ladybird/Userland/Libraries/LibWeb/CSS/Parser/Tokenizer.cpp
Sam Atkins c249fbd17c LibWeb: Correct escape handling in CSS Tokenizer
Calling is_valid_escape_sequence() with no arguments hides what it
is operating on, so I have removed that, so that you must explicitly
tell it what you are testing.

The call from consume_a_token() was using the wrong tokens, so it
returned false incorrectly. This was resulting in corrupted output
when faced with this code from Acid2. (Abbreviated)

```css
.parser { error: \}; }
.parser { }
```
2021-07-11 23:19:56 +02:00

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/*
* Copyright (c) 2020-2021, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/SourceLocation.h>
#include <AK/Vector.h>
#include <LibTextCodec/Decoder.h>
#include <LibWeb/CSS/Parser/Tokenizer.h>
#define CSS_TOKENIZER_TRACE 0
//U+FFFD REPLACEMENT CHARACTER (<28>)
#define REPLACEMENT_CHARACTER 0xFFFD
static const u32 TOKENIZER_EOF = 0xFFFFFFFF;
static inline void log_parse_error(const SourceLocation& location = SourceLocation::current())
{
dbgln_if(CSS_TOKENIZER_TRACE, "Parse error (css tokenization) {} ", location);
}
static inline bool is_eof(u32 code_point)
{
return code_point == TOKENIZER_EOF;
}
static inline bool is_quotation_mark(u32 code_point)
{
return code_point == 0x22;
}
static inline bool is_greater_than_maximum_allowed_code_point(u32 code_point)
{
return code_point > 0x10FFFF;
}
static inline bool is_low_line(u32 code_point)
{
return code_point == 0x5F;
}
static inline bool is_name_start_code_point(u32 code_point)
{
return is_ascii_alpha(code_point) || !is_ascii(code_point) || is_low_line(code_point);
}
static inline bool is_hyphen_minus(u32 code_point)
{
return code_point == 0x2D;
}
static inline bool is_name_code_point(u32 code_point)
{
return is_name_start_code_point(code_point) || is_ascii_digit(code_point) || is_hyphen_minus(code_point);
}
static inline bool is_non_printable(u32 code_point)
{
return code_point <= 0x8 || code_point == 0xB || (code_point >= 0xE && code_point <= 0x1F) || code_point == 0x7F;
}
static inline bool is_number_sign(u32 code_point)
{
return code_point == 0x23;
}
static inline bool is_reverse_solidus(u32 code_point)
{
return code_point == 0x5C;
}
static inline bool is_apostrophe(u32 code_point)
{
return code_point == 0x27;
}
static inline bool is_left_paren(u32 code_point)
{
return code_point == 0x28;
}
static inline bool is_right_paren(u32 code_point)
{
return code_point == 0x29;
}
static inline bool is_plus_sign(u32 code_point)
{
return code_point == 0x2B;
}
static inline bool is_comma(u32 code_point)
{
return code_point == 0x2C;
}
static inline bool is_full_stop(u32 code_point)
{
return code_point == 0x2E;
}
static inline bool is_newline(u32 code_point)
{
return code_point == 0xA;
}
static inline bool is_asterisk(u32 code_point)
{
return code_point == 0x2A;
}
static inline bool is_solidus(u32 code_point)
{
return code_point == 0x2F;
}
static inline bool is_colon(u32 code_point)
{
return code_point == 0x3A;
}
static inline bool is_semicolon(u32 code_point)
{
return code_point == 0x3B;
}
static inline bool is_less_than_sign(u32 code_point)
{
return code_point == 0x3C;
}
static inline bool is_greater_than_sign(u32 code_point)
{
return code_point == 0x3E;
}
static inline bool is_at(u32 code_point)
{
return code_point == 0x40;
}
static inline bool is_open_square_bracket(u32 code_point)
{
return code_point == 0x5B;
}
static inline bool is_closed_square_bracket(u32 code_point)
{
return code_point == 0x5D;
}
static inline bool is_open_curly_bracket(u32 code_point)
{
return code_point == 0x7B;
}
static inline bool is_closed_curly_bracket(u32 code_point)
{
return code_point == 0x7D;
}
static inline bool is_whitespace(u32 code_point)
{
return code_point == 0x9 || code_point == 0xA || code_point == 0x20;
}
static inline bool is_percent(u32 code_point)
