private static int DecodeHuffmanCode(ref JpegBitReader reader, JpegHuffmanDecodingTable table)
{
int bits = reader.PeekBits(16, out int bitsRead);
JpegHuffmanDecodingTable.Entry entry = table.Lookup(bits);
bitsRead = Math.Min(entry.CodeSize, bitsRead);
_ = reader.TryAdvanceBits(bitsRead, out _);
return(entry.SymbolValue);
}
private void ProcessDefineHuffmanTable(ReadOnlySequence <byte> segment, int currentOffset)
{
while (!segment.IsEmpty)
{
if (!JpegHuffmanDecodingTable.TryParse(segment, out JpegHuffmanDecodingTable? huffmanTable, out int bytesConsumed))
{
ThrowInvalidDataException(currentOffset, "Failed to parse Huffman table.");
return;
}
segment = segment.Slice(bytesConsumed);
currentOffset += bytesConsumed;
SetHuffmanTable(huffmanTable);
}
}
private void SetHuffmanTable(JpegHuffmanDecodingTable table)
{
List <JpegHuffmanDecodingTable>?list = _huffmanTables;
if (list is null)
{
list = _huffmanTables = new List <JpegHuffmanDecodingTable>(4);
}
for (int i = 0; i < list.Count; i++)
{
JpegHuffmanDecodingTable item = list[i];
if (item.TableClass == table.TableClass && item.Identifier == table.Identifier)
{
list[i] = table;
return;
}
}
list.Add(table);
}