fp16/lib/setFloat16.js

Half-precision 16-bit floating point numbers

import { float16Emin, float16Emax, float32Emax, float32Precision, float32View, } from "./utils.js";
export function setFloat16(view, offset, value, littleEndian) {
    if (isNaN(value)) {
        return view.setUint16(offset, 0x7e00, littleEndian);
    }
    else if (value === Infinity) {
        return view.setUint16(offset, 0x7c00, littleEndian);
    }
    else if (value === -Infinity) {
        return view.setUint16(offset, 0xfc00, littleEndian);
    }
    else if (Object.is(value, 0)) {
        return view.setUint16(offset, 0, littleEndian);
    }
    else if (Object.is(value, -0)) {
        return view.setUint16(offset, 0x8000, littleEndian);
    }
    float32View.setFloat32(0, value, littleEndian);
    const i32 = float32View.getInt32(0, littleEndian);
    const sign = i32 & (1 << 31);
    const exponent = i32 & 0x7f800000;
    const mantissa = i32 & 0x007fffff;
    const exponentValue = (exponent >>> float32Precision) - float32Emax;
    const e = exponentValue + float16Emax;
    if (float16Emax < exponentValue) {
        // overflow to +/- Infinity
        return view.setUint16(offset, (sign >>> 16) | 0x7c00, littleEndian);
    }
    if (exponentValue < float16Emin) {
        if (14 - e > 24) {
            // cannot be rounded to a subnormal number; underflow to +/- 0
            return view.setUint16(0, sign >>> 16, littleEndian);
        }
        else {
            // can be rounded to a subnormal number
            const c = mantissa | 0x00800000;
            const m = c >>> (14 - e);
            const r = 1 << (13 - e);
            if (c & r && c & (3 * r - 1)) {
                return view.setUint16(offset, (sign >>> 16) | (m + 1), littleEndian);
            }
            else {
                return view.setUint16(offset, (sign >>> 16) | m, littleEndian);
            }
        }
    }
    const r = 0x00001000;
    let i16 = (sign >>> 16) | (e << 10) | (mantissa >> 13);
    if (mantissa & r && mantissa & (3 * r - 1)) {
        return view.setUint16(offset, i16 + 1, littleEndian);
    }
    else {
        return view.setUint16(offset, i16, littleEndian);
    }
}