API · Low level
consumeSync()
Build a custom synchronous operator that handles one protocol record at a time.
Signature
consumeSync<U = T, C2 extends object = C>(
fn: (
error: ExstreamError<T> | null | undefined,
value: T | typeof exstream.nil,
push: (error?: unknown | null, value?: U | typeof exstream.nil | null, context?: C2) => boolean | void,
) => void,
): Exstream<U, C2>Protocol
The callback receives successful data, a record error, or the exstream.nil end marker. Use push(null, output) to emit data, push(error) to emit an error, and push(null, exstream.nil) to end. It may emit zero, one, or many records per input.
The callback must finish synchronously. For awaiting, delayed continuation, or explicit read control, use consume(). Output order follows callback push order; downstream pressure is reflected by push() and the connected graph.
Context and errors
push() inherits the active input context by default. A third context argument replaces it. Existing errors and end are not forwarded unless the callback pushes them. Avoid uncaught callback exceptions; standard operators wrap them with defined provenance, while low-level consumers leave policy to the adapter author.