[C/C++演算法]-Base64演算法
本篇要分享Base64演算法,有興趣的(C/P)同好,歡迎來(C/P)一下哈哈 ^ ^。
程式碼 |
#include #include staticconst std::string base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
std::string base64_encode(unsignedcharconst* , unsignedint len); std::string base64_decode(std::string const& s);
int main() { const std::string s = "ADP GmbH\nAnalyse Design & Programmierung\nGesellschaft mit beschrankter Haftung" ;
std::string encoded = base64_encode(reinterpret_cast<constunsignedchar*>(s.c_str()), s.length()); std::string decoded = base64_decode(encoded);
std::cout << "encoded: " << encoded << std::endl;
std::cout << "decoded: " << decoded << std::endl;
return 0; }
staticinlinebool is_base64(unsignedchar c) { return (isalnum(c) || (c == '+') || (c == '/')); }
std::string base64_encode(unsignedcharconst* bytes_to_encode, unsignedint in_len) { std::string ret;
int i = 0; int j = 0; unsignedchar char_array_3[3]; unsignedchar char_array_4[4];
while (in_len--) { char_array_3[i++] = *(bytes_to_encode++);
if (i == 3) { char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for(i = 0; (i <4) ; i++) ret += base64_chars[char_array_4[i]];
i = 0;
}
}
if (i) {
for(j = i; j < 3; j++) char_array_3[j] = '\0';
char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
char_array_4[3] = char_array_3[2] & 0x3f;
for (j = 0; (j < i + 1); j++) ret += base64_chars[char_array_4[j]];
while((i++ < 3)) ret += '=';
}
return ret;
}
std::string base64_decode(std::string const& encoded_string) { int in_len = encoded_string.size(); int i = 0; int j = 0; int in_ = 0; unsignedchar char_array_4[4], char_array_3[3]; std::string ret;
while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) { char_array_4[i++] = encoded_string[in_]; in_++;
if (i ==4) { for (i = 0; i <4; i++) char_array_4[i] = base64_chars.find(char_array_4[i]);
char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
for (i = 0; (i < 3); i++) ret += char_array_3[i];
i = 0;
}
}
if (i) { for (j = i; j <4; j++) char_array_4[j] = 0;
for (j = 0; j <4; j++) char_array_4[j] = base64_chars.find(char_array_4[j]);
char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
for (j = 0; (j < i - 1); j++) ret += char_array_3[j]; }
return ret; }
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