mirror of
https://github.com/RGBCube/serenity
synced 2025-10-31 16:32:45 +00:00
123 lines
4.5 KiB
C++
123 lines
4.5 KiB
C++
/*
|
||
* Copyright (c) 2022-2023, the SerenityOS developers.
|
||
*
|
||
* SPDX-License-Identifier: BSD-2-Clause
|
||
*/
|
||
|
||
#include <AK/Base64.h>
|
||
#include <AK/ByteBuffer.h>
|
||
#include <AK/CharacterTypes.h>
|
||
#include <AK/Error.h>
|
||
#include <AK/StringBuilder.h>
|
||
#include <AK/StringView.h>
|
||
#include <AK/Vector.h>
|
||
#include <LibWeb/Infra/Base64.h>
|
||
#include <LibWeb/Infra/CharacterTypes.h>
|
||
|
||
namespace Web::Infra {
|
||
|
||
// https://infra.spec.whatwg.org/#forgiving-base64
|
||
ErrorOr<ByteBuffer> decode_forgiving_base64(StringView input)
|
||
{
|
||
// 1. Remove all ASCII whitespace from data.
|
||
// FIXME: It is possible to avoid copying input here, it's just a bit tricky to remove the equal signs
|
||
StringBuilder builder;
|
||
for (auto character : input) {
|
||
if (!is_ascii_whitespace(character))
|
||
TRY(builder.try_append(character));
|
||
}
|
||
auto data = builder.string_view();
|
||
|
||
// 2. If data’s code point length divides by 4 leaving no remainder, then:
|
||
if (data.length() % 4 == 0) {
|
||
// If data ends with one or two U+003D (=) code points, then remove them from data.
|
||
if (data.ends_with("=="sv))
|
||
data = data.substring_view(0, data.length() - 2);
|
||
else if (data.ends_with('='))
|
||
data = data.substring_view(0, data.length() - 1);
|
||
}
|
||
|
||
// 3. If data’s code point length divides by 4 leaving a remainder of 1, then return failure.
|
||
if (data.length() % 4 == 1)
|
||
return Error::from_string_literal("Invalid input length in forgiving base64 decode");
|
||
|
||
// 4. If data contains a code point that is not one of
|
||
// U+002B (+), U+002F (/), ASCII alphanumeric
|
||
// then return failure.
|
||
for (auto point : data) {
|
||
if (point != '+' && point != '/' && !is_ascii_alphanumeric(point))
|
||
return Error::from_string_literal("Invalid character in forgiving base64 decode");
|
||
}
|
||
|
||
// 5. Let output be an empty byte sequence.
|
||
// 6. Let buffer be an empty buffer that can have bits appended to it.
|
||
Vector<u8> output;
|
||
u32 buffer = 0;
|
||
auto accumulated_bits = 0;
|
||
|
||
auto add_to_buffer = [&](u8 number) {
|
||
VERIFY(number < 64);
|
||
u32 buffer_mask = number;
|
||
|
||
if (accumulated_bits == 0)
|
||
buffer_mask <<= 18;
|
||
else if (accumulated_bits == 6)
|
||
buffer_mask <<= 12;
|
||
else if (accumulated_bits == 12)
|
||
buffer_mask <<= 6;
|
||
else if (accumulated_bits == 18)
|
||
buffer_mask <<= 0;
|
||
|
||
buffer |= buffer_mask;
|
||
|
||
accumulated_bits += 6;
|
||
};
|
||
|
||
auto append_bytes = [&]() {
|
||
output.append(static_cast<u8>((buffer & 0xff0000) >> 16));
|
||
output.append(static_cast<u8>((buffer & 0xff00) >> 8));
|
||
output.append(static_cast<u8>(buffer & 0xff));
|
||
|
||
buffer = 0;
|
||
accumulated_bits = 0;
|
||
};
|
||
|
||
auto alphabet_lookup_table = AK::base64_lookup_table();
|
||
|
||
// 7. Let position be a position variable for data, initially pointing at the start of data.
|
||
// 8. While position does not point past the end of data:
|
||
for (auto point : data) {
|
||
// 1. Find the code point pointed to by position in the second column of Table 1: The Base 64 Alphabet of RFC 4648.
|
||
// Let n be the number given in the first cell of the same row. [RFC4648]
|
||
auto n = alphabet_lookup_table[point];
|
||
VERIFY(n >= 0);
|
||
|
||
// 2. Append the six bits corresponding to n, most significant bit first, to buffer.
|
||
add_to_buffer(static_cast<u8>(n));
|
||
|
||
// 3. buffer has accumulated 24 bits,
|
||
if (accumulated_bits == 24) {
|
||
// interpret them as three 8-bit big-endian numbers.
|
||
// Append three bytes with values equal to those numbers to output, in the same order, and then empty buffer
|
||
append_bytes();
|
||
}
|
||
}
|
||
|
||
// 9. If buffer is not empty, it contains either 12 or 18 bits.
|
||
VERIFY(accumulated_bits == 0 || accumulated_bits == 12 || accumulated_bits == 18);
|
||
|
||
// If it contains 12 bits, then discard the last four and interpret the remaining eight as an 8-bit big-endian number.
|
||
if (accumulated_bits == 12)
|
||
output.append(static_cast<u8>((buffer & 0xff0000) >> 16));
|
||
|
||
// If it contains 18 bits, then discard the last two and interpret the remaining 16 as two 8-bit big-endian numbers.
|
||
// Append the one or two bytes with values equal to those one or two numbers to output, in the same order.
|
||
if (accumulated_bits == 18) {
|
||
output.append(static_cast<u8>((buffer & 0xff0000) >> 16));
|
||
output.append(static_cast<u8>((buffer & 0xff00) >> 8));
|
||
}
|
||
|
||
return ByteBuffer::copy(output);
|
||
}
|
||
|
||
}
|