@libp2p/multistream-select/dist/src/handle.js

JavaScript implementation of multistream-select

import { lpStream } from '@libp2p/utils';
import { encode } from 'it-length-prefixed';
import { Uint8ArrayList } from 'uint8arraylist';
import { fromString as uint8ArrayFromString } from 'uint8arrays/from-string';
import { MAX_PROTOCOL_LENGTH, PROTOCOL_ID } from './constants.js';
import { readString } from './multistream.js';
/**
 * Handle multistream protocol selections for the given list of protocols.
 *
 * Note that after a protocol is handled `listener` can no longer be used.
 *
 * @param stream - A duplex iterable stream to listen on
 * @param protocols - A list of protocols (or single protocol) that this listener is able to speak.
 * @param options - an options object containing an AbortSignal and an optional boolean `writeBytes` - if this is true, `Uint8Array`s will be written into `duplex`, otherwise `Uint8ArrayList`s will
 * @returns A stream for the selected protocol and the protocol that was selected from the list of protocols provided to `select`
 * @example
 *
 * ```TypeScript
 * import { pipe } from 'it-pipe'
 * import * as mss from '@libp2p/multistream-select'
 * import { Mplex } from '@libp2p/mplex'
 *
 * const muxer = new Mplex({
 *   async onStream (muxedStream) {
 *   // mss.handle(handledProtocols)
 *   // Returns selected stream and protocol
 *   const { stream, protocol } = await mss.handle(muxedStream, [
 *     '/ipfs-dht/1.0.0',
 *     '/ipfs-bitswap/1.0.0'
 *   ])
 *
 *   // Typically here we'd call the handler function that was registered in
 *   // libp2p for the given protocol:
 *   // e.g. handlers[protocol].handler(stream)
 *   //
 *   // If protocol was /ipfs-dht/1.0.0 it might do something like this:
 *   // try {
 *   //   await pipe(
 *   //     dhtStream,
 *   //     source => (async function * () {
 *   //       for await (const chunk of source)
 *   //         // Incoming DHT data -> process and yield to respond
 *   //     })(),
 *   //     dhtStream
 *   //   )
 *   // } catch (err) {
 *   //   // Error in stream
 *   // }
 *   }
 * })
 * ```
 */
export async function handle(stream, protocols, options = {}) {
    protocols = Array.isArray(protocols) ? protocols : [protocols];
    const log = stream.log.newScope('mss:handle');
    const lp = lpStream(stream, {
        ...options,
        maxDataLength: MAX_PROTOCOL_LENGTH,
        maxLengthLength: 2 // 2 bytes is enough to length-prefix MAX_PROTOCOL_LENGTH
    });
    while (true) {
        log.trace('reading incoming string');
        const protocol = await readString(lp, options);
        log.trace('read "%s"', protocol);
        if (protocol === PROTOCOL_ID) {
            log.trace('respond with "%s" for "%s"', PROTOCOL_ID, protocol);
            await lp.write(uint8ArrayFromString(`${PROTOCOL_ID}\n`), options);
            log.trace('responded with "%s" for "%s"', PROTOCOL_ID, protocol);
            continue;
        }
        if (protocols.includes(protocol)) {
            log.trace('respond with "%s" for "%s"', protocol, protocol);
            await lp.write(uint8ArrayFromString(`${protocol}\n`), options);
            log.trace('responded with "%s" for "%s"', protocol, protocol);
            lp.unwrap();
            return protocol;
        }
        if (protocol === 'ls') {
            // <varint-msg-len><varint-proto-name-len><proto-name>\n<varint-proto-name-len><proto-name>\n\n
            const protos = new Uint8ArrayList(...protocols.map(p => encode.single(uint8ArrayFromString(`${p}\n`))), uint8ArrayFromString('\n'));
            log.trace('respond with "%s" for %s', protocols, protocol);
            await lp.write(protos, options);
            log.trace('responded with "%s" for %s', protocols, protocol);
            continue;
        }
        log.trace('respond with "na" for "%s"', protocol);
        await lp.write(uint8ArrayFromString('na\n'), options);
        log('responded with "na" for "%s"', protocol);
    }
}
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