mirror of
https://github.com/SerenityOS/serenity
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50349de38c
It's prone to finding "technically uninitialized but can never happen"
cases, particularly in Optional<T> and Variant<Ts...>.
The general case seems to be that it cannot infer the dependency
between Variant's index (or Optional's boolean state) and a particular
alternative (or Optional's buffer) being untouched.
So it can flag cases like this:
```c++
if (index == StaticIndexForF)
new (new_buffer) F(move(*bit_cast<F*>(old_buffer)));
```
The code in that branch can _technically_ make a partially initialized
`F`, but that path can never be taken since the buffer holding an
object of type `F` and the condition being true are correlated, and so
will never be taken _unless_ the buffer holds an object of type `F`.
This commit also removed the various 'diagnostic ignored' pragmas used
to work around this warning, as they no longer do anything.
134 lines
3.6 KiB
C++
134 lines
3.6 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Array.h>
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#include <AK/Base64.h>
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#include <AK/ByteBuffer.h>
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#include <AK/String.h>
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#include <AK/StringBuilder.h>
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#include <AK/StringView.h>
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#include <AK/Types.h>
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#include <AK/Vector.h>
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namespace AK {
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static constexpr auto make_alphabet()
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{
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Array alphabet = {
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'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
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'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
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'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
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'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
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'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
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'w', 'x', 'y', 'z', '0', '1', '2', '3',
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'4', '5', '6', '7', '8', '9', '+', '/'
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};
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return alphabet;
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}
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static constexpr auto make_lookup_table()
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{
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constexpr auto alphabet = make_alphabet();
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Array<u8, 256> table {};
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for (size_t i = 0; i < alphabet.size(); ++i) {
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table[alphabet[i]] = i;
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}
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return table;
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}
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size_t calculate_base64_decoded_length(const StringView& input)
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{
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return input.length() * 3 / 4;
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}
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size_t calculate_base64_encoded_length(ReadonlyBytes input)
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{
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return ((4 * input.size() / 3) + 3) & ~3;
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}
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ByteBuffer decode_base64(const StringView& input)
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{
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auto get = [&](const size_t offset, bool* is_padding = nullptr) -> u8 {
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constexpr auto table = make_lookup_table();
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if (offset >= input.length())
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return 0;
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if (input[offset] == '=') {
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if (is_padding)
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*is_padding = true;
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return 0;
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}
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return table[input[offset]];
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};
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Vector<u8> output;
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output.ensure_capacity(calculate_base64_decoded_length(input));
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for (size_t i = 0; i < input.length(); i += 4) {
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bool in2_is_padding = false;
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bool in3_is_padding = false;
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const u8 in0 = get(i);
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const u8 in1 = get(i + 1);
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const u8 in2 = get(i + 2, &in2_is_padding);
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const u8 in3 = get(i + 3, &in3_is_padding);
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const u8 out0 = (in0 << 2) | ((in1 >> 4) & 3);
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const u8 out1 = ((in1 & 0xf) << 4) | ((in2 >> 2) & 0xf);
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const u8 out2 = ((in2 & 0x3) << 6) | in3;
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output.append(out0);
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if (!in2_is_padding)
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output.append(out1);
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if (!in3_is_padding)
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output.append(out2);
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}
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return ByteBuffer::copy(output.data(), output.size());
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}
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String encode_base64(ReadonlyBytes input)
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{
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constexpr auto alphabet = make_alphabet();
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StringBuilder output(calculate_base64_encoded_length(input));
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auto get = [&](const size_t offset, bool* need_padding = nullptr) -> u8 {
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if (offset >= input.size()) {
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if (need_padding)
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*need_padding = true;
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return 0;
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}
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return input[offset];
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};
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for (size_t i = 0; i < input.size(); i += 3) {
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bool is_8bit = false;
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bool is_16bit = false;
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const u8 in0 = get(i);
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const u8 in1 = get(i + 1, &is_16bit);
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const u8 in2 = get(i + 2, &is_8bit);
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const u8 index0 = (in0 >> 2) & 0x3f;
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const u8 index1 = ((in0 << 4) | (in1 >> 4)) & 0x3f;
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const u8 index2 = ((in1 << 2) | (in2 >> 6)) & 0x3f;
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const u8 index3 = in2 & 0x3f;
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const u8 out0 = alphabet[index0];
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const u8 out1 = alphabet[index1];
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const u8 out2 = is_16bit ? '=' : alphabet[index2];
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const u8 out3 = is_8bit ? '=' : alphabet[index3];
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output.append(out0);
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output.append(out1);
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output.append(out2);
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output.append(out3);
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}
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return output.to_string();
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}
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}
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