forked from mirrors/gecko-dev
360d89fad4
Depends on D31737 Differential Revision: https://phabricator.services.mozilla.com/D31738 --HG-- extra : moz-landing-system : lando
64 lines
2.3 KiB
Rust
64 lines
2.3 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/// Abstraction for avoiding a dependency from cssparser to an encoding library
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pub trait EncodingSupport {
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/// One character encoding
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type Encoding;
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/// https://encoding.spec.whatwg.org/#concept-encoding-get
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fn from_label(ascii_label: &[u8]) -> Option<Self::Encoding>;
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/// Return the UTF-8 encoding
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fn utf8() -> Self::Encoding;
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/// Whether the given encoding is UTF-16BE or UTF-16LE
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fn is_utf16_be_or_le(encoding: &Self::Encoding) -> bool;
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}
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/// Determine the character encoding of a CSS stylesheet.
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///
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/// This is based on the presence of a BOM (Byte Order Mark), an `@charset` rule, and
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/// encoding meta-information.
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///
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/// * `css_bytes`: A byte string.
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/// * `protocol_encoding`: The encoding label, if any, defined by HTTP or equivalent protocol.
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/// (e.g. via the `charset` parameter of the `Content-Type` header.)
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/// * `environment_encoding`: An optional `Encoding` object for the [environment encoding]
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/// (https://drafts.csswg.org/css-syntax/#environment-encoding), if any.
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///
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/// Returns the encoding to use.
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pub fn stylesheet_encoding<E>(
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css: &[u8],
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protocol_encoding_label: Option<&[u8]>,
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environment_encoding: Option<E::Encoding>,
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) -> E::Encoding
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where
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E: EncodingSupport,
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{
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// https://drafts.csswg.org/css-syntax/#the-input-byte-stream
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if let Some(label) = protocol_encoding_label {
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if let Some(protocol_encoding) = E::from_label(label) {
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return protocol_encoding;
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};
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};
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let prefix = b"@charset \"";
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if css.starts_with(prefix) {
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let rest = &css[prefix.len()..];
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if let Some(label_length) = rest.iter().position(|&b| b == b'"') {
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if rest[label_length..].starts_with(b"\";") {
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let label = &rest[..label_length];
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if let Some(charset_encoding) = E::from_label(label) {
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if E::is_utf16_be_or_le(&charset_encoding) {
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return E::utf8();
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} else {
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return charset_encoding;
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}
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}
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}
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}
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}
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environment_encoding.unwrap_or_else(E::utf8)
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}
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