fix(wrapper): fix write index

Former-commit-id: 98af046872115568f3b4e7859bf6b6970b0655f6

cpp/src/wrapper/Index.cpp

@@ -62,6 +62,10 @@ bool Index::search(idx_t n, const float *data, idx_t k, float *distances, long *
     return true;
 }
 
+void write_index(const Index_ptr &index, const std::string &file_name) {
+    write_index(index->index_.get(), file_name.c_str());
+}
+
 }
 }
 }

cpp/src/wrapper/Index.h

@@ -23,6 +23,9 @@ namespace zilliz {
 namespace vecwise {
 namespace engine {
 
+class Index;
+using Index_ptr = std::shared_ptr<Index>;
+
 class Index {
     typedef long idx_t;
 
@@ -61,6 +64,7 @@ public:
 //    virtual bool index_display();
 
 private:
+    friend void write_index(const Index_ptr &index, const std::string &file_name);
     std::shared_ptr<faiss::Index> index_ = nullptr;
 //    std::vector<faiss::gpu::GpuResources *> res_;
 //    std::vector<int> devs_;
@@ -69,9 +73,8 @@ private:
 //    faiss::gpu::GpuMultipleClonerOptions *options = new faiss::gpu::GpuMultipleClonerOptions();
 };
 
-using Index_ptr = std::shared_ptr<Index>;
 
-extern void write_index(const Index_ptr &index, const std::string &file_name);
+void write_index(const Index_ptr &index, const std::string &file_name);
 
 extern Index_ptr read_index(const std::string &file_name);
 
@@ -79,4 +82,3 @@ extern Index_ptr read_index(const std::string &file_name);
 }
 }
 }
-