16to32.test.js

import test from "ava";
import { getFloat16, setFloat16 } from "../lib/index.js";

const float16Buffer = new ArrayBuffer(2);
const float16View = new DataView(float16Buffer);

function test16to32(t, littleEndian) {
  for (let i = 0; i < 0xffff; i++) {
    float16View.setUint16(0, i, littleEndian);
    const f = getFloat16(float16View, 0, littleEndian);

    // The only values that don't round-trip are NaN, which always get serialized as 0x7e00
    // A value is NaN iff exponent === 0x7c00 AND mantissa !== 0
    const exponent = i & 0x7c00;
    const mantissa = i & 0x03ff;
    if (exponent === 0x7c00 && mantissa !== 0) {
      t.true(isNaN(f), "decode NaN value");
      setFloat16(float16View, 0, f, littleEndian);
      t.is(
        float16View.getUint16(0, littleEndian),
        0x7e00,
        "encode all NaN values as 0x7e00",
      );
    } else {
      setFloat16(float16View, 0, f, littleEndian);
      t.is(
        float16View.getUint16(0, littleEndian),
        i,
        "recover original uint16",
      );
    }
  }
}

test("round-trip every 16-bit value to float64 and back (big-endian)", (t) => {
  test16to32(t, false);
});

test("round-trip every 16-bit value to float64 and back (little-endian)", (t) => {
  test16to32(t, true);
});