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base64.cc
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base64.cc
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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/base64.h"
#include <stddef.h>
#include "base/check.h"
#include "base/numerics/checked_math.h"
#include "base/strings/string_util.h"
#include "base/third_party/modp_b64/modp_b64.h"
namespace base {
namespace {
ModpDecodePolicy GetModpPolicy(Base64DecodePolicy policy) {
switch (policy) {
case Base64DecodePolicy::kStrict:
return ModpDecodePolicy::kStrict;
case Base64DecodePolicy::kForgiving:
return ModpDecodePolicy::kForgiving;
}
}
} // namespace
std::string Base64Encode(span<const uint8_t> input) {
std::string output;
Base64EncodeAppend(input, &output);
return output;
}
void Base64EncodeAppend(span<const uint8_t> input, std::string* output) {
// Ensure `modp_b64_encode_data_len` will not overflow.
CHECK_LE(input.size(), MODP_B64_MAX_INPUT_LEN);
size_t encode_data_len = modp_b64_encode_data_len(input.size());
size_t prefix_len = output->size();
output->resize(base::CheckAdd(encode_data_len, prefix_len).ValueOrDie());
const size_t output_size = modp_b64_encode_data(
output->data() + prefix_len, reinterpret_cast<const char*>(input.data()),
input.size());
CHECK_EQ(output->size(), prefix_len + output_size);
}
std::string Base64Encode(StringPiece input) {
return Base64Encode(base::as_byte_span(input));
}
bool Base64Decode(StringPiece input,
std::string* output,
Base64DecodePolicy policy) {
std::string temp;
temp.resize(modp_b64_decode_len(input.size()));
// does not null terminate result since result is binary data!
size_t input_size = input.size();
size_t output_size = modp_b64_decode(&(temp[0]), input.data(), input_size,
GetModpPolicy(policy));
// Forgiving mode requires whitespace to be stripped prior to decoding.
// We don't do that in the above code to ensure that the "happy path" of
// input without whitespace is as fast as possible. Since whitespace in input
// will always cause `modp_b64_decode` to fail, just handle whitespace
// stripping on failure. This is not much slower than just scanning for
// whitespace first, even for input with whitespace.
if (output_size == MODP_B64_ERROR &&
policy == Base64DecodePolicy::kForgiving) {
// We could use `output` here to avoid an allocation when decoding is done
// in-place, but it violates the API contract that `output` is only modified
// on success.
std::string input_without_whitespace;
RemoveChars(input, kInfraAsciiWhitespace, &input_without_whitespace);
output_size =
modp_b64_decode(&(temp[0]), input_without_whitespace.data(),
input_without_whitespace.size(), GetModpPolicy(policy));
}
if (output_size == MODP_B64_ERROR)
return false;
temp.resize(output_size);
output->swap(temp);
return true;
}
std::optional<std::vector<uint8_t>> Base64Decode(StringPiece input) {
std::vector<uint8_t> ret(modp_b64_decode_len(input.size()));
size_t input_size = input.size();
size_t output_size = modp_b64_decode(reinterpret_cast<char*>(ret.data()),
input.data(), input_size);
if (output_size == MODP_B64_ERROR)
return std::nullopt;
ret.resize(output_size);
return ret;
}
} // namespace base