Support Ukrainian VITS models from coqui-ai/TTS (#469)

sherpa-onnx/csrc/offline-tts-character-frontend.h

@@ -0,0 +1,54 @@
+// sherpa-onnx/csrc/offline-tts-character-frontend.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_OFFLINE_TTS_CHARACTER_FRONTEND_H_
+#define SHERPA_ONNX_CSRC_OFFLINE_TTS_CHARACTER_FRONTEND_H_
+#include <cstdint>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "sherpa-onnx/csrc/offline-tts-frontend.h"
+#include "sherpa-onnx/csrc/offline-tts-vits-model-metadata.h"
+
+namespace sherpa_onnx {
+
+class OfflineTtsCharacterFrontend : public OfflineTtsFrontend {
+ public:
+  OfflineTtsCharacterFrontend(const std::string &tokens,
+                              const OfflineTtsVitsModelMetaData &meta_data);
+
+#if __ANDROID_API__ >= 9
+  OfflineTtsCharacterFrontend(AAssetManager *mgr, const std::string &tokens,
+                              const OfflineTtsVitsModelMetaData &meta_data);
+
+#endif
+  /** Convert a string to token IDs.
+   *
+   * @param text The input text.
+   *             Example 1: "This is the first sample sentence; this is the
+   *             second one." Example 2: "这是第一句。这是第二句。"
+   * @param voice Optional. It is for espeak-ng.
+   *
+   * @return Return a vector-of-vector of token IDs. Each subvector contains
+   *         a sentence that can be processed independently.
+   *         If a frontend does not support splitting the text into
+   * sentences, the resulting vector contains only one subvector.
+   */
+  std::vector<std::vector<int64_t>> ConvertTextToTokenIds(
+      const std::string &text, const std::string &voice = "") const override;
+
+ private:
+  OfflineTtsVitsModelMetaData meta_data_;
+  std::unordered_map<char32_t, int32_t> token2id_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_OFFLINE_TTS_CHARACTER_FRONTEND_H_