gecko/testing/extensions/community/chrome/content/prefs.js

var qaPref = {
   litmus : null,
   prefBase : "qa.extension",

   setPref : function(aName, aValue, aType) {
     
     var pref = Components.classes["@mozilla.org/preferences-service;1"]
        			.getService(Components.interfaces.nsIPrefBranch);     
     try{
       if(aType == "bool")
         pref.setBoolPref(aName, aValue);
       else if(aType == "int")   
         pref.setIntPref(aName, aValue);
       else if(aType == "char")
         pref.setCharPref(aName, aValue);
     }
     catch(e){ };
   },
   
   getPref : function(aName, aType) {
     
     var pref = Components.classes["@mozilla.org/preferences-service;1"]
        			.getService(Components.interfaces.nsIPrefBranch);
     try{
       var result;
       if(aType == "bool")
         result = pref.getBoolPref(aName);
       else if(aType == "int")   
         result = pref.getIntPref(aName);
       else if(aType == "char")      
         result = pref.getCharPref(aName);

     return result;
     }
     catch(e){
       if(aType == "bool"){
         return false;
       }          
       else if(aType == "int"){
         return 0;
       }
       else if(aType == "char"){
         return null; 
       }
     }
   return null;
   },
};

// public API:
//	qaPref.litmus.getUsername()
//	qaPref.litmus.getPassword()
//	qaPref.litmus.setPassword()
// everything else is abstracted away to deal with fx2 vs fx3 changes

var CC_passwordManager = Components.classes["@mozilla.org/passwordmanager;1"];
var CC_loginManager = Components.classes["@mozilla.org/login-manager;1"];

if (CC_passwordManager != null) { // old-fashioned password manager
	qaPref.litmus = {
	   passwordName : function() {return "mozqa-extension-litmus-"+litmus.baseURL},
	
	   manager : function() {
		   return Components.classes["@mozilla.org/passwordmanager;1"].
				   getService(Components.interfaces.nsIPasswordManager);
	   },
	   getPasswordObj : function() {
		   var m = this.manager();
		   var e = m.enumerator;
		   
		   // iterate through the PasswordManager service to find 
		   // our password:
		   var password;
		   while(e.hasMoreElements()) {
			   try {
				   var pass = e.getNext().
					   QueryInterface(Components.interfaces.nsIPassword);
				   if (pass.host == this.passwordName()) {
					   password=pass; // found it
					   return password;
				   }
			   } catch (ex) { return false; }
		   }
		   if (!password) { return false; }
		   return password;
	   },
	   getUsername : function() {
		   var password = this.getPasswordObj();
		   try {
			   return password.user;
		   } catch (ex) { return false; }
	   },
	   getPassword : function() {
		   var password=this.getPasswordObj();
		   try {
			   return password.password;
		   } catch (ex) { return false; }
	   },
	   setPassword : function(username, password) {
		   var m = this.manager();
		   // check to see whether we already have a password stored 
		   // for the current baseURL. If we do, remove it before adding 
		   // any new passwords:
		   var p;
		   while (p = this.getPasswordObj()) {
			   m.removeUser(p.host, p.user);
		   }
		   m.addUser(this.passwordName(), username, password);
	   },
	};	
} else if (CC_loginManager != null) { // use the new login manager interface
	qaPref.litmus = {
		manager : function() {
			return Components.classes["@mozilla.org/login-manager;1"]
						   .getService(Components.interfaces.nsILoginManager);
		},
		getUsername : function() {
		   var password = this.getPasswordObj();
		   try {
			   return password.username;
		   } catch (ex) { return false; }
		},
		getPassword : function() {
		   var password=this.getPasswordObj();
		   try {
			   return password.password;
		   } catch (ex) { return false; }
		},
		setPassword : function(username, password) {
			// if we already have a password stored, remove it first:
			var login = this.getPasswordObj();
			if (login != false) {
				this.manager().removeLogin(login);
			}
			
			var nsLoginInfo = new Components.Constructor("@mozilla.org/login-manager/loginInfo;1",
                                        Components.interfaces.nsILoginInfo,
                                        "init");
            var newLogin = new nsLoginInfo();
            newLogin.init('chrome://qa', 'Litmus Login', litmus.baseURL, 
            	username, password, null, null);
            this.manager().addLogin(newLogin);                                 
		},
		getPasswordObj: function() {
			try {
				var logins = this.manager().findLogins({}, 'chrome://qa', 
					'Litmus Login', litmus.baseURL);
				if (logins.length > 0 && logins[0] != null) 
					return logins[0];
				return false;
			} catch(ex) {
				return false;
			}
		},
	};
}