public override byte[] Encode(Bytes.Buffer rawData, PdfDirectObject parameters, IDictionary <PdfName, PdfDirectObject> header)
{
List <byte[]> codeTable = CreateCodeTable();
int chunk = 9;
byte[] inputPattern = null;
using (var output = new Bytes.Buffer())
{
output.WriteBits(CLEAR_TABLE, chunk);
int foundCode = -1;
int r;
while ((r = rawData.ReadByte()) != -1)
{
byte by = (byte)r;
if (inputPattern == null)
{
inputPattern = new byte[] { by };
foundCode = by & 0xff;
}
else
{
inputPattern = inputPattern.SubArray(0, inputPattern.Length + 1);
inputPattern[inputPattern.Length - 1] = by;
int newFoundCode = FindPatternCode(codeTable, inputPattern);
if (newFoundCode == -1)
{
// use previous
chunk = CalculateChunk(codeTable.Count - 1, 1);
output.WriteBits(foundCode, chunk);
// create new table entry
codeTable.Add(inputPattern);
if (codeTable.Count == 4096)
{
// code table is full
output.WriteBits(CLEAR_TABLE, chunk);
codeTable = CreateCodeTable();
}
inputPattern = new byte[] { by };
foundCode = by & 0xff;
}
else
{
foundCode = newFoundCode;
}
}
}
if (foundCode != -1)
{
chunk = CalculateChunk(codeTable.Count - 1, 1);
output.WriteBits(foundCode, chunk);
}
// PPDFBOX-1977: the decoder wouldn't know that the encoder would output
// an EOD as code, so he would have increased his own code table and
// possibly adjusted the chunk. Therefore, the encoder must behave as
// if the code table had just grown and thus it must be checked it is
// needed to adjust the chunk, based on an increased table size parameter
chunk = CalculateChunk(codeTable.Count, 1);
output.WriteBits(EOD, chunk);
// pad with 0
output.WriteBits(0, 7);
// must do or file will be empty :-(
return(output.GetBuffer());
}
}