385 lines
11 KiB
C
385 lines
11 KiB
C
/**************************************************************
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LZSS.C -- A Data Compression Program
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(tab = 4 spaces)
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***************************************************************
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4/6/1989 Haruhiko Okumura
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Use, distribute, and modify this program freely.
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Please send me your improved versions.
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PC-VAN SCIENCE
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NIFTY-Serve PAF01022
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CompuServe 74050,1022
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**************************************************************
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WARNING: order of match_position and match_lenght changed!
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see lines 178 to 182
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Mofication by <stephan.walter@gmx.ch>
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Also modified to have N,F,etc, etc to be parameters, not
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hard-coded -- vmw
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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/* output types */
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#define NORMAL_ASM 0
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#define num_trees 256
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/* initialize trees */
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static void newInitTree(int ring_buffer_size,int binary_search_index,
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int *rson, int *dad) {
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int i;
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/* For i = 0 to N - 1, rson[i] and lson[i] will be the right and
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left children of node i. These nodes need not be initialized.
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Also, dad[i] is the parent of node i. These are initialized to
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NIL (= N), which stands for 'not used.'
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For i = 0 to 255, rson[N + i + 1] is the root of the tree
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for strings that begin with character i. These are initialized
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to NIL. Note there are 256 trees. */
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for (i=ring_buffer_size+1; i<=ring_buffer_size+num_trees; i++) {
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rson[i] = binary_search_index;
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}
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for (i=0; i<ring_buffer_size; i++) {
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dad[i] = binary_search_index;
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}
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}
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static void newInsertNode(
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int r, int ring_buffer_size, int binary_search_index,
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int match_length_limit,
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unsigned char *text_buf, int *rson,int *lson, int *dad,
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int *match_length, int *match_position) {
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/* Inserts string of length F, text_buf[r..r+F-1], into one of the
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trees (text_buf[r]'th tree) and returns the longest-match position
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and length via the global variables match_position and match_length.
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If match_length = F, then removes the old node in favor of the new
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one, because the old one will be deleted sooner.
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Note r plays double role, as tree node and position in buffer. */
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int i, p, cmp;
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unsigned char *key;
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cmp = 1;
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key = text_buf+r;
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p = ring_buffer_size + 1 + key[0];
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rson[r] = lson[r] = binary_search_index;
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*match_length = 0;
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for( ; ; ) {
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if (cmp >= 0) {
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if (rson[p] != binary_search_index) p = rson[p];
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else {
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rson[p] = r;
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dad[r] = p;
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return;
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}
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}
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else {
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if (lson[p] != binary_search_index) p = lson[p];
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else {
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lson[p] = r;
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dad[r] = p;
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return;
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}
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}
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for(i = 1; i < match_length_limit; i++)
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if ((cmp = key[i] - text_buf[p + i]) != 0) break;
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if (i > *match_length) {
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*match_position = p;
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if ((*match_length = i) >= match_length_limit) break;
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}
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}
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dad[r] = dad[p];
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lson[r] = lson[p];
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rson[r] = rson[p];
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dad[lson[p]] = r;
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dad[rson[p]] = r;
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if (rson[dad[p]] == p) rson[dad[p]] = r;
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else lson[dad[p]] = r;
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dad[p] = binary_search_index; /* remove p */
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}
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/* deletes node p from tree */
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static void newDeleteNode(int p, int binary_search_index,
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int *dad, int *rson, int *lson) {
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int q;
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if (dad[p] == binary_search_index) return; /* not in tree */
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if (rson[p] == binary_search_index) q = lson[p];
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else if (lson[p] == binary_search_index) q = rson[p];
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else {
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q = lson[p];
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if (rson[q] != binary_search_index) {
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do { q = rson[q]; } while (rson[q] != binary_search_index);
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rson[dad[q]] = lson[q];
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dad[lson[q]] = dad[q];
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lson[q] = lson[p];
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dad[lson[p]] = q;
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}
