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LibWeb: Stop allocating Tokens and ComponentValues unnecessarily

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When the "Consume a component value from input, and do nothing."
step in `Parser::consume_the_remnants_of_a_bad_declaration` was
executed, it would allocate a `ComponentValue` that was then
immediately discarded.

Add explicitly `{}_and_do_nothing` functions for this case that never
allocate a `ComponentValue` in the first place.

Also remove a `(Token)` cast, which was unnecessarily copying a `Token`
as well.
This commit is contained in:
Jonne Ransijn 2024-11-30 18:31:04 +01:00 • committed by Andreas Kling
commit 3f5e32ee84
Notes: github-actions[bot] 2024-12-01 10:31:01 +00:00
2 changed files with 132 additions and 7 deletions
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133
Libraries/LibWeb/CSS/Parser/Parser.cpp
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@ -704,7 +704,7 @@ ComponentValue Parser::consume_a_component_value(TokenStream<T>& input)
// Process input:
for (;;) {
auto& token = input.next_token();
auto const& token = input.next_token();
// <{-token>
// <[-token>
@ -728,6 +728,52 @@ ComponentValue Parser::consume_a_component_value(TokenStream<T>& input)
}
}
template<>
void Parser::consume_a_component_value_and_do_nothing<ComponentValue>(TokenStream<ComponentValue>& tokens)
{
// AD-HOC: To avoid unnecessairy allocations, we explicitly define a "do nothing" variant that discards the result immediately.
// Note: This overload is called once tokens have already been converted into component values,
// so we do not need to do the work in the more general overload.
(void)tokens.consume_a_token();
}
// 5.4.7. Consume a component value
// https://drafts.csswg.org/css-syntax/#consume-component-value
template<typename T>
void Parser::consume_a_component_value_and_do_nothing(TokenStream<T>& input)
{
// AD-HOC: To avoid unnecessairy allocations, we explicitly define a "do nothing" variant that discards the result immediately.
// To consume a component value from a token stream input:
// Process input:
for (;;) {
auto const& token = input.next_token();
// <{-token>
// <[-token>
// <(-token>
if (token.is(Token::Type::OpenCurly) || token.is(Token::Type::OpenSquare) || token.is(Token::Type::OpenParen)) {
// Consume a simple block from input and return the result.
consume_a_simple_block_and_do_nothing(input);
return;
}
// <function-token>
if (token.is(Token::Type::Function)) {
// Consume a function from input and return the result.
consume_a_function_and_do_nothing(input);
return;
}
// anything else
{
// Consume a token from input and return the result.
input.discard_a_token();
return;
}
}
}
template<typename T>
Vector<ComponentValue> Parser::consume_a_list_of_component_values(TokenStream<T>& input, Optional<Token::Type> stop_token, Nested nested)
{
@ -778,11 +824,11 @@ SimpleBlock Parser::consume_a_simple_block(TokenStream<T>& input)
// To consume a simple block from a token stream input:
// Assert: the next token of input is <{-token>, <[-token>, or <(-token>.
auto& next = input.next_token();
auto const& next = input.next_token();
VERIFY(next.is(Token::Type::OpenCurly) || next.is(Token::Type::OpenSquare) || next.is(Token::Type::OpenParen));
// Let ending token be the mirror variant of the next token. (E.g. if it was called with <[-token>, the ending token is <]-token>.)
auto ending_token = ((Token)input.next_token()).mirror_variant();
auto ending_token = input.next_token().mirror_variant();
// Let block be a new simple block with its associated token set to the next token and with its value initially set to an empty list.
SimpleBlock block {
@ -795,7 +841,7 @@ SimpleBlock Parser::consume_a_simple_block(TokenStream<T>& input)
// Process input:
for (;;) {
auto& token = input.next_token();
auto const& token = input.next_token();
// <eof-token>
// ending token
@ -814,6 +860,45 @@ SimpleBlock Parser::consume_a_simple_block(TokenStream<T>& input)
}
}
// https://drafts.csswg.org/css-syntax/#consume-simple-block
template<typename T>
void Parser::consume_a_simple_block_and_do_nothing(TokenStream<T>& input)
{
// AD-HOC: To avoid unnecessairy allocations, we explicitly define a "do nothing" variant that discards the result immediately.
// To consume a simple block from a token stream input:
// Assert: the next token of input is <{-token>, <[-token>, or <(-token>.
auto const& next = input.next_token();
VERIFY(next.is(Token::Type::OpenCurly) || next.is(Token::Type::OpenSquare) || next.is(Token::Type::OpenParen));
// Let ending token be the mirror variant of the next token. (E.g. if it was called with <[-token>, the ending token is <]-token>.)
auto ending_token = input.next_token().mirror_variant();
// Let block be a new simple block with its associated token set to the next token and with its value initially set to an empty list.
// Discard a token from input.
input.discard_a_token();
// Process input:
for (;;) {
auto const& token = input.next_token();
// <eof-token>
// ending token
if (token.is(Token::Type::EndOfFile) || token.is(ending_token)) {
// Discard a token from input. Return block.
input.discard_a_token();
return;
}
// anything else
{
// Consume a component value from input and append the result to block’s value.
consume_a_component_value_and_do_nothing(input);
}
}
}
// https://drafts.csswg.org/css-syntax/#consume-function
template<typename T>
Function Parser::consume_a_function(TokenStream<T>& input)
@ -834,7 +919,7 @@ Function Parser::consume_a_function(TokenStream<T>& input)
// Process input:
for (;;) {
auto& token = input.next_token();
auto const& token = input.next_token();
// <eof-token>
// <)-token>
@ -853,6 +938,40 @@ Function Parser::consume_a_function(TokenStream<T>& input)
}
}
// https://drafts.csswg.org/css-syntax/#consume-function
template<typename T>
void Parser::consume_a_function_and_do_nothing(TokenStream<T>& input)
{
// AD-HOC: To avoid unnecessairy allocations, we explicitly define a "do nothing" variant that discards the result immediately.
// To consume a function from a token stream input:
// Assert: The next token is a <function-token>.
VERIFY(input.next_token().is(Token::Type::Function));
// Consume a token from input, and let function be a new function with its name equal the returned token’s value,
// and a value set to an empty list.
input.discard_a_token();
// Process input:
for (;;) {
auto const& token = input.next_token();
// <eof-token>
// <)-token>
if (token.is(Token::Type::EndOfFile) || token.is(Token::Type::CloseParen)) {
// Discard a token from input. Return function.
input.discard_a_token();
return;
}
// anything else
{
// Consume a component value from input and append the result to function’s value.
consume_a_component_value_and_do_nothing(input);
}
}
}
// https://drafts.csswg.org/css-syntax/#consume-declaration
template<typename T>
Optional<Declaration> Parser::consume_a_declaration(TokenStream<T>& input, Nested nested)
@ -1001,7 +1120,7 @@ void Parser::consume_the_remnants_of_a_bad_declaration(TokenStream<T>& input, Ne
// Process input:
for (;;) {
auto& token = input.next_token();
auto const& token = input.next_token();
// <eof-token>
// <semicolon-token>
@ -1023,7 +1142,7 @@ void Parser::consume_the_remnants_of_a_bad_declaration(TokenStream<T>& input, Ne
// anything else
{
// Consume a component value from input, and do nothing.
(void)consume_a_component_value(input);
consume_a_component_value_and_do_nothing(input);
continue;
}
}