Character space allocation

[David Buck]

If I have a structure as follows;

typedef struct {
double x;
double y;
int size;
char text[256];
} text;

I have allocated a space of 256 bytes for some text entered. If the text is
less than 256 bytes, what happens to the rest of them.

I am interested as I want to append other objects after the text in memory,
and if the user only enters a few bytes, I only want to use that amount of
data (rounded to the next word);

if C automatically either writes the remaining bytes to a specific value, or
currupts them, I will have to do this another way.

--
David Buck
2D CAD for RISC OS at www.risccad.freeuk.com

[Chris Dollin]

David Buck wrote:

If I have a structure as follows;

typedef struct {
double x;
double y;
int size;
char text[256];
} text;

I have allocated a space of 256 bytes for some text entered. If the text
is less than 256 bytes, what happens to the rest of them.
Nothing. You asked for 256 characters; that's what you got. If you don't
care to use them, well, that's fine.
I am interested as I want to append other objects after the text in
memory, and if the user only enters a few bytes, I only want to use that
amount of data (rounded to the next word);
C doesn't let you randomly append objects to the end of data structures.
if C automatically either writes the remaining bytes to a specific value,
No (not unless you allocate a static text).
or currupts them,
No (but it won't stop /you/ corrupting them).
I will have to do this another way.

Yes, if you only want to use "enough" space: point into larger character
buffers or use mallocated space.

--
Chris "hey, dude, where's my train?" Dollin

[David Buck]

Chris Dollin wrote:

David Buck wrote:

If I have a structure as follows;

typedef struct {
double x;
double y;
int size;
char text[256];
} text;

I have allocated a space of 256 bytes for some text entered. If the
text is less than 256 bytes, what happens to the rest of them.

Nothing. You asked for 256 characters; that's what you got. If you
don't care to use them, well, that's fine.

I am interested as I want to append other objects after the text in
memory, and if the user only enters a few bytes, I only want to use
that amount of data (rounded to the next word);

C doesn't let you randomly append objects to the end of data
structures.

I didn't say random, nor to the end of data structures, all I said was after
this object in memory. It would be another structure, but I will point it to
the next word aligned address after the text - hence the question.

if C automatically either writes the remaining bytes to a specific
value,

No (not unless you allocate a static text).

or currupts them,

No (but it won't stop /you/ corrupting them).

I will have to do this another way.

Yes, if you only want to use "enough" space: point into larger
character buffers or use mallocated space.

Sounds like it will work OK.

Thanks for the info - much appreciated.

--
David Buck
2D CAD for RISC OS at www.risccad.freeuk.com

[Mike Smith]

"David Buck" <da********@freeuk.com> wrote in message
news:dq**********@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...

Sounds like it will work OK.

Thanks for the info - much appreciated.

--
David Buck
2D CAD for RISC OS at www.risccad.freeuk.com

You might be interested in article 2.6 in the FAQ

http://c-faq.com/struct/structhack.html

--
Mike