private void EndChunkGoForNext()
{
// Called after readging the last byte of chunk
// Checks CRC, and read ID from next CHUNK
// Those values are left in idLastChunk / lenLastChunk
// Skips empty IDATS
do
{
int crc = Pngcs.PngHelperInternal.ReadInt4(inputStream); //
offset += 4;
if (checkCrc)
{
int crccalc = (int)crcEngine.GetValue();
if (lenLastChunk > 0 && crc != crccalc)
{
throw new PngjBadCrcException("error reading idat; offset: " + offset);
}
crcEngine.Reset();
}
lenLastChunk = Pngcs.PngHelperInternal.ReadInt4(inputStream);
if (lenLastChunk < 0)
{
throw new PngjInputException("invalid len for chunk: " + lenLastChunk);
}
toReadThisChunk = lenLastChunk;
Pngcs.PngHelperInternal.ReadBytes(inputStream, idLastChunk, 0, 4);
offset += 8;
ended = !PngCsUtils.arraysEqual4(idLastChunk, Pngcs.Chunks.ChunkHelper.b_IDAT);
if (!ended)
{
foundChunksInfo.Add(new PngIDatChunkInputStream.IdatChunkInfo(lenLastChunk, (offset - 8)));
if (checkCrc)
{
crcEngine.Update(idLastChunk, 0, 4);
}
}
// PngHelper.logdebug("IDAT ended. next len= " + lenLastChunk + " idat?" +
// (!ended));
} while (lenLastChunk == 0 && !ended);
// rarely condition is true (empty IDAT ??)
}
/// <summary>
/// Constructor must be called just after reading length and id of first IDAT
/// chunk
/// </summary>
///
public PngIDatChunkInputStream(Stream iStream, int lenFirstChunk, long offset_0)
{
this.idLastChunk = new byte[4];
this.toReadThisChunk = 0;
this.ended = false;
this.foundChunksInfo = new List <IdatChunkInfo>();
this.offset = offset_0;
checkCrc = true;
inputStream = iStream;
crcEngine = new CRC32();
this.lenLastChunk = lenFirstChunk;
toReadThisChunk = lenFirstChunk;
// we know it's a IDAT
System.Array.Copy((Array)(Pngcs.Chunks.ChunkHelper.b_IDAT), 0, (Array)(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...
}
}