Add vad clear api for better performance (#366)

* Add vad clear api for better performance

* rename to make naming consistent and remove macro

* Fix linker error

* Fix Vad.kt

@@ -161,9 +161,9 @@ class MainActivity : AppCompatActivity() {
                 val samples = FloatArray(ret) { buffer[it] / 32768.0f }
 
                 vad.acceptWaveform(samples)
-                while(!vad.empty()) {vad.pop();}
 
                 val isSpeechDetected = vad.isSpeechDetected()
+                vad.clear()
 
                 runOnUiThread {
                     onVad(isSpeechDetected)

@@ -46,6 +46,8 @@ class Vad(
     // [start: Int, samples: FloatArray]
     fun front() = front(ptr)
 
+    fun clear() = clear(ptr)
+
     fun isSpeechDetected(): Boolean = isSpeechDetected(ptr)
 
     fun reset() = reset(ptr)
@@ -64,6 +66,7 @@ class Vad(
     private external fun acceptWaveform(ptr: Long, samples: FloatArray)
     private external fun empty(ptr: Long): Boolean
     private external fun pop(ptr: Long)
+    private external fun clear(ptr: Long)
     private external fun front(ptr: Long): Array<Any>
     private external fun isSpeechDetected(ptr: Long): Boolean
     private external fun reset(ptr: Long)

@@ -493,12 +493,17 @@ int32_t SherpaOnnxVoiceActivityDetectorDetected(
   return p->impl->IsSpeechDetected();
 }
 
-SHERPA_ONNX_API void SherpaOnnxVoiceActivityDetectorPop(
+void SherpaOnnxVoiceActivityDetectorPop(
     SherpaOnnxVoiceActivityDetector *p) {
   p->impl->Pop();
 }
 
-SHERPA_ONNX_API const SherpaOnnxSpeechSegment *
+void SherpaOnnxVoiceActivityDetectorClear(
+    SherpaOnnxVoiceActivityDetector *p) {
+  p->impl->Clear();
+}
+
+const SherpaOnnxSpeechSegment *
 SherpaOnnxVoiceActivityDetectorFront(SherpaOnnxVoiceActivityDetector *p) {
   const sherpa_onnx::SpeechSegment &segment = p->impl->Front();
 

@@ -580,6 +580,10 @@ SherpaOnnxVoiceActivityDetectorDetected(SherpaOnnxVoiceActivityDetector *p);
 SHERPA_ONNX_API void SherpaOnnxVoiceActivityDetectorPop(
     SherpaOnnxVoiceActivityDetector *p);
 
+// Clear current speech segments.
+SHERPA_ONNX_API void SherpaOnnxVoiceActivityDetectorClear(
+    SherpaOnnxVoiceActivityDetector *p);
+
 // Return the first speech segment.
 // The user has to use SherpaOnnxDestroySpeechSegment() to free the returned
 // pointer to avoid memory leak.

@@ -76,6 +76,8 @@ class VoiceActivityDetector::Impl {
 
   void Pop() { segments_.pop(); }
 
+  void Clear() { std::queue<SpeechSegment>().swap(segments_); }
+
   const SpeechSegment &Front() const { return segments_.front(); }
 
   void Reset() {
@@ -121,6 +123,8 @@ bool VoiceActivityDetector::Empty() const { return impl_->Empty(); }
 
 void VoiceActivityDetector::Pop() { impl_->Pop(); }
 
+void VoiceActivityDetector::Clear() { impl_->Clear(); }
+
 const SpeechSegment &VoiceActivityDetector::Front() const {
   return impl_->Front();
 }

@@ -36,6 +36,7 @@ class VoiceActivityDetector {
   void AcceptWaveform(const float *samples, int32_t n);
   bool Empty() const;
   void Pop();
+  void Clear();
   const SpeechSegment &Front() const;
 
   bool IsSpeechDetected() const;

@@ -124,6 +124,8 @@ class SherpaOnnxVad {
 
   void Pop() { vad_.Pop(); }
 
+  void Clear() { vad_.Clear();}
+
   const SpeechSegment &Front() const { return vad_.Front(); }
 
   bool IsSpeechDetected() const { return vad_.IsSpeechDetected(); }
@@ -556,6 +558,14 @@ JNIEXPORT void JNICALL Java_com_k2fsa_sherpa_onnx_Vad_pop(JNIEnv *env,
   model->Pop();
 }
 
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT void JNICALL Java_com_k2fsa_sherpa_onnx_Vad_clear(JNIEnv *env,
+                                                          jobject /*obj*/,
+                                                          jlong ptr) {
+  auto model = reinterpret_cast<sherpa_onnx::SherpaOnnxVad *>(ptr);
+  model->Clear();
+}
+
 // see
 // https://stackoverflow.com/questions/29043872/android-jni-return-multiple-variables
 static jobject NewInteger(JNIEnv *env, int32_t value) {

@@ -551,7 +551,7 @@ class SherpaOnnxVoiceActivityDetectorWrapper {
     return SherpaOnnxVoiceActivityDetectorEmpty(vad) == 1
   }
 
-  func isDetected() -> Bool {
+  func isSpeechDetected() -> Bool {
     return SherpaOnnxVoiceActivityDetectorDetected(vad) == 1
   }
 
@@ -559,6 +559,10 @@ class SherpaOnnxVoiceActivityDetectorWrapper {
     SherpaOnnxVoiceActivityDetectorPop(vad)
   }
 
+  func clear() {
+    SherpaOnnxVoiceActivityDetectorClear(vad)
+  }
+
   func front() -> SherpaOnnxSpeechSegmentWrapper {
     let p: UnsafePointer<SherpaOnnxSpeechSegment>? = SherpaOnnxVoiceActivityDetectorFront(vad)
     return SherpaOnnxSpeechSegmentWrapper(p: p)

@@ -174,32 +174,31 @@ func run() {
 
   var segments: [SpeechSegment] = []
 
-  while array.count > windowSize {
-    // todo(fangjun): avoid extra copies here
-    vad.acceptWaveform(samples: [Float](array[0..<windowSize]))
-    array = [Float](array[windowSize..<array.count])
-
-    while !vad.isEmpty() {
-      let s = vad.front()
-      vad.pop()
-      let result = recognizer.decode(samples: s.samples)
+  for offset in stride(from: 0, to: array.count, by: windowSize) {
+      let end = min(offset + windowSize, array.count)
+      vad.acceptWaveform(samples: [Float](array[offset ..< end]))
+  }
 
-      segments.append(
-        SpeechSegment(
-          start: Float(s.start) / Float(sampleRate),
-          duration: Float(s.samples.count) / Float(sampleRate),
-          text: result.text))
+  var index: Int = 0
+  while !vad.isEmpty() {
+    let s = vad.front()
+    vad.pop()
+    let result = recognizer.decode(samples: s.samples)
 
-      print(segments.last!)
+    segments.append(
+      SpeechSegment(
+        start: Float(s.start) / Float(sampleRate),
+        duration: Float(s.samples.count) / Float(sampleRate),
+        text: result.text))
 
-    }
+    print(segments.last!)
   }
 
-  let srt = zip(segments.indices, segments).map { (index, element) in
+  let srt: String = zip(segments.indices, segments).map { (index, element) in
     return "\(index+1)\n\(element)"
   }.joined(separator: "\n\n")
 
-  let srtFilename = filePath.stringByDeletingPathExtension + ".srt"
+  let srtFilename: String = filePath.stringByDeletingPathExtension + ".srt"
   do {
     try srt.write(to: srtFilename.fileURL, atomically: true, encoding: .utf8)
   } catch {