oxjs/source/Ox/js/Function.js

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'use strict';
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/*@
Ox.cache <f> Memoize a function
fn <f> function
options <o>
async <b|false> function is async, last argument must be callback
key <f|JSON.stringify> return key for arguments
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<script>
Ox.test.fn = Ox.cache(function(n) { return n * Math.random(); });
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</script>
> Ox.test.fn(10) == Ox.test.fn(10);
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true
> Ox.test.fn(10) == Ox.test.fn.clear()(10);
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false
@*/
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// TODO: add async test
Ox.cache = function(fn, options) {
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var cache = {},
ret = function() {
options = Ox.extend({
async: false,
key: JSON.stringify
}, options || {});
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var args = Ox.toArray(arguments), key = options.key(args);
function callback() {
// cache all arguments passed to callback
cache[key] = Ox.toArray(arguments);
// call the original callback
Ox.last(args).apply(this, arguments);
}
if (options.async) {
if (!(key in cache)) {
// call function with patched callback
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fn.apply(this, args.slice(0, -1).concat(callback));
} else {
// call callback with cached arguments
setTimeout(function() {
callback.apply(this, cache[key]);
});
}
} else {
if (!(key in cache)) {
cache[key] = fn.apply(this, args);
}
return cache[key];
}
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};
ret.clear = function() {
if (arguments.length == 0) {
cache = {};
} else {
Ox.makeArray(arguments).forEach(function(key) {
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delete cache[key];
});
}
return ret;
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};
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return ret;
};
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/*@
Ox.identity <f> Returns its first argument
This can be used as a default iterator
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> Ox.identity(Infinity)
Infinity
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@*/
Ox.identity = function(value) {
return value;
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};
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/*@
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Ox.noop <f> Returns undefined and calls optional callback without arguments
This can be used as a default iterator in an asynchronous loop, or to
combine a synchronous and an asynchronous code path.
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> Ox.noop(1, 2, 3)
undefined
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> Ox.noop(1, 2, 3, function() { Ox.test(arguments.length, 0); })
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undefined
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@*/
Ox.noop = function() {
var callback = Ox.last(arguments);
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Ox.isFunction(callback) && callback();
};
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/*@
Ox.queue <f> Queue of asynchronous function calls with cached results
The results are cached based on all arguments to `fn`, except the last one,
which is the callback.
(fn, maxThreads) -> <f> Queue function
.cancel <f> Cancels all running function calls
.clear <f> Clears the queue
.reset <f> Cancels all running function calls and clears the queue
fn <f> Queued function
maxThreads <n|10> Number of parallel function calls
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@*/
Ox.queue = function(fn, maxThreads) {
var maxThreads = maxThreads || 10,
processing = [],
queued = [],
ret = Ox.cache(function() {
var args = Ox.toArray(arguments);
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queued.push({args: args, key: getKey(args)});
process();
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}, {async: true, key: getKey}),
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threads = 0;
ret.cancel = function() {
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threads -= processing.length;
processing = [];
return ret;
};
ret.clear = function() {
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threads = 0;
queued = [];
return ret;
};
ret.reset = function() {
return ret.cancel().clear();
};
function getKey(args) {
return JSON.stringify(args.slice(0, -1));
}
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function process() {
var n = Math.min(queued.length, maxThreads - threads);
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if (n) {
threads += n;
processing = processing.concat(queued.splice(0, n));
Ox.parallelForEach(
processing,
function(value, index, array, callback) {
var args = value.args, key = value.key;
fn.apply(this, args.slice(0, -1).concat(function(result) {
var index = Ox.indexOf(processing, function(value) {
return value.key == key;
});
if (index > -1) {
processing.splice(index, 1);
args.slice(-1)[0](result);
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threads--;
}
callback();
}));
},
process
);
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}
}
return ret;
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};