| 60 | } |
| 61 | |
| 62 | fl::vector<fl::u8> base64_decode(const fl::string& encoded) { |
| 63 | fl::vector<fl::u8> out; |
| 64 | if (encoded.empty()) return out; |
| 65 | |
| 66 | fl::size len = encoded.size(); |
| 67 | |
| 68 | // Validate length is multiple of 4 |
| 69 | if (len % 4 != 0) return out; |
| 70 | |
| 71 | fl::size out_len = (len / 4) * 3; |
| 72 | if (len >= 1 && encoded[len - 1] == '=') out_len--; |
| 73 | if (len >= 2 && encoded[len - 2] == '=') out_len--; |
| 74 | out.reserve(out_len); |
| 75 | |
| 76 | for (fl::size i = 0; i < len; i += 4) { |
| 77 | int a = base64_char_index(encoded[i]); |
| 78 | int b = base64_char_index(encoded[i + 1]); |
| 79 | int c = (encoded[i + 2] == '=') ? 0 : base64_char_index(encoded[i + 2]); |
| 80 | int d = (encoded[i + 3] == '=') ? 0 : base64_char_index(encoded[i + 3]); |
| 81 | |
| 82 | if (a < 0 || b < 0 || c < 0 || d < 0) { |
| 83 | return fl::vector<fl::u8>(); // invalid character |
| 84 | } |
| 85 | |
| 86 | fl::u32 triple = (fl::u32(a) << 18) | (fl::u32(b) << 12) | |
| 87 | (fl::u32(c) << 6) | fl::u32(d); |
| 88 | |
| 89 | out.push_back((triple >> 16) & 0xFF); |
| 90 | if (encoded[i + 2] != '=') { |
| 91 | out.push_back((triple >> 8) & 0xFF); |
| 92 | } |
| 93 | if (encoded[i + 3] != '=') { |
| 94 | out.push_back(triple & 0xFF); |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | return out; |
| 99 | } |
| 100 | |
| 101 | } // namespace fl |