Instance Method

reduceBytes(into:_:)

Fold the body’s bytes into a value, one chunk at a time.

func reduceBytes<R>(into initialResult: R, _ updateAccumulatingResult: @escaping (inout R, Span<UInt8>) async throws -> Void) async throws -> R

Parameters

initialResult: The value to start from.
updateAccumulatingResult: Folds each chunk into the accumulator.

Return Value

The accumulated value. An empty body returns initialResult untouched.

Discussion

The streaming counterpart to computing something over a whole body without ever holding it in memory - hashing, counting, checksumming, incremental parsing. Chunk delivery and backpressure are exactly withStreamingBytes(_:)’s, so a streaming body is folded as it arrives and a buffered one is folded in a single step.

let digest = try await body.reduceBytes(into: SHA256()) { hasher, span in
    span.withUnsafeBytes { hasher.update(bufferPointer: $0) }
}.finalize()

Like withStreamingBytes(_:) this consumes a streaming body.