Fix a perf regression around handling too-large numbers.

Fixes #130.
bhollis · Nov 25, 2016 · a92f048 · a92f048
1 parent 6f29fba
commit a92f048
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,7 @@ JSONView 1.2.0
 ---
 * Add a preference to use the built-in Firefox JSON viewer.
 * Tell Firefox we support multi-process mode.
+* Fix a performance regression that could severely slow down rendering large documents.
 
 JSONView 1.1.1
 ---

diff --git a/lib/jsonview.js b/lib/jsonview.js
@@ -93,50 +93,35 @@ var JSONView = Class({
    *  string with !isNaN() for number-ness, and render it with number styling, sans-quotes.
    */
   safeStringEncodeNums: function(jsonString) {
-    function betweenOrderedPairs(numberIndex) {
-      function betweenPair(pair, pairIndex, o) {
-        if (numberIndex < pair[0]) {
-          return false;
-        }
-        if (numberIndex <= pair[1]) {
-          return true;
-        }
-        if (pairIndex + 1 === o.length) {
-          return false;
-        }
-        return false;
-      }
-      return orderedPairs.some(betweenPair);
-    }
+    var viewString = jsonString.replace(/\u200B/g, "\u200B\u200B");
 
     // Find unescaped quotes by searching for a non-backslash followed by 0 or even
     // pairs of backslashes, then a quote
-    var quoteFinder = /[^\\](\\\\)*(?=")/g;
-
-    // JSON legal number matcher, Andrew Cheong, http://stackoverflow.com/questions/13340717
-    var numberFinder = /-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/g;
-    var quoteMap = [];
-    var orderedPairs = [];
-    var viewString = jsonString.replace(/\u200B/g, "\u200B\u200B");
-    var match;
-
-    while ((match = quoteFinder.exec(viewString)) !== null) {
-      quoteMap.push(match.index + match[0].length);
-    }
-
-    // If we don't have an even number of quotes, bail and parse viewString as-is.
-    if (quoteMap.length % 2 !== 0) {
-      return viewString;
+    var quoteFinder = /([^\\]|^)(\\\\)*(?=")/gm;
+
+    // This has some memory of what its last state was
+    var wasInQuotes = false;
+    function isInsideQuotes(str) {
+      var inQuotes = (str.match(quoteFinder) || []).length % 2 === 1;
+      if (wasInQuotes) {
+        inQuotes = !inQuotes;
+      }
+      wasInQuotes = inQuotes;
+      return inQuotes;
     }
 
-    while (quoteMap.length) {
-      orderedPairs.push(quoteMap.splice(0, 2));
+    var startIndex = 0;
+    function replaceNumbers(match, index) {
+      // Substring should be copy-on-write, and thus cheap
+      var lookback = viewString.substring(startIndex, index);
+      var insideQuotes = isInsideQuotes(lookback);
+      startIndex = index + match.length;
+      return insideQuotes ? match : '"\u200B' + match + '"';
     }
 
-    return viewString.replace(numberFinder,
-                              (match, ndx) =>
-                              (betweenOrderedPairs(ndx) ? match : '"\u200B' + match + '"')
-    );
+    // JSON legal number matcher, Andrew Cheong, http://stackoverflow.com/questions/13340717
+    var numberFinder = /-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/g;
+    return viewString.replace(numberFinder, replaceNumbers);
   },
 
   // nsIRequestObserver::onStopRequest