source: frontend/node_modules/es-abstract/helpers/valueToFloat16Bytes.js

'use strict';

var $abs = require('math-intrinsics/abs');
var $floor = require('math-intrinsics/floor');
var $pow = require('math-intrinsics/pow');

var isFinite = require('math-intrinsics/isFinite');
var isNaN = require('math-intrinsics/isNaN');
var isNegativeZero = require('math-intrinsics/isNegativeZero');

var maxFiniteFloat16 = 65504; // 2**16 - 2**5

module.exports = function valueToFloat16Bytes(value, isLittleEndian) {
        // NaN → exponent=all-ones, mantissa MSB=1 → 0x7e00
        if (isNaN(value)) {
                return isLittleEndian
                        ? [0x00, 0x7e]
                        : [0x7e, 0x00];
        }

        var leastSig;

        // ±0 → just the sign bit
        if (value === 0) {
                leastSig = isNegativeZero(value) ? 0x80 : 0x00;
                return isLittleEndian
                        ? [0x00, leastSig]
                        : [leastSig, 0x00];
        }

        // ±∞ → exponent=all-ones, mantissa=0 → 0x7c00 or 0xfc00
        if ($abs(value) > maxFiniteFloat16 || !isFinite(value)) {
                leastSig = value < 0 ? 0xfc : 0x7c;
                return isLittleEndian
                        ? [0x00, leastSig]
                        : [leastSig, 0x00];
        }

        var sign = value < 0 ? 1 : 0;
        value = $abs(value); // eslint-disable-line no-param-reassign

        // normalize to [1,2)
        var exponent = 0;
        while (value >= 2) {
                exponent += 1;
                value /= 2; // eslint-disable-line no-param-reassign
        }
        while (value < 1) {
                exponent -= 1;
                value *= 2; // eslint-disable-line no-param-reassign
        }

        // build mantissa (10 bits)
        var mantissa = value - 1;
        mantissa *= $pow(2, 10) + 0.5;
        mantissa = $floor(mantissa);

        // apply bias (15) and shift into place
        exponent += 15;
        exponent <<= 10;

        // pack sign, exponent, mantissa
        var result = (sign << 15) | exponent | mantissa;

        // split into two bytes
        var byte0 = result & 0xFF;
        result >>= 8;
        var byte1 = result & 0xFF;

        return isLittleEndian
                ? [byte0, byte1]
                : [byte1, byte0];
};