@simple-libs/stream-utils/dist/index.js

A small set of utilities for streams.

import { Readable } from 'stream';
/**
 * Get all items from an async iterable and return them as an array.
 * @param iterable
 * @returns A promise that resolves to an array of items.
 */
export async function toArray(iterable) {
    const result = [];
    for await (const item of iterable) {
        result.push(item);
    }
    return result;
}
/**
 * Concatenate all buffers from an async iterable into a single Buffer.
 * @param iterable
 * @returns A promise that resolves to a single Buffer containing all concatenated buffers.
 */
export async function concatBufferStream(iterable) {
    return Buffer.concat(await toArray(iterable));
}
/**
 * Concatenate all strings from an async iterable into a single string.
 * @param iterable
 * @returns A promise that resolves to a single string containing all concatenated strings.
 */
export async function concatStringStream(iterable) {
    return (await toArray(iterable)).join('');
}
/**
 * Get the first item from an async iterable.
 * @param stream
 * @returns A promise that resolves to the first item, or null if the iterable is empty.
 */
export async function firstFromStream(stream) {
    for await (const tag of stream) {
        return tag;
    }
    return null;
}
/**
 * Merges multiple Readable streams into a single Readable stream.
 * Each chunk will be an object containing the source stream name and the chunk data.
 * @param streams - An object where keys are stream names and values are Readable streams.
 * @returns A merged Readable stream.
 */
export function mergeReadables(streams) {
    const mergedStream = new Readable({
        objectMode: true,
        read() {
            /* no-op */
        }
    });
    let ended = 0;
    Object.entries(streams).forEach(([name, stream], _i, entries) => {
        stream
            .on('data', (chunk) => mergedStream.push({
            source: name,
            chunk
        }))
            .on('end', () => {
            ended += 1;
            if (ended === entries.length) {
                mergedStream.push(null);
            }
        })
            .on('error', err => mergedStream.destroy(err));
    });
    return mergedStream;
}
/**
 * Split stream by separator.
 * @param stream
 * @param separator
 * @yields String chunks.
 */
export async function* splitStream(stream, separator) {
    let chunk;
    let payload;
    let buffer = '';
    for await (chunk of stream) {
        buffer += chunk.toString();
        if (buffer.includes(separator)) {
            payload = buffer.split(separator);
            buffer = payload.pop() || '';
            yield* payload;
        }
    }
    if (buffer) {
        yield buffer;
    }
}
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