Issue 6957 - Add rulesFromStyleSheet function to ElemHide module

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 388 matching lines @@
                   createStyleSheet(getConditionalSelectors(knownSuffix,
                                                            false)));
       }
     }
 
     return {code, selectors: includeSelectors ? selectors : null};
   }
 };
 
 /**
+ * Yields rules from a style sheet returned by
+ * <code>{@link createStyleSheet}</code>.
+ *
+ * @param {string} styleSheet A style sheet returned by
+ *   <code>{@link createStyleSheet}</code>. If the given style sheet is
+ *   <em>not</em> a value previously returned by a call to
+ *   <code>{@link createStyleSheet}</code>, the behavior is undefined.
+ * @yields {string} A rule from the given style sheet.
+ */
+function* rulesFromStyleSheet(styleSheet)
+{
+  let startIndex = 0;
+  while (startIndex < styleSheet.length)
+  {
+    let ruleTerminatorIndex = styleSheet.indexOf("\n", startIndex);
+    yield styleSheet.substring(startIndex, ruleTerminatorIndex);
+    startIndex = ruleTerminatorIndex + 1;
+  }
+}
+
+exports.rulesFromStyleSheet = rulesFromStyleSheet;
+
+/**
  * Splits a list of selectors into groups determined by the value of
  * <code>{@link selectorGroupSize}</code>.
  *
  * @param {Array.<string>} selectors
  * @yields {Array.<string>}
  */
 function* splitSelectors(selectors)
 {
   // Chromium's Blink engine supports only up to 8,192 simple selectors, and
   // even fewer compound selectors, in a rule. The exact number of selectors
@@ skipping 37 matching lines @@
 {
   let styleSheet = "";
 
   for (let selectorGroup of splitSelectors(selectors))
     styleSheet += createRule(selectorGroup);
 
   return styleSheet;
 }
 
 exports.createStyleSheet = createStyleSheet;