{
return code_point == 0x25;
}
static inline bool is_exclamation_mark(u32 code_point)
{
return code_point == 0x21;
}
static inline bool is_e(u32 code_point)
{
return code_point == 0x65;
}
static inline bool is_E(u32 code_point)
{
return code_point == 0x45;
}
namespace Web::CSS {
Tokenizer::Tokenizer(const StringView& input, const String& encoding)
{
auto* decoder = TextCodec::decoder_for(encoding);
VERIFY(decoder);
// FIXME: preprocess the stream
// https://www.w3.org/TR/css-syntax-3/#input-preprocessing
m_decoded_input = decoder->to_utf8(input);
m_utf8_view = Utf8View(m_decoded_input);
m_utf8_iterator = m_utf8_view.begin();
}
Vector<Token> Tokenizer::parse()
{
Vector<Token> tokens;
for (;;) {
auto token = consume_a_token();
tokens.append(token);
if (token.is(Token::Type::EndOfFile)) {
return tokens;
}
}
}
u32 Tokenizer::next_code_point()
{
if (m_utf8_iterator == m_utf8_view.end())
return TOKENIZER_EOF;
m_prev_utf8_iterator = m_utf8_iterator;
++m_utf8_iterator;
dbgln_if(CSS_TOKENIZER_TRACE, "(Tokenizer) Next code_point: {:c}", (char)*m_prev_utf8_iterator);
return *m_prev_utf8_iterator;
}
u32 Tokenizer::peek_code_point(size_t offset) const
{
auto it = m_utf8_iterator;
for (size_t i = 0; i < offset && it != m_utf8_view.end(); ++i)
++it;
if (it == m_utf8_view.end())
return TOKENIZER_EOF;
return *it;
}
U32Twin Tokenizer::peek_twin() const
{
U32Twin values;
auto it = m_utf8_iterator;
for (size_t i = 0; i < 2 && it != m_utf8_view.end(); ++i) {
if (it == m_utf8_view.end())
values.set(i, TOKENIZER_EOF);
else
values.set(i, *it);
++it;
}
return values;
}
U32Triplet Tokenizer::peek_triplet() const
{
U32Triplet values;
auto it = m_utf8_iterator;
for (size_t i = 0; i < 3 && it != m_utf8_view.end(); ++i) {
if (it == m_utf8_view.end())
values.set(i, TOKENIZER_EOF);
else
values.set(i, *it);
++it;
}
return values;
}
Token Tokenizer::create_new_token(Token::Type type)
{
Token token = {};
token.m_type = type;
return token;
}
Token Tokenizer::create_eof_token()
{
return create_new_token(Token::Type::EndOfFile);
}
Token Tokenizer::create_value_token(Token::Type type, String value)
{
Token token;
token.m_type = type;
token.m_value.append(move(value));
return token;
}
Token Tokenizer::create_value_token(Token::Type type, u32 value)
{
Token token = {};
token.m_type = type;
token.m_value.append_code_point(value);
return token;
}
u32 Tokenizer::consume_escaped_code_point()
{
auto input = next_code_point();
if (is_eof(input)) {
log_parse_error();
return REPLACEMENT_CHARACTER;
}
if (is_ascii_hex_digit(input)) {
StringBuilder builder;
builder.append_code_point(input);
size_t counter = 0;
while (is_ascii_hex_digit(peek_code_point()) && counter++ < 5) {
builder.append_code_point(next_code_point());
}
if (is_whitespace(peek_code_point())) {
(void)next_code_point();
}
auto unhexed = strtoul(builder.to_string().characters(), nullptr, 16);
if (unhexed == 0 || is_unicode_surrogate(unhexed) || is_greater_than_maximum_allowed_code_point(unhexed)) {
return REPLACEMENT_CHARACTER;
}
return unhexed;
}
if (!input) {
log_parse_error();
return REPLACEMENT_CHARACTER;
}
return input;
}
Token Tokenizer::consume_an_ident_like_token()
{
auto string = consume_a_name();
if (string.equals_ignoring_case("url") && is_left_paren(peek_code_point())) {
(void)next_code_point();
for (;;) {
auto maybe_whitespace = peek_twin();
if (!(is_whitespace(maybe_whitespace.first) && is_whitespace(maybe_whitespace.second))) {
break;
}
(void)next_code_point();
}
auto next_two = peek_twin();
// if one of these ", ', ' "', " '"
if (is_quotation_mark(next_two.first) || is_apostrophe(next_two.first) || (is_whitespace(next_two.first) && (is_quotation_mark(next_two.second) || is_apostrophe(next_two.second)))) {
return create_value_token(Token::Type::Function, string);
}
return consume_a_url_token();
}
if (is_left_paren(peek_code_point())) {
(void)next_code_point();
