ndk: Add AMidi interface

ndk-sys/Cargo.toml

@@ -19,6 +19,7 @@ test = []
 audio = []
 bitmap = []
 media = []
+midi = []
 
 [package.metadata.docs.rs]
 rustdoc-args = ["--cfg", "docsrs"]

ndk-sys/src/lib.rs

@@ -51,3 +51,7 @@ extern "C" {}
 #[cfg(all(feature = "audio", target_os = "android"))]
 #[link(name = "aaudio")]
 extern "C" {}
+
+#[cfg(all(feature = "midi", target_os = "android"))]
+#[link(name = "amidi")]
+extern "C" {}

ndk/Cargo.toml

@@ -17,6 +17,7 @@ all = ["audio", "bitmap","media", "api-level-30"]
 audio = ["ffi/audio", "api-level-26"]
 bitmap = ["ffi/bitmap"]
 media = ["ffi/media"]
+midi = ["ffi/midi", "api-level-29"]
 
 api-level-23 = []
 api-level-24 = ["api-level-23"]

ndk/src/lib.rs

@@ -16,6 +16,7 @@ pub mod hardware_buffer_format;
 pub mod input_queue;
 pub mod looper;
 pub mod media;
+pub mod midi;
 pub mod native_activity;
 pub mod native_window;
 pub mod surface_texture;

ndk/src/media/mod.rs

@@ -1,23 +1,30 @@
 //! Bindings for the NDK media classes.
 //!
 //! See also [the NDK docs](https://developer.android.com/ndk/reference/group/media)
-#![cfg(feature = "media")]
+#![cfg(any(feature = "media", feature = "midi"))]
 
 mod error;
+
+#[cfg(feature = "media")]
 pub mod image_reader;
+#[cfg(feature = "media")]
 pub mod media_codec;
 
 pub use error::NdkMediaError;
-use std::{mem::MaybeUninit, ptr::NonNull};
+use std::mem::MaybeUninit;
+
+#[cfg(feature = "media")]
+use std::ptr::NonNull;
 
 pub type Result<T, E = NdkMediaError> = std::result::Result<T, E>;
 
-fn construct<T>(with_ptr: impl FnOnce(*mut T) -> ffi::media_status_t) -> Result<T> {
+pub(crate) fn construct<T>(with_ptr: impl FnOnce(*mut T) -> ffi::media_status_t) -> Result<T> {
     let mut result = MaybeUninit::uninit();
     let status = with_ptr(result.as_mut_ptr());
     NdkMediaError::from_status(status).map(|()| unsafe { result.assume_init() })
 }
 
+#[cfg(feature = "media")]
 fn construct_never_null<T>(
     with_ptr: impl FnOnce(*mut *mut T) -> ffi::media_status_t,
 ) -> Result<NonNull<T>> {
@@ -35,6 +42,7 @@ fn construct_never_null<T>(
 ///
 /// As such this function always asserts on `null` values,
 /// even when `cfg!(debug_assertions)` is disabled.
+#[cfg(feature = "media")]
 fn get_unlikely_to_be_null<T>(get_ptr: impl FnOnce() -> *mut T) -> NonNull<T> {
     let result = get_ptr();
     NonNull::new(result).expect("result should never be null")

