RDC压缩算法(Delphi源码).doc

RDC压缩算法源码 Unit Common; Interface Type PByte = ^Byte; ByteArray = Array[0..65000] Of Byte; PByteArray = ^ByteArray; PInteger = ^Integer; IntArray = Array[0..32000] Of Integer; PIntArray = ^IntArray; PWord = ^Word; WordArray = Array[0..32000] Of Word; PWordArray = ^WordArray; Implementation END. (*************************************************** * RDC Unit * * * * This is a Pascal port of C code from an article * * In The C Users Journal, 1/92 Written by * * Ed Ross. * * * * This particular code has worked well under, * * Real, Protected and Windows. * * * * The compression is not quite as good as PKZIP * * but it decompresses about 5 times faster. * ***************************************************) Unit RDCUnit; Interface Uses Common; Procedure Comp_FileToFile(Var infile, outfile: File); Procedure Decomp_FileToFile(Var infile, outfile: File); Implementation Const HASH_LEN = 4096; { # hash table entries } HASH_SIZE = HASH_LEN * Sizeof(word); BUFF_LEN = 16384; { size of disk io buffer } (* compress inbuff_len bytes of inbuff into outbuff using hash_len entries in hash_tbl. return length of outbuff, or 0 - inbuff_len if inbuff could not be compressed. *) Function rdc_compress(ibuff : Pointer; inbuff_len : Word; obuff : Pointer; htable : Pointer) : Integer; Var inbuff : PByte Absolute ibuff; outbuff : PByte Absolute obuff; hash_tbl : PWordArray Absolute htable; in_idx : PByte; in_idxa : PByteArray absolute in_idx; inbuff_end : PByte; anchor : PByte; pat_idx : PByte; cnt : Word; gap : Word; c : Word; hash