Line data    Source code

       1             : #include "base64.h"
       2             : 
       3             : #include <cstddef>
       4             : #include <cstdint>
       5             : 
       6             : namespace datadog {
       7             : namespace tracing {
       8             : 
       9             : constexpr uint8_t k_sentinel = 255;
      10             : constexpr uint8_t _ = k_sentinel;  // for brevity
      11             : constexpr uint8_t k_eol = 0;
      12             : 
      13             : // Invalid inputs are mapped to the value 255. '=' maps to 0.
      14             : constexpr uint8_t k_base64_table[] = {
      15             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      16             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      17             :     _,  _,  _,  _,  _,  _,  _,  62,    _,  _,  _,  63, 52, 53, 54, 55, 56, 57,
      18             :     58, 59, 60, 61, _,  _,  _,  k_eol, _,  _,  _,  0,  1,  2,  3,  4,  5,  6,
      19             :     7,  8,  9,  10, 11, 12, 13, 14,    15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
      20             :     25, _,  _,  _,  _,  _,  _,  26,    27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
      21             :     37, 38, 39, 40, 41, 42, 43, 44,    45, 46, 47, 48, 49, 50, 51, _,  _,  _,
      22             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      23             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      24             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      25             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      26             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      27             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      28             :     _,  _,  _,  _,  _,  _,  _,  _,     _,  _,  _,  _,  _,  _,  _,  _,  _,  _,
      29             :     _,  _,  _,  _};
      30             : 
      31          34 : std::string base64_decode(StringView input) {
      32          34 :   const size_t in_size = input.size();
      33             : 
      34          34 :   std::string output;
      35          34 :   output.reserve(in_size);
      36             : 
      37          34 :   size_t i = 0;
      38             : 
      39        2542 :   for (; i + 4 < in_size;) {
      40        2511 :     uint32_t c0 = k_base64_table[static_cast<size_t>(input[i++])];
      41        2511 :     uint32_t c1 = k_base64_table[static_cast<size_t>(input[i++])];
      42        2511 :     uint32_t c2 = k_base64_table[static_cast<size_t>(input[i++])];
      43        2511 :     uint32_t c3 = k_base64_table[static_cast<size_t>(input[i++])];
      44             : 
      45        2511 :     if (c0 == k_sentinel || c1 == k_sentinel || c2 == k_sentinel ||
      46             :         c3 == k_sentinel) {
      47           3 :       return "";
      48             :     }
      49             : 
      50        2508 :     output.push_back(c0 << 2 | (c1 & 0xF0) >> 4);
      51        2508 :     output.push_back((c1 & 0x0F) << 4 | ((c2 & 0x3C) >> 2));
      52        2508 :     output.push_back(((c2 & 0x03) << 6) | (c3 & 0x3F));
      53             :   }
      54             : 
      55             :   // If padding is missing, return the empty string in lieu of an Error.
      56          31 :   if ((in_size - i) < 4) return "";
      57             : 
      58          28 :   uint32_t c0 = k_base64_table[static_cast<size_t>(input[i++])];
      59          28 :   uint32_t c1 = k_base64_table[static_cast<size_t>(input[i++])];
      60          28 :   uint32_t c2 = k_base64_table[static_cast<size_t>(input[i++])];
      61          28 :   uint32_t c3 = k_base64_table[static_cast<size_t>(input[i++])];
      62             : 
      63          28 :   if (c0 == k_sentinel || c1 == k_sentinel || c2 == k_sentinel ||
      64             :       c3 == k_sentinel) {
      65           1 :     return "";
      66             :   }
      67             : 
      68          27 :   if (c2 == k_eol) {
      69             :     // The last quadruplet is of the form "xx==", where only one character needs
      70             :     // to be decoded.
      71           2 :     output.push_back(c0 << 2 | (c1 & 0xF0) >> 4);
      72          25 :   } else if (c3 == k_eol) {
      73             :     // The last quadruplet is of the form "xxx=", where only two character needs
      74             :     // to be decoded.
      75           7 :     output.push_back(c0 << 2 | (c1 & 0xF0) >> 4);
      76           7 :     output.push_back((c1 & 0x0F) << 4 | ((c2 & 0x3C) >> 2));
      77             :   } else {
      78             :     // The last quadruplet is not padded -> common use case
      79          18 :     output.push_back(c0 << 2 | (c1 & 0xF0) >> 4);
      80          18 :     output.push_back((c1 & 0x0F) << 4 | ((c2 & 0x3C) >> 2));
      81          18 :     output.push_back(((c2 & 0x03) << 6) | (c3 & 0x3F));
      82             :   }
      83             : 
      84          27 :   return output;
      85          34 : }
      86             : 
      87             : }  // namespace tracing
      88             : }  // namespace datadog