perf: reduce loop count in header parsing

jshttp · Dec 18, 2014 · 4c368e7 · 4c368e7
1 parent 6bd5402
commit 4c368e7
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Showing 4 changed files with 61 additions and 40 deletions.
diff --git a/lib/charset.js b/lib/charset.js
@@ -2,11 +2,20 @@ module.exports = preferredCharsets;
 preferredCharsets.preferredCharsets = preferredCharsets;
 
 function parseAcceptCharset(accept) {
-  return accept.split(',').map(function(e, i) {
-    return parseCharset(e.trim(), i);
-  }).filter(function(e) {
-    return e;
-  });
+  var accepts = accept.split(',');
+
+  for (var i = 0, j = 0; i < accepts.length; i++) {
+    var charset = parseCharset(accepts[i].trim(), i);
+
+    if (charset) {
+      accepts[j++] = charset;
+    }
+  }
+
+  // trim accepts
+  accepts.length = j;
+
+  return accepts;
 }
 
 function parseCharset(s, i) {

diff --git a/lib/encoding.js b/lib/encoding.js
@@ -2,41 +2,35 @@ module.exports = preferredEncodings;
 preferredEncodings.preferredEncodings = preferredEncodings;
 
 function parseAcceptEncoding(accept) {
-  var acceptableEncodings;
+  var accepts = accept.split(',');
+  var hasIdentity = false;
+  var minQuality = 1;
 
-  if (accept) {
-    acceptableEncodings = accept.split(',').map(function(e, i) {
-      return parseEncoding(e.trim(), i);
-    });
-  } else {
-    acceptableEncodings = [];
+  for (var i = 0, j = 0; i < accepts.length; i++) {
+    var encoding = parseEncoding(accepts[i].trim(), i);
+
+    if (encoding) {
+      accepts[j++] = encoding;
+      hasIdentity = hasIdentity || specify('identity', encoding);
+      minQuality = Math.min(minQuality, encoding.q);
+    }
   }
 
-  if (!acceptableEncodings.some(function(e) {
-    return e && specify('identity', e);
-  })) {
+  if (!hasIdentity) {
     /*
      * If identity doesn't explicitly appear in the accept-encoding header,
      * it's added to the list of acceptable encoding with the lowest q
-     *
      */
-    var lowestQ = 1;
-
-    for(var i = 0; i < acceptableEncodings.length; i++){
-      var e = acceptableEncodings[i];
-      if(e && e.q < lowestQ){
-        lowestQ = e.q;
-      }
-    }
-    acceptableEncodings.push({
+    accepts[j++] = {
       encoding: 'identity',
-      q: lowestQ / 2,
-    });
+      q: minQuality / 2
+    };
   }
 
-  return acceptableEncodings.filter(function(e) {
-    return e;
-  });
+  // trim accepts
+  accepts.length = j;
+
+  return accepts;
 }
 
 function parseEncoding(s, i) {

diff --git a/lib/language.js b/lib/language.js
@@ -2,11 +2,20 @@ module.exports = preferredLanguages;
 preferredLanguages.preferredLanguages = preferredLanguages;
 
 function parseAcceptLanguage(accept) {
-  return accept.split(',').map(function(e, i) {
-    return parseLanguage(e.trim(), i);
-  }).filter(function(e) {
-    return e;
-  });
+  var accepts = accept.split(',');
+
+  for (var i = 0, j = 0; i < accepts.length; i++) {
+    var langauge = parseLanguage(accepts[i].trim(), i);
+
+    if (langauge) {
+      accepts[j++] = langauge;
+    }
+  }
+
+  // trim accepts
+  accepts.length = j;
+
+  return accepts;
 }
 
 function parseLanguage(s, i) {

diff --git a/lib/mediaType.js b/lib/mediaType.js
@@ -2,11 +2,20 @@ module.exports = preferredMediaTypes;
 preferredMediaTypes.preferredMediaTypes = preferredMediaTypes;
 
 function parseAccept(accept) {
-  return accept.split(',').map(function(e, i) {
-    return parseMediaType(e.trim(), i);
-  }).filter(function(e) {
-    return e;
-  });
+  var accepts = accept.split(',');
+
+  for (var i = 0, j = 0; i < accepts.length; i++) {
+    var mediaType = parseMediaType(accepts[i].trim(), i);
+
+    if (mediaType) {
+      accepts[j++] = mediaType;
+    }
+  }
+
+  // trim accepts
+  accepts.length = j;
+
+  return accepts;
 };
 
 function parseMediaType(s, i) {