lzcode.cpp

lz编码与解码的c++实现

#include<stdio.h>
#include<map>
#include<iostream>
#include<fstream>
#include"MyWord.h"

#define SHORTMAX 32767
#define INTMIN (0-2147483648)

using namespace std;

typedef map <MyWord, long> MyDic;

void lzcode(ifstream& lzifs, ofstream& lzofs);

int main(int arg,char* argv[]){
	if(arg < 2) printf("请输入压缩源文件。\n格式如下:\nLzCode 压缩源文件名\n");//检查参数正确性
	else{
		ifstream lzifs;
		lzifs.open(argv[1],ios::in|ios::binary);
		if(!lzifs) printf("压缩源文件不存在。\n");//检查源文件
		else{
			printf("Processing,please wait...\n");
			ofstream lzofs;
			string ofname;
			ofname.assign(argv[1]);
			ofname.append(".LZ");
			lzofs.open(ofname.c_str(),ios::out|ios::binary);
			lzcode(lzifs,lzofs);
			lzifs.close();
			lzofs.flush();
			lzofs.close();
			printf("ok!\n");
		}
	}
	return 0;
}

void lzcode(ifstream& lzifs, ofstream& lzofs){
	MyDic dic;
	long no = 1;//全局，字典索引
	char rd = 0;
	MyWord * word = new MyWord();
	long code = 0, itemp = 0;
	short stemp = 0;


	while(lzifs.get(rd)){//读取一个字节
		
		word->index = code;//更改当前条目
		word->ch = rd;
		if(dic.find(*word) == dic.end()){//在字典中查询当前条目,查询不到则添加该条目
			dic.insert(MyDic::value_type(*word,no));
			if(code <= SHORTMAX) {stemp = (short)code; lzofs.write((char*)&stemp,2);}//能用short表示则写入short，不能则写入int，且为负数
			else {itemp = (code|INTMIN); lzofs.write((char*)(((short*)&itemp)+1),2); lzofs.write((char*)&itemp,2);}
			lzofs.put(rd);
			//printf("%d,%c,",code,rd);
			delete word;
			word = new MyWord();//新建条目
			no++;//全局索引加1
			code = 0;
		}
		else{
			code = dic[*word];	//查到条目则让code等于查询到的索引号
		}
	}
   	if(code != 0) {//将最后一次查询的索引写入
		if(code <= SHORTMAX) {stemp = (short)code; lzofs.write((char*)&stemp,2);}
		else {itemp = (code|INTMIN); lzofs.write((char*)(((short*)&itemp)+1),2); lzofs.write((char*)&itemp,2);}
	}
	if(!word) delete word;
}