Use tell for <File as Seek>::stream_position

Author: thaliaarchi

library/std/src/fs.rs

@@ -1229,6 +1229,9 @@ impl Seek for &File {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         self.inner.seek(pos)
     }
+    fn stream_position(&mut self) -> io::Result<u64> {
+        self.inner.tell()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1275,6 +1278,9 @@ impl Seek for File {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (&*self).seek(pos)
     }
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (&*self).stream_position()
+    }
 }
 
 #[stable(feature = "io_traits_arc", since = "1.73.0")]

library/std/src/sys/pal/hermit/fs.rs

@@ -425,6 +425,10 @@ impl File {
         Err(Error::from_raw_os_error(22))
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        Err(Error::from_raw_os_error(22))
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         Err(Error::from_raw_os_error(22))
     }

library/std/src/sys/pal/solid/fs.rs

@@ -465,6 +465,18 @@ impl File {
         }
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        unsafe {
+            let mut out_offset = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_Ftell(
+                self.fd.raw(),
+                out_offset.as_mut_ptr(),
+            ))
+            .map_err(|e| e.as_io_error())?;
+            Ok(out_offset.assume_init() as u64)
+        }
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         unsupported()
     }

library/std/src/sys/pal/uefi/fs.rs

@@ -258,6 +258,10 @@ impl File {
         self.0
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        self.0
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         self.0
     }

library/std/src/sys/pal/unix/fs.rs

@@ -1438,6 +1438,11 @@ impl File {
         Ok(n as u64)
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        let n = cvt(unsafe { lseek64(self.as_raw_fd(), 0, libc::SEEK_CUR) })?;
+        Ok(n as u64)
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         self.0.duplicate().map(File)
     }

library/std/src/sys/pal/unsupported/fs.rs

@@ -258,6 +258,10 @@ impl File {
         self.0
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        self.0
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         self.0
     }

library/std/src/sys/pal/wasi/fs.rs

@@ -517,6 +517,10 @@ impl File {
         self.fd.seek(pos)
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        self.fd.tell()
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         // https://github.com/CraneStation/wasmtime/blob/master/docs/WASI-rationale.md#why-no-dup
         unsupported()

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

@@ -631,6 +631,14 @@ impl File {
         Ok(newpos as u64)
     }
 
+    pub fn tell(&self) -> io::Result<u64> {
+        let mut newpos = 0;
+        cvt(unsafe {
+            c::SetFilePointerEx(self.handle.as_raw_handle(), 0, &mut newpos, c::FILE_CURRENT)
+        })?;
+        Ok(newpos as u64)
+    }
+
     pub fn duplicate(&self) -> io::Result<File> {
         Ok(Self { handle: self.handle.try_clone()? })
     }