Add timestamp stats gathering

The android_glue unit now collects timestamp stats and reports them up
through a ring buffer to the app. The app currently just displays a raw
line in a text view, but we'll expand that out to smarter aggregation.

android/res/layout/piano2.xml

@@ -46,11 +46,21 @@
         app:min="0"
         app:max="1"
         android:layout_margin="2px" />
+    <LinearLayout
+        android:orientation="vertical"
+        android:layout_span="4" >
     <Spinner
         android:id="@+id/presetSpinner"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_span="4" />
+        />
+      <TextView
+          android:id="@+id/status"
+          android:layout_width="wrap_content"
+          android:layout_height="wrap_content"
+          android:layout_span="6"
+      />
+    </LinearLayout>
   </TableRow>
   <TableRow>
     <LinearLayout

android/src/com/google/synthesizer/android/AndroidGlue.java

@@ -40,6 +40,13 @@ public class AndroidGlue extends MessageOutputProcessor {
     sendMidi(midiData);
   }
 
+  /**
+   * @return Number of stats bytes available from synth core
+   */
+  public native int statsBytesAvailable();
+
+  public native int readStatsBytes(byte[] buf, int off, int len);
+
   static {
     System.loadLibrary("synth");
   }

android/src/com/google/synthesizer/android/ui/PianoActivity2.java

@@ -18,6 +18,7 @@ package com.google.synthesizer.android.ui;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.HashMap;
 
@@ -33,6 +34,7 @@ import android.hardware.usb.UsbManager;
 import android.media.AudioManager;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.Handler;
 import android.util.Log;
 import android.view.View;
 import android.view.WindowManager;
@@ -117,6 +119,26 @@ public class PianoActivity2 extends Activity {
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
       tryConnectUsb();
     }
+
+    statusHandler_ = new Handler();
+    statusRunnable_ = new Runnable() {
+      public void run() {
+        int n = androidGlue_.statsBytesAvailable();
+        if (n > 0) {
+          byte[] buf = new byte[n];
+          androidGlue_.readStatsBytes(buf, 0, n);
+          TextView statusTextView = (TextView)findViewById(R.id.status);
+          String statusString = new String(buf);
+          int nlIndex = statusString.indexOf('\n');
+          if (nlIndex >= 0) {
+            statusString = statusString.substring(0, nlIndex);
+          }
+          statusTextView.setText(statusString);
+        }
+        statusHandler_.postDelayed(statusRunnable_, 10);
+      }
+    };
+    statusRunnable_.run();
   }
 
   @Override
@@ -228,4 +250,6 @@ public class PianoActivity2 extends Activity {
   private KnobView cutoffKnob_;
   private KnobView resonanceKnob_;
   private Spinner presetSpinner_;
+  private Handler statusHandler_;
+  private Runnable statusRunnable_;
 }

cpp/src/android_glue.cc

@@ -16,6 +16,8 @@
 
 #include <assert.h>
 #include <stddef.h>
+#include <stdio.h>
+#include <time.h>
 #include <jni.h>
 #include <SLES/OpenSLES.h>
 #include <SLES/OpenSLES_Android.h>
@@ -29,6 +31,7 @@
 #include "synth_unit.h"
 
 RingBuffer *ring_buffer;
+RingBuffer *stats_ring_buffer;
 SynthUnit *synth_unit;
 
 const int N_BUFFERS = 2;
@@ -37,7 +40,6 @@ int buffer_size;
 
 int16_t buffer[MAX_BUFFER_SIZE * N_BUFFERS];
 int cur_buffer = 0;
-int count = 0;
 
 // engine interfaces
 static SLObjectItf engineObject = NULL;
@@ -52,15 +54,30 @@ static SLPlayItf bq_player_play;
 static SLAndroidSimpleBufferQueueItf bq_player_buffer_queue;
 static SLBufferQueueItf buffer_queue_itf;
 
