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