mirror of
https://github.com/LadybirdBrowser/ladybird.git
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754ff41b9c
This was added in commit f2663f477f as a
partial implementation of what is now LibWeb's forgiving Base64 decoder.
All use cases within LibWeb that require whitespace skipping now use
that implementation instead.
Removing this feature from AK allows us to know the exact output size of
a decoded Base64 string. We can still trim whitespace at the start and
end of the input though; for example, this is useful when reading from a
file that may have a newline at the end of the file.
136 lines
3.9 KiB
C++
136 lines
3.9 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/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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static ErrorOr<ByteBuffer> decode_base64_impl(StringView input, ReadonlySpan<i16> alphabet_lookup_table)
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{
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input = input.trim_whitespace();
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auto get = [&](size_t offset, bool* is_padding) -> ErrorOr<u8> {
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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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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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u8 const in0 = TRY(get(input_offset++, nullptr));
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u8 const in1 = TRY(get(input_offset++, nullptr));
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u8 const in2 = TRY(get(input_offset++, &in2_is_padding));
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u8 const in3 = TRY(get(input_offset++, &in3_is_padding));
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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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static ErrorOr<String> encode_base64_impl(ReadonlyBytes input, ReadonlySpan<char> alphabet)
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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 = [&](size_t const 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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u8 const in0 = get(i);
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u8 const in1 = get(i + 1, &is_16bit);
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u8 const in2 = get(i + 2, &is_8bit);
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u8 const index0 = (in0 >> 2) & 0x3f;
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u8 const index1 = ((in0 << 4) | (in1 >> 4)) & 0x3f;
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u8 const index2 = ((in1 << 2) | (in2 >> 6)) & 0x3f;
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u8 const 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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static constexpr auto lookup_table = base64_lookup_table();
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return decode_base64_impl(input, lookup_table);
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}
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ErrorOr<ByteBuffer> decode_base64url(StringView input)
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{
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static constexpr auto lookup_table = base64url_lookup_table();
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return decode_base64_impl(input, lookup_table);
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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(input, base64_alphabet);
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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(input, base64url_alphabet);
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}
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}
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