@metamask/ocap-kernel/dist/store/methods/queue.mjs

OCap kernel core components

/**
 * Get a queue store object that provides functionality for managing queues.
 *
 * @param ctx - The store context.
 * @returns A queue store object that maps various persistent kernel data
 * structures onto `kv`.
 */
// eslint-disable-next-line @typescript-eslint/explicit-function-return-type
export function getQueueMethods(ctx) {
    /**
     * Find out how long some queue is.
     *
     * @param queueName - The name of the queue of interest.
     *
     * @returns the number of items in the given queue.
     */
    function getQueueLength(queueName) {
        const qk = `queue.${queueName}`;
        const head = ctx.kv.get(`${qk}.head`);
        const tail = ctx.kv.get(`${qk}.tail`);
        if (head === undefined || tail === undefined) {
            throw Error(`unknown queue ${queueName}`);
        }
        return Number(head) - Number(tail);
    }
    /**
     * Append a message to the kernel's run queue.
     *
     * @param message - The message to enqueue.
     */
    function enqueueRun(message) {
        ctx.runQueueLengthCache += 1;
        ctx.runQueue.enqueue(message);
    }
    /**
     * Fetch the next message on the kernel's run queue.
     *
     * @returns The next message on the run queue, or undefined if the queue is
     * empty.
     */
    function dequeueRun() {
        ctx.runQueueLengthCache -= 1;
        return ctx.runQueue.dequeue();
    }
    /**
     * Obtain the number of entries in the run queue.
     *
     * @returns the number of items in the run queue.
     */
    function runQueueLength() {
        if (ctx.runQueueLengthCache < 0) {
            ctx.runQueueLengthCache = getQueueLength('run');
        }
        return ctx.runQueueLengthCache;
    }
    return {
        getQueueLength,
        enqueueRun,
        dequeueRun,
        runQueueLength,
    };
}
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