C string into an int pointer

**cosmo1996** · 07-31-2007

I've bee having a problem with my code. I have a structure with a nested union that contains to pointers. I want to read the first 4bytes from a buffer into a the integer pointer from the structure.

This si the code:

Code:

typedef struct s_test{
		char	m_flag;
			union{
			char	*id;
			int		*value;
		}utest;
		
}ST;


int main()
{
	char 	test_buffer[]="abcdefghijkl12345678";
	ST s_table[100];
	int i=0;

	s_table.utest.id= test_buffer;
		
	for (i=0; i<3; i++)
	{
		s_table[i].utest.value=&test_buffer[i]; /* How do i make my structure point to the arra?????*/
		printf(" Buffer &#37;08x\n\n", *(s_table.utest.value));
	}
	
	  return 0;
}

Many thanks.

**matsp** · 07-31-2007

Ehm, exactly what do you want to do?

value is a pointer to an integer, and you are setting it to the address of a char in your test_buffer... That seems to be fine code as such.

Then you print the value that the pointer points at. I expect that to print 64636261 assuming it's an x86 processor (or other little endian one). Is this what you wanted?

By the way, a char * and int * is essentially the same type - the only difference is the size of the data it points to. So if you were to add a line to print a %x of *s_table.utest.id, you'd get 61.

--
Mats

**cosmo1996** · 07-31-2007

Yes i want to print 64636261, but I am not getting that ... I get an error in my int pointer when i make it point to the buffer....

Code:

s_table[i].utest.value=&test_buffer[i];

Thank you.

**matsp** · 07-31-2007

What error?

Shouldn't you index the printout too?

--
Mats

**cosmo1996** · 07-31-2007

At compilation it give me:
error #2168: Operands of = have incompatible types 'int *' and 'char *'.
*** Error code: 1 ***
on this line:
s_table[i].utest.value=&test_buffer[i];

Is this a wrong assignment????

**matsp** · 07-31-2007

So, there's two options:

1. use the fact that you are using a union in the first place: set the "id" part to point to the string.

2. use a cast (int *) before the & in that line. That tells the compiler "make this type compatible with "int *". Cast's aren't "pretty" programming, but sometimes you have to.

--
Mats

**cosmo1996** · 07-31-2007

Thank you very much... lets see if my boss likes it with the cast... I'll let you know later..

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