implement FusedIterator, DoubleEndedIterator, and nth[_back] for driver iterators

changelog.md

@@ -16,6 +16,8 @@ when upgrading from a version of rust-sdl2 to another.
 
 [PR #1332](https://github.com/Rust-SDL2/rust-sdl2/pull/1332) Fix `size_hint` implementations for `{audio,video,render}::DriverIterator`
 
+[PR #1333](https://github.com/Rust-SDL2/rust-sdl2/pull/1333) Implement `FusedIterator`, `DoubleEndedIterator`, `and nth[_back]` for `{audio,video,render}::DriverIterator`
+
 [PR #1337](https://github.com/Rust-SDL2/rust-sdl2/pull/1337) Fix "Cannot initialize Sdl from more than one thread" for tests / CI
 
 ### v0.35.2

src/sdl2/audio.rs

@@ -352,6 +352,18 @@ pub struct DriverIterator {
     index: i32,
 }
 
+// panics if SDL_GetAudioDriver returns a null pointer,
+// which only happens if index is outside the range
+// 0..SDL_GetNumAudioDrivers()
+fn get_audio_driver(index: i32) -> &'static str {
+    unsafe {
+        let buf = sys::SDL_GetAudioDriver(index);
+        assert!(!buf.is_null());
+
+        CStr::from_ptr(buf as *const _).to_str().unwrap()
+    }
+}
+
 impl Iterator for DriverIterator {
     type Item = &'static str;
 
@@ -360,13 +372,10 @@ impl Iterator for DriverIterator {
         if self.index >= self.length {
             None
         } else {
-            unsafe {
-                let buf = sys::SDL_GetAudioDriver(self.index);
-                assert!(!buf.is_null());
-                self.index += 1;
+            let driver = get_audio_driver(self.index);
+            self.index += 1;
 
-                Some(CStr::from_ptr(buf as *const _).to_str().unwrap())
-            }
+            Some(driver)
         }
     }
 
@@ -375,10 +384,49 @@ impl Iterator for DriverIterator {
         let remaining = (self.length - self.index) as usize;
         (remaining, Some(remaining))
     }
+
+    #[inline]
+    fn nth(&mut self, n: usize) -> Option<&'static str> {
+        use std::convert::TryInto;
+
+        self.index = match n.try_into().ok().and_then(|n| self.index.checked_add(n)) {
+            Some(index) if index < self.length => index,
+            _ => self.length,
+        };
+
+        self.next()
+    }
+}
+
+impl DoubleEndedIterator for DriverIterator {
+    #[inline]
+    fn next_back(&mut self) -> Option<&'static str> {
+        if self.index >= self.length {
+            None
+        } else {
+            self.length -= 1;
+
+            Some(get_audio_driver(self.length))
+        }
+    }
+
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<&'static str> {
+        use std::convert::TryInto;
+
+        self.length = match n.try_into().ok().and_then(|n| self.length.checked_sub(n)) {
+            Some(length) if length > self.index => length,
+            _ => self.index,
+        };
+
+        self.next_back()
+    }
 }
 
 impl ExactSizeIterator for DriverIterator {}
 
+impl std::iter::FusedIterator for DriverIterator {}
+
 /// Gets an iterator of all audio drivers compiled into the SDL2 library.
 #[doc(alias = "SDL_GetAudioDriver")]
 #[inline]

src/sdl2/render.rs

@@ -2556,6 +2556,17 @@ pub struct DriverIterator {
     index: i32,
 }
 
+// panics if SDL_GetRenderDriverInfo returns a nonzero value,
+// which should only happen if index is outside the range
+// 0..SDL_GetNumRenderDrivers()
+fn get_render_driver_info(index: i32) -> RendererInfo {
+    let mut out = mem::MaybeUninit::uninit();
+    let result = unsafe { sys::SDL_GetRenderDriverInfo(index, out.as_mut_ptr()) };
+    assert_eq!(result, 0);
+
+    unsafe { RendererInfo::from_ll(&out.assume_init()) }
+}
+
 impl Iterator for DriverIterator {
     type Item = RendererInfo;
 
@@ -2565,12 +2576,10 @@ impl Iterator for DriverIterator {
         if self.index >= self.length {
             None
         } else {
-            let mut out = mem::MaybeUninit::uninit();
-            let result = unsafe { sys::SDL_GetRenderDriverInfo(self.index, out.as_mut_ptr()) == 0 };
-            assert!(result, "{}", 0);
+            let driver = get_render_driver_info(self.index);
             self.index += 1;
 