return create_value_token(Token::Type::Function, string);
}
return create_value_token(Token::Type::Ident, string);
}
CSSNumber Tokenizer::consume_a_number()
{
StringBuilder repr;
Token::NumberType type = Token::NumberType::Integer;
auto next_input = peek_code_point();
if (is_plus_sign(next_input) || is_hyphen_minus(next_input)) {
repr.append_code_point(next_code_point());
}
for (;;) {
auto digits = peek_code_point();
if (!is_ascii_digit(digits))
break;
repr.append_code_point(next_code_point());
}
auto maybe_number = peek_twin();
if (is_full_stop(maybe_number.first) && is_ascii_digit(maybe_number.second)) {
repr.append_code_point(next_code_point());
repr.append_code_point(next_code_point());
type = Token::NumberType::Number;
for (;;) {
auto digit = peek_code_point();
if (!is_ascii_digit(digit))
break;
repr.append_code_point(next_code_point());
}
}
auto maybe_exp = peek_triplet();
if (is_E(maybe_exp.first) || is_e(maybe_exp.first)) {
if (is_plus_sign(maybe_exp.second) || is_hyphen_minus(maybe_exp.second)) {
if (is_ascii_digit(maybe_exp.third)) {
repr.append_code_point(next_code_point());
repr.append_code_point(next_code_point());
repr.append_code_point(next_code_point());
}
} else if (is_ascii_digit(maybe_exp.second)) {
repr.append_code_point(next_code_point());
repr.append_code_point(next_code_point());
}
type = Token::NumberType::Number;
for (;;) {
auto digits = peek_code_point();
if (!is_ascii_digit(digits))
break;
repr.append_code_point(next_code_point());
}
}
return { repr.to_string(), type };
}
String Tokenizer::consume_a_name()
{
StringBuilder result;
for (;;) {
auto input = next_code_point();
if (is_eof(input))
break;
if (is_name_code_point(input)) {
result.append_code_point(input);
continue;
}
auto next = peek_code_point();
if (!is_eof(next) && is_valid_escape_sequence({ input, next })) {
result.append_code_point(consume_escaped_code_point());
continue;
}
reconsume_current_input_code_point();
break;
}
return result.to_string();
}
Token Tokenizer::consume_a_url_token()
{
auto token = create_new_token(Token::Type::Url);
for (;;) {
if (!is_whitespace(peek_code_point())) {
break;
}
(void)next_code_point();
}
for (;;) {
auto input = peek_code_point();
if (is_eof(input)) {
log_parse_error();
return token;
}
if (is_right_paren(input)) {
(void)next_code_point();
return token;
}
if (is_whitespace(input)) {
for (;;) {
if (!is_whitespace(peek_code_point())) {
break;
}
input = next_code_point();
}
if (is_eof(input)) {
log_parse_error();
return token;
}
if (is_right_paren(input)) {
return token;
}
consume_the_remnants_of_a_bad_url();
return create_new_token(Token::Type::BadUrl);
}
if (is_quotation_mark(input) || is_apostrophe(input) || is_left_paren(input) || is_non_printable(input)) {
log_parse_error();
(void)next_code_point();
consume_the_remnants_of_a_bad_url();
return create_new_token(Token::Type::BadUrl);
}
if (is_reverse_solidus(input)) {
if (is_valid_escape_sequence(peek_twin())) {
token.m_value.append_code_point(consume_escaped_code_point());
} else {
log_parse_error();
(void)next_code_point();
consume_the_remnants_of_a_bad_url();
return create_new_token(Token::Type::BadUrl);
}
}
token.m_value.append_code_point(next_code_point());
}
}
void Tokenizer::consume_the_remnants_of_a_bad_url()
{
for (;;) {
auto next = peek_code_point();
if (is_eof(next)) {
return;
}
auto input = next;
if (is_right_paren(input)) {
(void)next_code_point();
return;
}
if (is_valid_escape_sequence(peek_twin())) {
[[maybe_unused]] auto cp = consume_escaped_code_point();
}
(void)next_code_point();
}
}
void Tokenizer::reconsume_current_input_code_point()
{
m_utf8_iterator = m_prev_utf8_iterator;
}
Token Tokenizer::consume_a_numeric_token()
{
auto number = consume_a_number();
if (would_start_an_identifier()) {
auto token = create_new_token(Token::Type::Dimension);
token.m_value.append(number.value);
