c print single precision floating point IEEE 754 little endian

flt.c

#include <stdio.h>

unsigned int u32pow( unsigned int x, unsigned int y )
{
	if(y == 0)
		return 1;
	for ( unsigned int i = 1; i < y; ++i )
		x += x;
	return x;
}

void extract_754_single(int value, int *mantissa, int *exp, int *sign)
{
	*sign = (value & (1 << 31)) != 0 ? -1 : 1;
	*exp = value;
	*exp &= ~(1 << 31);
	*exp &= ~0x7fffff;
	*exp >>= 23;
	*exp -= 127;
	*mantissa = value & 0x7fffff;
}

void convert_754_single(int value, int *integer, int *frac)
{
	int mantissa, exp, sign;
	extract_754_single(value, &mantissa, &exp, &sign);

	int pow = 1;
	int m = 10000;
	int total = m;
    
	for ( int i = 9; i < 32; ++i )
	{
		int set = ( mantissa & ( 1 << ( 32 - i - 1 ) ) );
		int p = m / u32pow(2, pow);
		if(!p) break;
		if ( set )
			total += p;
		++pow;
	}

	if ( exp > 0 )
		total *= u32pow( 2, exp );
	else
		total /= u32pow( 2, -exp );
	*integer = (total / m) * sign;
	*frac = total % m;
}

int build_754_single( int mantissa, int exp, int neg )
{
	int f = 0;
	if ( neg )
		f |= ( 1 << 31 );
	f |= ( ( ( exp + 127 ) & 0xff ) << 23 );
	f |= ( mantissa & 0x7fffff );
	return f;
}

int main()
{
	float flt = 3.14382;
	int f = *(int*)&flt;
	//int f = build_754( 7913472, 7, 1 );

	int m, e, n;
	extract_754_single( f, &m, &e, &n );
	printf( "m=%d,e=%d,n=%d\n", m, e, n );

	int integer, frac;
	convert_754_single(f, &integer, &frac);
	printf("approx: %d.%d\n", integer, frac);
	/*
	output:
	m=4797529,e=1,n=0
	approx: 3.14381998
	*/
	return 0;
}