Having a generic function

[polas]

Afternoon everyone. I am having some trouble and thought a few of you
might be able to help me... I have a simple function to copy the
contents of one array into another - the arguments to the function are
the first array (to copy into), the second array (copy from) and the
number of items to copy, the prototype is void cpyarray (float * a,
float * b, int numbertocopy) - this worked fine initially.

However, I would now like to use this function to, not only copy
contents of float array, but also double array (and in the future
other types such as int arrays, char array etc...) As this is the
case, is there any way I can change the type declaration of the two
arrays in the fn prototype so that it simply copys them, without
casting to or expecting a specific type? I tried void * a, void *b ..
but that did not work

Cheers,
Nick

[Mark Bluemel]

polas wrote:

Afternoon everyone. I am having some trouble and thought a few of you
might be able to help me... I have a simple function to copy the
contents of one array into another - the arguments to the function are
the first array (to copy into), the second array (copy from) and the
number of items to copy, the prototype is void cpyarray (float * a,
float * b, int numbertocopy) - this worked fine initially.

What's stopping you using memcpy() or memmove()?

[santosh]

polas wrote:

Afternoon everyone. I am having some trouble and thought a few of you
might be able to help me... I have a simple function to copy the
contents of one array into another - the arguments to the function are
the first array (to copy into), the second array (copy from) and the
number of items to copy, the prototype is void cpyarray (float * a,
float * b, int numbertocopy) - this worked fine initially.

However, I would now like to use this function to, not only copy
contents of float array, but also double array (and in the future
other types such as int arrays, char array etc...) As this is the
case, is there any way I can change the type declaration of the two
arrays in the fn prototype so that it simply copys them, without
casting to or expecting a specific type? I tried void * a, void *b ..
but that did not work

You cannot directly deference void *. It must be cast to a type before any
deferencing. In your case an extra parameter to the function could let the
caller specify the types of the arrays, with which you can cast the void *
to the appropriate types before copying.

You can also specify that the function accepts unsigned char *. This would
imply more work for the calling function though.

[polas]

On 4 Oct, 13:17, santosh <[e-mail]:

polas wrote:

Afternoon everyone. I am having some trouble and thought a few of you
might be able to help me... I have a simple function to copy the
contents of one array into another - the arguments to the function are
the first array (to copy into), the second array (copy from) and the
number of items to copy, the prototype is void cpyarray (float * a,
float * b, int numbertocopy) - this worked fine initially.

However, I would now like to use this function to, not only copy
contents of float array, but also double array (and in the future
other types such as int arrays, char array etc...) As this is the
case, is there any way I can change the type declaration of the two
arrays in the fn prototype so that it simply copys them, without
casting to or expecting a specific type? I tried void * a, void *b ..
but that did not work

You cannot directly deference void *. It must be cast to a type before any
deferencing. In your case an extra parameter to the function could let the
caller specify the types of the arrays, with which you can cast the void *
to the appropriate types before copying.

You can also specify that the function accepts unsigned char *. This would
imply more work for the calling function though.

Thanks for the help both of you - I have tried both methods and they
both work well :) - as for the memcpy I completely forgot that I could
use that

[CBFalconer]

polas wrote:

>
Afternoon everyone. I am having some trouble and thought a few of
you might be able to help me... I have a simple function to copy
the contents of one array into another - the arguments to the
function are the first array (to copy into), the second array
(copy from) and the number of items to copy, the prototype is
void cpyarray (float * a, float * b, int numbertocopy) - this
worked fine initially.

However, I would now like to use this function to, not only copy
contents of float array, but also double array (and in the future
other types such as int arrays, char array etc...) As this is the
case, is there any way I can change the type declaration of the
two arrays in the fn prototype so that it simply copys them,
without casting to or expecting a specific type? I tried void
* a, void *b .. but that did not work

After careful examination of the detailed code you published, I
have concluded that the problem lies in line 42. Correct that.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>

--
Posted via a free Usenet account from http://www.teranews.com

[Army1987]

On Thu, 04 Oct 2007 04:58:40 -0700, polas wrote:

Afternoon everyone. I am having some trouble and thought a few of you
might be able to help me... I have a simple function to copy the
contents of one array into another - the arguments to the function are
the first array (to copy into), the second array (copy from) and the
number of items to copy, the prototype is void cpyarray (float * a,
float * b, int numbertocopy) - this worked fine initially.

However, I would now like to use this function to, not only copy
contents of float array, but also double array (and in the future
other types such as int arrays, char array etc...) As this is the
case, is there any way I can change the type declaration of the two
arrays in the fn prototype so that it simply copys them, without
casting to or expecting a specific type? I tried void * a, void *b ..
but that did not work

If the function's parameter has type void*, the argument is
converted to that type. The function cannot know what the type of
elements of the array are in the caller. It is the caller who has
to pass the size of them.
Try memcpy(dest, src, numbertocopy * sizeof *dest) directly,
without using another function. If you *need* to use another
function, pass the size of elements with another parameter.
--
Army1987 (Replace "NOSPAM" with "email")
A hamburger is better than nothing.
Nothing is better than eternal happiness.
Therefore, a hamburger is better than eternal happiness.