ceph/src/jaegertracing/opentracing-cpp/mocktracer/src/base64.cpp

   1 /*
   2  * Envoy
   3  * Copyright 2016-2017 Lyft Inc.
   4  *
   5  * Licensed under Apache License 2.0.  See LICENSE.apache for terms.
   6  */
   7
   8 #include "base64.h"
   9
  10 #include <cstdint>
  11 #include <string>
  12
  13 namespace opentracing {
  14 BEGIN_OPENTRACING_ABI_NAMESPACE
  15 namespace mocktracer {
  16 static constexpr char CHAR_TABLE[] =
  17     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  18
  19 // Conversion table is taken from
  20 // https://opensource.apple.com/source/QuickTimeStreamingServer/QuickTimeStreamingServer-452/CommonUtilitiesLib/base64.c
  21 static const unsigned char REVERSE_LOOKUP_TABLE[256] = {
  22     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  23     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  24     64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60,
  25     61, 64, 64, 64, 64, 64, 64, 64, 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,
  26     11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64,
  27     64, 64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
  28     43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  29     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  30     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  31     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  32     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  33     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  34     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
  35     64, 64, 64, 64, 64, 64, 64, 64, 64};
  36
  37 std::string Base64::decode(const char* input, size_t length) {
  38   if (length % 4 || length == 0) {
  39     return {};
  40   }
  41
  42   // First position of "valid" padding character.
  43   uint64_t first_padding_index = length;
  44   int max_length = static_cast<int>(length) / 4 * 3;
  45   // At most last two chars can be '='.
  46   if (input[length - 1] == '=') {
  47     max_length--;
  48     first_padding_index = length - 1;
  49     if (input[length - 2] == '=') {
  50       max_length--;
  51       first_padding_index = length - 2;
  52     }
  53   }
  54   std::string result;
  55   result.reserve(static_cast<size_t>(max_length));
  56
  57   uint64_t bytes_left = length;
  58   uint64_t cur_read = 0;
  59
  60   // Read input string by group of 4 chars, length of input string must be
  61   // divided evenly by 4. Decode 4 chars 6 bits each into 3 chars 8 bits each.
  62   while (bytes_left > 0) {
  63     // Take first 6 bits from 1st converted char and first 2 bits from 2nd
  64     // converted char, make 8 bits char from it. Use conversion table to map
  65     // char to decoded value (value is between 0 and 63 inclusive for a valid
  66     // character).
  67     const unsigned char a =
  68         REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read])];
  69     const unsigned char b =
  70         REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 1])];
  71     if (a == 64 || b == 64) {
  72       // Input contains an invalid character.
  73       return {};
  74     }
  75     result.push_back(static_cast<char>(a << 2 | b >> 4));
  76     const unsigned char c =
  77         REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 2])];
  78
  79     // Decoded value 64 means invalid character unless we already know it is a
  80     // valid padding. If so, following characters are all padding. Also we
  81     // should check there are no unused bits.
  82     if (c == 64) {
  83       if (first_padding_index != cur_read + 2) {
  84         // Input contains an invalid character.
  85         return {};
  86       } else if (b & 15) {
  87         // There are unused bits at tail.
  88         return {};
  89       } else {
  90         return result;
  91       }
  92     }
  93     // Take last 4 bits from 2nd converted char and 4 first bits from 3rd
  94     // converted char.
  95     result.push_back(static_cast<char>(b << 4 | c >> 2));
  96
  97     const unsigned char d =
  98         REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 3])];
  99     if (d == 64) {
 100       if (first_padding_index != cur_read + 3) {
 101         // Input contains an invalid character.
 102         return {};
 103       } else if (c & 3) {
 104         // There are unused bits at tail.
 105         return {};
 106       } else {
 107         return result;
 108       }
 109     }
 110     // Take last 2 bits from 3rd converted char and all(6) bits from 4th
 111     // converted char.
 112     result.push_back(static_cast<char>(c << 6 | d));
 113
 114     cur_read += 4;
 115     bytes_left -= 4;
 116   }
 117
 118   return result;
 119 }
 120
 121 void Base64::encodeBase(const uint8_t cur_char, uint64_t pos, uint8_t& next_c,
 122                         std::string& ret) {
 123   switch (pos % 3) {
 124     case 0:
 125       ret.push_back(CHAR_TABLE[cur_char >> 2]);
 126       next_c = static_cast<uint8_t>((cur_char & 0x03) << 4);
 127       break;
 128     case 1:
 129       ret.push_back(CHAR_TABLE[next_c | (cur_char >> 4)]);
 130       next_c = static_cast<uint8_t>((cur_char & 0x0f) << 2);
 131       break;
 132     case 2:
 133       ret.push_back(CHAR_TABLE[next_c | (cur_char >> 6)]);
 134       ret.push_back(CHAR_TABLE[cur_char & 0x3f]);
 135       next_c = 0;
 136       break;
 137   }
 138 }
 139
 140 void Base64::encodeLast(uint64_t pos, uint8_t last_char, std::string& ret) {
 141   switch (pos % 3) {
 142     case 1:
 143       ret.push_back(CHAR_TABLE[last_char]);
 144       ret.push_back('=');
 145       ret.push_back('=');
 146       break;
 147     case 2:
 148       ret.push_back(CHAR_TABLE[last_char]);
 149       ret.push_back('=');
 150       break;
 151     default:
 152       break;
 153   }
 154 }
 155
 156 std::string Base64::encode(const char* input, uint64_t length) {
 157   uint64_t output_length = (length + 2) / 3 * 4;
 158   std::string ret;
 159   ret.reserve(output_length);
 160
 161   uint64_t pos = 0;
 162   uint8_t next_c = 0;
 163
 164   for (uint64_t i = 0; i < length; ++i) {
 165     encodeBase(static_cast<uint8_t>(input[i]), pos++, next_c, ret);
 166   }
 167
 168   encodeLast(pos, next_c, ret);
 169
 170   return ret;
 171 }
 172 }  // namespace mocktracer
 173 END_OPENTRACING_ABI_NAMESPACE
 174 }  // namespace opentracing