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/*
* Copyright 2015, Mozilla Foundation and contributors
*
* 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
*
* http://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 "ClearKeyBase64.h"
#include <algorithm>
using namespace std;
/**
* Take a base64-encoded string, convert (in-place) each character to its
* corresponding value in the [0x00, 0x3f] range, and truncate any padding.
*/
static bool
Decode6Bit(string& aStr)
{
for (size_t i = 0; i < aStr.length(); i++) {
if (aStr[i] >= 'A' && aStr[i] <= 'Z') {
aStr[i] -= 'A';
}
else if (aStr[i] >= 'a' && aStr[i] <= 'z') {
aStr[i] -= 'a' - 26;
}
else if (aStr[i] >= '0' && aStr[i] <= '9') {
aStr[i] -= '0' - 52;
}
else if (aStr[i] == '-' || aStr[i] == '+') {
aStr[i] = 62;
}
else if (aStr[i] == '_' || aStr[i] == '/') {
aStr[i] = 63;
}
else {
// Truncate '=' padding at the end of the aString.
if (aStr[i] != '=') {
aStr.erase(i, string::npos);
return false;
}
aStr[i] = '\0';
aStr.resize(i);
break;
}
}
return true;
}
bool
DecodeBase64(const string& aEncoded, vector<uint8_t>& aOutDecoded)
{
if (aEncoded.empty()) {
aOutDecoded.clear();
return true;
}
if (aEncoded.size() == 1) {
// Invalid Base64 encoding.
return false;
}
string encoded = aEncoded;
if (!Decode6Bit(encoded)) {
return false;
}
// The number of bytes we haven't yet filled in the current byte, mod 8.
int shift = 0;
aOutDecoded.resize((encoded.size() * 3) / 4);
vector<uint8_t>::iterator out = aOutDecoded.begin();
for (size_t i = 0; i < encoded.length(); i++) {
if (!shift) {
*out = encoded[i] << 2;
}
else {
*out |= encoded[i] >> (6 - shift);
out++;
if (out == aOutDecoded.end()) {
// Hit last 6bit octed in encoded, which is padding and can be ignored.
break;
}
*out = encoded[i] << (shift + 2);
}
shift = (shift + 2) % 8;
}
return true;
}
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