feat: stream model conversion (#1581)

src/model_io/streaming_writer.h

@@ -0,0 +1,26 @@
+#ifndef __SD_MODEL_IO_STREAMING_WRITER_H__
+#define __SD_MODEL_IO_STREAMING_WRITER_H__
+
+#include <cstdint>
+#include <iosfwd>
+#include <string>
+#include <vector>
+
+#include "tensor_storage.h"
+
+class StreamingModelWriter {
+public:
+    virtual ~StreamingModelWriter() = default;
+
+    virtual bool write_metadata(const std::string& file_path,
+                                const std::vector<TensorWritePlan>& tensors,
+                                std::string* error = nullptr)     = 0;
+    virtual bool write_tensor(std::ostream& output,
+                              size_t tensor_index,
+                              const uint8_t* data,
+                              size_t size,
+                              std::string* error = nullptr) const = 0;
+    virtual uint64_t file_size() const                            = 0;
+};
+
+#endif  // __SD_MODEL_IO_STREAMING_WRITER_H__