| 65 | } |
| 66 | |
| 67 | bool decode(const std::string &in, BinaryArray *ret) { |
| 68 | // Make sure the *intended* string length is a multiple of 4 |
| 69 | size_t encoded_size = in.size(); |
| 70 | |
| 71 | while ((encoded_size % 4) != 0) |
| 72 | ++encoded_size; |
| 73 | |
| 74 | const size_t N = in.size(); |
| 75 | ret->clear(); |
| 76 | ret->reserve(3 * encoded_size / 4); |
| 77 | |
| 78 | for (size_t i = 0; i < encoded_size; i += 4) { |
| 79 | // Get values for each group of four base 64 characters |
| 80 | const uint8_t b4_0 = |
| 81 | (static_cast<uint8_t>(in[i + 0]) <= 'z') ? from_base64[static_cast<uint8_t>(in[i + 0])] : uint8_t(0xff); |
| 82 | const uint8_t b4_1 = (i + 1 < N && static_cast<uint8_t>(in[i + 1]) <= 'z') |
| 83 | ? from_base64[static_cast<uint8_t>(in[i + 1])] |
| 84 | : uint8_t(0xff); |
| 85 | const uint8_t b4_2 = (i + 2 < N && static_cast<uint8_t>(in[i + 2]) <= 'z') |
| 86 | ? from_base64[static_cast<uint8_t>(in[i + 2])] |
| 87 | : uint8_t(0xff); |
| 88 | const uint8_t b4_3 = (i + 3 < N && static_cast<uint8_t>(in[i + 3]) <= 'z') |
| 89 | ? from_base64[static_cast<uint8_t>(in[i + 3])] |
| 90 | : uint8_t(0xff); |
| 91 | |
| 92 | // Transform into a group of three bytes |
| 93 | const uint8_t b3_0 = ((b4_0 & 0x3f) << 2) + ((b4_1 & 0x30) >> 4); |
| 94 | const uint8_t b3_1 = ((b4_1 & 0x0f) << 4) + ((b4_2 & 0x3c) >> 2); |
| 95 | const uint8_t b3_2 = ((b4_2 & 0x03) << 6) + ((b4_3 & 0x3f) >> 0); |
| 96 | |
| 97 | // Add the byte to the return value if it isn't part of an '=' character (indicated by 0xff) |
| 98 | if (b4_1 != 0xff) |
| 99 | ret->push_back(b3_0); |
| 100 | if (b4_2 != 0xff) |
| 101 | ret->push_back(b3_1); |
| 102 | if (b4_3 != 0xff) |
| 103 | ret->push_back(b3_2); |
| 104 | } |
| 105 | return true; // TODO - find decoder which returns false on invalid data |
| 106 | } |
| 107 | }} // namespace common::base64 |