在上次的程式中，已經實現好了基類的搭建，現在實現一種最簡單的編碼方式。

編碼方式為：在資料的頭部和尾部加入：01111110，在資料中，只要出現5個1，就在後面新增0。

問題的一個難點在於：變化之後的資料很可能不再是8的整數倍，我將最後的幾個位空出來，設定為0，來湊齊8的整數位。此類命名為：SimpleCoder，在coder.h中實現，總的coder.h程式碼如下：

// coder.h

#ifndef CODER_H
#define CODER_H

#include "datareader.h"
#include <iostream>
#include <vector>

class Coder
{
protected:
	unsigned char* storage;
	int size;
	int length;
	DataReader& data;
	int prtlen;
public:
	Coder(DataReader* dr) : data(*dr)
	{
		storage = data.storage;
		size = data.size;
		length = data.length;
		prtlen = size * length;
	}
	void update()
	{
		storage = data.storage;
		size = data.size;
		length = data.length;
		prtlen = size * length;
	}
	DataReader& getDataReader()
	{
		return data;
	}
	// This print function show how to show the magic memory.
	// But I will use the real magic memory method,
	// because it's easy to code and decode.
	/*std::ostream& print(std::ostream& out)
	{
		for (int i = 0; i < length; i++)
			for (int j = size - 1; j >= 0; j--)
				for(int k = 7; k >= 0; k--)
					if (storage[i * size + j] & (1 << k))
						out << 1;
					else
						out << 0;
		return out;
	}*/
	std::ostream& print(std::ostream& out)
	{
		for (int i = 0; i < prtlen; i++)
			for (int j = 7; j >= 0; j--)
				if (storage[i] & (1 << j))
					out << 1;
				else
					out << 0;
		return out;
	}
	void print()
	{
		print(std::cout);
	}
	
	virtual void code() {}
	//virtual void decode() = 0;
};

std::ostream& operator<<(std::ostream& out, Coder& coder) {
		return coder.print(out);
}

class SimpleCoder : public Coder
{
	void addFlag(std::vector<unsigned short>& data)
	{
		data.push_back(0);
		for (int i = 0; i < 6; i++)
			data.push_back(1);
		data.push_back(0);
	}
public:
	SimpleCoder(DataReader* dr) : Coder(dr){}

	void code()
	{
		std::vector<unsigned short> data;
		addFlag(data);
		int count = 0;
		for (int i = 0; i < prtlen; i++)
			for (int j = 7; j >= 0; j--)
			{
				if (count == 5)
				{
					data.push_back(0);
					count = 0;
				}
				if (storage[i] & (1 << j))
				{
					data.push_back(1);
					count++;
				} else {
					data.push_back(0);
					count = 0;
				}
			}
		addFlag(data);
		unsigned char* store = new unsigned char[data.size() / 8 + 1];
		for (int i = 0; i < data.size() / 8 + 1; i++)
		{
			store[i] = 0;
			for (int j = 7; j >= 0; j--)
				if (7 - j + 8 * i < data.size())
					store[i] |= (data[7 - j + 8 * i] << j);
		}
		delete [] storage;
		storage = store;
		prtlen = data.size() / 8 + 1;
	}
};


#endif
 

測試程式碼如下：

//test.cpp
#include <iostream>
#include "coder.h"
using namespace std;

int main()
{
	int a[] = {1, 4, -1};
	SimpleCoder coder(new DataReader(a, 3));
	cout << coder << endl;
	coder.code();
	cout << coder << endl;

	DataReader& dr = coder.getDataReader();
	dr.setStorage('a');
	coder.update();
	cout << coder << endl;
	char s[] = "aaaab";
	dr.setStorage(s, 6);
	coder.update();
	cout << coder << endl;

	return 0;
}