Add fallback impl for File::truncate and File::seek

- Fallback for `SetFilePointerEx` based on `SetFilePointer`
- Fallback for `SetFileInformationByHandle` with `FileEndOfFileInfo`
  based on `SetFilePointerEx` and `SetEndOfFile`

Author: seritools

library/std/src/sys/windows/c.rs

@@ -350,6 +350,52 @@ compat_fn_with_fallback! {
         GetSystemTime(&mut st);
         crate::sys::cvt(SystemTimeToFileTime(&st, lpSystemTimeAsFileTime)).unwrap();
     }
+
+    // >= 2000
+    // https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-setfilepointerex
+    pub fn SetFilePointerEx(
+        hfile: HANDLE,
+        lidistancetomove: i64,
+        lpnewfilepointer: *mut i64,
+        dwmovemethod: SET_FILE_POINTER_MOVE_METHOD,
+    ) -> BOOL {
+        let lDistanceToMove = lidistancetomove as i32;
+        let mut distance_to_move_high = (lidistancetomove >> 32) as i32;
+
+        let newPos_low = SetFilePointer(hfile, lDistanceToMove, &mut distance_to_move_high, dwmovemethod);
+
+        // since (-1 as u32) could be a valid value for the lower 32 bits of the new file pointer
+        // position, a call to GetLastError is needed to actually see if it failed
+        if newPos_low == INVALID_SET_FILE_POINTER && GetLastError() != NO_ERROR {
+            return FALSE;
+        }
+
+        if !lpnewfilepointer.is_null() {
+            *lpnewfilepointer = (distance_to_move_high as i64) << 32 | (newPos_low as i64);
+        }
+
+        TRUE
+    }
+}
+
+compat_fn_lazy! {
+    pub static KERNEL32: &CStr = c"kernel32" => { load: false, unicows: false };
+    // >= Vista / Server 2008 (XP / Server 2003 when linking a supported FileExtd.lib)
+    // https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-setfileinformationbyhandle
+    pub fn SetFileInformationByHandle(
+        hfile: HANDLE,
+        fileinformationclass: FILE_INFO_BY_HANDLE_CLASS,
+        lpfileinformation: *const ::core::ffi::c_void,
+        dwbuffersize: u32,
+    ) -> BOOL;
+    // >= Vista / Server 2008 (XP / Server 2003 when linking a supported FileExtd.lib)
+    // https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex
+    pub fn GetFileInformationByHandleEx(
+        hfile: HANDLE,
+        fileinformationclass: FILE_INFO_BY_HANDLE_CLASS,
+        lpfileinformation: *mut ::core::ffi::c_void,
+        dwbuffersize: u32,
+    ) -> BOOL;
 }
 
 compat_fn_optional! {

library/std/src/sys/windows/c/windows_sys.lst

@@ -2612,3 +2612,8 @@ Windows.Win32.System.Threading.CONDITION_VARIABLE
 // system time fallback
 Windows.Win32.System.SystemInformation.GetSystemTime
 Windows.Win32.System.Time.SystemTimeToFileTime
+
+// seek and truncate fallbacks
+Windows.Win32.Storage.FileSystem.SetFilePointer
+Windows.Win32.Storage.FileSystem.SetEndOfFile
+Windows.Win32.Storage.FileSystem.INVALID_SET_FILE_POINTER

library/std/src/sys/windows/c/windows_sys.rs

@@ -516,6 +516,10 @@ extern "system" {
     pub fn SetCurrentDirectoryW(lppathname: PCWSTR) -> BOOL;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn SetEndOfFile(hfile: HANDLE) -> BOOL;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn SetEnvironmentVariableW(lpname: PCWSTR, lpvalue: PCWSTR) -> BOOL;
 }
@@ -536,6 +540,15 @@ extern "system" {
     ) -> BOOL;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn SetFilePointer(
+        hfile: HANDLE,
+        ldistancetomove: i32,
+        lpdistancetomovehigh: *mut i32,
+        dwmovemethod: SET_FILE_POINTER_MOVE_METHOD,
+    ) -> u32;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn SetFilePointerEx(
         hfile: HANDLE,
@@ -3585,6 +3598,7 @@ impl ::core::clone::Clone for INIT_ONCE {
 }
 pub const INIT_ONCE_INIT_FAILED: u32 = 4u32;
 pub const INVALID_FILE_ATTRIBUTES: u32 = 4294967295u32;
+pub const INVALID_SET_FILE_POINTER: u32 = 4294967295u32;
 pub const INVALID_SOCKET: SOCKET = -1i32 as _;
 #[repr(C)]
 pub struct IN_ADDR {

