feat: stream model conversion (#1581)

src/model_io/safetensors_io.h

@@ -4,6 +4,7 @@
 #include <string>
 #include <vector>
 
+#include "streaming_writer.h"
 #include "tensor_storage.h"
 
 bool is_safetensors_file(const std::string& file_path);
@@ -14,4 +15,26 @@ bool write_safetensors_file(const std::string& file_path,
                             const std::vector<TensorWriteInfo>& tensors,
                             std::string* error = nullptr);
 
+class SafetensorsStreamingWriter : public StreamingModelWriter {
+public:
+    SafetensorsStreamingWriter() = default;
+
+    bool write_metadata(const std::string& file_path,
+                        const std::vector<TensorWritePlan>& tensors,
+                        std::string* error = nullptr) override;
+    bool write_tensor(std::ostream& output,
+                      size_t tensor_index,
+                      const uint8_t* data,
+                      size_t size,
+                      std::string* error = nullptr) const override;
+    uint64_t file_size() const override;
+
+private:
+    std::string file_path_;
+    std::vector<TensorWritePlan> tensors_;
+    std::vector<uint64_t> tensor_offsets_;
+    uint64_t data_start_ = 0;
+    uint64_t file_size_  = 0;
+};
+
 #endif  // __SD_MODEL_IO_SAFETENSORS_IO_H__