From 078def0ff8501bb07f3f286515acd8c6a2181037 Mon Sep 17 00:00:00 2001
From: Divy Srivastava <dj.srivastava23@gmail.com>
Date: Wed, 17 Jul 2024 05:35:51 -0700
Subject: perf(ext/node): optimize fs.exists[Sync] (#24613)

Use `access` on *nix and `GetFileAttributesW` on Windows.

[Benchmark](https://paste.divy.work/p/-gq8Ark.js):
```
$ deno run -A bench.mjs # main (568dd)
existsSync: 8980.636629ms

$ target/release/deno run -A bench.mjs # this PR
existsSync: 6448.7604519999995ms

$ bun bench.mjs
existsSync: 6562.88671ms

$ node bench.mjs
existsSync: 7740.064653ms
```

Ref https://github.com/denoland/deno/pull/24434#discussion_r1679777912
---
 ext/fs/interface.rs |  3 +++
 ext/fs/std_fs.rs    | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

(limited to 'ext/fs')

diff --git a/ext/fs/interface.rs b/ext/fs/interface.rs
index 2fdfa2186..09e16aff1 100644
--- a/ext/fs/interface.rs
+++ b/ext/fs/interface.rs
@@ -315,6 +315,9 @@ pub trait FileSystem: std::fmt::Debug + MaybeSend + MaybeSync {
   fn exists_sync(&self, path: &Path) -> bool {
     self.stat_sync(path).is_ok()
   }
+  async fn exists_async(&self, path: PathBuf) -> FsResult<bool> {
+    Ok(self.stat_async(path).await.is_ok())
+  }
 
   fn read_text_file_lossy_sync(
     &self,
diff --git a/ext/fs/std_fs.rs b/ext/fs/std_fs.rs
index 7903700c3..7fc33a8ad 100644
--- a/ext/fs/std_fs.rs
+++ b/ext/fs/std_fs.rs
@@ -173,6 +173,15 @@ impl FileSystem for RealFs {
     spawn_blocking(move || lstat(&path)).await?.map(Into::into)
   }
 
+  fn exists_sync(&self, path: &Path) -> bool {
+    exists(path)
+  }
+  async fn exists_async(&self, path: PathBuf) -> FsResult<bool> {
+    spawn_blocking(move || exists(&path))
+      .await
+      .map_err(Into::into)
+  }
+
   fn realpath_sync(&self, path: &Path) -> FsResult<PathBuf> {
     realpath(path)
   }
@@ -837,6 +846,32 @@ fn stat_extra(
   }
 }
 
+fn exists(path: &Path) -> bool {
+  #[cfg(unix)]
+  {
+    use nix::unistd::access;
+    use nix::unistd::AccessFlags;
+    access(path, AccessFlags::F_OK).is_ok()
+  }
+
+  #[cfg(windows)]
+  {
+    use std::os::windows::ffi::OsStrExt;
+    use winapi::um::fileapi::GetFileAttributesW;
+    use winapi::um::fileapi::INVALID_FILE_ATTRIBUTES;
+
+    let path = path
+      .as_os_str()
+      .encode_wide()
+      .chain(std::iter::once(0))
+      .collect::<Vec<_>>();
+    // Safety: `path` is a null-terminated string
+    let attrs = unsafe { GetFileAttributesW(path.as_ptr()) };
+
+    attrs != INVALID_FILE_ATTRIBUTES
+  }
+}
+
 fn realpath(path: &Path) -> FsResult<PathBuf> {
   Ok(deno_core::strip_unc_prefix(path.canonicalize()?))
 }
-- 
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