76 lines
2.1 KiB
C++
76 lines
2.1 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "flutter/fml/base32.h"
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#include <cstdint> // uint8_t
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#include <limits>
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#include <string>
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namespace fml {
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static constexpr char kEncoding[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
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std::pair<bool, std::string> Base32Encode(std::string_view input) {
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if (input.empty()) {
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return {true, ""};
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}
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if (input.size() > std::numeric_limits<size_t>::max() / 8) {
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return {false, ""};
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}
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std::string output;
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const size_t encoded_length = (input.size() * 8 + 4) / 5;
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output.reserve(encoded_length);
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Base32EncodeConverter converter;
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converter.Append(static_cast<uint8_t>(input[0]));
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size_t next_byte_index = 1;
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while (converter.CanExtract()) {
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output.push_back(kEncoding[converter.Extract()]);
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if (converter.CanAppend() && next_byte_index < input.size()) {
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converter.Append(static_cast<uint8_t>(input[next_byte_index++]));
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}
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}
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if (converter.BitsAvailable() > 0) {
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output.push_back(kEncoding[converter.Peek()]);
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}
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return {true, output};
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}
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static constexpr signed char kDecodeMap[] = {
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// starting from ASCII 50 '2'
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26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
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13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25};
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static constexpr int kDecodeMapSize =
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sizeof(kDecodeMap) / sizeof(kDecodeMap[0]);
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std::pair<bool, std::string> Base32Decode(const std::string& input) {
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std::string result;
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Base32DecodeConverter converter;
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for (char c : input) {
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int map_index = c - '2';
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if (map_index < 0 || map_index >= kDecodeMapSize ||
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kDecodeMap[map_index] == -1) {
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return {false, result};
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}
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converter.Append(kDecodeMap[map_index]);
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if (converter.CanExtract()) {
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result.push_back(converter.Extract());
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}
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}
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if (converter.Peek() != 0) {
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// The padding should always be zero. Return false if not.
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return {false, result};
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}
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return {true, result};
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}
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} // namespace fml
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