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81ad6de41b
There's no need to copy the result. We can also avoid increasing the size of the output buffer by 1 for each written byte. This reduces the runtime of `./bin/base64 -d enwik8.base64 >/dev/null` from 0.917s to 0.632s. (enwik8 is a 100MB test file from http://mattmahoney.net/dc/enwik8.zip)
141 lines
4 KiB
C++
141 lines
4 KiB
C++
/*
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* Copyright (c) 2020-2022, 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/Assertions.h>
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#include <AK/Base64.h>
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#include <AK/CharacterTypes.h>
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#include <AK/Error.h>
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#include <AK/StringBuilder.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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size_t calculate_base64_decoded_length(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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template<auto alphabet_lookup_table>
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ErrorOr<ByteBuffer> decode_base64_impl(StringView input)
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{
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auto get = [&](size_t& offset, bool* is_padding, bool& parsed_something) -> ErrorOr<u8> {
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while (offset < input.length() && is_ascii_space(input[offset]))
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++offset;
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if (offset >= input.length())
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return 0;
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auto ch = static_cast<unsigned char>(input[offset++]);
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parsed_something = true;
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if (ch == '=') {
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if (!is_padding)
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return Error::from_string_literal("Invalid '=' character outside of padding in base64 data");
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*is_padding = true;
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return 0;
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}
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i16 result = alphabet_lookup_table[ch];
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if (result < 0)
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return Error::from_string_literal("Invalid character in base64 data");
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VERIFY(result < 256);
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return { result };
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};
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ByteBuffer output;
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TRY(output.try_resize(calculate_base64_decoded_length(input)));
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size_t input_offset = 0;
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size_t output_offset = 0;
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while (input_offset < input.length()) {
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bool in2_is_padding = false;
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bool in3_is_padding = false;
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bool parsed_something = false;
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const u8 in0 = TRY(get(input_offset, nullptr, parsed_something));
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const u8 in1 = TRY(get(input_offset, nullptr, parsed_something));
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const u8 in2 = TRY(get(input_offset, &in2_is_padding, parsed_something));
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const u8 in3 = TRY(get(input_offset, &in3_is_padding, parsed_something));
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if (!parsed_something)
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break;
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output[output_offset++] = (in0 << 2) | ((in1 >> 4) & 3);
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if (!in2_is_padding)
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output[output_offset++] = ((in1 & 0xf) << 4) | ((in2 >> 2) & 0xf);
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if (!in3_is_padding)
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output[output_offset++] = ((in2 & 0x3) << 6) | in3;
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}
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if (output_offset < output.size())
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output.trim(output_offset, false);
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return output;
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}
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template<auto alphabet>
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ErrorOr<String> encode_base64_impl(ReadonlyBytes input)
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{
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Vector<u8> output;
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TRY(output.try_ensure_capacity(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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output.unchecked_append(alphabet[index0]);
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output.unchecked_append(alphabet[index1]);
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output.unchecked_append(is_16bit ? '=' : alphabet[index2]);
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output.unchecked_append(is_8bit ? '=' : alphabet[index3]);
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}
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return String::from_utf8_without_validation(output);
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}
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ErrorOr<ByteBuffer> decode_base64(StringView input)
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{
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return decode_base64_impl<base64_lookup_table()>(input);
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}
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ErrorOr<ByteBuffer> decode_base64url(StringView input)
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{
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return decode_base64_impl<base64url_lookup_table()>(input);
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}
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ErrorOr<String> encode_base64(ReadonlyBytes input)
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{
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return encode_base64_impl<base64_alphabet>(input);
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}
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ErrorOr<String> encode_base64url(ReadonlyBytes input)
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{
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return encode_base64_impl<base64url_alphabet>(input);
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}
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}
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