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//! Defines syntactical properties of HTML tags, attributes, and text.
/// Check whether a character is in a tag name.
pub const fn is_valid_in_tag_name(c: char) -> bool {
c.is_ascii_alphanumeric()
}
/// Check whether a character is valid in an attribute name.
pub const fn is_valid_in_attribute_name(c: char) -> bool {
match c {
// These are forbidden.
'\0' | ' ' | '"' | '\'' | '>' | '/' | '=' => false,
c if is_whatwg_control_char(c) => false,
c if is_whatwg_non_char(c) => false,
// _Everything_ else is allowed, including U+2029 paragraph
// separator. Go wild.
_ => true,
}
}
/// Check whether a character can be an used in an attribute value without
/// escaping.
///
/// See <https://html.spec.whatwg.org/multipage/syntax.html#attributes-2>
pub const fn is_valid_in_attribute_value(c: char) -> bool {
match c {
// Ampersands are sometimes legal (i.e. when they are not _ambiguous
// ampersands_) but it is not worth the trouble to check for that.
'&' => false,
// Quotation marks are not allowed in double-quote-delimited attribute
// values.
'"' => false,
// All other text characters are allowed.
c => is_w3c_text_char(c),
}
}
/// Check whether a character can be an used in normal text without
/// escaping.
pub const fn is_valid_in_normal_element_text(c: char) -> bool {
match c {
// Ampersands are sometimes legal (i.e. when they are not _ambiguous
// ampersands_) but it is not worth the trouble to check for that.
'&' => false,
// Less-than signs are not allowed in text.
'<' => false,
// All other text characters are allowed.
c => is_w3c_text_char(c),
}
}
/// Check if something is valid text in HTML.
pub const fn is_w3c_text_char(c: char) -> bool {
match c {
// Non-characters are obviously not text characters.
c if is_whatwg_non_char(c) => false,
// Control characters are disallowed, except for whitespace.
c if is_whatwg_control_char(c) => c.is_ascii_whitespace(),
// Everything else is allowed.
_ => true,
}
}
const fn is_whatwg_non_char(c: char) -> bool {
match c {
'\u{fdd0}'..='\u{fdef}' => true,
// Non-characters matching xxFFFE or xxFFFF up to x10FFFF (inclusive).
c if c as u32 & 0xfffe == 0xfffe && c as u32 <= 0x10ffff => true,
_ => false,
}
}
const fn is_whatwg_control_char(c: char) -> bool {
match c {
// C0 control characters.
'\u{00}'..='\u{1f}' => true,
// Other control characters.
'\u{7f}'..='\u{9f}' => true,
_ => false,
}
}
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