Add a method for setting permissions directly on an open file.

On unix like systems, the underlying file corresponding to any given path may
change at any time. This function makes it possible to set the permissions of
the a file corresponding to a `File` object even if its path changes.

3 files changed, 32 insertions, 0 deletions

diff --git a/src/libstd/sys/unix/fs.rs b/src/libstd/sys/unix/fs.rs
index 0b43fd2ac8c..9ee0458b5da 100644
--- a/src/libstd/sys/unix/fs.rs
+++ b/src/libstd/sys/unix/fs.rs
@@ -526,6 +526,11 @@ impl File {
     pub fn fd(&self) -> &FileDesc { &self.0 }
 
     pub fn into_fd(self) -> FileDesc { self.0 }
+
+    pub fn set_permissions(&self, perm: FilePermissions) -> io::Result<()> {
+        cvt_r(|| unsafe { libc::fchmod(self.0.raw(), perm.mode) })?;
+        Ok(())
+    }
 }
 
 impl DirBuilder {
diff --git a/src/libstd/sys/windows/c.rs b/src/libstd/sys/windows/c.rs
index dfc998b88e3..1a563127f7f 100644
--- a/src/libstd/sys/windows/c.rs
+++ b/src/libstd/sys/windows/c.rs
@@ -390,6 +390,15 @@ pub enum FILE_INFO_BY_HANDLE_CLASS {
 }
 
 #[repr(C)]
+pub struct FILE_BASIC_INFO {
+    pub CreationTime: LARGE_INTEGER,
+    pub LastAccessTime: LARGE_INTEGER,
+    pub LastWriteTime: LARGE_INTEGER,
+    pub ChangeTime: LARGE_INTEGER,
+    pub FileAttributes: DWORD,
+}
+
+#[repr(C)]
 pub struct FILE_END_OF_FILE_INFO {
     pub EndOfFile: LARGE_INTEGER,
 }
diff --git a/src/libstd/sys/windows/fs.rs b/src/libstd/sys/windows/fs.rs
index 98fd15f863b..7d7d78bbd87 100644
--- a/src/libstd/sys/windows/fs.rs
+++ b/src/libstd/sys/windows/fs.rs
@@ -417,6 +417,24 @@ impl File {
             Ok(PathBuf::from(OsString::from_wide(subst)))
         }
     }
+
+    pub fn set_permissions(&self, perm: FilePermissions) -> io::Result<()> {
+        let mut info = c::FILE_BASIC_INFO {
+            CreationTime: 0,
+            LastAccessTime: 0,
+            LastWriteTime: 0,
+            ChangeTime: 0,
+            FileAttributes: perm.attrs,
+        };
+        let size = mem::size_of_val(&info);
+        cvt(unsafe {
+            c::SetFileInformationByHandle(self.handle.raw(),
+                                          c::FileBasicInfo,
+                                          &mut info as *mut _ as *mut _,
+                                          size as c::DWORD)
+        })?;
+        Ok(())
+    }
 }
 
 impl FromInner<c::HANDLE> for File {