Refactor hotwords，support loading hotwords from file (#296)

sherpa-onnx/csrc/online-recognizer-transducer-impl.h

@@ -7,6 +7,8 @@
 
 #include <algorithm>
 #include <memory>
+#include <regex>  // NOLINT
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -20,6 +22,7 @@
 #include "sherpa-onnx/csrc/online-transducer-model.h"
 #include "sherpa-onnx/csrc/online-transducer-modified-beam-search-decoder.h"
 #include "sherpa-onnx/csrc/symbol-table.h"
+#include "sherpa-onnx/csrc/utils.h"
 
 namespace sherpa_onnx {
 
@@ -57,6 +60,9 @@ 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>"];
     }
@@ -106,18 +112,24 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
 #endif
 
   std::unique_ptr<OnlineStream> CreateStream() const override {
-    auto stream = std::make_unique<OnlineStream>(config_.feat_config);
+    auto stream =
+        std::make_unique<OnlineStream>(config_.feat_config, hotwords_graph_);
     InitOnlineStream(stream.get());
     return stream;
   }
 
   std::unique_ptr<OnlineStream> CreateStream(
-      const std::vector<std::vector<int32_t>> &contexts) const override {
-    // We create context_graph at this level, because we might have default
-    // context_graph(will be added later if needed) that belongs to the whole
-    // model rather than each stream.
+      const std::string &hotwords) const override {
+    auto hws = std::regex_replace(hotwords, std::regex("/"), "\n");
+    std::istringstream is(hws);
+    std::vector<std::vector<int32_t>> current;
+    if (!EncodeHotwords(is, sym_, &current)) {
+      SHERPA_ONNX_LOGE("Encode hotwords failed, skipping, hotwords are : %s",
+                       hotwords.c_str());
+    }
+    current.insert(current.end(), hotwords_.begin(), hotwords_.end());
     auto context_graph =
-        std::make_shared<ContextGraph>(contexts, config_.context_score);
+        std::make_shared<ContextGraph>(current, config_.hotwords_score);
     auto stream =
         std::make_unique<OnlineStream>(config_.feat_config, context_graph);
     InitOnlineStream(stream.get());
@@ -253,6 +265,24 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     s->Reset();
   }
 
+  void InitHotwords() {
+    // each line in hotwords_file contains space-separated words
+
+    std::ifstream is(config_.hotwords_file);
+    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);
+  }
+
  private:
   void InitOnlineStream(OnlineStream *stream) const {
     auto r = decoder_->GetEmptyResult();
@@ -271,6 +301,8 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
 
  private:
   OnlineRecognizerConfig config_;
+  std::vector<std::vector<int32_t>> hotwords_;
+  ContextGraphPtr hotwords_graph_;
   std::unique_ptr<OnlineTransducerModel> model_;
   std::unique_ptr<OnlineLM> lm_;
   std::unique_ptr<OnlineTransducerDecoder> decoder_;