+double ts_to_double(const struct timespec *tp) {
+  return tp->tv_sec + 1e-9 * tp->tv_nsec;
+}
+
 extern "C" void BqPlayerCallback(SLAndroidSimpleBufferQueueItf queueItf,
   void *data) {
-  if (count >= 1000) return;
+  struct timespec tp;
+  clock_gettime(CLOCK_MONOTONIC, &tp);
+  double start_time = ts_to_double(&tp);
   int16_t *buf_ptr = buffer + buffer_size * cur_buffer;
   synth_unit->GetSamples(buffer_size, buf_ptr);
+  clock_gettime(CLOCK_MONOTONIC, &tp);
+  double end_time = ts_to_double(&tp);
   SLresult result = (*queueItf)->Enqueue(bq_player_buffer_queue,
     buf_ptr, buffer_size * 2);
   assert(SL_RESULT_SUCCESS == result);
   cur_buffer = (cur_buffer + 1) % N_BUFFERS;
+  char buf[64];
+  int n = sprintf(buf, "ts %.6f %.6f\n", start_time, end_time);
+  if (n <= stats_ring_buffer->WriteBytesAvailable()) {
+    stats_ring_buffer->Write((const uint8_t *)buf, n);
+  }
+  // Could potentially defer writing indication of overrun, but probably
+  // not worth it.
 }
 
 void CreateEngine() {
@@ -122,6 +139,7 @@ Java_com_google_synthesizer_android_AndroidGlue_start(JNIEnv *env,
   Freqlut::init(sample_rate);
   Sin::init();
   ring_buffer = new RingBuffer();
+  stats_ring_buffer = new RingBuffer();
   synth_unit = new SynthUnit(ring_buffer);
   for (int i = 0; i < N_BUFFERS - 1; ++i) {
     BqPlayerCallback(bq_player_buffer_queue, NULL);
@@ -153,6 +171,8 @@ Java_com_google_synthesizer_android_AndroidGlue_shutdown(JNIEnv *env,
   }
   delete ring_buffer;
   ring_buffer = NULL;
+  delete stats_ring_buffer;
+  stats_ring_buffer = NULL;
   delete synth_unit;
   synth_unit = NULL;
 }
@@ -175,3 +195,28 @@ Java_com_google_synthesizer_android_AndroidGlue_setPlayState(JNIEnv *env,
   assert(SL_RESULT_SUCCESS == result);
 }
 
+extern "C" JNIEXPORT jint JNICALL
+Java_com_google_synthesizer_android_AndroidGlue_statsBytesAvailable(
+    JNIEnv *env, jobject thiz) {
+  return stats_ring_buffer->BytesAvailable();
+}
+
+extern "C" JNIEXPORT jint JNICALL
+Java_com_google_synthesizer_android_AndroidGlue_readStatsBytes(
+    JNIEnv *env, jobject thiz, jbyteArray jb, jint off, jint len) {
+  int bytes_available = stats_ring_buffer->BytesAvailable();
+  int n = min(bytes_available, len);
+  if (n) {
+    size_t uoff = off;
+    size_t ulen = len;
+    if (off >= 0 && len >= 0 && uoff + ulen <= env->GetArrayLength(jb)) {
+      uint8_t *buf = (uint8_t *)env->GetByteArrayElements(jb, NULL);
+      stats_ring_buffer->Read(n, buf + uoff);
+      env->ReleaseByteArrayElements(jb, (jbyte *)buf, 0);
+    } else {
+      env->ThrowNew(env->FindClass("java/lang/ArrayIndexOutOfBoundsException"),
+        "out of bounds in AndroidGlue.readStatsBytes");
+    }
+  }
+  return n;
+}

cpp/src/ringbuffer.cc

@@ -29,6 +29,10 @@ int RingBuffer::BytesAvailable() {
   return (wr_ix_ - rd_ix_) & (kBufSize - 1);
 }
 
+int RingBuffer::WriteBytesAvailable() {
+  return (rd_ix_ - wr_ix_ - 1) & (kBufSize - 1);
+}
+
 int RingBuffer::Read(int size, uint8_t *bytes) {
   int rd_ix = rd_ix_;
   SynthMemoryBarrier();  // read barrier, make sure data is committed before ix

cpp/src/ringbuffer.h

@@ -24,6 +24,9 @@ class RingBuffer {
   // Returns number of bytes available for reading.
   int BytesAvailable();
 
+  // Returns number of bytes that can be written without blocking.
+  int WriteBytesAvailable();
+
   // Reads bytes. It is the caller's responsibility to make sure that
   // size <= a previous value of BytesAvailable().
   int Read(int size, uint8_t *bytes);
@@ -34,8 +37,8 @@ class RingBuffer {
  private:
   static const int kBufSize = 8192;
   uint8_t buf_[kBufSize];
-  volatile int rd_ix_;
-  volatile int wr_ix_;
+  volatile unsigned int rd_ix_;
+  volatile unsigned int wr_ix_;
 };
 
 #endif  // SYNTH_RINGBUFFER_H_