Added Float16

deno.json

@@ -4,7 +4,8 @@
 	"license": "MIT",
 	"exports": {
 		".": "./mod.ts",
-		"./i24": "./i24.ts"
+		"./i24": "./i24.ts",
+		"./f16": "./f16.ts"
 	},
 	"imports": {
 		"@deno/dnt": "jsr:@deno/dnt@^0.41.3",

f16.test.ts

@@ -0,0 +1,71 @@
+import { assertEquals } from '@std/assert';
+
+import { getFloat16, setFloat16 } from './f16.ts';
+import f16 from './spec/f16.json' with { type: 'json' };
+import f64i16 from './spec/f64i16.json' with { type: 'json' };
+
+const F16 = (f16 as (string | number)[]).map(Number);
+const F64I16 = (f64i16 as (string | number)[][]).map((a) => a.map(Number)) as [
+	number,
+	number,
+][];
+
+Deno.test('getFloat16 BE', () => {
+	const dataView = new DataView(new ArrayBuffer(2));
+	Object.defineProperty(dataView, 'getFloat16', {
+		value: null,
+	});
+	for (let i = 0; i < F16.length; i++) {
+		dataView.setUint16(0, i, false);
+		assertEquals(getFloat16(dataView, 0, false), F16[i]);
+	}
+});
+
+Deno.test('getFloat16 LE', () => {
+	const dataView = new DataView(new ArrayBuffer(2));
+	Object.defineProperty(dataView, 'getFloat16', {
+		value: null,
+	});
+	for (let i = 0; i < F16.length; i++) {
+		dataView.setUint16(0, i, true);
+		assertEquals(getFloat16(dataView, 0, true), F16[i]);
+	}
+});
+
+Deno.test('setFloat16 BE', () => {
+	const dataView = new DataView(new ArrayBuffer(2));
+	Object.defineProperty(dataView, 'setFloat16', {
+		value: null,
+	});
+	for (let i = 0; i < F16.length; i++) {
+		setFloat16(dataView, 0, F16[i], false);
+		assertEquals(getFloat16(dataView, 0, false), F16[i]);
+		setFloat16(dataView, 0, F16[i] + Number.EPSILON, false);
+		assertEquals(getFloat16(dataView, 0, false), F16[i]);
+		setFloat16(dataView, 0, F16[i] - Number.EPSILON, false);
+		assertEquals(getFloat16(dataView, 0, false), F16[i]);
+	}
+	for (const [f64, i16] of F64I16) {
+		setFloat16(dataView, 0, f64, false);
+		assertEquals(dataView.getUint16(0, false), i16);
+	}
+});
+
+Deno.test('setFloat16 LE', () => {
+	const dataView = new DataView(new ArrayBuffer(2));
+	Object.defineProperty(dataView, 'setFloat16', {
+		value: null,
+	});
+	for (let i = 0; i < F16.length; i++) {
+		setFloat16(dataView, 0, F16[i], true);
+		assertEquals(getFloat16(dataView, 0, true), F16[i]);
+		setFloat16(dataView, 0, F16[i] + Number.EPSILON, true);
+		assertEquals(getFloat16(dataView, 0, true), F16[i]);
+		setFloat16(dataView, 0, F16[i] - Number.EPSILON, true);
+		assertEquals(getFloat16(dataView, 0, true), F16[i]);
+	}
+	for (const [f64, i16] of F64I16) {
+		setFloat16(dataView, 0, f64, true);
+		assertEquals(dataView.getUint16(0, true), i16);
+	}
+});

f16.ts

@@ -0,0 +1,67 @@
+let b;
+
+/**
+ * Get 16-bit float.
+ *
+ * @param dataView Data view.
+ * @param byteOffset Byte offset.
+ * @param littleEndian Little endian.
+ * @returns Float value.
+ */
+export function getFloat16(
+	dataView: DataView,
+	offset: number,
+	littleEndian = false,
+): number {
+	let m = dataView.getUint16(offset, littleEndian);
+	const s = m >> 8;
+	let e = s & 127;
+	m = (e & 3) * 256 + (m & 255);
+	if ((e >>= 2) === 31) {
+		m = m ? NaN : Infinity;
+	} else {
+		if (e) {
+			m += 1024;
+			e--;
+		}
+		m *= Math.pow(2, e - 24);
+	}
+	return (s >> 7) ? -m : m;
+}
+
+/**
+ * Set 16-bit float.
+ *
+ * @param dataView Data view.
+ * @param byteOffset Byte offset.
+ * @param value Float value.
+ * @param littleEndian Little endian.
+ */
+export function setFloat16(
+	dataView: DataView,
+	offset: number,
+	value: number,
+	littleEndian = false,
+): void {
+	b ??= new DataView(new ArrayBuffer(4));
+	b.setFloat32(0, value);
+	let f = b.getUint32(0);
+	let v = f & 0x80000000;
+	f ^= v;
+	v >>= 16;
+	if (f >= 0x47800000) {
+		v |= 0x7c00 | (f > 0x7f800000 ? 512 | f >> 13 & 1023 : 0);
+	} else if (f >= 0x33000000) {
+		let e = f >> 23;
+		if (f >= 0x38800000) {
+			v |= e - 112 << 10 | f >> 13 & 1023;
+			v += f >> 12 & (f << 20 ? 1 : v & 1);
+		} else {
+			e = 126 - e;
+			f = f & 0x7fffff | 0x800000;
+			v |= f >> e--;
+			v += f >> e & (f << 32 - e ? 1 : v & 1);
+		}
+	}
+	dataView.setUint16(offset, v, littleEndian);
+}

mod.ts

@@ -1 +1,2 @@
+export * from './f16.ts';
 export * from './i24.ts';