Function stringHashCode

runtime/JavaScript/src/antlr4/utils/stringHashCode.js:8–70

(value)

export const StringSeedHashCode = Math.round(Math.random() * Math.pow(2, 32));

export function stringHashCode (value) {
    if (!value) {
        return 0;
    }
    const type = typeof value;
    const key = type === 'string' ? value : type === 'object' && value.toString ? value.toString() : false;
    if (!key) {
        return 0;
    }
    let h1b, k1;

    const remainder = key.length & 3; // key.length % 4
    const bytes = key.length - remainder;
    let h1 = StringSeedHashCode;
    const c1 = 0xcc9e2d51;
    const c2 = 0x1b873593;
    let i = 0;

    while (i < bytes) {
        k1 =
            ((key.charCodeAt(i) & 0xff)) |
            ((key.charCodeAt(++i) & 0xff) << 8) |
            ((key.charCodeAt(++i) & 0xff) << 16) |
            ((key.charCodeAt(++i) & 0xff) << 24);
        ++i;

        k1 = ((((k1 & 0xffff) * c1) + ((((k1 >>> 16) * c1) & 0xffff) << 16))) & 0xffffffff;
        k1 = (k1 << 15) | (k1 >>> 17);
        k1 = ((((k1 & 0xffff) * c2) + ((((k1 >>> 16) * c2) & 0xffff) << 16))) & 0xffffffff;

        h1 ^= k1;
        h1 = (h1 << 13) | (h1 >>> 19);
        h1b = ((((h1 & 0xffff) * 5) + ((((h1 >>> 16) * 5) & 0xffff) << 16))) & 0xffffffff;
        h1 = (((h1b & 0xffff) + 0x6b64) + ((((h1b >>> 16) + 0xe654) & 0xffff) << 16));
    }

    k1 = 0;

    switch (remainder) {
        case 3:
            k1 ^= (key.charCodeAt(i + 2) & 0xff) << 16;
        // no-break
        case 2:
            k1 ^= (key.charCodeAt(i + 1) & 0xff) << 8;
        // no-break
        case 1:
            k1 ^= (key.charCodeAt(i) & 0xff);
            k1 = (((k1 & 0xffff) * c1) + ((((k1 >>> 16) * c1) & 0xffff) << 16)) & 0xffffffff;
            k1 = (k1 << 15) | (k1 >>> 17);
            k1 = (((k1 & 0xffff) * c2) + ((((k1 >>> 16) * c2) & 0xffff) << 16)) & 0xffffffff;
            h1 ^= k1;
    }

    h1 ^= key.length;

    h1 ^= h1 >>> 16;
    h1 = (((h1 & 0xffff) * 0x85ebca6b) + ((((h1 >>> 16) * 0x85ebca6b) & 0xffff) << 16)) & 0xffffffff;
    h1 ^= h1 >>> 13;