142 lines
2.9 KiB
JavaScript
142 lines
2.9 KiB
JavaScript
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var async = require('./async.js');
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// API
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module.exports = {
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iterator: wrapIterator,
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callback: wrapCallback
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};
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/**
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* Wraps iterators with long signature
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*
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* @this ReadableAsyncKit#
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* @param {function} iterator - function to wrap
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* @returns {function} - wrapped function
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*/
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function wrapIterator(iterator)
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{
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var stream = this;
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return function(item, key, cb)
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{
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var aborter
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, wrappedCb = async(wrapIteratorCallback.call(stream, cb, key))
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;
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stream.jobs[key] = wrappedCb;
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// it's either shortcut (item, cb)
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if (iterator.length == 2)
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{
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aborter = iterator(item, wrappedCb);
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}
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// or long format (item, key, cb)
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else
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{
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aborter = iterator(item, key, wrappedCb);
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}
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return aborter;
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};
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}
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/**
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* Wraps provided callback function
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* allowing to execute snitch function before
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* real callback
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*
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* @this ReadableAsyncKit#
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* @param {function} callback - function to wrap
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* @returns {function} - wrapped function
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*/
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function wrapCallback(callback)
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{
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var stream = this;
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var wrapped = function(error, result)
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{
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return finisher.call(stream, error, result, callback);
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};
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return wrapped;
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}
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/**
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* Wraps provided iterator callback function
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* makes sure snitch only called once,
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* but passes secondary calls to the original callback
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*
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* @this ReadableAsyncKit#
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* @param {function} callback - callback to wrap
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* @param {number|string} key - iteration key
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* @returns {function} wrapped callback
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*/
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function wrapIteratorCallback(callback, key)
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{
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var stream = this;
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return function(error, output)
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{
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// don't repeat yourself
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if (!(key in stream.jobs))
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{
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callback(error, output);
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return;
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}
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// clean up jobs
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delete stream.jobs[key];
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return streamer.call(stream, error, {key: key, value: output}, callback);
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};
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}
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/**
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* Stream wrapper for iterator callback
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*
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* @this ReadableAsyncKit#
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* @param {mixed} error - error response
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* @param {mixed} output - iterator output
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* @param {function} callback - callback that expects iterator results
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*/
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function streamer(error, output, callback)
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{
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if (error && !this.error)
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{
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this.error = error;
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this.pause();
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this.emit('error', error);
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// send back value only, as expected
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callback(error, output && output.value);
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return;
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}
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// stream stuff
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this.push(output);
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// back to original track
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// send back value only, as expected
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callback(error, output && output.value);
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}
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/**
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* Stream wrapper for finishing callback
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*
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* @this ReadableAsyncKit#
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* @param {mixed} error - error response
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* @param {mixed} output - iterator output
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* @param {function} callback - callback that expects final results
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*/
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function finisher(error, output, callback)
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{
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// signal end of the stream
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// only for successfully finished streams
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if (!error)
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{
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this.push(null);
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}
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// back to original track
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callback(error, output);
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}
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