Implement audio_read_samples()

api/syscalls.json

@@ -766,6 +766,26 @@
         "permission": "audio_input",
         "const_idx": 12,
         "description": "Open an audio input device, then spawn a new thread which will regularly call the specified callback function to process audio samples."
+      },
+      {
+        "name": "audio_read_samples",
+        "args": [
+          [
+            "i16*",
+            "dst_buf"
+          ],
+          [
+            "u32",
+            "num_samples"
+          ]
+        ],
+        "returns": [
+          "void",
+          ""
+        ],
+        "permission": "audio_input",
+        "const_idx": 13,
+        "description": "Read available input samples. Must be called from the audio input thread."
       }
     ],
     "constants": [

doc/syscalls.md

@@ -312,6 +312,14 @@ u32 audio_open_input(u32 sample_rate, u16 num_channels, u16 format, void* callba
 
 Open an audio input device, then spawn a new thread which will regularly call the specified callback function to process audio samples.
 
+## audio_read_samples
+
+```
+void audio_read_samples(i16* dst_buf, u32 num_samples)
+```
+
+Read available input samples. Must be called from the audio input thread.
+
 ## Constants
 These are the constants associated with the audio subsystem:
 

ncc/include/uvm/syscalls.h

@@ -101,6 +101,10 @@
 // Open an audio input device, then spawn a new thread which will regularly call the specified callback function to process audio samples.
 #define audio_open_input(__sample_rate, __num_channels, __format, __callback) asm (__sample_rate, __num_channels, __format, __callback) -> u32 { syscall audio_open_input; }
 
+// void audio_read_samples(i16* dst_buf, u32 num_samples)
+// Read available input samples. Must be called from the audio input thread.
+#define audio_read_samples(__dst_buf, __num_samples) asm (__dst_buf, __num_samples) -> void { syscall audio_read_samples; }
+
 // u64 net_listen(const char* listen_addr, void* on_new_conn)
 // Open a listening TCP socket to accept incoming connections. A callback function is called when a new connection request is received.
 #define net_listen(__listen_addr, __on_new_conn) asm (__listen_addr, __on_new_conn) -> u64 { syscall net_listen; }

vm/src/audio.rs

@@ -240,3 +240,26 @@ pub fn audio_open_input(thread: &mut Thread, sample_rate: Value, num_channels: V
     // FIXME: return the device_id (u32)
     Value::from(1)
 }
+
+/// Read audio samples from an audio input thread
+pub fn audio_read_samples(thread: &mut Thread, dst_ptr: Value, num_samples: Value)
+{
+    let dst_ptr = dst_ptr.as_usize();
+    let num_samples = num_samples.as_usize();
+
+    INPUT_STATE.with_borrow_mut(|s| {
+        if s.input_tid != thread.id {
+            panic!("can only read audio samples from audio input thread");
+        }
+
+        // For now, force reading all available samples
+        if num_samples != s.samples.len() {
+            panic!("must read all available samples");
+        }
+
+        let dst_buf: &mut [i16] = thread.get_heap_slice_mut(dst_ptr, num_samples);
+        dst_buf.copy_from_slice(&s.samples);
+
+        s.samples.clear();
+    });
+}

vm/src/constants.rs

@@ -19,6 +19,7 @@ pub const WINDOW_POLL_EVENT: u16 = 9;
 pub const WINDOW_DRAW_FRAME: u16 = 10;
 pub const EXIT: u16 = 11;
 pub const AUDIO_OPEN_INPUT: u16 = 12;
+pub const AUDIO_READ_SAMPLES: u16 = 13;
 pub const VM_HEAP_SIZE: u16 = 14;
 pub const MEMSET32: u16 = 16;
 pub const VM_GROW_HEAP: u16 = 17;
@@ -58,7 +59,7 @@ pub const SYSCALL_DESCS: [Option<SysCallDesc>; SYSCALL_TBL_LEN] = [
     Some(SysCallDesc { name: "window_draw_frame", const_idx: 10, argc: 2, has_ret: false }),
     Some(SysCallDesc { name: "exit", const_idx: 11, argc: 1, has_ret: false }),
     Some(SysCallDesc { name: "audio_open_input", const_idx: 12, argc: 4, has_ret: true }),
-    None,
+    Some(SysCallDesc { name: "audio_read_samples", const_idx: 13, argc: 2, has_ret: false }),
     Some(SysCallDesc { name: "vm_heap_size", const_idx: 14, argc: 0, has_ret: true }),
     None,
     Some(SysCallDesc { name: "memset32", const_idx: 16, argc: 3, has_ret: false }),

vm/src/host.rs

@@ -120,6 +120,8 @@ pub fn get_syscall(const_idx: u16) -> HostFn
         WINDOW_WAIT_EVENT => HostFn::Fn1_0(window_wait_event),
 
         AUDIO_OPEN_OUTPUT => HostFn::Fn4_1(audio_open_output),
+        AUDIO_OPEN_INPUT => HostFn::Fn4_1(audio_open_input),
+        AUDIO_READ_SAMPLES => HostFn::Fn2_0(audio_read_samples),
 
         _ => panic!("unknown syscall \"{}\"", const_idx),
     }