gio: add content_type_guess_for_filename helper

gio/src/content_type.rs

@@ -0,0 +1,27 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+use std::ptr;
+
+use glib::translate::*;
+
+use crate::ffi;
+
+/// Guesses the content type based on only a filename.
+///
+/// This function is equivalent to calling `g_content_type_guess()` with the `data` parameter set to NULL.
+///
+/// See [`crate::content_type_guess`] for more information.
+pub fn content_type_guess_for_filename(
+    filename: impl AsRef<std::path::Path>,
+) -> (glib::GString, bool) {
+    unsafe {
+        let mut result_uncertain = std::mem::MaybeUninit::uninit();
+        let ret = from_glib_full(ffi::g_content_type_guess(
+            filename.as_ref().to_glib_none().0,
+            ptr::null_mut(),
+            0,
+            result_uncertain.as_mut_ptr(),
+        ));
+        (ret, from_glib(result_uncertain.assume_init()))
+    }
+}

gio/src/lib.rs

@@ -21,6 +21,8 @@ mod async_initable;
 mod cancellable;
 mod cancellable_future;
 pub use crate::cancellable_future::{CancellableFuture, Cancelled};
+mod content_type;
+pub use self::content_type::content_type_guess_for_filename;
 mod converter;
 mod credentials;
 mod data_input_stream;

gio/tests/content_type.rs

@@ -0,0 +1,15 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+#[cfg(unix)]
+#[test]
+fn test_content_type_guess_for_filename() {
+    // We only test for directory and file without extension here as we can't guarantee the
+    // CI runners will have any mimetypes installed.
+    let filename = std::path::Path::new("test/");
+    let ret: (glib::GString, bool) = gio::content_type_guess_for_filename(filename);
+    assert_eq!(ret.0, "inode/directory");
+
+    let filename = std::path::Path::new("test");
+    let ret: (glib::GString, bool) = gio::content_type_guess_for_filename(filename);
+    assert_eq!(ret.0, "application/octet-stream");
+}