dev-cpp-users

[Dev-C++] pointers of pointers structures memory allocation

[<and...@su...>]

1-#include <stdlib.h>
2-#include <stdio.h>
3-int main()
4-{
5-
6-   char **p, name[80];
7-
8-   ... commands ...
9-
10-  return(0)
11-}

Suppose p will store a set of names (strings), that is, on position *p will
be the variable sized "text1", position *(p+1) will be "text2" and so on.
Variable sizes are up to 80. I will do:
    1-some gets(name) commands to store the several "texts" at each
iteraction;
    2-execute a malloc command;
    3-store name contents inside each position of p, one per address; and
    4-free the pointer at the end of the program.

Question(s):
A) Is that clear my statement for you? If its,
B) How can I use the malloc command for this case? At each
iteraction/storage? One malloc for
each *p and other for the **p one?

Thanks
Andre

Re: [Dev-C++] pointers of pointers structures memory allocation

[Ricardo R. <ri...@po...>]

Essentially you want to allocate memory for a char matrix in a dynamical 
way.

(1) First you must allocate memory for the rows.
Imagine you need to store 50 strings, then p should point
to a pointer array able to allocate the 50 memory positions
of your 50 strings:

      p = (char **) malloc(50*sizeof(char*));

(2) Second you want allocate in each row a string with a maximum
of 80 characters, then you should reserve this memory:

    for(i=0 ; i<50 ; i++)
              p[i] = (char *) malloc(80*sizeof(char));

(3) Now tou can store your strings:

   for(i=0 ; i<50 ; i++)   
  {
        printf("\n Give me a char string: ");
        gets(p[i]);
  }    

(4) Finally you free the allocated memory in this way:

          for(i=0 ; i<50 ; i++)  free(p[i]);
          free (p);
     

Hope this can help you.
Ricardo.

RES: [Dev-C++] pointers of pointers structures memory allocation

[<and...@su...>]

<<This>> is what I like this list!!!
objetive answers and useful discussions

Thank you all
Andre

-----Mensagem original-----
De: Ricardo Lopez Ruiz [mailto:ri...@po...]
Enviada em: sexta-feira, 21 de marco de 2003 07:03
Para: Andre Macario Barros; Dev-C++
Assunto: Re: [Dev-C++] pointers of pointers structures memory allocation


Essentially you want to allocate memory for a char matrix in a dynamical 
way.

(1) First you must allocate memory for the rows.
Imagine you need to store 50 strings, then p should point
to a pointer array able to allocate the 50 memory positions
of your 50 strings:

      p = (char **) malloc(50*sizeof(char*));

(2) Second you want allocate in each row a string with a maximum
of 80 characters, then you should reserve this memory:

    for(i=0 ; i<50 ; i++)
              p[i] = (char *) malloc(80*sizeof(char));

(3) Now tou can store your strings:

   for(i=0 ; i<50 ; i++)   
  {
        printf("\n Give me a char string: ");
        gets(p[i]);
  }    

(4) Finally you free the allocated memory in this way:

          for(i=0 ; i<50 ; i++)  free(p[i]);
          free (p);
     

Hope this can help you.
Ricardo.