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