function readFixed64(/* this: Reader */) {

    /* istanbul ignore if */
    if (this.pos + 8 > this.len)
        throw indexOutOfRange(this, 8);

    return new LongBits(readFixed32_end(this.buf, this.pos += 4), readFixed32_end(this.buf, this.pos += 4));
}
Reads fixed 32 bits as a signed 32 bit integer.
@returns {number} Value read