1.c

这是一个关于lzss压缩的C的源代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define N		 4096	
#define F		   18	
#define THRESHOLD	2   
#define NIL			N	

unsigned long int
		textsize = 0,	
		codesize = 0,	
		printcount = 0;	
unsigned char text_buf[N + F - 1];	
int		match_position, match_length, lson[N + 1], rson[N + 257], dad[N + 1];  
FILE	*infile, *outfile;  

void InitTree(void)  
{
	int  i;
    for (i = N + 1; i <= N + 256; i++) rson[i] = NIL;
	for (i = 0; i < N; i++) dad[i] = NIL;
}

void InsertNode(int r)
{
	int  i, p, cmp;
	unsigned char  *key;

	cmp = 1;  key = &text_buf[r];  p = N + 1 + key[0];
	rson[r] = lson[r] = NIL;  match_length = 0;
	for ( ; ; ) {
		if (cmp >= 0) {
			if (rson[p] != NIL) p = rson[p];
			else {  rson[p] = r;  dad[r] = p;  return;  }
		} else {
			if (lson[p] != NIL) p = lson[p];
			else {  lson[p] = r;  dad[r] = p;  return;  }
		}
		for (i = 1; i < F; i++)
			if ((cmp = key[i] - text_buf[p + i]) != 0)  break;
		if (i > match_length) {
			match_position = p;
			if ((match_length = i) >= F)  break;
		}
	}
	dad[r] = dad[p];  lson[r] = lson[p];  rson[r] = rson[p];
	dad[lson[p]] = r;  dad[rson[p]] = r;
	if (rson[dad[p]] == p) rson[dad[p]] = r;
	else                   lson[dad[p]] = r;
	dad[p] = NIL; 
}

void DeleteNode(int p) 
{
	int  q;
	
	if (dad[p] == NIL) return;  
	if (rson[p] == NIL) q = lson[p];
	else if (lson[p] == NIL) q = rson[p];
	else {
		q = lson[p];
		if (rson[q] != NIL) {
			do {  q = rson[q];  } while (rson[q] != NIL);
			rson[dad[q]] = lson[q];  dad[lson[q]] = dad[q];
			lson[q] = lson[p];  dad[lson[p]] = q;
		}
		rson[q] = rson[p];  dad[rson[p]] = q;
	}
	dad[q] = dad[p];
	if (rson[dad[p]] == p) rson[dad[p]] = q;  else lson[dad[p]] = q;
	dad[p] = NIL;
}

void Encode(void)
{
	int  i, c, len, r, s, last_match_length, code_buf_ptr;
	unsigned char  code_buf[17], mask;
	
	InitTree();  
	code_buf[0] = 0;  
	code_buf_ptr = mask = 1;
	s = 0;  r = N - F;
	for (i = s; i < r; i++) text_buf[i] = ' ';  
	for (len = 0; len < F && (c = getc(infile)) != EOF; len++)
		text_buf[r + len] = c; 
	if ((textsize = len) == 0) return;  
	for (i = 1; i <= F; i++) InsertNode(r - i);  
	InsertNode(r);  
	do {
		if (match_length > len) match_length = len;  
		if (match_length <= THRESHOLD) {
			match_length = 1;  
			code_buf[0] |= mask; 
			code_buf[code_buf_ptr++] = text_buf[r]; 
		} else {
			code_buf[code_buf_ptr++] = (unsigned char) match_position;
			code_buf[code_buf_ptr++] = (unsigned char)
				(((match_position >> 4) & 0xf0)
			  | (match_length - (THRESHOLD + 1))); 
		}
		if ((mask <<= 1) == 0) {  
			for (i = 0; i < code_buf_ptr; i++)  
				putc(code_buf[i], outfile);     
			codesize += code_buf_ptr;
			code_buf[0] = 0;  code_buf_ptr = mask = 1;
		}
		last_match_length = match_length;
		for (i = 0; i < last_match_length &&
				(c = getc(infile)) != EOF; i++) {
			DeleteNode(s);		
			text_buf[s] = c;
			if (s < F - 1) text_buf[s + N] = c;  
			s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);
			InsertNode(r);	
		}
		if ((textsize += i) > printcount) {
			printf("%12ld\r", textsize);  printcount += 1024;
		}
		while (i++ < last_match_length) {	
			DeleteNode(s);					
			s = (s + 1) & (N - 1);  r = (r + 1) & (N - 1);
			if (--len) InsertNode(r);		
		}
	} while (len > 0);
	if (code_buf_ptr > 1) {	
		for (i = 0; i < code_buf_ptr; i++) putc(code_buf[i], outfile);
		codesize += code_buf_ptr;
	}
	printf("In : %ld bytes\n", textsize);	
	printf("Out: %ld bytes\n", codesize);
	printf("Out/In: %.3f\n", (double)codesize / textsize);
}

void Decode(void)
{
	int  i, j, k, r, c;
	unsigned int  flags;
	
	for (i = 0; i < N - F; i++) text_buf[i] = ' ';
	r = N - F;  flags = 0;
	for ( ; ; ) {
		if (((flags >>= 1) & 256) == 0) {
			if ((c = getc(infile)) == EOF) break;
			flags = c | 0xff00;		
		}							
		if (flags & 1) {
			if ((c = getc(infile)) == EOF) break;
			putc(c, outfile);  text_buf[r++] = c;  r &= (N - 1);
		} else {
			if ((i = getc(infile)) == EOF) break;
			if ((j = getc(infile)) == EOF) break;
			i |= ((j & 0xf0) << 4);  j = (j & 0x0f) + THRESHOLD;
			for (k = 0; k <= j; k++) {
				c = text_buf[(i + k) & (N - 1)];
				putc(c, outfile);  text_buf[r++] = c;  r &= (N - 1);
			}
		}
	}
}

int main(int argc, char *argv[])
{
	char  *s;
	
	if (argc != 4) {
		printf("'lzss e file1 file2' encodes file1 into file2.\n"
			   "'lzss d file2 file1' decodes file2 into file1.\n");
		return EXIT_FAILURE;
	}
	if ((s = argv[1], s[1] || strpbrk(s, "DEde") == NULL)
	 || (s = argv[2], (infile  = fopen(s, "rb")) == NULL)
	 || (s = argv[3], (outfile = fopen(s, "wb")) == NULL)) {
		printf("??? %s\n", s);  return EXIT_FAILURE;
	}
	if (toupper(*argv[1]) == 'E') Encode();  else Decode();
	fclose(infile);  fclose(outfile);
	return EXIT_SUCCESS;
}