querystring: improve parse() performance

PR-URL: https://github.com/nodejs/node/pull/10874
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 62 insertions, 42 deletions

diff --git a/lib/querystring.js b/lib/querystring.js
index ff1b47fb51..c22c7c998d 100644
--- a/lib/querystring.js
+++ b/lib/querystring.js
@@ -1,8 +1,19 @@
-// Query String Utilities
-
 'use strict';
 
-const QueryString = exports;
+const QueryString = module.exports = {
+  unescapeBuffer,
+  // `unescape()` is a JS global, so we need to use a different local name
+  unescape: qsUnescape,
+
+  // `escape()` is a JS global, so we need to use a different local name
+  escape: qsEscape,
+
+  stringify,
+  encode: stringify,
+
+  parse,
+  decode: parse
+};
 const Buffer = require('buffer').Buffer;
 
 // This constructor is used to store parsed query string values. Instantiating
@@ -13,7 +24,7 @@ ParsedQueryString.prototype = Object.create(null);
 
 
 // a safe fast alternative to decodeURIComponent
-QueryString.unescapeBuffer = function(s, decodeSpaces) {
+function unescapeBuffer(s, decodeSpaces) {
   var out = Buffer.allocUnsafe(s.length);
   var state = 0;
   var n, m, hexchar;
@@ -77,7 +88,7 @@ QueryString.unescapeBuffer = function(s, decodeSpaces) {
   // TODO support returning arbitrary buffers.
 
   return out.slice(0, outIndex - 1);
-};
+}
 
 
 function qsUnescape(s, decodeSpaces) {
@@ -87,13 +98,12 @@ function qsUnescape(s, decodeSpaces) {
     return QueryString.unescapeBuffer(s, decodeSpaces).toString();
   }
 }
-QueryString.unescape = qsUnescape;
 
 
 var hexTable = new Array(256);
 for (var i = 0; i < 256; ++i)
   hexTable[i] = '%' + ((i < 16 ? '0' : '') + i.toString(16)).toUpperCase();
-QueryString.escape = function(str) {
+function qsEscape(str) {
   // replaces encodeURIComponent
   // http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.3.4
   if (typeof str !== 'string') {
@@ -164,9 +174,9 @@ QueryString.escape = function(str) {
   if (lastPos < str.length)
     return out + str.slice(lastPos);
   return out;
-};
+}
 
-var stringifyPrimitive = function(v) {
+function stringifyPrimitive(v) {
   if (typeof v === 'string')
     return v;
   if (typeof v === 'number' && isFinite(v))
@@ -174,10 +184,10 @@ var stringifyPrimitive = function(v) {
   if (typeof v === 'boolean')
     return v ? 'true' : 'false';
   return '';
-};
+}
 
 
-QueryString.stringify = QueryString.encode = function(obj, sep, eq, options) {
+function stringify(obj, sep, eq, options) {
   sep = sep || '&';
   eq = eq || '=';
 
@@ -215,34 +225,43 @@ QueryString.stringify = QueryString.encode = function(obj, sep, eq, options) {
     return fields;
   }
   return '';
-};
+}
 
-// Parse a key/val string.
-QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
-  sep = sep || '&';
-  eq = eq || '=';
+function charCodes(str) {
+  if (str.length === 0) return [];
+  if (str.length === 1) return [str.charCodeAt(0)];
+  const ret = [];
+  for (var i = 0; i < str.length; ++i)
+    ret[ret.length] = str.charCodeAt(i);
+  return ret;
+}
+const defSepCodes = [38]; // &
+const defEqCodes = [61]; // =
 
+// Parse a key/val string.
+function parse(qs, sep, eq, options) {
   const obj = new ParsedQueryString();
 
   if (typeof qs !== 'string' || qs.length === 0) {
     return obj;
   }
 
-  if (typeof sep !== 'string')
-    sep += '';
-
-  const eqLen = eq.length;
-  const sepLen = sep.length;
+  var sepCodes = (!sep ? defSepCodes : charCodes(sep + ''));
+  var eqCodes = (!eq ? defEqCodes : charCodes(eq + ''));
+  const sepLen = sepCodes.length;
+  const eqLen = eqCodes.length;
 
