网络通信中数字的转换

野性酷女 2022-03-17 07:08 128阅读 0赞

在网络通信中，经常用到需要保存结构体的一些数字，到另一端获取之后读取出来，这里给出一种转换为十六进制字符串的方法保存并读取。

#include <iostream>
    
    struct peer_request
    { 
    	// the index of the piece in which the range starts.
    	int piece;
    	// the offset within that piece where the range starts.
    	int start;
    	// the size of the range, in bytes.
    	int length;
    
    	/* returns true if the right hand side peer_request refers to the same * range as this does. */
    	bool operator==(peer_request const& r) const
    	{ 
    		return piece == r.piece && start == r.start && length == r.length;
    	}
    };
    
    void int_to_hex(int val, char *ptr)
    { 
    	for (int i = int(sizeof(val)) - 1; i >= 0; --i)
    	{ 
    		*ptr = static_cast<unsigned char>((val >> (i * 8)) & 0xff);
    		++ptr;
    	}
    }
    
    int hexs_to_int(char *in, int len)
    { 
    	int val = 0;
    	int base, multi;
    	for (int i = 0; i < len; i ++)
    	{ 
    		base = int(*(in + i));
    		multi = pow(2, 8 * (len - i -1));
    		std::cout << "base = " << base << ", multi = " << multi << std::endl;
    		val += base * multi;
    	}
    	std::cout << std::endl;
    	return val;
    }
    
    void test1()
    { 
    	char ch[8] = { 0, 0, 0, 1};
    	int_to_hex(10000, ch);
    	int_to_hex(6666, ch + 4);
    	
    	int len = hexs_to_int(ch, 4);
    	int num = hexs_to_int(ch + 4, 4);
    
    	std::cout << "len = " << len << ", num = " << num << std::endl;
    }
    
    void test2()
    { 
    	peer_request pr;
    	pr.length = 65536;
    	pr.piece = 270;
    	pr.start = (270 - 1) * 65536;
    
    	char msg[17] = {  0, 0, 0, 13, 6 };
    	char *ptr = msg + 5;
    	int_to_hex(pr.piece, ptr); // index 270
    	int_to_hex(pr.start, ptr + 4); // begin 
    	int_to_hex(pr.length, ptr + 8); // length 65536
    
    	peer_request r;
    
    	r.piece = hexs_to_int(msg + 5, 4);
    	r.start = hexs_to_int(msg + 9, 4);
    	r.length = hexs_to_int(msg + 13, 4);
    
    	std::cout << "r.piece = " << r.piece << ", r.start = " << r.start << ", r.length = " << r.length << std::endl;
    
    }
    
    
    int main()
    { 
    	test1();
    
    	test2();
    
        getchar();
    
    }```