SpeechSynthesis.java: expose the different voice options from eSpeak

This makes the following changes:

1.  setVoice takes a Voice object instead of a language string.

    This is to make the API cleaner and allows SpeechSynthesis
    to pass the correct parameter (identifier for SetVoiceByName,
    or name for SetVoiceByProperties) to espeak.

2.  The espeak_SetVoiceByName API is also exposed to support passing
    the voice variant to use.

3.  The age parameter has been re-added with the constants:
    *  SpeechSynthesis.AGE_ANY
    *  SpeechSynthesis.AGE_YOUNG
    *  SpeechSynthesis.AGE_OLD
    based on the behaviour of the eSpeak voice selection algorithm.

NOTE: Due to the way that voice selection is implemented in eSpeak,
if variant is specified, the age and gender cannot be specified and
vice versa.

android/jni/jni/eSpeakService.cpp

 }
 
 JNIEXPORT jboolean
-JNICALL Java_com_reecedunn_espeak_SpeechSynthesis_nativeSetVoice(
-    JNIEnv *env, jobject object, jstring language, jint gender) {
+JNICALL Java_com_reecedunn_espeak_SpeechSynthesis_nativeSetVoiceByName(
+    JNIEnv *env, jobject object, jstring name) {
+  const char *c_name = name ? env->GetStringUTFChars(name, NULL) : NULL;
+
+  if (DEBUG) LOGV("%s(name=%s)", __FUNCTION__, c_name);
+
+  const espeak_ERROR result = espeak_SetVoiceByName(c_name);
+
+  if (c_name) env->ReleaseStringUTFChars(name, c_name);
+
+  switch (result) {
+    case EE_OK:             return JNI_TRUE;
+    case EE_INTERNAL_ERROR: LOGE("espeak_SetVoiceByName: internal error."); break;
+    case EE_BUFFER_FULL:    LOGE("espeak_SetVoiceByName: buffer full."); break;
+    case EE_NOT_FOUND:      LOGE("espeak_SetVoiceByName: not found."); break;
+  }
+
+  return JNI_FALSE;
+}
+
+JNIEXPORT jboolean
+JNICALL Java_com_reecedunn_espeak_SpeechSynthesis_nativeSetVoiceByProperties(
+    JNIEnv *env, jobject object, jstring language, jint gender, jint age) {
   const char *c_language = language ? env->GetStringUTFChars(language, NULL) : NULL;
 
-  if (DEBUG) LOGV("%s(language=%s, gender=%d)", __FUNCTION__, c_language, gender);
+  if (DEBUG) LOGV("%s(language=%s, gender=%d, age=%d)", __FUNCTION__, c_language, gender, age);
 
   espeak_VOICE voice_select;
   memset(&voice_select, 0, sizeof(espeak_VOICE));
   voice_select.languages = c_language;
   voice_select.gender = (int) gender;
+  voice_select.age = (int) age;
 
   const espeak_ERROR result = espeak_SetVoiceByProperties(&voice_select);
 

android/src/com/reecedunn/espeak/SpeechSynthesis.java

     public static final int GENDER_MALE = 1;
     public static final int GENDER_FEMALE = 2;
 
+    public static final int AGE_ANY = 0;
+    public static final int AGE_YOUNG = 12;
+    public static final int AGE_OLD = 60;
+
     static {
         System.loadLibrary("ttsespeak");
 
         return voices;
     }
 
-    public void setVoice(String language, int gender) {
-        nativeSetVoice(language, gender);
+    public void setVoice(Voice voice, String variant, int gender, int age) {
+        // NOTE: espeak_SetVoiceByProperties does not support specifying the
+        // voice variant (e.g. klatt), but espeak_SetVoiceByName does.
+        if (variant == null) {
+            nativeSetVoiceByProperties(voice.name, gender, age);
+        } else {
+            nativeSetVoiceByName(voice.identifier + "+" + variant);
+        }
     }
 
     public void setRate(int rate) {
 
     private native final String[] nativeGetAvailableVoices();
 
-    private native final boolean nativeSetVoice(String language, int gender);
+    private native final boolean nativeSetVoiceByName(String name);
+
+    private native final boolean nativeSetVoiceByProperties(String language, int gender, int age);
 
     private native final boolean nativeSetRate(int rate);
 

android/src/com/reecedunn/espeak/TtsService.java

         mCallback.start(mEngine.getSampleRate(), mEngine.getAudioFormat(),
                 mEngine.getChannelCount());
 
-        mEngine.setVoice(mMatchingVoice.name, gender);
+        mEngine.setVoice(mMatchingVoice, null, gender, SpeechSynthesis.AGE_ANY);
         mEngine.setRate(rate);
         mEngine.setPitch(pitch);
         mEngine.synthesize(text, text.startsWith("<speak"));