at design time I could have declare a variable like this:
char szDesignTimeArray[120][128];
The above declaration is 120 arrays of size 128. At run time I need to allocate the following:
char szRunTime[?][128];
I know the size of the arrays but I do not how many arrays I need to allocate. How can I declare this and allocate them when I know the number?
Thnaks all
I assume at run-time you know the Row_Size as well.
You can dynamically allocate a multidimensional array at run time, as follows:
#include <stdlib.h>
int **array;
array = malloc(nrows * sizeof(int *));
if(array == NULL)
{
fprintf(stderr, "out of memory\n");
exit or return
}
for(i = 0; i < nrows; i++)
{
array[i] = malloc(ncolumns * sizeof(int));
if(array[i] == NULL)
{
fprintf(stderr, "out of memory\n");
exit or return
}
}
Reference:
free(array);.
calloc be used instead of malloc here?
With the length of the rows statically know, you could also allocate
char (*szRunTime)[128];
// obtain row count
szRunTime = malloc(rowCount * sizeof *szRunTime);
memory to a pointer to char[128]. That way, you get a contiguous block of memory, which may give better locality, and you need only free one pointer.
If the number of rows is not too large, using a variable length array,
rowCount = whatever;
char szRunTime[rowCount][128];
may however be the best option if C99 or later is supported.
use this ,, where Variable is the how many array you want :
char **szRunTime = malloc(sizeof(char *)*Variable);
int i;
for(i=0 ; i<Variable ; i++)
szRunTime[i] = malloc(sizeof(char)*128);
