[CMake] Support disable SentencePiece tokenizer (mlc-ai#38)

This PR supports turning off SentencePiece tokenizer to reduce binary
size.

Author: MasterJH5574

CMakeLists.txt

@@ -88,6 +88,8 @@ set(TOKENIZERS_CPP_CARGO_SOURCE_PATH ${TOKENIZERS_CPP_ROOT}/rust)
 option(MSGPACK_USE_BOOST "Use Boost libraried" OFF)
 add_subdirectory(msgpack)
 
+option(MLC_ENABLE_SENTENCEPIECE_TOKENIZER "Enable SentencePiece tokenizer" OFF)
+
 if(MSVC)
   set(TOKENIZERS_RUST_LIB "${TOKENIZERS_CPP_CARGO_BINARY_DIR}/tokenizers_c.lib")
 else()
@@ -120,6 +122,9 @@ add_library(tokenizer_cpp_objs OBJECT ${TOKENIZER_CPP_SRCS})
 target_include_directories(tokenizer_cpp_objs PRIVATE sentencepiece/src)
 target_include_directories(tokenizer_cpp_objs PRIVATE msgpack/include)
 target_include_directories(tokenizer_cpp_objs PUBLIC ${TOKENIZERS_CPP_INCLUDE})
+if (MLC_ENABLE_SENTENCEPIECE_TOKENIZER STREQUAL "ON")
+  target_compile_definitions(tokenizer_cpp_objs PUBLIC MLC_ENABLE_SENTENCEPIECE_TOKENIZER)
+endif ()
 target_link_libraries(tokenizer_cpp_objs PRIVATE msgpack-cxx)
 
 # sentencepiece config

src/sentencepiece_tokenizer.cc

@@ -10,6 +10,7 @@
 
 namespace tokenizers {
 
+#ifdef MLC_ENABLE_SENTENCEPIECE_TOKENIZER
 class SentencePieceTokenizer : public Tokenizer {
  public:
   explicit SentencePieceTokenizer(const std::string& model_blob) {
@@ -46,4 +47,11 @@ class SentencePieceTokenizer : public Tokenizer {
 std::unique_ptr<Tokenizer> Tokenizer::FromBlobSentencePiece(const std::string& model_blob) {
   return std::make_unique<SentencePieceTokenizer>(model_blob);
 }
+#else
+std::unique_ptr<Tokenizer> Tokenizer::FromBlobSentencePiece(const std::string& model_blob) {
+  assert(false);
+  throw;
+}
+#endif  // MLC_ENABLE_SENTENCEPIECE_TOKENIZER
+
 }  // namespace tokenizers