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Dynamic Allocation

Posted on 1998-03-09
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Last Modified: 2010-04-10
Hi,
    basically I'm writing some stuff using char pointers that are dynamically created via new for example:
new char *p = "Hi Mom, hows it going?"; but my real question is, then when I want to say append, or prepend to that data, how do I ensure memory is allocated for that, or do I have to create a new object for that purpose?

thanks
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Question by:jwilcox
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6 Comments
 
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Accepted Solution

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q2guo earned 70 total points
ID: 1183299
When you are working with a char array, operations like append, prepend is not going to allocate memory by itself.  The programmer will have to create another char array with enough space to hold the new array.

For example, to append to a char array
#include <string.h>

char *p = "Hi Mom, ";
char *s = "hows it going?";
strcat(p, s);   // don't do this
             // since p can only hold up to 8 chars, so you can't
             // append s to p.
// below is what you might do
char *newchar = new char [strlen(p)+strlen(s)+1];
strcat(newchar, p);
strcat(newchar, s);
// now newchar contains "Hi Mom, hows it going?"

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Expert Comment

by:q2guo
ID: 1183300
Jwilcox, since you are using C++.  Why not use some kind of existing String class.  It will make you life a lot easier.
You can perform operations such as prepend, append easily and most of the memory management is handled by the string class itself.
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Author Comment

by:jwilcox
ID: 1183301
Alright, that is what I was plannin to do in the first place, but I couldn't find the include file for the string class that is part of the proposed standard library, so figured I'd try this way.
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LVL 1

Author Comment

by:jwilcox
ID: 1183302
Alright, that is what I was plannin to do in the first place, but I couldn't find the include file for the string class that is part of the proposed standard library, so figured I'd try this way, as far as using a built in string class.
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Expert Comment

by:q2guo
ID: 1183303
What compiler are you using?
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Author Comment

by:jwilcox
ID: 1183304
g++ 2.7.2.3
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