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rson[q] = rson[p]; dad[rson[p]] = q;
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}
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dad[q] = dad[p];
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if (rson[dad[p]] == p) rson[dad[p]] = q;
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else lson[dad[p]] = q;
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dad[p] = binary_search_index;
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}
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static int lzss_encode_better(
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FILE *infile,
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unsigned char frequent_char,
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int ring_buffer_size, int position_length_threshold,
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int output_type) {
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// unsigned char frequent_char='#';
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// int ring_buffer_size=1024; /* N */
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int match_length_limit; //=64; /* F */
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/*int position_length_threshold=2; THRESHOLD */
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int binary_search_index=ring_buffer_size; /* NIL */
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int position_bits; //=10;
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// int length_bits=16-position_bits;
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unsigned long int codesize = 0; /* code size counter */
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int i, c, len, r, s, last_match_length, code_buf_ptr;
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unsigned char code_buf[8*2+1], mask;
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unsigned char *text_buf;
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int match_position, match_length; /* of longest match. These are
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set by the InsertNode() procedure. */
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int *lson, *rson, *dad; /* left & right children &
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parents -- These constitute
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binary search trees. */
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/* determine stuff from ring_buffer_size */
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/* fake log2 algorithm */
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i=1;
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while (((ring_buffer_size-1)>>i) >=1) {
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i++;
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};
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position_bits=i;
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match_length_limit=1<<(16-position_bits);
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// printf("%i, %i %i %i '%c'\n",ring_buffer_size,position_bits,match_length_limit
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// ,position_length_threshold,frequent_char);
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/* ring buffer of size N, with extra F-1
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bytes to facilitate string comparison */
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text_buf=calloc(ring_buffer_size+match_length_limit-1,sizeof(unsigned char));
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lson=calloc(ring_buffer_size+1,sizeof(int));
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rson=calloc(ring_buffer_size+num_trees+1,sizeof(int));
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dad=calloc(ring_buffer_size+1,sizeof(int));
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/* initialize trees */
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newInitTree(ring_buffer_size,binary_search_index,rson,dad);
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/* code_buf[1..16] saves eight units of code, and
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code_buf[0] works as eight flags, "1" representing
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that the unit is an unencoded letter (1 byte),
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"0" a position-and-length pair (2 bytes).
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Thus, eight units require at most 16 bytes of code. */
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code_buf[0] = 0;
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code_buf_ptr = mask = 1;
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s = 0;
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r = ring_buffer_size - match_length_limit;
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if (frequent_char<32) {
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printf(";FREQUENT_CHAR EQU %d\n",frequent_char);
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}
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else {
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printf(";FREQUENT_CHAR EQU '%c'\n",frequent_char);
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}
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printf(";N EQU %i\n",ring_buffer_size);
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printf(";F EQU %i\n",match_length_limit);
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printf(";THRESHOLD EQU %i\n",position_length_threshold);
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printf(";P_BITS EQU %i\n",position_bits);
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printf(";POSITION_MASK EQU %i\n",(0xff>>(8-(position_bits-8))));
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printf("logo:\n");
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/* Clear the buffer with any character that will appear often. */
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for(i=0; i<(ring_buffer_size-match_length_limit); i++) {
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text_buf[i]=frequent_char;
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}
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// printf("%i to %i = %i\n",0,ring_buffer_size-match_length_limit,frequent_char);
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// printf("%i to %i = ",r,r+match_length_limit);
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for(len=0; len<match_length_limit && (c=getc(infile))!=EOF; len++) {
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/* Read F bytes into the last F bytes of the buffer */
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text_buf[r+len]=c;
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// printf("%i ",text_buf[r+len]);
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}
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// printf("\n");
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if (len== 0) return 0; /* trying to compress empty file */
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for(i = 1; i <= match_length_limit; i++) {
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newInsertNode(r-i,ring_buffer_size,binary_search_index,
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match_length_limit,text_buf,rson,lson,dad,
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&match_length,&match_position);
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}
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/* Insert the F strings,
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each of which begins with one or more 'space' characters. Note
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the order in which these strings are inserted. This way,
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degenerate trees will be less likely to occur. */
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newInsertNode(r,ring_buffer_size,binary_search_index,
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match_length_limit,text_buf,rson,lson,dad,
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&match_length,&match_position);
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/* Finally, insert the whole string just read. The
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global variables match_length and match_position are set. */
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do {
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/* match_length may be spuriously long near the end of text. */
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if (match_length > len) match_length = len;
