'use strict'
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var fs = require('fs')
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var Queue = require('./Queue')
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/**
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* Limits the number of concurrent file handlers.
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* Use it as a wrapper over fs.open() and fs.close().
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* Example:
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* var fdQueue = new FileDescriptorQueue(8)
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* fdQueue.open(path, flags, (err, fd) =>{
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* ...
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* fdQueue.close(fd, (err) =>{
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* ...
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* })
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* })
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* As of node v7, calling fd.close without a callback is deprecated.
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*/
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var FileDescriptorQueue = function (maxFilesNo) {
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var pendingJobs = new Queue()
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var activeCount = 0
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var open = function (path, flags, callback) {
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pendingJobs.enqueue({
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path: path,
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flags: flags,
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callback: callback
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})
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process()
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}
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var process = function () {
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if (pendingJobs.getLength() > 0 && activeCount < maxFilesNo) {
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var job = pendingJobs.dequeue()
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activeCount++
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fs.open(job.path, job.flags, job.callback)
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}
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}
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var close = function (fd, callback) {
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activeCount--
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fs.close(fd, callback)
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process()
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}
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var promises = {
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open: function (path, flags) {
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return new Promise(function (resolve, reject) {
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open(path, flags, function (err, fd) {
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if (err) {
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reject(err)
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} else {
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resolve(fd)
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}
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})
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})
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},
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close: function (fd) {
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return new Promise(function (resolve, reject) {
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close(fd, function (err) {
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if (err) {
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reject(err)
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} else {
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resolve()
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}
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})
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})
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}
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}
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return {
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open: open,
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close: close,
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promises: promises
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}
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}
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module.exports = FileDescriptorQueue
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