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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/ByteBuffer.h>
#include <AK/StringView.h>
#include <AK/Types.h>
#include <AK/Vector.h>
namespace AK {
static constexpr u8 s_alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static u8 s_table[256] = {};
static bool s_initialized = false;
static void build_lookup_table_if_needed()
{
if (s_initialized)
return;
for (size_t i = 0; i < sizeof(s_alphabet) - 1; ++i)
s_table[s_alphabet[i]] = i;
s_initialized = true;
}
ByteBuffer decode_base64(const StringView& input)
{
build_lookup_table_if_needed();
auto get = [&](size_t offset, bool* is_padding = nullptr) -> u8 {
if (offset >= input.length())
return 0;
if (input[offset] == '=') {
if (is_padding)
*is_padding = true;
return 0;
}
return s_table[(u8)input[offset]];
};
Vector<u8> output;
for (size_t i = 0; i < input.length(); i += 4) {
bool in2_is_padding = false;
bool in3_is_padding = false;
u8 in0 = get(i);
u8 in1 = get(i + 1);
u8 in2 = get(i + 2, &in2_is_padding);
u8 in3 = get(i + 3, &in3_is_padding);
u8 out0 = (in0 << 2) | ((in1 >> 4) & 3);
u8 out1 = ((in1 & 0xf) << 4) | ((in2 >> 2) & 0xf);
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());
}
}
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