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LibWeb: Add spec comments and fixups to "get an attribute" prescan algo

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In particular, make some minor adjustments so it flows a little more
like the spec.
This commit is contained in:
Andreas Kling 2023-12-28 22:49:53 +01:00
parent bf5ad56085
commit 83f43310fa
1 changed files with 103 additions and 15 deletions
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118
Userland/Libraries/LibWeb/HTML/Parser/HTMLEncodingDetection.cpp
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@ -94,65 +94,153 @@ Optional<StringView> extract_character_encoding_from_meta_element(ByteString con
return TextCodec::get_standardized_encoding(encoding);
}
// https://html.spec.whatwg.org/multipage/parsing.html#concept-get-attributes-when-sniffing
JS::GCPtr<DOM::Attr> prescan_get_attribute(DOM::Document& document, ByteBuffer const& input, size_t& position)
{
// 1. If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), 0x20 (SP), or 0x2F (/) then advance position to the next byte and redo this step.
if (!prescan_skip_whitespace_and_slashes(input, position))
return {};
// 2. If the byte at position is 0x3E (>), then abort the get an attribute algorithm. There isn't one.
if (input[position] == '>')
return {};
// 3. Otherwise, the byte at position is the start of the attribute name. Let attribute name and attribute value be the empty string.
// 4. Process the byte at position as follows:
StringBuilder attribute_name;
while (true) {
// -> If it is 0x3D (=), and the attribute name is longer than the empty string
if (input[position] == '=' && !attribute_name.is_empty()) {
// Advance position to the next byte and jump to the step below labeled value.
++position;
goto value;
} else if (input[position] == '\t' || input[position] == '\n' || input[position] == '\f' || input[position] == '\r' || input[position] == ' ')
}
// -> If it is 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), or 0x20 (SP)
if (input[position] == '\t' || input[position] == '\n' || input[position] == '\f' || input[position] == '\r' || input[position] == ' ') {
// Jump to the step below labeled spaces.
goto spaces;
else if (input[position] == '/' || input[position] == '>')
return *DOM::Attr::create(document, MUST(attribute_name.to_string()), String {});
else
attribute_name.append_as_lowercase(input[position]);
}
// -> If it is 0x2F (/) or 0x3E (>)
if (input[position] == '/' || input[position] == '>') {
// Abort the get an attribute algorithm. The attribute's name is the value of attribute name, its value is the empty string.
return DOM::Attr::create(document, MUST(attribute_name.to_string()), String {});
}
// -> If it is in the range 0x41 (A) to 0x5A (Z)
if (input[position] >= 'A' && input[position] <= 'Z') {
// Append the code point b+0x20 to attribute name (where b is the value of the byte at position). (This converts the input to lowercase.)
attribute_name.append(input[position] + 0x20);
}
// -> Anything else
else {
// Append the code point with the same value as the byte at position to attribute name.
// (It doesn't actually matter how bytes outside the ASCII range are handled here,
// since only ASCII bytes can contribute to the detection of a character encoding.)
attribute_name.append_code_point(input[position]);
}
// 5. Advance position to the next byte and return to the previous step.
++position;
if (prescan_should_abort(input, position))
return {};
}
spaces:
// 6. Spaces: If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), or 0x20 (SP)
// then advance position to the next byte, then, repeat this step.
if (!prescan_skip_whitespace_and_slashes(input, position))
return {};
// 7. If the byte at position is not 0x3D (=), abort the get an attribute algorithm.
// The attribute's name is the value of attribute name, its value is the empty string.
if (input[position] != '=')
return DOM::Attr::create(document, MUST(attribute_name.to_string()), String {});
// 8. Advance position past the 0x3D (=) byte.
++position;
value:
// 9. Value: If the byte at position is one of 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), or 0x20 (SP)
// then advance position to the next byte, then, repeat this step.
if (!prescan_skip_whitespace_and_slashes(input, position))
return {};
StringBuilder attribute_value;
// 10. Process the byte at position as follows:
// -> If it is 0x22 (") or 0x27 (')
if (input[position] == '"' || input[position] == '\'') {
// 1. Let b be the value of the byte at position.
u8 quote_character = input[position];
// 2. Quote loop: Advance position to the next byte.
++position;
for (; !prescan_should_abort(input, position); ++position) {
// 3. If the value of the byte at position is the value of b, then advance position to the next byte
// and abort the "get an attribute" algorithm.
// The attribute's name is the value of attribute name, and its value is the value of attribute value.
if (input[position] == quote_character)
return DOM::Attr::create(document, MUST(attribute_name.to_string()), MUST(attribute_value.to_string()));
else
attribute_value.append_as_lowercase(input[position]);
// 4. Otherwise, if the value of the byte at position is in the range 0x41 (A) to 0x5A (Z),
// then append a code point to attribute value whose value is 0x20 more than the value of the byte at position.
if (input[position] >= 'A' && input[position] <= 'Z') {
attribute_value.append(input[position] + 0x20);
}
// 5. Otherwise, append a code point to attribute value whose value is the same as the value of the byte at position.
else {
attribute_value.append_code_point(input[position]);
}
// 6. Return to the step above labeled quote loop.
}
return {};
} else if (input[position] == '>')
return DOM::Attr::create(document, MUST(attribute_name.to_string()), String {});
else
attribute_value.append_as_lowercase(input[position]);
}
// -> If it is 0x3E (>)
if (input[position] == '>') {
// Abort the get an attribute algorithm. The attribute's name is the value of attribute name, its value is the empty string.
return DOM::Attr::create(document, MUST(attribute_name.to_string()), String {});
}
// -> If it is in the range 0x41 (A) to 0x5A (Z)
if (input[position] >= 'A' && input[position] <= 'Z') {
// Append a code point b+0x20 to attribute value (where b is the value of the byte at position).
attribute_value.append(input[position] + 0x20);
// Advance position to the next byte.
++position;
}
// -> Anything else
else {
// Append a code point with the same value as the byte at position to attribute value.
attribute_value.append(input[position]);
// Advance position to the next byte.
++position;
}
++position;
if (prescan_should_abort(input, position))
return {};
// 11. Process the byte at position as follows:
for (; !prescan_should_abort(input, position); ++position) {
if (input[position] == '\t' || input[position] == '\n' || input[position] == '\f' || input[position] == '\r' || input[position] == ' ' || input[position] == '>')
// -> If it is 0x09 (HT), 0x0A (LF), 0x0C (FF), 0x0D (CR), 0x20 (SP), or 0x3E (>)
if (input[position] == '\t' || input[position] == '\n' || input[position] == '\f' || input[position] == '\r' || input[position] == ' ' || input[position] == '>') {
// Abort the get an attribute algorithm. The attribute's name is the value of attribute name and its value is the value of attribute value.
return DOM::Attr::create(document, MUST(attribute_name.to_string()), MUST(attribute_value.to_string()));
else
attribute_value.append_as_lowercase(input[position]);
}
// -> If it is in the range 0x41 (A) to 0x5A (Z)
if (input[position] >= 'A' && input[position] <= 'Z') {
// Append a code point b+0x20 to attribute value (where b is the value of the byte at position).
attribute_value.append(input[position] + 0x20);
}
// -> Anything else
else {
// Append a code point with the same value as the byte at position to attribute value.
attribute_value.append(input[position]);
}
// 12. Advance position to the next byte and return to the previous step.
}
return {};
}