graph-explorer/src/graph-explorer/data/utils.ts

Graph Explorer can be used to explore and RDF graphs in SPARQL endpoints or on the web.

/** Generates random 32-digit hexadecimal string. */
export function generate128BitID() {
  function random32BitDigits() {
    return Math.floor((1 + Math.random()) * 0x100000000)
      .toString(16)
      .substring(1);
  }
  // generate by half because of restricted numerical precision
  return (
    random32BitDigits() +
    random32BitDigits() +
    random32BitDigits() +
    random32BitDigits()
  );
}

/**
 * Calculate a 32 bit FNV-1a hash
 * Found here: https://gist.github.com/vaiorabbit/5657561
 * Ref.: http://isthe.com/chongo/tech/comp/fnv/
 *
 * @param {string} str the input value
 * @param {integer} [seed] optionally pass the hash of the previous chunk
 * @returns {integer}
 */
export function hashFnv32a(str: string, seed = 0x811c9dc5): number {
  let i: number,
    l: number,
    hval = seed & 0x7fffffff;

  for (i = 0, l = str.length; i < l; i++) {
    hval ^= str.charCodeAt(i);
    hval +=
      (hval << 1) + (hval << 4) + (hval << 7) + (hval << 8) + (hval << 24);
  }
  return hval >>> 0;
}

/**
 * Extracts local name for URI the same way as it's done in RDF4J.
 */
export function getUriLocalName(uri: string): string | undefined {
  let index = uri.indexOf("#");
  if (index < 0) {
    index = uri.lastIndexOf("/");
  }
  if (index < 0) {
    index = uri.lastIndexOf(":");
  }
  if (index < 0) {
    return undefined;
  }
  return uri.substring(index + 1);
}