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var fs = require('fs')
var wx = 'wx'
if (process.version.match(/^v0.[456]/)) {
var c = require('constants')
wx = c.O_TRUNC | c.O_CREAT | c.O_WRONLY | c.O_EXCL
}
var locks = {}
function hasOwnProperty (obj, prop) {
return Object.prototype.hasOwnProperty.call(obj, prop)
}
process.on('exit', function () {
// cleanup
Object.keys(locks).forEach(exports.unlockSync)
})
// XXX https://github.com/joyent/node/issues/3555
// Remove when node 0.8 is deprecated.
process.on('uncaughtException', function H (er) {
var l = process.listeners('uncaughtException').filter(function (h) {
return h !== H
})
if (!l.length) {
// cleanup
try { Object.keys(locks).forEach(exports.unlockSync) } catch (e) {}
process.removeListener('uncaughtException', H)
throw er
}
})
exports.unlock = function (path, cb) {
// best-effort. unlocking an already-unlocked lock is a noop
if (hasOwnProperty(locks, path))
fs.close(locks[path], unlink)
else
unlink()
function unlink () {
delete locks[path]
fs.unlink(path, function (unlinkEr) { cb() })
}
}
exports.unlockSync = function (path) {
// best-effort. unlocking an already-unlocked lock is a noop
try { fs.closeSync(locks[path]) } catch (er) {}
try { fs.unlinkSync(path) } catch (er) {}
delete locks[path]
}
// if the file can be opened in readonly mode, then it's there.
// if the error is something other than ENOENT, then it's not.
exports.check = function (path, opts, cb) {
if (typeof opts === 'function') cb = opts, opts = {}
fs.open(path, 'r', function (er, fd) {
if (er) {
if (er.code !== 'ENOENT') return cb(er)
return cb(null, false)
}
if (!opts.stale) {
return fs.close(fd, function (er) {
return cb(er, true)
})
}
fs.fstat(fd, function (er, st) {
if (er) return fs.close(fd, function (er2) {
return cb(er)
})
fs.close(fd, function (er) {
var age = Date.now() - st.ctime.getTime()
return cb(er, age <= opts.stale)
})
})
})
}
exports.checkSync = function (path, opts) {
opts = opts || {}
if (opts.wait) {
throw new Error('opts.wait not supported sync for obvious reasons')
}
try {
var fd = fs.openSync(path, 'r')
} catch (er) {
if (er.code !== 'ENOENT') throw er
return false
}
if (!opts.stale) {
fs.closeSync(fd)
return true
}
// file exists. however, might be stale
if (opts.stale) {
try {
var st = fs.fstatSync(fd)
} finally {
fs.closeSync(fd)
}
var age = Date.now() - st.ctime.getTime()
return (age <= opts.stale)
}
}
exports.lock = function (path, opts, cb) {
if (typeof opts === 'function') cb = opts, opts = {}
if (typeof opts.retries === 'number' && opts.retries > 0) {
cb = (function (orig) { return function (er, fd) {
if (!er) return orig(er, fd)
var newRT = opts.retries - 1
opts_ = Object.create(opts, { retries: { value: newRT }})
if (opts.retryWait) setTimeout(function() {
exports.lock(path, opts_, orig)
}, opts.retryWait)
else exports.lock(path, opts_, orig)
}})(cb)
}
// try to engage the lock.
// if this succeeds, then we're in business.
fs.open(path, wx, function (er, fd) {
if (!er) {
locks[path] = fd
return cb(null, fd)
}
// something other than "currently locked"
// maybe eperm or something.
if (er.code !== 'EEXIST') return cb(er)
// someone's got this one. see if it's valid.
if (opts.stale) fs.stat(path, function (er, st) {
if (er) {
if (er.code === 'ENOENT') {
// expired already!
var opts_ = Object.create(opts, { stale: { value: false }})
exports.lock(path, opts_, cb)
return
}
return cb(er)
}
var age = Date.now() - st.ctime.getTime()
if (age > opts.stale) {
exports.unlock(path, function (er) {
if (er) return cb(er)
var opts_ = Object.create(opts, { stale: { value: false }})
exports.lock(path, opts_, cb)
})
} else notStale(er, path, opts, cb)
})
else notStale(er, path, opts, cb)
})
}
function notStale (er, path, opts, cb) {
// if we can't wait, then just call it a failure
if (typeof opts.wait !== 'number' || opts.wait <= 0)
return cb(er)
// console.error('wait', path, opts.wait)
// wait for some ms for the lock to clear
var start = Date.now()
var end = start + opts.wait
function retry () {
var now = Date.now()
var newWait = end - now
var newOpts = Object.create(opts, { wait: { value: newWait }})
exports.lock(path, newOpts, cb)
}
var timer = setTimeout(retry, 10)
}
exports.lockSync = function (path, opts) {
opts = opts || {}
if (opts.wait || opts.retryWait) {
throw new Error('opts.wait not supported sync for obvious reasons')
}
try {
var fd = fs.openSync(path, wx)
locks[path] = fd
return fd
} catch (er) {
if (er.code !== 'EEXIST') return retryThrow(path, opts, er)
if (opts.stale) {
var st = fs.statSync(path)
var age = Date.now() - st.ctime.getTime()
if (age > opts.stale) {
exports.unlockSync(path)
return exports.lockSync(path, opts)
}
}
// failed to lock!
return retryThrow(path, opts, er)
}
}
function retryThrow (path, opts, er) {
if (typeof opts.retries === 'number' && opts.retries > 0) {
var newRT = opts.retries - 1
var opts_ = Object.create(opts, { retries: { value: newRT }})
return exports.lockSync(path, opts_)
}
throw er
}
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