ieee754.c


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/*
 * Copyright (C) 2018 Tomasz Kramkowski <tk@the-tk.com>
 * SPDX-License-Identifier: MIT
 */
#include <assert.h>
#include <math.h>
#include <stdbool.h>
#include <stdio.h>

#include "ieee754.h"

// ieee754f: convert f32 to float
float ieee754f(unsigned long b)
{
	bool isneg;
	int exp;
	float n;

	isneg = (b >> 31) & 0x1;
	exp = (b >> 23) & 0xff;
	n = b & 0x7fffff;

	if (exp == 0xff) {
		if (n) {
			/* TODO: work out what a negative NaN means */
			assert(!isneg);
			return NAN;
		} else {
			return isneg ? -INFINITY : INFINITY;
		}
	} else if (exp == 0) {
		if (n == 0)
			return isneg ? -0 : 0;
		exp = -126;
	} else {
		n += 0x1p23f;
		exp -= 127;
	}

	n = ldexpf(n, exp - 23);

	return isneg ? -n : n;
}