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easejs/lib/util.js

443 lines
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JavaScript

/**
* Contains utilities functions shared by modules
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package core
*/
/**
* Whether getters/setters are supported
* @var {boolean}
*/
var getset = ( Object.prototype.__defineGetter__ === undefined )
? false
: true
;
/**
* Freezes an object if freezing is supported
*
* @param {Object} obj object to freeze
*
* @return {Object} object passed to function
*/
exports.freeze = function( obj )
{
// if freezing is not supported (ES5), do nothing
if ( Object.freeze === undefined )
{
return;
}
Object.freeze( obj );
return obj;
}
/**
* Attempts to define a non-enumerable, non-writable and non-configurable
* property on the given object
*
* If the operation is unsupported, a normal property will be set.
*
* @param {Object} obj object to set property on
* @param {string} prop name of property to set
* @param {mixed} value value to set
*
* @return {undefined}
*/
exports.defineSecureProp = function( obj, prop, value )
{
if ( Object.defineProperty === undefined )
{
func[ prop ] = value;
}
else
{
Object.defineProperty( obj, prop,
{
value: value,
enumerable: false,
writable: false,
configurable: false,
});
}
}
/**
* Clones an object
*
* @param {Object} data object to clone
*
* @return {Object} cloned object
*/
exports.clone = function( data )
{
if ( data instanceof Array )
{
// return a copy of the array
return data.slice( 0 );
}
else if ( data instanceof Object )
{
var newobj = {};
// copy data to the new object
for ( prop in data )
{
if ( data.hasOwnProperty( prop ) )
{
newobj[ prop ] = data[ prop ];
}
}
return newobj;
}
// primitive type; cloning unnecessary
return data;
};
/**
* Parses object properties to determine how they should be interpreted in an
* Object Oriented manner
*
* @param {Object} data properties with names as the key
* @param {Object} options parser options and callbacks
*
* @return undefined
*/
exports.propParse = function( data, options )
{
var fvoid = function() {},
callback_each = options.each || undefined,
callback_prop = options.property || fvoid,
callback_method = options.method || fvoid,
callback_getter = options.getter || fvoid,
callback_setter = options.setter || fvoid;
// for each of the given properties, determine what type of property we're
// dealing with (in the classic OO sense)
for ( prop in data )
{
// ignore properties of instance prototypes
if ( !( data.hasOwnProperty( prop ) ) )
{
continue;
}
var value = data[ prop ],
getter = ( ( getset ) ? data.__lookupGetter__( prop ) : null ),
setter = ( ( getset ) ? data.__lookupSetter__( prop ) : null );
// if an 'each' callback was provided, pass the data before parsing it
if ( callback_each )
{
callback_each.call( callback_each, prop, value );
}
// getter/setter
if ( getter || setter )
{
callback_getter.call( callback_getter, prop, getter );
callback_setter.call( callback_setter, prop, setter );
// we're done
continue;
}
// method
else if ( value instanceof Function )
{
callback_method.call(
callback_method,
prop,
value,
exports.isAbstractMethod( value )
);
}
// simple property
else
{
callback_prop.call( callback_prop, prop, value );
}
}
}
/**
* Copies properties to the destination object
*
* If the method already exists, it will be overridden and accessible via either
* the parent prototype or by invoking this.__super().
*
* The destination object is directly modified.
*
* The result data will be populated with information from the copy that may be
* useful to the creation of the class (e.g. list of the abstract methods).
