LZW.rar_lzw

#include <stdio.h> #include <conio.h> #include <string.h> #include "lzw.h" char *decode(unsigned char *buffer,unsigned int code) { int i=0; while(code>257) { *buffer++=lzw->suffix[code]; code=lzw->prefix[code]; if (i++>=TABLE_SIZE) { printf("内存溢出！\n"); exit(1); } } *buffer=code; return(buffer); } unsigned int hashsearch(int prefix,unsigned int suffix) { int index; int offset; index=(suffix<<HASHING_SHIFT)^prefix; if(index==0) offset=1; else offset=TABLE_SIZE-index; while(1) { if(lzw->code[index]==-1) return(index); if(lzw->prefix[index]==prefix&&lzw->suffix[index]==suffix) return(index); index-=offset; if(index<0) index+=TABLE_SIZE; } } void outcode(FILE *output,unsigned int code) { static int ob=0; static unsigned long obb=0L; obb |=(unsigned long) code<<(32-BITS-ob); ob+=BITS; while(ob>=8) { putc(obb>>24,output); obb<<=8; ob-=8; } return; } unsigned int incode(FILE *input) { unsigned int ret; static unsigned long ibb=0L; static int ib=0; //使用静态变量，保存输入的位数 while(ib<=24) { ibb|=(unsigned long)getc(input)<<(24-ib); ib+=8; } ret=ibb>>(32-BITS); ibb<<=BITS; ib-=BITS; return(ret); } void compress(FILE *input,FILE *output) { unsigned int curr_code; //当前使用的标号 unsigned int suffix; //后缀字符 unsigned int prefix; //前缀字符 unsigned int index; int i; lzw1.code=malloc(TABLE_SIZE*sizeof(unsigned int)); //标号值数组 lzw1.prefix=malloc(TABLE_SIZE*sizeof(unsigned int)); //前缀数据 lzw1.suffix=malloc(TABLE_SIZE*sizeof(unsigned char)); //后缀数据 if (lzw1.code==NULL||lzw1.prefix==NULL||lzw1.suffix==NULL) { printf("内存分配失败！\n"); getch(); exit(1); } lzw=&lzw1; curr_code=258; for(i=0;i<TABLE_SIZE;i++) lzw->code[i]=-1; i=0; printf("\nCompressing."); prefix=getc(input); while((suffix=getc(input))!=(unsigned)EOF) { if(++i==100) { i=0; printf("."); } index=hashsearch(prefix,suffix); if(lzw->code[index]!=-1) prefix=lzw->code[index]; else{ if (curr_code<=MAX_CODE){ lzw->code[index]=curr_code++; lzw->prefix[index]=prefix; lzw->suffix[index]=suffix; } outcode(output,prefix); prefix=suffix; } } outcode(output,prefix); outcode(output,(MAX_VALUE)); outcode(output,0); free(lzw->code); free(lzw->prefix); free(lzw->suffix); } void expand(FILE *input,FILE *output) { unsigned int curr_code; unsigned int suffix; unsigned int prefix; int ch; int i; unsigned char *ps; char *decode(unsigned char *buffer,unsigned int code); lzw1.code=malloc(TABLE_SIZE*sizeof(unsigned int)); //代码值数组 lzw1.prefix=malloc(TABLE_SIZE*sizeof(unsigned int)); //压缩前数据 lzw1.suffix=malloc(TABLE_SIZE*sizeof(unsigned char)); //压缩后数据 lzw=&lzw1; if(lzw1.code==NULL||lzw1.prefix==NULL||lzw1.suffix==NULL) { printf("Fatal error allocating table space!\n"); getch(); exit(1); } curr_code=258; i=0; printf("\nExpanding."); prefix=incode(input); ch=prefix; putc(prefix,output); while((suffix=incode(input))!=(MAX_VALUE)) { if(++i==100) { i=0; printf("."); } if(suffix>=curr_code) { *decode_stack=ch; ps=decode(decode_stack+1,prefix); } else ps=decode(decode_stack,suffix); ch=*ps; while(ps>=decode_stack) putc(*ps--,output); if(curr_code<=MAX_CODE) { lzw->prefix[curr_code]=prefix; lzw->suffix[curr_code]=ch; curr_code++; } prefix=suffix; } free(lzw->code); free(lzw->prefix); free(lzw->suffix); } int main(int argc,char *argv[]) { FILE *fp1,*fp2; int flag=0; char *op; if(argc!=4) flag=1; else{ op=argv[1]; if((strcmp(op,"-z")!=0)&&strcmp(op,"-e")!=0) flag=1; } if(flag) { printf("usage:lzw -z/-e source dest\n"); exit(1); } if((fp1=fopen(argv[2],"rb"))==NULL) { printf("不能打开源文件！\n"); exit(1); } if((fp2=fopen(argv[3],"wb"))==NULL) { printf("不能创建目标文件！\n"); exit(1); } if(strcmp(op,"-z")==0) compress(fp1,fp2); //压缩 else expand(fp1,fp2); //解压缩 fclose(fp1); fclose(fp2); getch(); return 0; }