Base64基础实现 

大致说明：
数据按每6位[0,63]进行拆分
将拆分后的数值对应编码成64个可见字符
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"



 1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 class Base64
 6 {
 7     static char * base64Table;
 8     static char resTable[128];
 9     static char retStr[7];
10     static char retNum[5];
11 
12     static char getTable(char c)
13     {
14         if(resTable['A'] == 0)
15         {
16             for(int i = 0; i < 64; ++i)
17                 resTable[(int)base64Table[i]] = i;
18         }
19         return resTable[(int)c];
20     }
21     static char * longToStr(int val)
22     {
23         for(int i = 0; i < 6; ++i)
24         {
25             retStr[i] = base64Table[val & 0x3F];
26             val >>= 6;
27         }
28         return retStr;
29     }
30     static char * strToLong(const char * str)
31     {
32         *(int*)retNum = 0;
33         for(int i = 5; i >= 0; --i)
34         {
35             *(int*)retNum <<= 6;
36             *(int*)retNum |= getTable(str[i]);
37         }
38         return &retNum[0];
39     }
40 public:
41     static std::string base64_encode(const std::string &input)
42     {
43         int inputLen = (input.size() + 3) / 4 * 4;
44         char buffer[inputLen] = {0};
45         input.copy(buffer, input.size());
46 
47         std::string output;
48         for(int i = 0; i < inputLen / 4; ++i)
49         {
50             output += longToStr(*((unsigned int *)&buffer[i*4]));
51         }
52         return output;
53     }
54     static std::string base64_decode(const std::string &input)
55     {
56         int inputLen = (input.size() + 5) / 6 * 6;
57         char buffer[inputLen] = {0};
58         input.copy(buffer, input.size());
59 
60         std::string output;
61         for(int i = 0; i < inputLen / 6; ++i)
62         {
63             output += std::string(strToLong(&buffer[i*6]), 4);
64         }
65         return output;
66     }
67 };
68 char * Base64::base64Table = (char *)"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
69 char Base64::resTable[128] = {0};
70 char Base64::retStr[7] = {0};
71 char Base64::retNum[5] = {0};
72 
73 
74 
75 int main()
76 {
77     // 任意类型数据都ok,用std::string((char*)str, len)构造就OK;
78     std::string str = "1234567";
79     auto encStr = Base64::base64_encode(str);
80     cout << encStr.size() << ":" << encStr << endl;
81     auto decStr = Base64::base64_decode(encStr);
82     cout << decStr.size() << ":" << decStr << endl;
83     return 0;
84 }

 

posted @ 2021-05-06 16:20  zyh123101  阅读(80)  评论(0)    收藏  举报