| // Copyright 2020 The Pigweed Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| // use this file except in compliance with the License. You may obtain a copy of |
| // the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| // License for the specific language governing permissions and limitations under |
| // the License. |
| |
| #include "pw_base64/base64.h" |
| |
| #include <cstdint> |
| |
| namespace pw::base64 { |
| namespace { |
| |
| // Encoding functions |
| constexpr size_t kEncodedGroupSize = 4; |
| constexpr char kChar62 = '+'; // URL safe encoding uses - instead |
| constexpr char kChar63 = '/'; // URL safe encoding uses _ instead |
| constexpr char kPadding = '='; |
| |
| // Table that encodes a 6-bit pattern as a Base64 character |
| constexpr char encode_bits[64] = { |
| 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', |
| 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', |
| 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', |
| 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', |
| '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', kChar62, kChar63}; |
| |
| constexpr char BitGroup0Char(uint8_t byte0) { |
| return encode_bits[(byte0 & 0b11111100) >> 2]; |
| } |
| constexpr char BitGroup1Char(uint8_t byte0, uint8_t byte1 = 0) { |
| return encode_bits[((byte0 & 0b00000011) << 4) | ((byte1 & 0b11110000) >> 4)]; |
| } |
| constexpr char BitGroup2Char(uint8_t byte1, uint8_t byte2 = 0) { |
| return encode_bits[((byte1 & 0b00001111) << 2) | ((byte2 & 0b11000000) >> 6)]; |
| } |
| constexpr char BitGroup3Char(uint8_t byte2) { |
| return encode_bits[byte2 & 0b00111111]; |
| } |
| |
| // Decoding functions |
| constexpr char kMinValidChar = '+'; |
| constexpr char kMaxValidChar = 'z'; |
| constexpr uint8_t kX = 0xff; // Value used for invalid characters |
| |
| // Table that decodes a Base64 character to its 6-bit value. Supports the |
| // standard (+/) and URL-safe (-_) alphabets. Starts from the lowest-value valid |
| // character, which is +. |
| constexpr uint8_t decode_char[] = { |
| 62, kX, 62, kX, 63, 52, 53, 54, 55, 56, // 0 - 09 |
| 57, 58, 59, 60, 61, kX, kX, kX, 0, kX, // 10 - 19 |
| kX, kX, 0, 1, 2, 3, 4, 5, 6, 7, // 20 - 29 |
| 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, // 30 - 39 |
| 18, 19, 20, 21, 22, 23, 24, 25, kX, kX, // 40 - 49 |
| kX, kX, 63, kX, 26, 27, 28, 29, 30, 31, // 50 - 59 |
| 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, // 60 - 69 |
| 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 70 - 79 |
| }; |
| |
| constexpr uint8_t CharToBits(char ch) { |
| return decode_char[ch - kMinValidChar]; |
| } |
| |
| constexpr uint8_t Byte0(uint8_t bits0, uint8_t bits1) { |
| return (bits0 << 2) | ((bits1 & 0b110000) >> 4); |
| } |
| constexpr uint8_t Byte1(uint8_t bits1, uint8_t bits2) { |
| return ((bits1 & 0b001111) << 4) | ((bits2 & 0b111100) >> 2); |
| } |
| constexpr uint8_t Byte2(uint8_t bits2, uint8_t bits3) { |
| return ((bits2 & 0b000011) << 6) | bits3; |
| } |
| |
| } // namespace |
| |
| extern "C" void pw_Base64Encode(const void* binary_data, |
| const size_t binary_size_bytes, |
| char* output) { |
| const uint8_t* bytes = static_cast<const uint8_t*>(binary_data); |
| |
| // Encode groups of 3 source bytes into 4 output characters. |
| size_t remaining = binary_size_bytes; |
| for (; remaining >= 3u; remaining -= 3u, bytes += 3) { |
| *output++ = BitGroup0Char(bytes[0]); |
| *output++ = BitGroup1Char(bytes[0], bytes[1]); |
| *output++ = BitGroup2Char(bytes[1], bytes[2]); |
| *output++ = BitGroup3Char(bytes[2]); |
| } |
| |
| // If the source data length isn't a multiple of 3, pad the end with either 1 |
| // or 2 '=' characters, to stay Python-compatible. |
| if (remaining > 0u) { |
| *output++ = BitGroup0Char(bytes[0]); |
| if (remaining == 1u) { |
| *output++ = BitGroup1Char(bytes[0]); |
| *output++ = kPadding; |
| } else { |
| *output++ = BitGroup1Char(bytes[0], bytes[1]); |
| *output++ = BitGroup2Char(bytes[1]); |
| } |
| *output++ = kPadding; |
| } |
| } |
| |
| extern "C" size_t pw_Base64Decode(const char* base64, |
| size_t base64_size_bytes, |
| void* output) { |
| // If too small, can't be valid input, due to likely missing padding |
| if (base64_size_bytes < 4) { |
| return 0; |
| } |
| |
| uint8_t* binary = static_cast<uint8_t*>(output); |
| for (size_t ch = 0; ch < base64_size_bytes; ch += kEncodedGroupSize) { |
| const uint8_t char0 = CharToBits(base64[ch + 0]); |
| const uint8_t char1 = CharToBits(base64[ch + 1]); |
| const uint8_t char2 = CharToBits(base64[ch + 2]); |
| const uint8_t char3 = CharToBits(base64[ch + 3]); |
| |
| *binary++ = Byte0(char0, char1); |
| *binary++ = Byte1(char1, char2); |
| *binary++ = Byte2(char2, char3); |
| } |
| |
| size_t pad = 0; |
| if (base64[base64_size_bytes - 2] == kPadding) { |
| pad = 2; |
| } else if (base64[base64_size_bytes - 1] == kPadding) { |
| pad = 1; |
| } |
| |
| return binary - static_cast<uint8_t*>(output) - pad; |
| } |
| |
| extern "C" bool pw_Base64IsValid(const char* base64_data, size_t base64_size) { |
| if (base64_size % kEncodedGroupSize != 0) { |
| return false; |
| } |
| |
| for (size_t i = 0; i < base64_size; ++i) { |
| if (base64_data[i] < kMinValidChar || base64_data[i] > kMaxValidChar || |
| CharToBits(base64_data[i]) == kX /* invalid char */) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| size_t Encode(span<const std::byte> binary, span<char> output_buffer) { |
| const size_t required_size = EncodedSize(binary.size_bytes()); |
| if (output_buffer.size_bytes() < required_size) { |
| return 0; |
| } |
| pw_Base64Encode(binary.data(), binary.size_bytes(), output_buffer.data()); |
| return required_size; |
| } |
| |
| size_t Decode(std::string_view base64, span<std::byte> output_buffer) { |
| if (output_buffer.size_bytes() < MaxDecodedSize(base64.size()) || |
| !IsValid(base64)) { |
| return 0; |
| } |
| return Decode(base64, output_buffer.data()); |
| } |
| |
| } // namespace pw::base64 |