Adding argument hashing

README.md

@@ -7,7 +7,7 @@ Memoize asynchronous function calls using memcached
         mmemoize = require('mmemoize');
 
     var memcached = new Memcached('localhost:11211'),
-        mmemoizer = mmemoize(memcached, { ttl: 120 }); // in seconds
+        mmemoizer = mmemoize(memcached /*, config */);
 
     var a = function (/* someArguments, */ callback) {
        // some potentially expensive computations, database fetches etc.
@@ -24,6 +24,13 @@ Memoize asynchronous function calls using memcached
     // just in case:
     a = a.dememoize(); // or: a = mmemoizer.dememoize(a);
 
+## Configuration
+
+Send config object as the second parameter of mmemoize(), use the following options:
+
+- `ttl`: Key TTL in seconds; default: `120`
+- `hashAlgorithm`: Algorithm used for hashing function arguments in memcached keys, set to `null` for no hashing at all, for possible values see [node.js' crypto documentation](http://nodejs.org/docs/latest/api/crypto.html#crypto.createHash); default: `sha1`
+
 ## Deployment dependencies
 - [node-memcached](https://github.com/3rd-Eden/node-memcached) (of course)
 

index.js

@@ -1,8 +1,12 @@
 var mmemoize = function (memcached, config) {
+  var crypto = require('crypto');
+
+  var that = {};
+
   var configDefaults = {
-    ttl: 120
+    ttl: 120,
+    hashAlgorithm: 'sha1'
   };
-  var that = {};
   var cProp;
   for (cProp in configDefaults) {
     if (configDefaults.hasOwnProperty(cProp) && config[cProp] === undefined) {
@@ -21,7 +25,7 @@ var mmemoize = function (memcached, config) {
       if (typeof args.slice(-1).pop() === 'function') {
         fctCallback = args.pop(); // cache and remove original callback
       }
-      key = keyPrefix + ':' + JSON.stringify(args);
+      key = calcKey(keyPrefix, args);
       memcached.get(key, function (err, mcdResult) {
         if (err !== undefined || mcdResult === undefined || mcdResult === false) { // memcache error or miss:
           args.push(function () {  // register our new callback:
@@ -59,6 +63,24 @@ var mmemoize = function (memcached, config) {
   };
   that.dememoize = dememoize;
 
+  // PRIVATE METHODS:
+  var calcKey = function (prefix, args) {
+    var key,
+        hasher;
+    if (typeof args !== 'string') {
+      args = JSON.stringify(args);
+    }
+    if (config.hashAlgorithm !== null) { // hash arguments:
+      hasher = crypto.createHash(config.hashAlgorithm);
+      hasher.update(args);
+      key = prefix + ':' + hasher.digest('hex');
+    }
+    else {
+      key = prefix + ':' + args;
+    }
+    return key;
+  };
+
   return that;
 };
 module.exports = mmemoize;