fs: include more fs.stat*() optimizations

Including:

* Move async *stat() functions to FillStatsArray() now used by the
sync *stat() functions

* Avoid creating fs.Stats instances for implicit async/sync *stat()
calls used in various fs functions

* Store reference to Float64Array data on C++ side for easier/faster
access, instead of passing from JS to C++ on every async/sync *stat()
call

PR-URL: https://github.com/nodejs/node/pull/11665
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

1 files changed, 100 insertions, 53 deletions

diff --git a/lib/fs.js b/lib/fs.js
index d8ae0b09ba..7b50412ea7 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -25,6 +25,7 @@
 'use strict';
 
 const constants = process.binding('constants').fs;
+const { S_IFMT, S_IFREG, S_IFLNK } = constants;
 const util = require('util');
 const pathModule = require('path');
 const { isUint8Array } = process.binding('util');
@@ -135,6 +136,24 @@ function makeCallback(cb) {
   };
 }
 
+// Special case of `makeCallback()` that is specific to async `*stat()` calls as
+// an optimization, since the data passed back to the callback needs to be
+// transformed anyway.
+function makeStatsCallback(cb) {
+  if (cb === undefined) {
+    return rethrow();
+  }
+
+  if (typeof cb !== 'function') {
+    throw new TypeError('"callback" argument must be a function');
+  }
+
+  return function(err) {
+    if (err) return cb(err);
+    cb(err, statsFromValues());
+  };
+}
+
 function nullCheck(path, callback) {
   if (('' + path).indexOf('\u0000') !== -1) {
     var er = new Error('Path must be a string without null bytes');
@@ -151,7 +170,7 @@ function isFd(path) {
   return (path >>> 0) === path;
 }
 
-// Static method to set the stats properties on a Stats object.
+// Constructor for file stats.
 function Stats(
     dev,
     mode,
@@ -184,41 +203,49 @@ function Stats(
 }
 fs.Stats = Stats;
 
-// Create a C++ binding to the function which creates a Stats object.
-binding.FSInitialize(fs.Stats);
-
-fs.Stats.prototype._checkModeProperty = function(property) {
-  return ((this.mode & constants.S_IFMT) === property);
+Stats.prototype._checkModeProperty = function(property) {
+  return ((this.mode & S_IFMT) === property);
 };
 
-fs.Stats.prototype.isDirectory = function() {
+Stats.prototype.isDirectory = function() {
   return this._checkModeProperty(constants.S_IFDIR);
 };
 
-fs.Stats.prototype.isFile = function() {
-  return this._checkModeProperty(constants.S_IFREG);
+Stats.prototype.isFile = function() {
+  return this._checkModeProperty(S_IFREG);
 };
 
-fs.Stats.prototype.isBlockDevice = function() {
+Stats.prototype.isBlockDevice = function() {
   return this._checkModeProperty(constants.S_IFBLK);
 };
 
-fs.Stats.prototype.isCharacterDevice = function() {
+Stats.prototype.isCharacterDevice = function() {
   return this._checkModeProperty(constants.S_IFCHR);
 };
 
-fs.Stats.prototype.isSymbolicLink = function() {
-  return this._checkModeProperty(constants.S_IFLNK);
+Stats.prototype.isSymbolicLink = function() {
+  return this._checkModeProperty(S_IFLNK);
 };
 
-fs.Stats.prototype.isFIFO = function() {
+Stats.prototype.isFIFO = function() {
   return this._checkModeProperty(constants.S_IFIFO);
 };
 
-fs.Stats.prototype.isSocket = function() {
+Stats.prototype.isSocket = function() {
   return this._checkModeProperty(constants.S_IFSOCK);
 };
 
+const statValues = binding.getStatValues();
+
+function statsFromValues() {
+  return new Stats(statValues[0], statValues[1], statValues[2], statValues[3],
+                   statValues[4], statValues[5],
+                   statValues[6] < 0 ? undefined : statValues[6], statValues[7],
+                   statValues[8], statValues[9] < 0 ? undefined : statValues[9],
+                   statValues[10], statValues[11], statValues[12],
+                   statValues[13]);
+}
+
 // Don't allow mode to accidentally be overwritten.
 ['F_OK', 'R_OK', 'W_OK', 'X_OK'].forEach(function(key) {
   Object.defineProperty(fs, key, {
@@ -275,7 +302,7 @@ fs.exists = function(path, callback) {
   var req = new FSReqWrap();
   req.oncomplete = cb;
   binding.stat(pathModule._makeLong(path), req);
-  function cb(err, stats) {
+  function cb(err) {
     if (callback) callback(err ? false : true);
   }
 };
@@ -284,7 +311,7 @@ fs.existsSync = function(path) {
   try {
     handleError((path = getPathFromURL(path)));
     nullCheck(path);
-    binding.stat(pathModule._makeLong(path), statValues);
+    binding.stat(pathModule._makeLong(path));
     return true;
   } catch (e) {
     return false;
@@ -387,13 +414,19 @@ function readFileAfterOpen(err, fd) {
   binding.fstat(fd, req);
 }
 
