How to store a 64 bit value into 2 unsigned long variables?

[ariyan]

'C' help needed

How to store a 64 bit value into 2 unsigned long variable (of 32 bit)?

Let,

unsigned long a; // variable 'a' will be incremented regularly and 'll be stored in b
void fun(void)
{
unsigned long double b;
b += a; // if b is a 64 bit variable ,
// regular addition of 'a' into 'b' will increase the value greater than 32 bit
};

Now instead of using variable b of using 64 bit, I have to use two unsigned long variable(let c, d of 32 bit each) and store the value in a into c and d, which is not a problem in case of storing that value into 'b'.

 

[bobcat1]

Re: 'C' help needed

Hi

You can use UNION to share data variables

All the best

Bobi

 

[StefB]

Re: 'C' help needed

Or...

extern unsigned long a;

unsigned long c = 0UL;
unsigned long d = 0UL;

void fun(void)
{
/* check overflow for c += a */
if ( (0xFFFFFFFFUL - a) <= c )
{
d += 1;
}

/* overflow is ignored now */
c += a;

/* example: use of the 'big' number */
{
unsigned long double big_number;
big_number = ((unsigned long double) d)<<32 + c;
}
}