token.m_number_type = number.type;
auto unit = consume_a_name();
token.m_unit.append(unit);
return token;
}
if (is_percent(peek_code_point())) {
(void)next_code_point();
auto token = create_new_token(Token::Type::Percentage);
token.m_value.append(number.value);
return token;
}
auto token = create_new_token(Token::Type::Number);
token.m_value.append(number.value);
token.m_number_type = number.type;
return token;
}
bool Tokenizer::starts_with_a_number() const
{
return starts_with_a_number(peek_triplet());
}
bool Tokenizer::starts_with_a_number(U32Triplet values)
{
if (is_plus_sign(values.first) || is_hyphen_minus(values.first)) {
if (is_ascii_digit(values.second))
return true;
if (is_full_stop(values.second) && is_ascii_digit(values.third))
return true;
return false;
}
if (is_full_stop(values.first))
return is_ascii_digit(values.second);
if (is_ascii_digit(values.first))
return true;
return false;
}
bool Tokenizer::is_valid_escape_sequence(U32Twin values)
{
if (!is_reverse_solidus(values.first)) {
return false;
}
if (is_newline(values.second)) {
return false;
}
return true;
}
bool Tokenizer::would_start_an_identifier()
{
return would_start_an_identifier(peek_triplet());
}
bool Tokenizer::would_start_an_identifier(U32Triplet values)
{
if (is_hyphen_minus(values.first)) {
if (is_name_start_code_point(values.second) || is_hyphen_minus(values.second) || is_valid_escape_sequence(values.to_twin_23()))
return true;
return false;
}
if (is_name_start_code_point(values.first)) {
return true;
}
if (is_reverse_solidus(values.first)) {
if (is_valid_escape_sequence(values.to_twin_12()))
return true;
return false;
}
return false;
}
Token Tokenizer::consume_string_token(u32 ending_code_point)
{
auto token = create_new_token(Token::Type::String);
for (;;) {
auto input = next_code_point();
if (is_eof(input)) {
log_parse_error();
return token;
}
if (input == ending_code_point)
return token;
if (is_newline(input)) {
reconsume_current_input_code_point();
return create_new_token(Token::Type::BadString);
}
if (is_reverse_solidus(input)) {
auto next_input = peek_code_point();
if (is_eof(next_input))
continue;
if (is_newline(next_input)) {
(void)next_code_point();
continue;
}
auto escaped = consume_escaped_code_point();
token.m_value.append_code_point(escaped);
}
token.m_value.append_code_point(input);
}
}
void Tokenizer::consume_comments()
{
start:
auto twin = peek_twin();
if (!(is_solidus(twin.first) && is_asterisk(twin.second)))
return;
(void)next_code_point();
(void)next_code_point();
for (;;) {
auto twin_inner = peek_twin();
if (is_eof(twin_inner.first) || is_eof(twin_inner.second)) {
log_parse_error();
return;
}
if (is_asterisk(twin_inner.first) && is_solidus(twin_inner.second)) {
(void)next_code_point();
(void)next_code_point();
goto start;
}
(void)next_code_point();
}
}
Token Tokenizer::consume_a_token()
{
consume_comments();
auto input = next_code_point();
if (is_eof(input)) {
return create_new_token(Token::Type::EndOfFile);
}
if (is_whitespace(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is whitespace");
auto next = peek_code_point();
while (is_whitespace(next)) {
(void)next_code_point();
next = peek_code_point();
}
return create_new_token(Token::Type::Whitespace);
}
if (is_quotation_mark(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is quotation mark");
return consume_string_token(input);
}
if (is_number_sign(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is number sign");
auto next_input = peek_code_point();
auto maybe_escape = peek_twin();
if (is_name_code_point(next_input) || is_valid_escape_sequence(maybe_escape)) {
auto token = create_new_token(Token::Type::Hash);
if (would_start_an_identifier())
token.m_hash_type = Token::HashType::Id;
auto name = consume_a_name();
token.m_value.append(name);
return token;
}
return create_value_token(Token::Type::Delim, input);
}