-function readFileAfterStat(err, st) {
+function readFileAfterStat(err) {
   var context = this.context;
 
   if (err)
     return context.close(err);
 
-  var size = context.size = st.isFile() ? st.size : 0;
+  // Use stats array directly to avoid creating an fs.Stats instance just for
+  // our internal use.
+  var size;
+  if ((statValues[1/*mode*/] & S_IFMT) === S_IFREG)
+    size = context.size = statValues[8/*size*/];
+  else
+    size = context.size = 0;
 
   if (size === 0) {
     context.buffers = [];
@@ -467,14 +500,13 @@ function tryToString(buf, encoding, callback) {
 
 function tryStatSync(fd, isUserFd) {
   var threw = true;
-  var st;
   try {
-    st = fs.fstatSync(fd);
+    binding.fstat(fd);
     threw = false;
   } finally {
     if (threw && !isUserFd) fs.closeSync(fd);
   }
-  return st;
+  return !threw;
 }
 
 function tryCreateBuffer(size, fd, isUserFd) {
@@ -506,8 +538,13 @@ fs.readFileSync = function(path, options) {
   var isUserFd = isFd(path); // file descriptor ownership
   var fd = isUserFd ? path : fs.openSync(path, options.flag || 'r', 0o666);
 
-  var st = tryStatSync(fd, isUserFd);
-  var size = st.isFile() ? st.size : 0;
+  // Use stats array directly to avoid creating an fs.Stats instance just for
+  // our internal use.
+  var size;
+  if (tryStatSync(fd, isUserFd) && (statValues[1/*mode*/] & S_IFMT) === S_IFREG)
+    size = statValues[8/*size*/];
+  else
+    size = 0;
   var pos = 0;
   var buffer; // single buffer with file data
   var buffers; // list for when size is unknown
@@ -854,12 +891,12 @@ fs.readdirSync = function(path, options) {
 
 fs.fstat = function(fd, callback) {
   var req = new FSReqWrap();
-  req.oncomplete = makeCallback(callback);
+  req.oncomplete = makeStatsCallback(callback);
   binding.fstat(fd, req);
 };
 
 fs.lstat = function(path, callback) {
-  callback = makeCallback(callback);
+  callback = makeStatsCallback(callback);
   if (handleError((path = getPathFromURL(path)), callback))
     return;
   if (!nullCheck(path, callback)) return;
@@ -869,7 +906,7 @@ fs.lstat = function(path, callback) {
 };
 
 fs.stat = function(path, callback) {
-  callback = makeCallback(callback);
+  callback = makeStatsCallback(callback);
   if (handleError((path = getPathFromURL(path)), callback))
     return;
   if (!nullCheck(path, callback)) return;
@@ -878,32 +915,22 @@ fs.stat = function(path, callback) {
   binding.stat(pathModule._makeLong(path), req);
 };
 
-const statValues = new Float64Array(14);
-function statsFromValues() {
-  return new Stats(statValues[0], statValues[1], statValues[2], statValues[3],
-                   statValues[4], statValues[5],
-                   statValues[6] < 0 ? undefined : statValues[6], statValues[7],
-                   statValues[8], statValues[9] < 0 ? undefined : statValues[9],
-                   statValues[10], statValues[11], statValues[12],
-                   statValues[13]);
-}
-
 fs.fstatSync = function(fd) {
-  binding.fstat(fd, statValues);
+  binding.fstat(fd);
   return statsFromValues();
 };
 
 fs.lstatSync = function(path) {
   handleError((path = getPathFromURL(path)));
   nullCheck(path);
-  binding.lstat(pathModule._makeLong(path), statValues);
+  binding.lstat(pathModule._makeLong(path));
   return statsFromValues();
 };
 
 fs.statSync = function(path) {
   handleError((path = getPathFromURL(path)));
   nullCheck(path);
-  binding.stat(pathModule._makeLong(path), statValues);
+  binding.stat(pathModule._makeLong(path));
   return statsFromValues();
 };
 
