Minimum identical consecutive run length data units compression method by searching consecutive data pair comparison results stored in a string

摘要

A method of detecting certain runs of data, such as identical consecutive runs of data, is disclosed. The logical operation exclusive OR (XOR) is performed on each pair of adjacent bytes in a source string of data bytes in a single machine instruction, resulting in a comparison data string of bytes. The comparison data string is then sequentially searched for a byte which matches a predetermined byte. In the case of a search, the predetermined byte may be any value, which value is determined by the XOR of two adjacent bytes that are to be found. In the case of compression, as used in this invention, the predetermined byte has a value of zero, indicating that two adjacent bytes in the source string are identical. The sequential search occurs in a single Translate and Test (TRT) machine instruction. Once an all-zero byte is located, the subsequent byte in the comparision data string is examined. If the subsequent byte is also an all-zero byte, three identical, consecutive bytes in the source string have been located and are considered to be compressible. Additional bytes in the identical, consecutive run of bytes are located by further searching. If the subsequent byte in the comparison data string is not also an all-zero byte, the search for an all-zero byte is restarted with the byte following the subsequent byte in the comparison data string.