OpenEuphoria

Re: testing for size of pointer

• Posted by Matt Lewis <matthewwalkerlewis at gmail.com> Aug 19, 2005
• 477 views

Damien wrote:
> 
> how do you get the size of a pointer? or rather the size of the value the
> pointer points
> to? 
> 
> say I am using a function from a C library that returns a pointer, the pointer
> points
> to a string, now when I try to peek() the pointer to get the string it only
> returns
> the first letter in that string. How do I get the size of the string being
> pointed
> to?

You have to know what sort of data you're pointing at.  For a null terminated
string, you can just scan memory and look for a zero.  Some types of strings
(and other data structures) store their size as part of the structure.  Your
string is probably of the null-terminated type.  A typical null-termination
routine looks like this:

function peek_string( atom string )
	atom offset
	while peek(offset) do offset += 1 end while
	return peek( {string, offset-string})
end function

In general, you need to look at the documentation for whatever the data is.  
For complex structures, this may require knowing (or figuring out) sizes for 
lots of different types of data, and how the compiler handles offsets.

Matt Lewis