@@ -1380,6 +1407,15 @@ function emitStop(self) {
   self.emit('stop');
 }
 
+function statsFromPrevValues() {
+  return new Stats(statValues[14], statValues[15], statValues[16],
+                   statValues[17], statValues[18], statValues[19],
+                   statValues[20] < 0 ? undefined : statValues[20],
+                   statValues[21], statValues[22],
+                   statValues[23] < 0 ? undefined : statValues[23],
+                   statValues[24], statValues[25], statValues[26],
+                   statValues[27]);
+}
 function StatWatcher() {
   EventEmitter.call(this);
 
@@ -1390,13 +1426,13 @@ function StatWatcher() {
   // the sake of backwards compatibility
   var oldStatus = -1;
 
-  this._handle.onchange = function(current, previous, newStatus) {
+  this._handle.onchange = function(newStatus) {
     if (oldStatus === -1 &&
         newStatus === -1 &&
-        current.nlink === previous.nlink) return;
+        statValues[2/*new nlink*/] === statValues[16/*old nlink*/]) return;
 
     oldStatus = newStatus;
-    self.emit('change', current, previous);
+    self.emit('change', statsFromValues(), statsFromPrevValues());
   };
 
   this._handle.onstop = function() {
@@ -1544,7 +1580,7 @@ fs.realpathSync = function realpathSync(p, options) {
 
   // On windows, check that the root exists. On unix there is no need.
   if (isWindows && !knownHard[base]) {
-    fs.lstatSync(base);
+    binding.lstat(pathModule._makeLong(base));
     knownHard[base] = true;
   }
 
@@ -1576,8 +1612,12 @@ fs.realpathSync = function realpathSync(p, options) {
     if (maybeCachedResolved) {
       resolvedLink = maybeCachedResolved;
     } else {
-      var stat = fs.lstatSync(base);
-      if (!stat.isSymbolicLink()) {
+      // Use stats array directly to avoid creating an fs.Stats instance just
+      // for our internal use.
+
+      binding.lstat(pathModule._makeLong(base));
+
+      if ((statValues[1/*mode*/] & S_IFMT) !== S_IFLNK) {
         knownHard[base] = true;
         if (cache) cache.set(base, base);
         continue;
@@ -1588,14 +1628,16 @@ fs.realpathSync = function realpathSync(p, options) {
       var linkTarget = null;
       var id;
       if (!isWindows) {
-        id = `${stat.dev.toString(32)}:${stat.ino.toString(32)}`;
+        var dev = statValues[0/*dev*/].toString(32);
+        var ino = statValues[7/*ino*/].toString(32);
+        id = `${dev}:${ino}`;
         if (seenLinks.hasOwnProperty(id)) {
           linkTarget = seenLinks[id];
         }
       }
       if (linkTarget === null) {
-        fs.statSync(base);
-        linkTarget = fs.readlinkSync(base);
+        binding.stat(pathModule._makeLong(base));
+        linkTarget = binding.readlink(pathModule._makeLong(base));
       }
       resolvedLink = pathModule.resolve(previous, linkTarget);
 
@@ -1614,7 +1656,7 @@ fs.realpathSync = function realpathSync(p, options) {
 
     // On windows, check that the root exists. On unix there is no need.
     if (isWindows && !knownHard[base]) {
-      fs.lstatSync(base);
+      binding.lstat(pathModule._makeLong(base));
       knownHard[base] = true;
     }
   }
@@ -1694,11 +1736,14 @@ fs.realpath = function realpath(p, options, callback) {
     return fs.lstat(base, gotStat);
   }
 
-  function gotStat(err, stat) {
+  function gotStat(err) {
     if (err) return callback(err);
 
+    // Use stats array directly to avoid creating an fs.Stats instance just for
+    // our internal use.
+
     // if not a symlink, skip to the next path part
-    if (!stat.isSymbolicLink()) {
+    if ((statValues[1/*mode*/] & S_IFMT) !== S_IFLNK) {
       knownHard[base] = true;
       return process.nextTick(LOOP);
     }
@@ -1708,7 +1753,9 @@ fs.realpath = function realpath(p, options, callback) {
     // dev/ino always return 0 on windows, so skip the check.
     let id;
     if (!isWindows) {
-      id = `${stat.dev.toString(32)}:${stat.ino.toString(32)}`;
+      var dev = statValues[0/*ino*/].toString(32);
+      var ino = statValues[7/*ino*/].toString(32);
+      id = `${dev}:${ino}`;
       if (seenLinks.hasOwnProperty(id)) {
         return gotTarget(null, seenLinks[id], base);
       }