*
* @param {Object} props properties to copy
* @param {Object} dest destination object
* @param {Object} actions parser actions (see propParse())
*
* @return undefined
*/
exports.propCopy = function( props, dest, actions )
{
actions = actions || {};
var use_or = function( use, or )
{
if ( use instanceof Function )
{
// allow the override to invoke the default implementation
use.performDefault = or;
return use;
}
// use the default
return or;
};
// substitute default functionality if needed
var parse_actions = {
each: use_or( actions.each, function( name, value )
{
// methods can only be overridden with methods
if ( ( dest[ name ] instanceof Function )
&& ( !( value instanceof Function ) )
)
{
throw new TypeError( "Cannot override method with non-method" );
}
} ),
property: use_or( actions.property, function( name, value )
{
dest[ name ] = value;
} ),
getter: use_or( actions.getter, function( name, func )
{
dest.__defineGetter__( name, func );
} ),
setter: use_or( actions.setter, function( name, func )
{
dest.__defineSetter__( name, func );
} ),
method: use_or( actions.method, function( name, func, is_abstract )
{
var pre = dest[ name ];
// check for override
if ( pre !== undefined )
{
if ( pre instanceof Function )
{
// use provided method override action, or fall back to
// generic override
var override_func = use_or( actions.methodOverride,
function( name, pre, func )
{
return exports.overrideMethod( name, pre, func );
}
);
// use call(), passing self in as context, to ensure 'this'
// will reference the function itself
dest[ name ] = override_func.call(
override_func, name, pre, func
);
}
else
{
throw new TypeError(
"Cannot override property '" + name + "' with method"
);
}
}
else
{
// simply copy over the method
dest[ name ] = func;
}
} ),
};
exports.propParse( props, parse_actions );
}
/**
* Creates an abstract method
*
* Abstract methods must be implemented by a subclass and cannot be called
* directly. If a class contains a single abstract method, the class itself is
* considered to be abstract and cannot be instantiated. It may only be
* extended.
*
* @param {...string} definition function definition that concrete
* implementations must follow
*
* @return {Function}
*/
exports.createAbstractMethod = function()
{
var definition = Array.prototype.slice.call( arguments );
var method = function()
{
throw new Error( "Cannot call abstract method" );
};
exports.defineSecureProp( method, 'abstractFlag', true );
exports.defineSecureProp( method, 'definition', definition );
return method;
}
/**
* Determines if the given function is an abstract method
*
* @param {Function} function function to inspect
*
* @return {boolean} true if function is an abstract method, otherwise false
*/
exports.isAbstractMethod = function( func )
{
return ( ( func instanceof Function ) && ( func.abstractFlag === true ) )
? true
: false
;
}
/**
* Overrides a method
*
* The given method must be a function or an exception will be thrown.
*
* @param {string} name method name
* @param {Function} super_method method to override
* @param {Function} new_method method to override with
* @param {Array.<string>=} abstract_methods list of abstract methods
*
* @return {Function} overridden method
*/
exports.overrideMethod = function(
name, super_method, new_method, abstract_methods
)
{
abstract_methods = abstract_methods || [];
// it's much faster to lookup a hash than it is to iterate through an entire
// array each time we need to find an existing abstract method
var abstract_map = {};
for ( var i = 0, len = abstract_methods.length; i < len; i++ )
{
var method = abstract_methods[ i ];
abstract_map[ method ] = i;
}
if ( abstract_map[ name ] !== undefined )
{
var is_abstract = exports.isAbstractMethod( new_method );
if ( super_method.definition instanceof Array )
{
var arg_len = ( is_abstract )
? new_method.definition.length
: new_method.length;
// ensure the concrete definition is compatible with
// that of its supertype
if ( arg_len < super_method.definition.length )
{
throw new TypeError(
"Declaration of " + name + " must be compatiable " +
"with that of its supertype"
);
}
}
// if this was a concrete method, then it should no longer be marked as
// abstract
if ( is_abstract === false )
{
delete abstract_methods[ abstract_map[ name ] ];
}
}
// this is the method that will be invoked when the requested
// method is called, so note that in the context of this
// function, `this` will represent the current class instance
return function()
{
var tmp = this.__super;
// assign _super temporarily for the method invocation so
// that the method can call the parent method
this.__super = super_method;
var retval = new_method.apply( this, arguments );
this.__super = tmp;
return retval;
}
};
/**
* Shrinks an array, removing undefined elements
*
* Pushes all items onto a new array, removing undefined elements. This ensures
* that the length of the array represents correctly the number of elements in
* the array.
*
* @param {Array} items array to shrink
*
* @return {Array} shrunken array
*/
exports.arrayShrink = function( items )
{
// copy the methods into a new array by pushing them onto it, to ensure
// the length property of the array will work properly
var arr_new = [];
for ( var i = 0, len = items.length; i < len; i++ )
{
var item = items[ i ];
if ( item === undefined )
{
continue;
}
arr_new.push( item );
}
return arr_new;
}