// A path exclusive reservation system
|
// reserve([list, of, paths], fn)
|
// When the fn is first in line for all its paths, it
|
// is called with a cb that clears the reservation.
|
//
|
// Used by async unpack to avoid clobbering paths in use,
|
// while still allowing maximal safe parallelization.
|
|
const assert = require('assert')
|
const normalize = require('./normalize-unicode.js')
|
const stripSlashes = require('./strip-trailing-slashes.js')
|
const { join } = require('path')
|
|
const platform = process.env.TESTING_TAR_FAKE_PLATFORM || process.platform
|
const isWindows = platform === 'win32'
|
|
module.exports = () => {
|
// path => [function or Set]
|
// A Set object means a directory reservation
|
// A fn is a direct reservation on that path
|
const queues = new Map()
|
|
// fn => {paths:[path,...], dirs:[path, ...]}
|
const reservations = new Map()
|
|
// return a set of parent dirs for a given path
|
// '/a/b/c/d' -> ['/', '/a', '/a/b', '/a/b/c', '/a/b/c/d']
|
const getDirs = path => {
|
const dirs = path.split('/').slice(0, -1).reduce((set, path) => {
|
if (set.length) {
|
path = join(set[set.length - 1], path)
|
}
|
set.push(path || '/')
|
return set
|
}, [])
|
return dirs
|
}
|
|
// functions currently running
|
const running = new Set()
|
|
// return the queues for each path the function cares about
|
// fn => {paths, dirs}
|
const getQueues = fn => {
|
const res = reservations.get(fn)
|
/* istanbul ignore if - unpossible */
|
if (!res) {
|
throw new Error('function does not have any path reservations')
|
}
|
return {
|
paths: res.paths.map(path => queues.get(path)),
|
dirs: [...res.dirs].map(path => queues.get(path)),
|
}
|
}
|
|
// check if fn is first in line for all its paths, and is
|
// included in the first set for all its dir queues
|
const check = fn => {
|
const { paths, dirs } = getQueues(fn)
|
return paths.every(q => q[0] === fn) &&
|
dirs.every(q => q[0] instanceof Set && q[0].has(fn))
|
}
|
|
// run the function if it's first in line and not already running
|
const run = fn => {
|
if (running.has(fn) || !check(fn)) {
|
return false
|
}
|
running.add(fn)
|
fn(() => clear(fn))
|
return true
|
}
|
|
const clear = fn => {
|
if (!running.has(fn)) {
|
return false
|
}
|
|
const { paths, dirs } = reservations.get(fn)
|
const next = new Set()
|
|
paths.forEach(path => {
|
const q = queues.get(path)
|
assert.equal(q[0], fn)
|
if (q.length === 1) {
|
queues.delete(path)
|
} else {
|
q.shift()
|
if (typeof q[0] === 'function') {
|
next.add(q[0])
|
} else {
|
q[0].forEach(fn => next.add(fn))
|
}
|
}
|
})
|
|
dirs.forEach(dir => {
|
const q = queues.get(dir)
|
assert(q[0] instanceof Set)
|
if (q[0].size === 1 && q.length === 1) {
|
queues.delete(dir)
|
} else if (q[0].size === 1) {
|
q.shift()
|
|
// must be a function or else the Set would've been reused
|
next.add(q[0])
|
} else {
|
q[0].delete(fn)
|
}
|
})
|
running.delete(fn)
|
|
next.forEach(fn => run(fn))
|
return true
|
}
|
|
const reserve = (paths, fn) => {
|
// collide on matches across case and unicode normalization
|
// On windows, thanks to the magic of 8.3 shortnames, it is fundamentally
|
// impossible to determine whether two paths refer to the same thing on
|
// disk, without asking the kernel for a shortname.
|
// So, we just pretend that every path matches every other path here,
|
// effectively removing all parallelization on windows.
|
paths = isWindows ? ['win32 parallelization disabled'] : paths.map(p => {
|
// don't need normPath, because we skip this entirely for windows
|
return normalize(stripSlashes(join(p))).toLowerCase()
|
})
|
|
const dirs = new Set(
|
paths.map(path => getDirs(path)).reduce((a, b) => a.concat(b))
|
)
|
reservations.set(fn, { dirs, paths })
|
paths.forEach(path => {
|
const q = queues.get(path)
|
if (!q) {
|
queues.set(path, [fn])
|
} else {
|
q.push(fn)
|
}
|
})
|
dirs.forEach(dir => {
|
const q = queues.get(dir)
|
if (!q) {
|
queues.set(dir, [new Set([fn])])
|
} else if (q[q.length - 1] instanceof Set) {
|
q[q.length - 1].add(fn)
|
} else {
|
q.push(new Set([fn]))
|
}
|
})
|
|
return run(fn)
|
}
|
|
return { check, reserve }
|
}
|
