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 }
