FrameWriter¶

Encodes values into values frames, in the request frame layout: [u16 count], then for each value [i32 length][bytes]. Length -1 is null, and -2 is unset.

The writer reuses its buffer between frames. A frame is a view of that buffer, valid until the next frame of the same writer. Thus, pass a frame to Rust immediately. This is safe, because Rust copies the frame before the native call returns.

Callers must obey these rules. Otherwise, concurrent requests can send each other's values, with no error:

• Do not await between writing a frame and passing it to Rust. Another request can write its own frame during the await.
• Do not keep a frame after the native call returns. Copy it if you need it later, for example in a test.

In the driver, only RustSession uses a writer. Its structure enforces these rules. See its documentation.

A writer writes one frame at a time. A nested frame on the same writer throws, because it would overwrite the frame in progress.