if (is_apostrophe(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is apostrophe");
return consume_string_token(input);
}
if (is_left_paren(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is left paren");
return create_new_token(Token::Type::OpenParen);
}
if (is_right_paren(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is right paren");
return create_new_token(Token::Type::CloseParen);
}
if (is_plus_sign(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is plus sign");
if (starts_with_a_number()) {
reconsume_current_input_code_point();
return consume_a_numeric_token();
}
return create_value_token(Token::Type::Delim, input);
}
if (is_comma(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is comma");
return create_new_token(Token::Type::Comma);
}
if (is_hyphen_minus(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is hyphen minus");
if (starts_with_a_number()) {
reconsume_current_input_code_point();
return consume_a_numeric_token();
}
auto next_twin = peek_twin();
if (is_hyphen_minus(next_twin.first) && is_greater_than_sign(next_twin.second)) {
(void)next_code_point();
(void)next_code_point();
return create_new_token(Token::Type::CDC);
}
if (would_start_an_identifier()) {
reconsume_current_input_code_point();
return consume_an_ident_like_token();
}
return create_value_token(Token::Type::Delim, input);
}
if (is_full_stop(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is full stop");
if (starts_with_a_number()) {
reconsume_current_input_code_point();
return consume_a_numeric_token();
}
return create_value_token(Token::Type::Delim, input);
}
if (is_colon(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is colon");
return create_new_token(Token::Type::Colon);
}
if (is_semicolon(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is semicolon");
return create_new_token(Token::Type::Semicolon);
}
if (is_less_than_sign(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is less than");
auto maybe_cdo = peek_triplet();
if (is_exclamation_mark(maybe_cdo.first) && is_hyphen_minus(maybe_cdo.second) && is_hyphen_minus(maybe_cdo.third)) {
(void)next_code_point();
(void)next_code_point();
(void)next_code_point();
return create_new_token(Token::Type::CDO);
}
return create_value_token(Token::Type::Delim, input);
}
if (is_at(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is at");
if (would_start_an_identifier()) {
auto name = consume_a_name();
return create_value_token(Token::Type::AtKeyword, input);
}
return create_value_token(Token::Type::Delim, input);
}
if (is_open_square_bracket(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is open square");
return create_new_token(Token::Type::OpenSquare);
}
if (is_reverse_solidus(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is reverse solidus");
if (is_valid_escape_sequence({ input, peek_code_point() })) {
reconsume_current_input_code_point();
return consume_an_ident_like_token();
}
log_parse_error();
return create_value_token(Token::Type::Delim, input);
}
if (is_closed_square_bracket(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is closed square");
return create_new_token(Token::Type::CloseSquare);
}
if (is_open_curly_bracket(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is open curly");
return create_new_token(Token::Type::OpenCurly);
}
if (is_closed_curly_bracket(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is closed curly");
return create_new_token(Token::Type::CloseCurly);
}
if (is_ascii_digit(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is digit");
reconsume_current_input_code_point();
return consume_a_numeric_token();
}
if (is_name_start_code_point(input)) {
dbgln_if(CSS_TOKENIZER_TRACE, "is name start");
reconsume_current_input_code_point();
return consume_an_ident_like_token();
}
dbgln_if(CSS_TOKENIZER_TRACE, "is delimiter");
return create_value_token(Token::Type::Delim, input);
}
}