59 lines
2.2 KiB
JavaScript
59 lines
2.2 KiB
JavaScript
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// freeze Array#slice, just in case of funny business later.
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var _slice = Array.prototype.slice;
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var getPromise = require('./_promise.js');
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// deferred gets its own scope to prevent inadvertent capture in the closure
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var deferred = function(options) {
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var Promise = getPromise();
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var resolve, reject, p = new Promise(function(_resolve, _reject) {
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resolve = _resolve; reject = _reject;
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});
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var pattern = (options && options.pattern);
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var noError = (options && options.noError);
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var cb = pattern ? function(err) {
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if (err && !noError) { return reject(err); }
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var result = {}, i, offset = noError ? 0 : 1;
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for (i = 0; i < pattern.length; i++) {
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result[pattern[i]] = arguments[i+offset];
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}
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resolve(result);
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} : noError ? resolve : function(err, val) {
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if (err) { reject(err); } else { resolve(val); }
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};
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return { promise: p, callback: cb };
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};
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var promisify = module.exports = function(context, func, mandatoryArgs, options) {
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if (options && options.callbackIsFirstArg) {
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// duplicate some code here so we don't have to process this unusual
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// situation at runtime in the common case.
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return function(cb) {
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if (typeof(cb) === 'function') {
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return func.apply(context, arguments);
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}
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var d = deferred(options);
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var a = _slice.call(arguments, 0);
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a.unshift(d.callback);
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func.apply(context, a);
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return d.promise;
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};
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}
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return function() {
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var cb = arguments[arguments.length - 1];
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if (typeof(cb) === 'function') {
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return func.apply(context, arguments);
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}
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// ooh, promises.
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var d = deferred(options);
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var a = _slice.call(arguments, 0);
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while (a.length < mandatoryArgs) { a.push(undefined); }
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a.push(d.callback);
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var retval = func.apply(context, a);
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if (options && options.returnsObject) {
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// it would be nice to have a better convention here
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Object.defineProperty(retval, 'promise', { value: d.promise });
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return retval;
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}
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return d.promise;
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};
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};
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