Fix reading hotwords file for android (#354)

@@ -12,6 +12,13 @@
 #include <utility>
 #include <vector>
 
+#if __ANDROID_API__ >= 9
+#include <strstream>
+
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
 #include "sherpa-onnx/csrc/file-utils.h"
 #include "sherpa-onnx/csrc/macros.h"
 #include "sherpa-onnx/csrc/online-lm.h"
@@ -62,14 +69,15 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
         model_(OnlineTransducerModel::Create(config.model_config)),
         sym_(config.model_config.tokens),
         endpoint_(config_.endpoint_config) {
-    if (!config_.hotwords_file.empty()) {
-      InitHotwords();
-    }
     if (sym_.contains("<unk>")) {
       unk_id_ = sym_["<unk>"];
     }
 
     if (config.decoding_method == "modified_beam_search") {
+      if (!config_.hotwords_file.empty()) {
+        InitHotwords();
+      }
+
       if (!config_.lm_config.model.empty()) {
         lm_ = OnlineLM::Create(config.lm_config);
       }
@@ -99,6 +107,17 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     }
 
     if (config.decoding_method == "modified_beam_search") {
+#if 0
+      // TODO(fangjun): Implement it
+      if (!config_.lm_config.model.empty()) {
+        lm_ = OnlineLM::Create(mgr, config.lm_config);
+      }
+#endif
+
+      if (!config_.hotwords_file.empty()) {
+        InitHotwords(mgr);
+      }
+
       decoder_ = std::make_unique<OnlineTransducerModifiedBeamSearchDecoder>(
           model_.get(), lm_.get(), config_.max_active_paths,
           config_.lm_config.scale, unk_id_);
@@ -268,6 +287,7 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     s->Reset();
   }
 
+ private:
   void InitHotwords() {
     // each line in hotwords_file contains space-separated words
 
@@ -286,7 +306,29 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
         std::make_shared<ContextGraph>(hotwords_, config_.hotwords_score);
   }
 
- private:
+#if __ANDROID_API__ >= 9
+  void InitHotwords(AAssetManager *mgr) {
+    // each line in hotwords_file contains space-separated words
+
+    auto buf = ReadFile(mgr, config_.hotwords_file);
+
+    std::istrstream is(buf.data(), buf.size());
+
+    if (!is) {
+      SHERPA_ONNX_LOGE("Open hotwords file failed: %s",
+                       config_.hotwords_file.c_str());
+      exit(-1);
+    }
+
+    if (!EncodeHotwords(is, sym_, &hotwords_)) {
+      SHERPA_ONNX_LOGE("Encode hotwords failed.");
+      exit(-1);
+    }
+    hotwords_graph_ =
+        std::make_shared<ContextGraph>(hotwords_, config_.hotwords_score);
+  }
+#endif
+
   void InitOnlineStream(OnlineStream *stream) const {
     auto r = decoder_->GetEmptyResult();