RustSession¶

The native session of the driver.

Rust gives the session to JS as an External, not as an instance of a native class. A method call on an instance of a native class costs napi_unwrap and a borrow check of napi-rs. JS uses the session in each execution, so this cost adds up. This class gives the session the same methods that the native class had. Each method calls one Rust function with the External.

This class also owns the values frames of the session. Its methods take the values, encode them into a frame, and pass the frame to Rust. A frame is a view of one shared FrameWriter buffer, and the next frame overwrites it. Thus, these rules keep concurrent requests from sending each other's values:

• A frame never leaves this class. Callers cannot keep one across an await.
• Each method that writes a frame is not async. Thus, await between writing the frame and the native call is a compile error. Do not make these methods async.
• Rust copies the frame before the native call returns.