fs: use async directory processing in cp()

cjihrig · Linkgoron · commit 7487c2de364c · 2022-01-31T11:11:46.000+02:00
The readdir() functions do not scale well, which is why opendir(), etc. were introduced. This is exacerbated in the current cp() implementation, which calls readdir() recursively. This commit updates cp() to use the opendir() style iteration. PR-URL: nodejs#41351 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Tierney Cyren <hello@bnb.im> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
diff --git a/lib/internal/fs/cp/cp-sync.js b/lib/internal/fs/cp/cp-sync.js
@@ -32,7 +32,7 @@ const {
   existsSync,
   lstatSync,
   mkdirSync,
-  readdirSync,
+  opendirSync,
   readlinkSync,
   statSync,
   symlinkSync,
@@ -275,14 +275,22 @@ function mkDirAndCopy(srcMode, src, dest, opts) {
 }
 
 function copyDir(src, dest, opts) {
-  readdirSync(src).forEach((item) => copyDirItem(item, src, dest, opts));
-}
+  const dir = opendirSync(src);
+
+  try {
+    let dirent;
 
-function copyDirItem(item, src, dest, opts) {
-  const srcItem = join(src, item);
-  const destItem = join(dest, item);
-  const { destStat } = checkPathsSync(srcItem, destItem, opts);
-  return startCopy(destStat, srcItem, destItem, opts);
+    while ((dirent = dir.readSync()) !== null) {
+      const { name } = dirent;
+      const srcItem = join(src, name);
+      const destItem = join(dest, name);
+      const { destStat } = checkPathsSync(srcItem, destItem, opts);
+
+      startCopy(destStat, srcItem, destItem, opts);
+    }
+  } finally {
+    dir.closeSync();
+  }
 }
 
 function onLink(destStat, src, dest) {
diff --git a/lib/internal/fs/cp/cp.js b/lib/internal/fs/cp/cp.js
@@ -41,7 +41,7 @@ const {
   copyFile,
   lstat,
   mkdir,
-  readdir,
+  opendir,
   readlink,
   stat,
   symlink,
@@ -325,11 +325,11 @@ async function mkDirAndCopy(srcMode, src, dest, opts) {
 }
 
 async function copyDir(src, dest, opts) {
-  const dir = await readdir(src);
-  for (let i = 0; i < dir.length; i++) {
-    const item = dir[i];
-    const srcItem = join(src, item);
-    const destItem = join(dest, item);
+  const dir = await opendir(src);
+
+  for await (const { name } of dir) {
+    const srcItem = join(src, name);
+    const destItem = join(dest, name);
     const { destStat } = await checkPaths(srcItem, destItem, opts);
     await startCopy(destStat, srcItem, destItem, opts);
   }