-  var maxKeys = 1000;
+  var pairs = 1000;
   if (options && typeof options.maxKeys === 'number') {
-    maxKeys = options.maxKeys;
+    // -1 is used in place of a value like Infinity for meaning
+    // "unlimited pairs" because of additional checks V8 (at least as of v5.4)
+    // has to do when using variables that contain values like Infinity. Since
+    // `pairs` is always decremented and checked explicitly for 0, -1 works
+    // effectively the same as Infinity, while providing a significant
+    // performance boost.
+    pairs = (options.maxKeys > 0 ? options.maxKeys : -1);
   }
 
-  var pairs = Infinity;
-  if (maxKeys > 0)
-    pairs = maxKeys;
-
   var decode = QueryString.unescape;
   if (options && typeof options.decodeURIComponent === 'function') {
     decode = options.decodeURIComponent;
@@ -262,7 +281,7 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
     const code = qs.charCodeAt(i);
 
     // Try matching key/value pair separator (e.g. '&')
-    if (code === sep.charCodeAt(sepIdx)) {
+    if (code === sepCodes[sepIdx]) {
       if (++sepIdx === sepLen) {
         // Key/value pair separator match!
         const end = i - sepIdx + 1;
@@ -284,10 +303,10 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
           keys[keys.length] = key;
         } else {
           const curValue = obj[key];
-          // `instanceof Array` is used instead of Array.isArray() because it
-          // is ~15-20% faster with v8 4.7 and is safe to use because we are
-          // using it with values being created within this function
-          if (curValue instanceof Array)
+          // A simple Array-specific property check is enough here to
+          // distinguish from a string value and is faster and still safe since
+          // we are generating all of the values being assigned.
+          if (curValue.pop)
             curValue[curValue.length] = value;
           else
             obj[key] = [curValue, value];
@@ -322,7 +341,7 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
 
     // Try matching key/value separator (e.g. '=') if we haven't already
     if (eqIdx < eqLen) {
-      if (code === eq.charCodeAt(eqIdx)) {
+      if (code === eqCodes[eqIdx]) {
         if (++eqIdx === eqLen) {
           // Key/value separator match!
           const end = i - eqIdx + 1;
@@ -354,12 +373,12 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
 
     if (code === 43/*+*/) {
       if (eqIdx < eqLen) {
-        if (i - lastPos > 0)
+        if (lastPos < i)
           key += qs.slice(lastPos, i);
         key += '%20';
         keyEncoded = true;
       } else {
-        if (i - lastPos > 0)
+        if (lastPos < i)
           value += qs.slice(lastPos, i);
         value += '%20';
         valEncoded = true;
@@ -369,7 +388,7 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
   }
 
   // Check if we have leftover key or value data
-  if (pairs > 0 && (lastPos < qs.length || eqIdx > 0)) {
+  if (pairs !== 0 && (lastPos < qs.length || eqIdx > 0)) {
     if (lastPos < qs.length) {
       if (eqIdx < eqLen)
         key += qs.slice(lastPos);
@@ -387,10 +406,10 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
       keys[keys.length] = key;
     } else {
       const curValue = obj[key];
-      // `instanceof Array` is used instead of Array.isArray() because it
-      // is ~15-20% faster with v8 4.7 and is safe to use because we are
-      // using it with values being created within this function
-      if (curValue instanceof Array)
+      // A simple Array-specific property check is enough here to
+      // distinguish from a string value and is faster and still safe since
+      // we are generating all of the values being assigned.
+      if (curValue.pop)
         curValue[curValue.length] = value;
       else
         obj[key] = [curValue, value];
@@ -398,11 +417,12 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
   }
 
   return obj;
-};
+}
 
 
 // v8 does not optimize functions with try-catch blocks, so we isolate them here
-// to minimize the damage
+// to minimize the damage (Note: no longer true as of V8 5.4 -- but still will
+// not be inlined).
 function decodeStr(s, decoder) {
   try {
     return decoder(s);