#include <iostream>

#include <map>

#include <fstream>

using namespace std;

/*编码表*/

class ArithmeticEncodingTable

{

private:

double low; //数据区间开始

double high; //数据区间结束

double delta; //数据区间大小

public:

ArithmeticEncodingTable();

~ArithmeticEncodingTable();

double get_low();

double get_high();

double get_delta();

void set_low(double low);

void set_high(double high);

void set_delta(double delta);

};

/*编码解码类*/

class ArithmeticEncoding

{

private:

std::map<char, ArithmeticEncodingTable> CodeTable;

public:

ArithmeticEncoding(/* args */);

~ArithmeticEncoding();

void CreateTable(); //生成编码表

double Encoding(string encode); //编码

string Decoding(double decode); //解码

};

/*编码所需数据类实现*/

ArithmeticEncodingTable::ArithmeticEncodingTable(/* args */)

{

low = 0.0;

high = 1.0;

delta = 1.0;

}

ArithmeticEncodingTable::~ArithmeticEncodingTable()

{

}

double ArithmeticEncodingTable::get_low()

{

return low;

}

double ArithmeticEncodingTable::get_high()

{

return high;

}

double ArithmeticEncodingTable::get_delta()

{

return delta;

}

void ArithmeticEncodingTable::set_low(double low)

{

this->low = low;

}

void ArithmeticEncodingTable::set_high(double high)

{

this->high = high;

}

void ArithmeticEncodingTable::set_delta(double delta)

{

this->delta = delta;

}

/*编码解码实现*/

ArithmeticEncoding::ArithmeticEncoding(/* args */)

{

}

ArithmeticEncoding::~ArithmeticEncoding()

{

}

void ArithmeticEncoding::CreateTable()

{

ifstream in("table.txt");

if (!in)

{

cout << "error" << endl;

return;

}

int codenum;

char code;

double delta;

double low = 0.0;

double high = 0.0;

cout << "please input number of the char:" << endl;

in >> codenum;

for (int i = 0; i < codenum; i++)

{

cout << "please input " << i << "th char:";

in >> code;

cout << "please input " << i << "th probability:";

in >> delta;

ArithmeticEncodingTable table;

table.set_delta(delta);

low = high;

table.set_low(low);

high = low + delta;

table.set_high(high);

CodeTable.insert(std::pair<char, ArithmeticEncodingTable>(code, table));

}

}

double ArithmeticEncoding::Encoding(string encode)

{

double low = 0.0;

double high = 1.0;

for (string::iterator it = encode.begin(); it != encode.end(); it++)

{

double delta = high - low;

high = low + delta * CodeTable[*it].get_high();

low = low + delta * CodeTable[*it].get_low();

}

return low;

}

string ArithmeticEncoding::Decoding(double value)

{

double low, high; //编码区间

double prelow = 0.0, prehigh = 1.0; //设置先前区间，方便每次遍历后能回到先前的值

string symbol = ""; //输出的解码字符串

while (true)

{

low = prelow;

high = prehigh;

for (std::map<char, ArithmeticEncodingTable>::iterator i = CodeTable.begin(); i != CodeTable.end(); ++i)

{

double delta = high - low;

high = low + delta * (i->second).get_high();

low = low + delta * (i->second).get_low();

if (low < value && high > value) //判断位置所在区间，在区间内就进行下一次遍历

{

prelow = low;

prehigh = high;

symbol += (i->first);

break;

}

else if (low == value)

{

symbol += (i->first); //最后一个字符输出

return symbol;

}

else //如果不区间，也不是结果，然后回到先前位置

{

low = prelow;

high = prehigh;

}

}

}

}

/*主函数*/

int main()

{

ArithmeticEncoding AE;

AE.CreateTable();

double out = AE.Encoding("CADACDB");

cout << endl;

cout << out << endl;

cout << AE.Decoding(out);

system("pause");

return 0;

}