PureYAMLStreaming

Experimental full-streaming incubator for PureYAML.

This package is intentionally separate from PureYAML while the chunked input, document streaming, and eventual event streaming APIs settle. It depends on PureYAML for the stable model and parser semantics, then adds streaming input adapters around that stable core.

Status

Prototype.

The current implementation streams YAML input in chunks, detects document-boundary candidates, and emits one parsed PureYAML.Stream.Document at a time. That gives bounded memory for multi-document streams where each document fits in memory.

It is not yet a token-level YAML scanner. A future milestone will replace the document-boundary scanner with a resumable token scanner that can feed event-level consumers directly.

Memory Contract

• parseDocuments is bounded by the largest current document plus parser state.
• collectDocuments is a convenience helper and retains all returned documents.
• Anchors, aliases, merge keys, and PureYAML.Model.Value construction can require retaining semantic state until the current document is complete.
• Future event-level APIs should be lower memory than document-level APIs, but they still cannot promise constant memory for every YAML feature.

Example

import Foundation
import PureYAMLStreaming

let url = URL(fileURLWithPath: "stream.yaml")
let parser = PureYAMLStreaming.Parser()

try parser.parseDocuments(from: url) { document in
    print("document", document.index, document.value)
}

WASM Browser Benchmark Site

Live site:

https://mihaelamj.github.io/PureYAMLStreaming/

Build the Swift WASI benchmark executable and copy it into the static test site:

bash scripts/build-wasm-site.sh

The build script requires npm so it can stage the pinned browser WASI shim as a local WasmSite/vendor/ asset. The deployed page does not import the shim from a runtime CDN.

Serve the site locally:

bash scripts/serve-wasm-site.sh

Then open http://localhost:8080 and click Run Benchmark. The page loads pureyaml-streaming-wasm-smoke.wasm, lets you choose from 10+ public multi-megabyte YAML files, fetches the selected file in JavaScript, feeds the bytes to Swift through WASI stdin, and reports fetch time, parse time, throughput, document count, and stdout JSON.

The browser fetch step currently buffers the selected YAML file before invoking the WASM guest. Inside Swift, the parser path counts documents through parseDocuments callbacks rather than retaining all parsed documents.

Relationship To PureYAML

PureYAML remains the dependency-free core package. This package is the incubator for file, byte, and async streaming APIs. Stable pieces can move back into PureYAML later once the API and memory behavior are proven.