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/*
* Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/GenericLexer.h>
#include <AK/StringBuilder.h>
#include <LibIMAP/QuotedPrintable.h>
namespace IMAP {
static constexpr bool is_illegal_character(char c)
{
return (u8)c > 0x7E || (is_ascii_control(c) && c != '\t' && c != '\r' && c != '\n');
}
// RFC 2045 Section 6.7 "Quoted-Printable Content-Transfer-Encoding", https://datatracker.ietf.org/doc/html/rfc2045#section-6.7
ByteBuffer decode_quoted_printable(StringView input)
{
GenericLexer lexer(input);
StringBuilder output;
// NOTE: The RFC says that encoded lines must not be longer than 76 characters.
// However, the RFC says implementations can ignore this and parse as is,
// which is the approach we're taking.
while (!lexer.is_eof()) {
char potential_character = lexer.consume();
if (is_illegal_character(potential_character))
continue;
if (potential_character == '=') {
if (lexer.is_eof()) {
TODO();
}
char first_escape_character = lexer.consume();
// The RFC doesn't formally allow lowercase, but says implementations can treat lowercase the same as uppercase.
// Thus we can use is_ascii_hex_digit.
if (is_ascii_hex_digit(first_escape_character)) {
if (lexer.is_eof()) {
TODO();
}
char second_escape_character = lexer.consume();
if (is_ascii_hex_digit(second_escape_character)) {
u8 actual_character = (parse_ascii_hex_digit(first_escape_character) << 4) | parse_ascii_hex_digit(second_escape_character);
output.append(actual_character);
} else {
TODO();
}
} else if (first_escape_character == '\r') {
if (lexer.is_eof()) {
TODO();
}
char second_escape_character = lexer.consume();
if (second_escape_character == '\n') {
// This is a soft line break. Don't append anything to the output.
} else {
TODO();
}
} else {
if (is_illegal_character(first_escape_character)) {
TODO();
}
// Invalid escape sequence. RFC 2045 says a reasonable solution is just to append '=' followed by the character.
output.append('=');
output.append(first_escape_character);
}
} else {
output.append(potential_character);
}
}
return output.to_byte_buffer();
}
}
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