Zlib.CRC32();
this.lenLastChunk = lenFirstChunk;
toReadThisChunk = lenFirstChunk;
// we know it's a IDAT
System.Array.Copy(Chunks.ChunkHelper.b_IDAT, 0, idLastChunk, 0, 4);
crcEngine.Update(idLastChunk, 0, 4);
foundChunksInfo.Add(
new PngIDatChunkInputStream.IdatChunkInfo(lenLastChunk, offset_0 - 8)
);
// PngHelper.logdebug("IDAT Initial fragment: len=" + lenLastChunk);
if (this.lenLastChunk == 0)
{
EndChunkGoForNext(); // rare, but...
}
}