quadstore/dist/get/leveliterator.js

Quadstore is a LevelDB-backed RDF graph database / triplestore for JavaScript runtimes (browsers, Node.js, Deno, Bun, ...) that implements the RDF/JS interfaces and supports SPARQL queries and querying across named graphs.

import { AsyncIterator } from 'asynciterator';
export class LevelIterator extends AsyncIterator {
    #source;
    #sourceEnded;
    #mapper;
    #bufsize;
    #nextbuf;
    #currbuf;
    #curridx;
    #loading;
    constructor(source, mapper, maxBufferSize = 256) {
        super();
        this.#source = source;
        this.#sourceEnded = false;
        this.#mapper = mapper;
        this.#bufsize = maxBufferSize;
        this.#currbuf = null;
        this.#nextbuf = null;
        this.#curridx = 0;
        this.#loading = false;
        this.readable = false;
        queueMicrotask(this.#loadNextBuffer);
    }
    read() {
        let item = null;
        if (!this.#currbuf) {
            this.#currbuf = this.#nextbuf;
            this.#nextbuf = null;
            this.#curridx = 0;
            this.#loadNextBuffer();
        }
        if (this.#currbuf) {
            if (this.#curridx < this.#currbuf.length) {
                item = this.#mapper(this.#currbuf[this.#curridx++]);
            }
            if (this.#curridx === this.#currbuf.length) {
                this.#currbuf = null;
            }
        }
        if (item === null) {
            this.readable = false;
            if (this.#sourceEnded) {
                this.close();
            }
        }
        return item;
    }
    #loadNextBuffer = () => {
        if (!this.#loading && !this.#nextbuf) {
            this.#loading = true;
            this.#source.nextv(this.#bufsize)
                .then(this.#onNextBuffer)
                .catch(this.#onNextBufferError);
        }
    };
    #onNextBuffer = (entries) => {
        this.#loading = false;
        if (entries.length) {
            this.readable = true;
            this.#nextbuf = entries;
        }
        else {
            this.#nextbuf = null;
            this.#sourceEnded = true;
            if (!this.#currbuf) {
                this.close();
            }
        }
    };
    #onNextBufferError = (err) => {
        this.#loading = false;
        this.#sourceEnded = true;
        if (!this.#currbuf) {
            this.close();
        }
    };
}
//# sourceMappingURL=leveliterator.js.map