feat: use initial_prompt param instead of rn_whisper_convert_prompt

ref: ggml-org/whisper.cpp#645

Author: jhen0409

android/src/main/jni/whisper/jni.cpp

@@ -163,11 +163,7 @@ Java_com_rnwhisper_WhisperContext_fullTranscribe(
         params.temperature_inc = temperature_inc;
     }
     if (prompt != nullptr) {
-        rn_whisper_convert_prompt(
-            context,
-            params,
-            new std::string(env->GetStringUTFChars(prompt, nullptr))
-        );
+        params.initial_prompt = env->GetStringUTFChars(prompt, nullptr);
     }
 
     params.encoder_begin_callback = [](struct whisper_context * /*ctx*/, struct whisper_state * /*state*/, void * user_data) {

cpp/rn-whisper.cpp

@@ -6,29 +6,6 @@
 
 extern "C" {
 
-void rn_whisper_convert_prompt(
-  struct whisper_context * ctx,
-  struct whisper_full_params params,
-  std::string * prompt
-) {
-  std::vector<whisper_token> prompt_tokens;
-  if (!prompt->empty()) {
-    prompt_tokens.resize(1024);
-    prompt_tokens.resize(whisper_tokenize(ctx, prompt->c_str(), prompt_tokens.data(), prompt_tokens.size()));
-
-    // fprintf(stderr, "\n");
-    // fprintf(stderr, "initial prompt: '%s'\n", prompt->c_str());
-    // fprintf(stderr, "initial tokens: [ ");
-    // for (int i = 0; i < (int) prompt_tokens.size(); ++i) {
-    //     fprintf(stderr, "%d ", prompt_tokens[i]);
-    // }
-    // fprintf(stderr, "]\n");
-
-    params.prompt_tokens = prompt_tokens.data();
-    params.prompt_n_tokens = prompt_tokens.size();
-  }
-}
-
 std::unordered_map<int, bool> abort_map;
 
 bool* rn_whisper_assign_abort_map(int job_id) {

cpp/rn-whisper.h

@@ -5,12 +5,6 @@
 extern "C" {
 #endif
 
-void rn_whisper_convert_prompt(
-  struct whisper_context * ctx,
-  struct whisper_full_params params,
-  std::string * prompt
-);
-
 bool* rn_whisper_assign_abort_map(int job_id);
 void rn_whisper_remove_abort_map(int job_id);
 void rn_whisper_abort_transcribe(int job_id);

ios/RNWhisperContext.mm

@@ -354,12 +354,7 @@ - (int)fullTranscribe:(int)jobId audioData:(float *)audioData audioDataCount:(in
     }
 
     if (options[@"prompt"] != nil) {
-        std::string *prompt = new std::string([options[@"prompt"] UTF8String]);
-        rn_whisper_convert_prompt(
-            self->ctx,
-            params,
-            prompt
-        );
+        params.initial_prompt = [options[@"prompt"] UTF8String];
     }
 
     params.encoder_begin_callback = [](struct whisper_context * /*ctx*/, struct whisper_state * /*state*/, void * user_data) {