unpack: accept fflag as an option

README.md

@@ -335,6 +335,7 @@ advanced use cases, such as re-using caches between runs.
   Defaults to 16 MB.
 - `umask` Filter the modes of entries like `process.umask()`.
 - `dmode` Default mode for directories
+- `fflag` Default flag for files
 - `fmode` Default mode for files
 - `dirCache` A Map object of which directories exist.
 - `maxMetaEntrySize` The maximum size of meta entries that is
@@ -599,6 +600,7 @@ Most unpack errors will cause a `warn` event to be emitted.  If the
   any warnings encountered.
 - `umask` Filter the modes of entries like `process.umask()`.
 - `dmode` Default mode for directories
+- `fflag` Default flag for files
 - `fmode` Default mode for files
 - `dirCache` A Map object of which directories exist.
 - `maxMetaEntrySize` The maximum size of meta entries that is

benchmarks/extract/node-tar-fmap-async.js

@@ -0,0 +1,17 @@
+const cwd = __dirname + '/cwd'
+const rimraf = require('rimraf')
+rimraf.sync(cwd)
+require('mkdirp').sync(cwd)
+process.on('exit', _ => rimraf.sync(cwd))
+const path = require('path')
+const file = process.argv[2] || path.resolve(__dirname, '../npm.tar')
+const fs = require('fs')
+const { O_CREAT, O_TRUNC, O_WRONLY, UV_FS_O_FILEMAP = 0 } = fs.constants
+
+const tar = require('../..')
+const timer = require('../timer.js')()
+tar.x({
+  fflag: (UV_FS_O_FILEMAP | O_TRUNC | O_CREAT | O_WRONLY),
+  file: file,
+  cwd: cwd
+}).then(timer)

benchmarks/extract/node-tar-fmap-sync.js

@@ -0,0 +1,19 @@
+const cwd = __dirname + '/cwd'
+const rimraf = require('rimraf')
+rimraf.sync(cwd)
+require('mkdirp').sync(cwd)
+process.on('exit', _ => rimraf.sync(cwd))
+const path = require('path')
+const file = process.argv[2] || path.resolve(__dirname, '../npm.tar')
+const fs = require('fs')
+const { O_CREAT, O_TRUNC, O_WRONLY, UV_FS_O_FILEMAP = 0 } = fs.constants
+
+const tar = require('../..')
+const timer = require('../timer.js')()
+tar.x({
+  fflag: (UV_FS_O_FILEMAP | O_TRUNC | O_CREAT | O_WRONLY),
+  file: file,
+  sync: true,
+  cwd: cwd
+})
+timer()

lib/unpack.js

@@ -159,6 +159,7 @@ class Unpack extends Parser {
     this.umask = typeof opt.umask === 'number' ? opt.umask : this.processUmask
     // default mode for dirs created as parents
     this.dmode = opt.dmode || (0o0777 & (~this.umask))
+    this.fflag = opt.fflag || 'w'
     this.fmode = opt.fmode || (0o0666 & (~this.umask))
     this.on('entry', entry => this[ONENTRY](entry))
   }
@@ -294,6 +295,7 @@ class Unpack extends Parser {
   [FILE] (entry) {
     const mode = entry.mode & 0o7777 || this.fmode
     const stream = new fsm.WriteStream(entry.absolute, {
+      flags: this.fflag,
       mode: mode,
       autoClose: false
     })
@@ -515,7 +517,7 @@ class UnpackSync extends Unpack {
     let stream
     let fd
     try {
-      fd = fs.openSync(entry.absolute, 'w', mode)
+      fd = fs.openSync(entry.absolute, this.fflag, mode)
     } catch (er) {
       return oner(er)
     }

test/unpack.js

@@ -11,6 +11,7 @@ const makeTar = require('./make-tar.js')
 const Header = require('../lib/header.js')
 const z = require('minizlib')
 const fs = require('fs')
+const { O_CREAT, O_TRUNC, O_WRONLY, UV_FS_O_FILEMAP = 0 } = fs.constants
 const path = require('path')
 const fixtures = path.resolve(__dirname, 'fixtures')
 const files = path.resolve(fixtures, 'files')
@@ -100,7 +101,7 @@ t.test('basic file unpack tests', t => {
       t.plan(2)
 
       t.test('async unpack', t => {
-        t.plan(2)
+        t.plan(3)
         t.test('strict', t => {
           const unpack = new Unpack({ cwd: linkdir, strict: true })
           fs.createReadStream(tf).pipe(unpack)
@@ -111,10 +112,16 @@ t.test('basic file unpack tests', t => {
           fs.createReadStream(tf).pipe(unpack)
           eos(unpack, _ => check(t))
         })
+        t.test('fmap', t => {
+          const mw = UV_FS_O_FILEMAP | O_TRUNC | O_CREAT | O_WRONLY
+          const unpack = new Unpack({ cwd: linkdir, fflag: mw })
+          fs.createReadStream(tf).pipe(unpack)
+          eos(unpack, _ => check(t))
+        })
       })
 
       t.test('sync unpack', t => {
-        t.plan(2)
+        t.plan(3)
         t.test('strict', t => {
           const unpack = new UnpackSync({ cwd: linkdir })
           unpack.end(fs.readFileSync(tf))
@@ -125,6 +132,12 @@ t.test('basic file unpack tests', t => {
           unpack.end(fs.readFileSync(tf))
           check(t)
         })
+        t.test('fmap', t => {
+          const mw = UV_FS_O_FILEMAP | O_TRUNC | O_CREAT | O_WRONLY
+          const unpack = new UnpackSync({ cwd: linkdir, fflag: mw })
+          unpack.end(fs.readFileSync(tf))
+          check(t)
+        })
       })
     })
   })