From 610eedc2da262f245502e7c35c1fbb8b438d498c Mon Sep 17 00:00:00 2001
From: Julius Liu <juliusl@microsoft.com>
Date: Mon, 5 Jun 2023 15:59:29 -0700
Subject: [PATCH] Feat. adding ext that returns change_time for Windows

---
 library/std/src/os/windows/fs.rs      | 11 +++++++++++
 library/std/src/sys/pal/windows/fs.rs | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/library/std/src/os/windows/fs.rs b/library/std/src/os/windows/fs.rs
index e9d7a13e9d5b2..9180b6433251b 100644
--- a/library/std/src/os/windows/fs.rs
+++ b/library/std/src/os/windows/fs.rs
@@ -471,6 +471,14 @@ pub trait MetadataExt {
     /// `fs::metadata` or `File::metadata`, then this will return `Some`.
     #[unstable(feature = "windows_by_handle", issue = "63010")]
     fn file_index(&self) -> Option<u64>;
+
+
+    /// Returns the change time, which is the last time file metadata was changed, such as 
+    /// renames, attributes, etc.
+    /// 
+    /// This will return `None` if the `Metdata` instance was not created using the FILE_BASIC_INFO type,
+    #[unstable(feature = "windows_change_time", issue = "121478")]
+    fn change_time(&self) -> Option<u64>;
 }
 
 #[stable(feature = "metadata_ext", since = "1.1.0")]
@@ -499,6 +507,9 @@ impl MetadataExt for Metadata {
     fn file_index(&self) -> Option<u64> {
         self.as_inner().file_index()
     }
+    fn change_time(&self) -> Option<u64> {
+        self.as_inner().changed_u64()
+    }
 }
 
 /// Windows-specific extensions to [`fs::FileType`].
diff --git a/library/std/src/sys/pal/windows/fs.rs b/library/std/src/sys/pal/windows/fs.rs
index b82a83ae7a3e8..c409961330661 100644
--- a/library/std/src/sys/pal/windows/fs.rs
+++ b/library/std/src/sys/pal/windows/fs.rs
@@ -29,6 +29,7 @@ pub struct FileAttr {
     creation_time: c::FILETIME,
     last_access_time: c::FILETIME,
     last_write_time: c::FILETIME,
+    change_time: Option<c::FILETIME>,
     file_size: u64,
     reparse_tag: c::DWORD,
     volume_serial_number: Option<u32>,
@@ -375,6 +376,7 @@ impl File {
                 creation_time: info.ftCreationTime,
                 last_access_time: info.ftLastAccessTime,
                 last_write_time: info.ftLastWriteTime,
+                change_time: None, // Only available in FILE_BASIC_INFO
                 file_size: (info.nFileSizeLow as u64) | ((info.nFileSizeHigh as u64) << 32),
                 reparse_tag,
                 volume_serial_number: Some(info.dwVolumeSerialNumber),
@@ -411,6 +413,10 @@ impl File {
                     dwLowDateTime: info.LastWriteTime as c::DWORD,
                     dwHighDateTime: (info.LastWriteTime >> 32) as c::DWORD,
                 },
+                change_time: Some(c::FILETIME {
+                    dhLowDateTime: info.ChangeTime as c::DWORD,
+                    dhHighDateTime: (info.ChangeTime >> 32) as c::DWORD,
+                }),
                 file_size: 0,
                 reparse_tag: 0,
                 volume_serial_number: None,
@@ -952,6 +958,10 @@ impl FileAttr {
         to_u64(&self.creation_time)
     }
 
+    pub fn changed_u64(&self) -> Option<u64> {
+        self.change_time.as_ref().map(|c| to_u64(c))
+    }
+
     pub fn volume_serial_number(&self) -> Option<u32> {
         self.volume_serial_number
     }
@@ -971,6 +981,7 @@ impl From<c::WIN32_FIND_DATAW> for FileAttr {
             creation_time: wfd.ftCreationTime,
             last_access_time: wfd.ftLastAccessTime,
             last_write_time: wfd.ftLastWriteTime,
+            change_time: None,
             file_size: ((wfd.nFileSizeHigh as u64) << 32) | (wfd.nFileSizeLow as u64),
             reparse_tag: if wfd.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0 {
                 // reserved unless this is a reparse point