@tai-kun/surrealdb/src/cbor/_float.ts

The SurrealDB SDK for JavaScript

export function getFloat16(view: DataView, offset: number): number {
  // https://www.rfc-editor.org/rfc/rfc8949.html#name-half-precision
  // の JavaScript バージョン:

  function ldexp(mantissa: number, exponent: number): number {
    return mantissa * Math.pow(2, exponent);
  }

  const half = (view.getUint8(offset) << 8) + view.getUint8(offset + 1);
  const exp = (half >> 10) & 0x1f;
  const mant = half & 0x3ff;
  const value = exp === 0
    ? ldexp(mant, -24)
    : exp !== 31
    ? ldexp(mant + 1024, exp - 25)
    : mant === 0
    ? Infinity
    : NaN;

  return half & 0x8000
    ? -value
    : value;
}