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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4.  
  5. #define BASE64BIT 6
  6.  
  7. /* pre-fetch, pre-masking-set */
  8. /* ビットスライシング用クラス */
  9.  
  10. class bitcut {
  11. private:
  12.   std::string buffer;
  13.   std::string::const_iterator p;;
  14.   uint_least8_t mask;
  15.   uint_least8_t fetch_byte;
  16.   int width;
  17.  
  18. public:
  19.   bool isEOL; /* 外部呼び出し側では、このフラグを見てスライスするかどうかを判断する */
  20.  
  21.   bitcut(std::string input, int width) { /*コンストラクタにスライスする文字列と、文字列を構成するバイトの有効ビット幅を設定 */
  22.     this->buffer = input;
  23.     this->p = buffer.begin();
  24.     this->width = width;
  25.  
  26.     if (p == buffer.end()) {
  27.       isEOL = true;
  28.     } else {
  29.       isEOL = false;
  30.       fetch_byte = *p;
  31.       mask = 1 << (this->width - 1);
  32.     }
  33.   }
  34.  
  35.   /* bit 数分スライス、tailignore = bit 数分スライスしようとして、残りビットが bit に足りないとき無視するのなら true */
  36.   int_least8_t cut(int bit, bool tailignore) { /* bit <= 16 */
  37.     uint_least8_t buff = 0;
  38.     for (int i = 0; i < bit; i++) {
  39.       if (isEOL == false) {
  40.         int t = fetch_byte & mask;
  41.         buff = buff | ((t > 0) ? 1 : 0);
  42.         buff = buff << 1;
  43.         mask = mask >> 1;
  44.         if (mask == 0) {
  45.           this->p++;
  46.           if (this->p == buffer.end()) {
  47.             this->isEOL = true;
  48.           } else {
  49.             fetch_byte = *p;
  50.             mask = 1 << (this->width - 1);
  51.           }
  52.         }
  53.       } else { /* isEOL == true */
  54.         if (tailignore != true)
  55.           buff = buff << 1;
  56.       }
  57.     }
  58.     buff = buff >> 1;
  59.     return buff;
  60.   }
  61. };
  62.  
  63. /* エンコード */
  64. std::string encode(std::string key) {
  65.   std::string ret;
  66.  
  67.   bitcut bc(key, 8);
  68.   if (bc.isEOL == true)
  69.     return ret;
  70.  
  71.   int_least8_t c;
  72.   do {
  73.     for (int i = 0 ; i < 4; i++) {
  74.       if (bc.isEOL == true) {
  75.         c = '=';
  76.       } else {
  77.         c = bc.cut(BASE64BIT, false);
  78.         if (c <= 25) c += 'A';
  79.         else if (c <= 51) c = c - 26 + 'a';
  80.         else if (c <= 61) c = c - 52 + '0';
  81.         else if (c == 62) c = '+';
  82.         else if (c == 63) c = '/';
  83.       }
  84.       ret.push_back(c);
  85.     }
  86.   } while (bc.isEOL == false);
  87.   return ret;
  88. }
  89.  
  90. /* デコード */
  91. std::string decode(std::string key) {
  92.   std::string ret;
  93.  
  94.   for (std::string::iterator p = key.begin(); p != key.end(); ) {
  95.     if (*p == '=') {
  96.       p = key.erase(p);
  97.       continue;
  98.     } else if (*p == '+') {
  99.       *p = 62;
  100.       p++;
  101.     } else if (*p == '/') {
  102.       *p = 63;
  103.       p++;
  104.     } else if (*p <= '9') {
  105.       *p = *p - '0' + 52;
  106.       p++;
  107.     } else if (*p <= 'Z') {
  108.       *p = *p - 'A';
  109.       p++;
  110.     } else if (*p <= 'z') {
  111.       *p = *p - 'a' + 26;
  112.       p++;
  113.     }
  114.   }
  115.  
  116.   bitcut bc(key, BASE64BIT);
  117.   if (bc.isEOL == true)
  118.     return ret;
  119.   int_least8_t c2;
  120.   do {
  121.     c2 = bc.cut(8, true);
  122.     ret.push_back(c2);
  123.   } while (bc.isEOL == false);
  124.   return ret;
  125. }
  126.  
  127. void f(std::string key) {
  128.   std::string out;
  129.   std::cout << "input:  " << key << std::endl;
  130.   std::cout << "encode: " << (out = encode(key)) << std::endl;
  131.   std::cout << "decode: " << decode(out) << std::endl;
  132. }
  133.  
  134. int main() {
  135. //  f("ghi");
  136.   f("ABCDEFG");
  137.   f("Hello, World!");
  138.   f("0123456789\"#$%&\'()`=@");
  139.   f("12ab34cd56ef78");
  140.   return 0;
  141. }
  142. /* end */
Success #stdin #stdout 0s 15248KB
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stdin
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Standard input is empty
stdout
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input:  ABCDEFG
encode: QUJDREVGRw==
decode: ABCDEFG
input:  Hello, World!
encode: SGVsbG8sIFdvcmxkIQ==
decode: Hello, World!
input:  0123456789"#$%&'()`=@
encode: MDEyMzQ1Njc4OSIjJCUmJygpYD1A
decode: 0123456789"#$%&'()`=@
input:  12ab34cd56ef78
encode: MTJhYjM0Y2Q1NmVmNzg=
decode: 12ab34cd56ef78
https://ideone.com/5iv9m9
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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