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