/// <summary>
/// Reads chunkd from input stream, adds to ChunksList, and returns it.
/// If it's skipped, a PngChunkSkipped object is created
/// </summary>
/// <returns></returns>
private AbstractPngChunk ReadChunk(byte[] chunkid, int clen, bool skipforced)
{
if (clen < 0)
{
throw new PngjInputException("invalid chunk lenght: " + clen);
}
// skipChunksByIdSet is created lazyly, if fist IHDR has already been read
if (skipChunkIdsSet is null && CurrentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR)
{
skipChunkIdsSet = new Dictionary <string, int>();
if (SkipChunkIds is object)
{
foreach (var id in SkipChunkIds)
{
skipChunkIdsSet.Add(id, 1);
}
}
}
var chunkidstr = ChunkHelper.ToString(chunkid);
var critical = ChunkHelper.IsCritical(chunkidstr);
var skip = skipforced;
if (MaxTotalBytesRead > 0 && clen + offset > MaxTotalBytesRead)
{
throw new PngjInputException("Maximum total bytes to read exceeeded: " + MaxTotalBytesRead + " offset:"
+ offset + " clen=" + clen);
}
// an ancillary chunks can be skipped because of several reasons:
if (CurrentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR && !ChunkHelper.IsCritical(chunkidstr))
{
skip = skip || (SkipChunkMaxSize > 0 && clen >= SkipChunkMaxSize) || skipChunkIdsSet.ContainsKey(chunkidstr) ||
(MaxBytesMetadata > 0 && clen > MaxBytesMetadata - bytesChunksLoaded) ||
!ChunkHelper.ShouldLoad(chunkidstr, ChunkLoadBehaviour);
}
AbstractPngChunk pngChunk;
if (skip)
{
PngHelperInternal.SkipBytes(inputStream, clen);
PngHelperInternal.ReadInt4(inputStream); // skip - we dont call PngHelperInternal.skipBytes(inputStream, clen + 4) for risk of overflow
pngChunk = new PngChunkSkipped(chunkidstr, ImgInfo, clen);
}
else
{
var chunk = new ChunkRaw(clen, chunkid, true);
_ = chunk.ReadChunkData(inputStream, critical);
pngChunk = AbstractPngChunk.Factory(chunk, ImgInfo);
if (!pngChunk.Crit)
{
bytesChunksLoaded += chunk.Len;
}
}
pngChunk.Offset = offset - 8L;
chunksList.AppendReadChunk(pngChunk, CurrentChunkGroup);
offset += clen + 4L;
return(pngChunk);
}
public sealed override void CloneDataFromRead(AbstractPngChunk other)
{
throw new PngjException("Non supported for a skipped chunk");
}
