/// <summary>
/// sometimes last row read does not fully consumes the chunk here we read the
/// reamaing dummy bytes
/// </summary>
public void ForceChunkEnd()
{
if (!ended)
{
byte[] dummy = new byte[toReadThisChunk];
PngHelperInternal.ReadBytes(inputStream, dummy, 0, toReadThisChunk);
if (checkCrc)
{
crcEngine.Update(dummy, 0, toReadThisChunk);
}
EndChunkGoForNext();
}
}
/// <summary>
/// Position before: just after chunk id. positon after: after crc Data should
/// be already allocated. Checks CRC Return number of byte read.
/// </summary>
internal int ReadChunkData(System.IO.Stream stream, bool checkCrc)
{
PngHelperInternal.ReadBytes(stream, Data, 0, Len);
crcval = PngHelperInternal.ReadInt4(stream);
if (checkCrc)
{
int crc = ComputeCrc();
if (crc != crcval)
{
throw new System.Exception($"crc invalid for chunk {this} calc={crc} read={crcval}");
}
}
return(Len + 4);
}
internal int ReadChunkData(Stream stream, bool checkCrc)
{
PngHelperInternal.ReadBytes(stream, Data, 0, Length);
crcval = PngHelperInternal.ReadInt4(stream);
if (checkCrc)
{
int num = ComputeCrc();
if (num != crcval)
{
throw new PngjBadCrcException("crc invalid for chunk " + ToString() + " calc=" + num.ToString() + " read=" + crcval.ToString());
}
}
return(Length + 4);
}
/// <summary>
/// Position before: just after chunk id. positon after: after crc Data should
/// be already allocated. Checks CRC Return number of byte read.
/// </summary>
///
internal int ReadChunkData(Stream stream, bool checkCrc)
{
PngHelperInternal.ReadBytes(stream, Data, 0, Len);
crcval = PngHelperInternal.ReadInt4(stream);
if (checkCrc)
{
var crc = ComputeCrc();
if (crc != crcval)
{
throw new PngjBadCrcException("crc invalid for chunk " + ToString() + " calc="
+ crc.ToString(CultureInfo.CurrentCulture) + " read=" + crcval.ToString(CultureInfo.CurrentCulture));
}
}
return(Len + 4);
}
public override void Close() => base.Close(); // nothing
void EndChunkGoForNext()
{
// Called after readging the last byte of chunk
// Checks CRC, and read ID from next CHUNK
// Those values are left in idLastChunk / lenLastChunk
// Skips empty IDATS
do
{
int crc = PngHelperInternal.ReadInt4(inputStream);
offset += 4;
if (checkCrc)
{
int crccalc = (int)crcEngine.GetValue();
if (lenLastChunk > 0 && crc != crccalc)
{
throw new System.Exception($"error reading idat; offset: {offset}");
}
crcEngine.Reset();
}
lenLastChunk = PngHelperInternal.ReadInt4(inputStream);
if (lenLastChunk < 0)
{
throw new System.IO.IOException($"invalid len for chunk: {lenLastChunk}");
}
toReadThisChunk = lenLastChunk;
PngHelperInternal.ReadBytes(inputStream, idLastChunk, 0, 4);
offset += 8;
ended = !PngCsUtils.UnSafeEquals(idLastChunk, 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 ??)
}