64 lines
1.6 KiB
JavaScript
64 lines
1.6 KiB
JavaScript
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var Promise = require('any-promise')
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var assert = require('assert')
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module.exports = thenify
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/**
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* Turn async functions into promises
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*
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* @param {Function} $$__fn__$$
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* @return {Function}
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* @api public
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*/
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function thenify($$__fn__$$) {
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assert(typeof $$__fn__$$ === 'function')
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return eval(createWrapper($$__fn__$$.name))
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}
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/**
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* Turn async functions into promises and backward compatible with callback
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*
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* @param {Function} $$__fn__$$
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* @return {Function}
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* @api public
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*/
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thenify.withCallback = function ($$__fn__$$) {
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assert(typeof $$__fn__$$ === 'function')
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return eval(createWrapper($$__fn__$$.name, true))
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}
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function createCallback(resolve, reject) {
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return function(err, value) {
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if (err) return reject(err)
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var length = arguments.length
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if (length <= 2) return resolve(value)
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var values = new Array(length - 1)
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for (var i = 1; i < length; ++i) values[i - 1] = arguments[i]
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resolve(values)
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}
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}
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function createWrapper(name, withCallback) {
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name = (name || '').replace(/\s|bound(?!$)/g, '')
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withCallback = withCallback ?
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'var lastType = typeof arguments[len - 1]\n'
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+ 'if (lastType === "function") return $$__fn__$$.apply(self, arguments)\n'
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: ''
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return '(function ' + name + '() {\n'
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+ 'var self = this\n'
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+ 'var len = arguments.length\n'
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+ withCallback
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+ 'var args = new Array(len + 1)\n'
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+ 'for (var i = 0; i < len; ++i) args[i] = arguments[i]\n'
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+ 'var lastIndex = i\n'
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+ 'return new Promise(function (resolve, reject) {\n'
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+ 'args[lastIndex] = createCallback(resolve, reject)\n'
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+ '$$__fn__$$.apply(self, args)\n'
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+ '})\n'
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+ '})'
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}
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