ndk/src/midi.rs

@@ -0,0 +1,305 @@
+//! Bindings for [`AMidiDevice`], [`AMidiInputPort`], and [`AMidiOutputPort`]
+//!
+//! See [the NDK guide](https://developer.android.com/ndk/guides/audio/midi) for
+//! design and usage instructions, and [the NDK reference](https://developer.android.com/ndk/reference/group/midi)
+//! for an API overview.
+//!
+//! [`AMidiDevice`]: https://developer.android.com/ndk/reference/group/midi#amididevice
+//! [`AMidiInputPort`]: https://developer.android.com/ndk/reference/group/midi#amidiinputport
+//! [`AMidiOutputPort`]: https://developer.android.com/ndk/reference/group/midi#amidioutputport
+#![cfg(feature = "midi")]
+
+pub use super::media::Result;
+use super::media::{construct, NdkMediaError};
+
+use num_enum::{IntoPrimitive, TryFromPrimitive};
+use std::convert::TryFrom;
+use std::fmt;
+use std::marker::PhantomData;
+use std::os::raw::{c_int, c_uint};
+use std::ptr::NonNull;
+
+// There is no mention about thread-safety in the NDK reference, but the official Android C++ MIDI
+// sample stores `AMidiDevice *` and `AMidi{Input,Output}Port *` in global variables and accesses the
+// ports from separate threads.
+// See https://github.com/android/ndk-samples/blob/7f6936ea044ee29c36b5c3ebd62bb3a64e1e6014/native-midi/app/src/main/cpp/AppMidiManager.cpp
+unsafe impl Send for MidiDevice {}
+unsafe impl<'a> Send for MidiInputPort<'a> {}
+unsafe impl<'a> Send for MidiOutputPort<'a> {}
+
+/// Result of [`MidiOutputPort::receive`].
+#[derive(Copy, Clone, Debug)]
+pub enum MidiOpcode {
+    /// No MIDI messages are available.
+    NoMessage,
+    /// Received a MIDI message with the given length and the timestamp.
+    Data { length: usize, timestamp: i64 },
+    /// Instructed to discard all pending MIDI data.
+    Flush,
+}
+
+#[repr(u32)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
+pub enum MidiDeviceType {
+    Bluetooth = ffi::AMIDI_DEVICE_TYPE_BLUETOOTH,
+    USB = ffi::AMIDI_DEVICE_TYPE_USB,
+    Virtual = ffi::AMIDI_DEVICE_TYPE_VIRTUAL,
+}
+
+#[derive(Debug)]
+pub struct MidiDevice {
+    ptr: NonNull<ffi::AMidiDevice>,
+}
+
+impl MidiDevice {
+    /// Assumes ownership of `ptr`
+    ///
+    /// # Safety
+    /// `ptr` must be a valid pointer to an Android [`ffi::AMidiDevice`].
+    pub unsafe fn from_ptr(ptr: NonNull<ffi::AMidiDevice>) -> Self {
+        Self { ptr }
+    }
+
+    pub fn ptr(&self) -> NonNull<ffi::AMidiDevice> {
+        self.ptr
+    }
+
+    fn as_ptr(&self) -> *mut ffi::AMidiDevice {
+        self.ptr.as_ptr()
+    }
+
+    /// Connects a native Midi Device object to the associated Java MidiDevice object.
+    ///
+    /// Use the returned [`MidiDevice`] to access the rest of the native MIDI API.
+    pub fn from_java(
+        env: *mut jni_sys::JNIEnv,
+        midi_device_obj: jni_sys::jobject,
+    ) -> Result<MidiDevice> {
+        unsafe {
+            let ptr = construct(|res| ffi::AMidiDevice_fromJava(env, midi_device_obj, res))?;
+            Ok(Self::from_ptr(NonNull::new_unchecked(ptr)))
+        }
+    }
+
+    /// Gets the number of input (sending) ports available on the specified MIDI device.
+    pub fn num_input_ports(&self) -> Result<usize> {
+        let num_input_ports = unsafe { ffi::AMidiDevice_getNumInputPorts(self.as_ptr()) };
+        if num_input_ports >= 0 {
+            Ok(num_input_ports as usize)
+        } else {
+            NdkMediaError::from_status(ffi::media_status_t(num_input_ports as c_int)).map(|_| 0)
+        }
+    }
+
+    /// Gets the number of output (receiving) ports available on the specified MIDI device.
+    pub fn num_output_ports(&self) -> Result<usize> {
+        let num_output_ports = unsafe { ffi::AMidiDevice_getNumOutputPorts(self.as_ptr()) };
+        if num_output_ports >= 0 {
+            Ok(num_output_ports as usize)
+        } else {
+            Err(
+                NdkMediaError::from_status(ffi::media_status_t(num_output_ports as c_int))
+                    .unwrap_err(),
+            )
+        }
+    }
+
+    /// Gets the MIDI device type.
+    pub fn device_type(&self) -> Result<MidiDeviceType> {
+        let device_type = unsafe { ffi::AMidiDevice_getType(self.as_ptr()) };
+        if device_type >= 0 {
+            let device_type = MidiDeviceType::try_from(device_type as u32).map_err(|e| {
+                NdkMediaError::UnknownResult(ffi::media_status_t(e.number as c_int))
+            })?;
+            Ok(device_type)
+        } else {
+            Err(NdkMediaError::from_status(ffi::media_status_t(device_type)).unwrap_err())
+        }
+    }
+
+    /// Opens the input port so that the client can send data to it.
+    pub fn open_input_port(&self, port_number: i32) -> Result<MidiInputPort> {
+        unsafe {
+            let input_port =
+                construct(|res| ffi::AMidiInputPort_open(self.as_ptr(), port_number, res))?;
+            Ok(MidiInputPort::from_ptr(NonNull::new_unchecked(input_port)))
+        }
+    }
+
+    /// Opens the output port so that the client can receive data from it.
+    pub fn open_output_port(&self, port_number: i32) -> Result<MidiOutputPort> {
+        unsafe {
+            let output_port =
+                construct(|res| ffi::AMidiOutputPort_open(self.as_ptr(), port_number, res))?;
