lzw data compression / decompression device and - a method with embedded run length coding / decoding

摘要

In an LZW data compressor, the occurrence of a character run in the input character stream is determined and the run count is added to the existing code in the compressor code counter to generate a compressor code output representative of the run count. The LZW data decompressor subtracts the existing code in the decompressor code counter from the received compressed code to recover the run count. In accordance with a further feature, large length runs are processed by reducing the run count to less than the system maximum code by subtracting a selected predetermined constant from the run count. The reduced run count is outputted by the compressor preceded by a reserved code representative of the selected predetermined constant. In response to the received reserved code and the reduced count that follows, the decompressor adds the selected predetermined constant corresponding to the received reserved code to the received reduced count to recover the original run count.