lzw.cpp

实现对数据的LZW的方法进行压缩和解压缩 fs

#include "LZW.h"
#include <iostream>
using std::cout;
using std::endl;

#include <algorithm>

// 构造函数
LZW::LZW( string source ){

	_source = source;
	_code = "";
	_dictionary = new vector< CEntry >;
	CEntry entry;
	
	char tmp;
	string tmp_E;
	for(int i=0;i<256;++i){
		entry.SetCode( i );
   
		tmp_E=tmp;
		entry.SetEntry( tmp_E );
		_dictionary->push_back( entry );
		++tmp;
	}

	_initLength = _dictionary->size();
}
	
// 析构函数
LZW::~LZW(){
	if( _dictionary ){
		delete _dictionary;
	}
}

// 压缩
void LZW::Compression(){

	int code = _initLength;
	std::vector< CEntry >::iterator begin = _dictionary->begin();
	string s;
	s.assign( _source, 0, 1 );
	t=0;//my
	
	for( int i = 1; i <= _source.size() - 1; i++ ){

		string c;
		c.assign( _source, i, 1 );

		
		cout << "i: " << i << "; s: " << s << ";  c: " << c 
			 << " s + c = " << s + c ;
		std::vector< CEntry >::iterator iter;
		
		CEntry entry;
		entry.SetEntry( s + c );
		iter = std::find( _dictionary->begin(), _dictionary->end(), entry );
		if( iter != _dictionary->end() ){
			// s + c在词典中
			cout << "在词典中" ;
			s += c;
		}
		else{
			
			cout << "不在词典中,输出 "; 
			std::vector< CEntry >::iterator iterS;
			CEntry entry;
			entry.SetEntry( s );
			iterS = std::find( _dictionary->begin(), _dictionary->end(), entry  );
			CEntry entryS = ( CEntry )( *iterS );
			cout << entryS.GetCode() << " " ;

			//保存编码值
			Codes[t]=entryS.GetCode();
			t++;

				
			code++;
			entry.SetCode( code );
			entry.SetEntry( s + c );
			_dictionary->push_back( entry );
			s = c;
		}

		cout<<endl ;
	
	}

	CEntry entry;
	entry.SetEntry( s );
    std::vector< CEntry >::iterator iterS;
	iterS = std::find( _dictionary->begin(), _dictionary->end(), entry  );
	CEntry entryS = ( CEntry )( *iterS );
	cout << entryS.GetCode() << " ";
	//保存编码值
	Codes[t]=entryS.GetCode();
		
	std::cout << std::endl;	
	
}

void LZW::ShowCodes(){
	
	cout<<"The Codes:";
	for(int i=0;i<=t;i++)
		cout<<Codes[i];
	cout<<endl<<endl;
}


// 解压缩
void LZW::Depression(){
	cout<<"Depression:"<<endl;
	string text;
	
	std::vector< CEntry >::iterator iter_end ;
	std::vector< CEntry >::iterator iter;
	
	string s;
	CEntry entry;

	for(int i=0;i<=t;i++)
	{
		int k=Codes[i];

		//从字典中取出等于K的字符
	
		iter = _dictionary->begin();
		iter_end = _dictionary->end();	
		
		for(iter;iter!=iter_end;++iter){
			if((*iter).GetCode()==k)
			{
				entry.SetEntry((*iter).GetEntry());
			    entry.SetCode((*iter).GetCode());	
			}	
		}
		
		/*exception handler*/
		if(entry.GetEntry().empty()==true)
			entry.SetEntry(s+s[0]);
		cout << "i: " << i << "; s: " << s << ";  k: " << k 
			 << " output = " << entry.GetEntry() ;
		cout<<endl;

		text=text+entry.GetEntry();

		if(entry.GetEntry().empty()==false){
			CEntry tmp_entry;
			tmp_entry.SetCode( _dictionary->size()+1 );
			tmp_entry.SetEntry(s+ entry.GetEntry()[0] );
			_dictionary->push_back( entry );
		}
		s=entry.GetEntry();		
	}
	cout<<endl;
	cout<<"The Text:"<<text<<endl;
}




// 设置原始字符串
void LZW::SetSource( string source ){
	_source = source;
}

string LZW::GetSource(){
	return _source;
}

// 字典
void LZW::SetDictionary( vector< CEntry > dictionary ){

	if( _dictionary->empty() == false ){
		_dictionary->erase( _dictionary->begin(), _dictionary->end() );
	}

	std::vector< CEntry >::iterator iter;
	std::vector< CEntry >::iterator begin = dictionary.begin();
	std::vector< CEntry >::iterator end = dictionary.end();
	for( iter = begin; iter <= end - 1; iter++ ){
		_dictionary->push_back( ( CEntry )*iter );
	}

}
vector< CEntry > * LZW::GetDictionary(){
	return _dictionary;
}