+            Ok(MidiOutputPort::from_ptr(NonNull::new_unchecked(
+                output_port,
+            )))
+        }
+    }
+}
+
+impl Drop for MidiDevice {
+    fn drop(&mut self) {
+        let status = unsafe { ffi::AMidiDevice_release(self.as_ptr()) };
+        NdkMediaError::from_status(status).unwrap();
+    }
+}
+
+pub struct MidiInputPort<'a> {
+    ptr: NonNull<ffi::AMidiInputPort>,
+    _marker: PhantomData<&'a MidiDevice>,
+}
+
+impl<'a> fmt::Debug for MidiInputPort<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("MidiInputPort")
+            .field("inner", &self.ptr)
+            .finish()
+    }
+}
+
+impl<'a> MidiInputPort<'a> {
+    /// Assumes ownership of `ptr`
+    ///
+    /// # Safety
+    /// `ptr` must be a valid pointer to an Android [`ffi::AMidiInputPort`].
+    pub unsafe fn from_ptr(ptr: NonNull<ffi::AMidiInputPort>) -> Self {
+        Self {
+            ptr,
+            _marker: PhantomData,
+        }
+    }
+
+    pub fn ptr(&self) -> NonNull<ffi::AMidiInputPort> {
+        self.ptr
+    }
+
+    fn as_ptr(&self) -> *mut ffi::AMidiInputPort {
+        self.ptr.as_ptr()
+    }
+
+    /// Sends data to the specified input port.
+    pub fn send(&self, buffer: &[u8]) -> Result<usize> {
+        let num_bytes_sent = unsafe {
+            ffi::AMidiInputPort_send(self.as_ptr(), buffer.as_ptr(), buffer.len() as ffi::size_t)
+        };
+        if num_bytes_sent >= 0 {
+            Ok(num_bytes_sent as usize)
+        } else {
+            Err(
+                NdkMediaError::from_status(ffi::media_status_t(num_bytes_sent as c_int))
+                    .unwrap_err(),
+            )
+        }
+    }
+
+    /// Sends a message with a 'MIDI flush command code' to the specified port.
+    ///
+    /// This should cause a receiver to discard any pending MIDI data it may have accumulated and
+    /// not processed.
+    pub fn send_flush(&self) -> Result<()> {
+        let result = unsafe { ffi::AMidiInputPort_sendFlush(self.as_ptr()) };
+        NdkMediaError::from_status(result)
+    }
+
+    pub fn send_with_timestamp(&self, buffer: &[u8], timestamp: i64) -> Result<usize> {
+        let num_bytes_sent = unsafe {
+            ffi::AMidiInputPort_sendWithTimestamp(
+                self.as_ptr(),
+                buffer.as_ptr(),
+                buffer.len() as ffi::size_t,
+                timestamp,
+            )
+        };
+        if num_bytes_sent >= 0 {
+            Ok(num_bytes_sent as usize)
+        } else {
+            Err(
+                NdkMediaError::from_status(ffi::media_status_t(num_bytes_sent as c_int))
+                    .unwrap_err(),
+            )
+        }
+    }
+}
+
+impl<'a> Drop for MidiInputPort<'a> {
+    fn drop(&mut self) {
+        unsafe { ffi::AMidiInputPort_close(self.as_ptr()) };
+    }
+}
+
+pub struct MidiOutputPort<'a> {
+    ptr: NonNull<ffi::AMidiOutputPort>,
+    _marker: PhantomData<&'a MidiDevice>,
+}
+
+impl<'a> fmt::Debug for MidiOutputPort<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("MidiOutputPort")
+            .field("inner", &self.ptr)
+            .finish()
+    }
+}
+
+impl<'a> MidiOutputPort<'a> {
+    /// Assumes ownership of `ptr`
+    ///
+    /// # Safety
+    /// `ptr` must be a valid pointer to an Android [`ffi::AMidiOutputPort`].
+    pub unsafe fn from_ptr(ptr: NonNull<ffi::AMidiOutputPort>) -> Self {
+        Self {
+            ptr,
+            _marker: PhantomData,
+        }
+    }
+
+    pub fn ptr(&self) -> NonNull<ffi::AMidiOutputPort> {
+        self.ptr
+    }
+
+    fn as_ptr(&self) -> *mut ffi::AMidiOutputPort {
+        self.ptr.as_ptr()
+    }
+
+    /// Receives the next pending MIDI message.
+    ///
+    /// To retrieve all pending messages, the client should repeatedly call this method until it
+    /// returns [`Ok(MidiOpcode::NoMessage)`].
+    ///
+    /// Note that this is a non-blocking call. If there are no Midi messages are available, the
+    /// function returns [`Ok(MidiOpcode::NoMessage)`] immediately (for 0 messages received).
+    pub fn receive(&self, buffer: &mut [u8]) -> Result<MidiOpcode> {
+        let mut opcode = 0i32;
+        let mut timestamp = 0i64;
+        let mut num_bytes_received: ffi::size_t = 0;
+        let result = unsafe {
+            ffi::AMidiOutputPort_receive(
+                self.as_ptr(),
+                &mut opcode,
+                buffer.as_mut_ptr(),
+                buffer.len() as ffi::size_t,
+                &mut num_bytes_received,
+                &mut timestamp,
+            )
+        };
+
+        if result < 0 {
+            Err(NdkMediaError::from_status(ffi::media_status_t(result as c_int)).unwrap_err())
+        } else if result == 0 {
+            Ok(MidiOpcode::NoMessage)
+        } else if opcode as c_uint == ffi::AMIDI_OPCODE_DATA {
+            Ok(MidiOpcode::Data {
+                length: num_bytes_received as usize,
+                timestamp,
+            })
+        } else {
+            Ok(MidiOpcode::Flush)
+        }
+    }
+}
+
+impl<'a> Drop for MidiOutputPort<'a> {
+    fn drop(&mut self) {
+        unsafe { ffi::AMidiOutputPort_close(self.as_ptr()) };
+    }
+}