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if (match_length <= position_length_threshold) {
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match_length=1; /* Not long enough match. Send one byte. */
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code_buf[0] |= mask; /* 'send one byte' flag */
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code_buf[code_buf_ptr++] = text_buf[r]; /* Send uncoded. */
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// printf("single: %i @ %i\n",text_buf[r],r);
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} else {
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// printf("pos : %i\tlen : %i\n",match_position,match_length);
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code_buf[code_buf_ptr++] = (unsigned char) match_position;
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code_buf[code_buf_ptr++] = (unsigned char)
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( ((match_position>>8) & (0xff >> (8-(position_bits-8)))) |
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((match_length-(position_length_threshold+1))<<(position_bits-8)) );
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// code_buf[code_buf_ptr++] = (unsigned char)
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// (((match_position >> 8) & 7) |
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// (match_length - (position_length_threshold+1))<<3);
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}
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if ((mask <<= 1) == 0) { /* Shift mask left one bit. */
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printf("\t.byte\t");
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for(i=0; i<code_buf_ptr; i++) { /* Send at most 8 units of */
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printf("$%02X%c",code_buf[i],(i==code_buf_ptr-1)?'\n':',');
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}
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codesize += code_buf_ptr;
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code_buf[0] = 0; code_buf_ptr = mask = 1;
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}
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last_match_length = match_length;
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for (i = 0; i < last_match_length && (c = getc(infile)) != EOF; i++) {
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/* Delete old strings and */
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newDeleteNode(s,binary_search_index,dad,rson,lson);
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/* read new bytes */
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text_buf[s] = c;
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/* If the position is near the end of buffer,
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extend the buffer to make string comparison easier. */
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if (s < match_length_limit - 1) {
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text_buf[s + ring_buffer_size] = c;
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}
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s = (s + 1) & (ring_buffer_size - 1);
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r = (r + 1) & (ring_buffer_size - 1);
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/* Since this is a ring buffer, increment the position
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modulo N. */
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newInsertNode(r,ring_buffer_size,binary_search_index,
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match_length_limit,text_buf,rson,lson,dad,
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&match_length,&match_position);
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/* Register the string in text_buf[r..r+F-1] */
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}
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/* After the end of text, */
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while (i++ < last_match_length) {
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/* no need to read, but */
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newDeleteNode(s,binary_search_index,dad,rson,lson);
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s = (s + 1) & (ring_buffer_size - 1);
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r = (r + 1) & (ring_buffer_size - 1);
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if (--len) {
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newInsertNode(r,ring_buffer_size,binary_search_index,
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match_length_limit,text_buf,rson,lson,dad,
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&match_length,&match_position);
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}
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/* buffer may not be empty. */
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}
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/* until length of string to be processed is zero */
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} while (len > 0);
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/* Send remaining code. */
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if (code_buf_ptr > 1) {
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printf("\t.byte\t");
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for(i=0; i<code_buf_ptr; i++) {
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printf("$%02x",code_buf[i]);
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if (i==code_buf_ptr-1) {
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printf("\n");
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} else {
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printf(",");
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}
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}
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codesize += code_buf_ptr;
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}
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printf("logo_end:\n");
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free(text_buf);
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free(lson);
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free(rson);
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free(dad);
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return codesize;
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}
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int main(int argc, char **argv) {
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FILE *input;
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int ch,byte_count=0,orig_byte_count=0;
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/* Check command line arguments */
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if (argc<2) {
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printf("\nUsage:\n\t%s file_to_compress\n\n",argv[0]);
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return 3;
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}
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/* Open input file */
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input=fopen(argv[1],"r");
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if (input==NULL) {
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printf("Could not open \"%s\"\n",argv[1]);
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return 2;
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}
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byte_count=lzss_encode_better(input,'\0',1024,2,NORMAL_ASM);
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rewind(input);
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/* calculate size of original */
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/* Why aren't we using stat()? */
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while((ch=fgetc(input))!=EOF) {
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orig_byte_count++;
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}
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fclose(input);
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printf("; Size of original version: %i\n",orig_byte_count);
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printf("; Size of compressed version: %i\n",byte_count);
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return 0;
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}
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