library/std/src/sys/windows/fs.rs

@@ -308,22 +308,7 @@ impl File {
                 && creation == c::OPEN_ALWAYS
                 && unsafe { c::GetLastError() } == c::ERROR_ALREADY_EXISTS
             {
-                unsafe {
-                    // This originally used `FileAllocationInfo` instead of
-                    // `FileEndOfFileInfo` but that wasn't supported by WINE.
-                    // It's arguable which fits the semantics of `OpenOptions`
-                    // better so let's just use the more widely supported method.
-                    let eof = c::FILE_END_OF_FILE_INFO { EndOfFile: 0 };
-                    let result = c::SetFileInformationByHandle(
-                        handle.as_raw_handle(),
-                        c::FileEndOfFileInfo,
-                        ptr::addr_of!(eof).cast::<c_void>(),
-                        mem::size_of::<c::FILE_END_OF_FILE_INFO>() as u32,
-                    );
-                    if result == 0 {
-                        return Err(io::Error::last_os_error());
-                    }
-                }
+                Self::truncate_inner(handle.as_raw_handle(), 0)?
             }
             Ok(File { handle: Handle::from_inner(handle) })
         } else {
@@ -341,8 +326,30 @@ impl File {
     }
 
     pub fn truncate(&self, size: u64) -> io::Result<()> {
-        let info = c::FILE_END_OF_FILE_INFO { EndOfFile: size as i64 };
-        api::set_file_information_by_handle(self.handle.as_raw_handle(), &info).io_result()
+        Self::truncate_inner(self.handle.as_raw_handle(), size)
+    }
+
+    pub fn truncate_inner(handle: RawHandle, size: u64) -> io::Result<()> {
+        if c::SetFileInformationByHandle::option().is_some() {
+            let info = c::FILE_END_OF_FILE_INFO { EndOfFile: size as i64 };
+            api::set_file_information_by_handle(handle, &info).io_result()
+        } else {
+            let mut saved_pos = 0i64;
+            unsafe {
+                // get current file pointer position
+                cvt(c::SetFilePointerEx(handle, 0, &mut saved_pos, c::FILE_CURRENT))?;
+
+                // seek to new end position
+                cvt(c::SetFilePointerEx(handle, size as i64, ptr::null_mut(), c::FILE_BEGIN))?;
+
+                // set current position as end of file
+                cvt(c::SetEndOfFile(handle))?;
+
+                // go back to saved position
+                cvt(c::SetFilePointerEx(handle, saved_pos, ptr::null_mut(), c::FILE_BEGIN))?;
+            }
+            Ok(())
+        }
     }
 
     #[cfg(not(target_vendor = "uwp"))]
@@ -351,7 +358,9 @@ impl File {
             let mut info: c::BY_HANDLE_FILE_INFORMATION = mem::zeroed();
             cvt(c::GetFileInformationByHandle(self.handle.as_raw_handle(), &mut info))?;
             let mut reparse_tag = 0;
-            if info.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0 {
+            if info.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0
+                && c::GetFileInformationByHandleEx::option().is_some()
+            {
                 let mut attr_tag: c::FILE_ATTRIBUTE_TAG_INFO = mem::zeroed();
                 cvt(c::GetFileInformationByHandleEx(
                     self.handle.as_raw_handle(),

library/std/src/sys/windows/io.rs

@@ -121,6 +121,10 @@ unsafe fn msys_tty_on(handle: c::HANDLE) -> bool {
         return false;
     }
 
+    let Some(get_file_info_ex) = c::GetFileInformationByHandleEx::option() else {
+        return false;
+    };
+
     /// Mirrors [`FILE_NAME_INFO`], giving it a fixed length that we can stack
     /// allocate
     ///
@@ -133,7 +137,7 @@ unsafe fn msys_tty_on(handle: c::HANDLE) -> bool {
     }
     let mut name_info = FILE_NAME_INFO { FileNameLength: 0, FileName: [0; c::MAX_PATH as usize] };
     // Safety: buffer length is fixed.
-    let res = c::GetFileInformationByHandleEx(
+    let res = get_file_info_ex(
         handle,
         c::FileNameInfo,
         &mut name_info as *mut _ as *mut c_void,