layout/style/ImportScanner.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 sw=2 et tw=78: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ImportScanner_h
   8 #define mozilla_ImportScanner_h
   9
  10 /* A simple best-effort scanner for @import rules for the HTML parser */
  11
  12 #include "nsString.h"
  13 #include "nsTArray.h"
  14
  15 namespace mozilla {
  16
  17 struct ImportScanner final {
  18   ImportScanner() = default;
  19
  20   // Called when a <style> element starts.
  21   //
  22   // Note that this function cannot make assumptions about the internal state,
  23   // as you can nest <svg:style> elements.
  24   void Start();
  25
  26   // Called when a <style> element ends. Returns the list of URLs scanned.
  27   nsTArray<nsString> Stop();
  28
  29   // Whether Scan() should be called.
  30   bool ShouldScan() const {
  31     return mState != State::OutsideOfStyleElement && mState != State::Done;
  32   }
  33
  34   // Scan() should be called when text content is parsed, and returns an array
  35   // of found URLs, if any.
  36   //
  37   // Asserts ShouldScan() returns true.
  38   nsTArray<nsString> Scan(Span<const char16_t> aFragment);
  39
  40  private:
  41   enum class State {
  42     // Initial state, doesn't scan anything until Start() is called.
  43     OutsideOfStyleElement,
  44     // In an idle state during the stylesheet scanning, either at the
  45     // beginning or after parsing a rule.
  46     Idle,
  47     // We've seen a '/' character, but not the '*' yet, so we don't know if
  48     // it's a comment.
  49     MaybeAtCommentStart,
  50     // We're inside a comment.
  51     AtComment,
  52     // We've seen a '*' while we're in a comment, but we don't now yet whether
  53     // '/' comes afterwards (thus ending the comment).
  54     MaybeAtCommentEnd,
  55     // We're parsing the '@' rule name.
  56     AtRuleName,
  57     // We're parsing the '@' rule value.
  58     AtRuleValue,
  59     // We're parsing the '@' rule value and we've seen the delimiter (quote or
  60     // url() function) that encloses the url.
  61     AtRuleValueDelimited,
  62     // We've seen the url, but haven't seen the ';' finishing the rule yet.
  63     AfterRuleValue,
  64     // We've seen anything that is not an @import or a @charset rule, and thus
  65     // further @import / @charset should not be parsed.
  66     Done,
  67   };
  68
  69   void ResetState();
  70   void EmitUrl();
  71   [[nodiscard]] State Scan(char16_t aChar);
  72
  73   static constexpr const uint32_t kMaxRuleNameLength = 7;  // (charset, import)
  74
  75   State mState = State::OutsideOfStyleElement;
  76   nsAutoStringN<kMaxRuleNameLength> mRuleName;
  77   nsAutoStringN<128> mRuleValue;
  78   nsAutoStringN<128> mAfterRuleValue;
  79   nsTArray<nsString> mUrlsFound;
  80
  81   // This is conceptually part of the AtRuleValue* / AfterRuleValue states,
  82   // and serves to differentiate between @import (where we actually care about
  83   // the value) and @charset (where we don't). It's just more convenient this
  84   // way than having separate states for them.
  85   bool mInImportRule = false;
  86   // If we're in the AtRuleValueDelimited state, what is the closing character
  87   // that will end the value. This is either a parenthesis (for unquoted
  88   // urls), or a quote, either single or double.
  89   char16_t mUrlValueDelimiterClosingChar = 0;
  90 };
  91
  92 }  // namespace mozilla
  93
  94 #endif