-            unsafe { Some(RendererInfo::from_ll(&out.assume_init())) }
+            Some(driver)
         }
     }
 
@@ -2579,10 +2588,49 @@ impl Iterator for DriverIterator {
         let remaining = (self.length - self.index) as usize;
         (remaining, Some(remaining))
     }
+
+    #[inline]
+    fn nth(&mut self, n: usize) -> Option<RendererInfo> {
+        use std::convert::TryInto;
+
+        self.index = match n.try_into().ok().and_then(|n| self.index.checked_add(n)) {
+            Some(index) if index < self.length => index,
+            _ => self.length,
+        };
+
+        self.next()
+    }
+}
+
+impl DoubleEndedIterator for DriverIterator {
+    #[inline]
+    fn next_back(&mut self) -> Option<RendererInfo> {
+        if self.index >= self.length {
+            None
+        } else {
+            self.length -= 1;
+
+            Some(get_render_driver_info(self.length))
+        }
+    }
+
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<RendererInfo> {
+        use std::convert::TryInto;
+
+        self.length = match n.try_into().ok().and_then(|n| self.length.checked_sub(n)) {
+            Some(length) if length > self.index => length,
+            _ => self.index,
+        };
+
+        self.next_back()
+    }
 }
 
 impl ExactSizeIterator for DriverIterator {}
 
+impl std::iter::FusedIterator for DriverIterator {}
+
 /// Gets an iterator of all render drivers compiled into the SDL2 library.
 #[inline]
 #[doc(alias = "SDL_GetNumRenderDrivers")]

src/sdl2/video.rs

@@ -1990,6 +1990,20 @@ pub struct DriverIterator {
     index: i32,
 }
 
+// panics if SDL_GetVideoDriver returns a null pointer,
+// which only happens if index is outside the range
+// 0..SDL_GetNumVideoDrivers()
+fn get_video_driver(index: i32) -> &'static str {
+    use std::str;
+
+    unsafe {
+        let buf = sys::SDL_GetVideoDriver(index);
+        assert!(!buf.is_null());
+
+        str::from_utf8(CStr::from_ptr(buf as *const _).to_bytes()).unwrap()
+    }
+}
+
 impl Iterator for DriverIterator {
     type Item = &'static str;
 
@@ -1998,15 +2012,10 @@ impl Iterator for DriverIterator {
         if self.index >= self.length {
             None
         } else {
-            use std::str;
-
-            unsafe {
-                let buf = sys::SDL_GetVideoDriver(self.index);
-                assert!(!buf.is_null());
-                self.index += 1;
+            let driver = get_video_driver(self.index);
+            self.index += 1;
 
-                Some(str::from_utf8(CStr::from_ptr(buf as *const _).to_bytes()).unwrap())
-            }
+            Some(driver)
         }
     }
 
@@ -2015,10 +2024,49 @@ impl Iterator for DriverIterator {
         let remaining = (self.length - self.index) as usize;
         (remaining, Some(remaining))
     }
+
+    #[inline]
+    fn nth(&mut self, n: usize) -> Option<&'static str> {
+        use std::convert::TryInto;
+
+        self.index = match n.try_into().ok().and_then(|n| self.index.checked_add(n)) {
+            Some(index) if index < self.length => index,
+            _ => self.length,
+        };
+
+        self.next()
+    }
+}
+
+impl DoubleEndedIterator for DriverIterator {
+    #[inline]
+    fn next_back(&mut self) -> Option<&'static str> {
+        if self.index >= self.length {
+            None
+        } else {
+            self.length -= 1;
+
+            Some(get_video_driver(self.length))
+        }
+    }
+
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<&'static str> {
+        use std::convert::TryInto;
+
+        self.length = match n.try_into().ok().and_then(|n| self.length.checked_sub(n)) {
+            Some(length) if length > self.index => length,
+            _ => self.index,
+        };
+
+        self.next_back()
+    }
 }
 
 impl ExactSizeIterator for DriverIterator {}
 
+impl std::iter::FusedIterator for DriverIterator {}
+
 /// Gets an iterator of all video drivers compiled into the SDL2 library.
 #[inline]
 #[doc(alias = "SDL_GetVideoDriver")]