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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Array.h>
#include <AK/Base64.h>
#include <AK/ByteBuffer.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/StringView.h>
#include <AK/Types.h>
#include <AK/Vector.h>
namespace AK {
static constexpr auto make_alphabet()
{
Array alphabet = {
'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', '+', '/'
};
return alphabet;
}
static constexpr auto make_lookup_table()
{
constexpr auto alphabet = make_alphabet();
Array<u8, 256> table {};
for (size_t i = 0; i < alphabet.size(); ++i) {
table[alphabet[i]] = i;
}
return table;
}
size_t calculate_base64_decoded_length(const StringView& input)
{
return input.length() * 3 / 4;
}
size_t calculate_base64_encoded_length(ReadonlyBytes input)
{
return ((4 * input.size() / 3) + 3) & ~3;
}
ByteBuffer decode_base64(const StringView& input)
{
auto get = [&](const size_t offset, bool* is_padding = nullptr) -> u8 {
constexpr auto table = make_lookup_table();
if (offset >= input.length())
return 0;
if (input[offset] == '=') {
if (is_padding)
*is_padding = true;
return 0;
}
return table[input[offset]];
};
Vector<u8> output;
output.ensure_capacity(calculate_base64_decoded_length(input));
for (size_t i = 0; i < input.length(); i += 4) {
bool in2_is_padding = false;
bool in3_is_padding = false;
const u8 in0 = get(i);
const u8 in1 = get(i + 1);
const u8 in2 = get(i + 2, &in2_is_padding);
const u8 in3 = get(i + 3, &in3_is_padding);
const u8 out0 = (in0 << 2) | ((in1 >> 4) & 3);
const u8 out1 = ((in1 & 0xf) << 4) | ((in2 >> 2) & 0xf);
const u8 out2 = ((in2 & 0x3) << 6) | in3;
output.append(out0);
if (!in2_is_padding)
output.append(out1);
if (!in3_is_padding)
output.append(out2);
}
return ByteBuffer::copy(output.data(), output.size());
}
String encode_base64(ReadonlyBytes input)
{
constexpr auto alphabet = make_alphabet();
StringBuilder output(calculate_base64_encoded_length(input));
auto get = [&](const size_t offset, bool* need_padding = nullptr) -> u8 {
if (offset >= input.size()) {
if (need_padding)
*need_padding = true;
return 0;
}
return input[offset];
};
for (size_t i = 0; i < input.size(); i += 3) {
bool is_8bit = false;
bool is_16bit = false;
const u8 in0 = get(i);
const u8 in1 = get(i + 1, &is_16bit);
const u8 in2 = get(i + 2, &is_8bit);
const u8 index0 = (in0 >> 2) & 0x3f;
const u8 index1 = ((in0 << 4) | (in1 >> 4)) & 0x3f;
const u8 index2 = ((in1 << 2) | (in2 >> 6)) & 0x3f;
const u8 index3 = in2 & 0x3f;
const u8 out0 = alphabet[index0];
const u8 out1 = alphabet[index1];
const u8 out2 = is_16bit ? '=' : alphabet[index2];
const u8 out3 = is_8bit ? '=' : alphabet[index3];
output.append(out0);
output.append(out1);
output.append(out2);
output.append(out3);
}
return output.to_string();
}
}
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