Published
Edited
Nov 29, 2021
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Importers
3 stars
print_hexfloat(3.141592653589793)
parse_hexfloat('0x1.921fb54442d18p+1')
['+0x1.ff00000000000p+0010', '0x1.ffp10', '0x1ff.0p2', '0x7fc.0p0'].map(parse_hexfloat)
['+0x1.6b00000000000p-1066', '+0x0.000000000016bp-1022'].map(parse_hexfloat)
print_hexfloat = {
const flt_arr = new Float64Array([1]);
const int_arr = new Int32Array(flt_arr.buffer);
const SIGN_MASK = 0x7fffffff; // 0111 1111 1111 1111 1111 1111 1111 1111
const EXP_MASK = 0x7ff00000; // 0111 1111 1111 0000 0000 0000 0000 0000
// HI = 1 on little endian platforms, 0 on big-endian platforms.
const HI = little_endian, LO = 1 - little_endian;
return (x) => {
if (isNaN(x)) return `NaN`;
if (!isFinite(x)) return `${x < 0 ? '-' : '+'}Infinity`;
if (x === 0) return `${1/x < 0 ? '-' : '+'}0x0.0000000000000p+0000`;
flt_arr[0] = x;
// extract exponent, set exponent to 0
var exp = ((int_arr[HI] & EXP_MASK) >> 20) - 0x3ff;
if (exp == -1023) { // denormal
flt_arr[0] = x * 2 ** 1023;
exp += ((int_arr[HI] & EXP_MASK) >> 20) - 0x3ff;
}
int_arr[HI] = (int_arr[HI] & ~EXP_MASK) ^ 0x3ff00000;
// extract sign, set sign to 0
var minus = !!(int_arr[HI] & ~SIGN_MASK) ? '-' : '+';
int_arr[HI] = int_arr[HI] & SIGN_MASK;
var hex = flt_arr[0].toString(16) + ((flt_arr[0] === 1) ? '.' : '');
hex = (hex + '0000000000000').slice(0, 15);
var expstr = (exp >= 0 ? '+' : '-') + ('0000' + Math.abs(exp)).slice(-4);
return `${minus}0x${hex}p${expstr}`;
}
}
parse_hexfloat = {
var re = RegExp(`
(?<sign>[+-])?
(?:
(?<inf>Infinity) | (?<nan>NaN) | # for round-trip with print_float
(?<type>0[xX])
(?= [0-9a-fA-F] | \\.[0-9a-fA-F] ) # force at least 1 digit
(?<int>[0-9a-fA-F]*)
(?:\\.(?<frac>[0-9a-fA-F]*))?
(?:[pP]
(?<esign>[+-])?
(?<exp>[0-9]+)
)? # required by the spec, but optional here
)
`.replace(/[#].*$|\s/gm, ''));
return (str) => {
try {
var grp = re.exec(str).groups;
var sign = (grp.sign === '-') ? -1 : 1;
if (grp.nan === 'NaN') return NaN;
if (grp.inf === 'Infinity') return Infinity * sign;
var int = grp.int ? parseInt(grp.int, 16) : 0;
var frac = grp.frac ? parseInt(grp.frac, 16) * 16**(-grp.frac.length) : 0;
var exp = grp.exp ? parseInt(grp.exp, 10) * (grp.esign === '-' ? -1 : 1) : 0;
return sign * (int + frac) * 2 ** exp;
}
catch {
throw new Error(`Invalid hexadecimal float literal: ${str}`);
}
}
}
print_decfloat = (x) => {
if (isNaN(x)) return `NaN`;
if (!isFinite(x)) return `${x < 0 ? '-' : '+'}Infinity`;
var str = Number.parseFloat(eval(x)).toExponential(16);
if (!(str[0] === '-')) str = '+' + str;
if ((x === 0) && (1/x < 0)) str = '-' + str.slice(1);
return str.slice(0,21) + ('00' + str.slice(21)).slice(-3);
}
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