*: make internal pointer handling safer

src/device/extensions.rs

@@ -9,7 +9,9 @@ use libc::c_int;
 
 impl Context {
 	pub fn devices(&self) -> Result<DeviceIter, Error> {
-		DeviceIter::new(self.ptr)
+		unsafe {
+			DeviceIter::wrap(self.as_ptr())
+		}
 	}
 }
 
@@ -21,20 +23,20 @@ pub struct DeviceIter<'a> {
 }
 
 impl<'a> DeviceIter<'a> {
-	pub fn new(ctx: *mut AVFormatContext) -> Result<Self, Error> {
-		unsafe {
-			let mut ptr: *mut AVDeviceInfoList = ptr::null_mut();
+	pub unsafe fn wrap(ctx: *const AVFormatContext) -> Result<Self, Error> {
+		let mut ptr: *mut AVDeviceInfoList = ptr::null_mut();
 
-			match avdevice_list_devices(ctx, &mut ptr) {
-				n if n < 0 =>
-					Err(Error::from(n)),
+		match avdevice_list_devices(ctx, &mut ptr) {
+			n if n < 0 =>
+				Err(Error::from(n)),
 
-				_ =>
-					Ok(DeviceIter { ptr: ptr, cur: 0, _marker: PhantomData })
-			}
+			_ =>
+				Ok(DeviceIter { ptr: ptr, cur: 0, _marker: PhantomData })
 		}
 	}
+}
 
+impl<'a> DeviceIter<'a> {
 	pub fn default(&self) -> usize {
 		unsafe {
 			(*self.ptr).default_device as usize

src/device/mod.rs

@@ -15,19 +15,29 @@ pub struct Info<'a> {
 }
 
 impl<'a> Info<'a> {
-	pub fn wrap(ptr: *mut AVDeviceInfo) -> Self {
+	pub unsafe fn wrap(ptr: *mut AVDeviceInfo) -> Self {
 		Info { ptr: ptr, _marker: PhantomData }
 	}
 
+	pub unsafe fn as_ptr(&self) -> *const AVDeviceInfo {
+		self.ptr as *const _
+	}
+
+	pub unsafe fn as_mut_ptr(&mut self) -> *mut AVDeviceInfo {
+		self.ptr
+	}
+}
+
+impl<'a> Info<'a> {
 	pub fn name(&self) -> &str {
 		unsafe {
-			from_utf8_unchecked(CStr::from_ptr((*self.ptr).device_name).to_bytes())
+			from_utf8_unchecked(CStr::from_ptr((*self.as_ptr()).device_name).to_bytes())
 		}
 	}
 
 	pub fn description(&self) -> &str {
 		unsafe {
-			from_utf8_unchecked(CStr::from_ptr((*self.ptr).device_description).to_bytes())
+			from_utf8_unchecked(CStr::from_ptr((*self.as_ptr()).device_description).to_bytes())
 		}
 	}
 }