Deallocation of Dynamic Arrays? - c

Question

Here's the code I am working with...
while(temp[i]!=0){
while(temp[i]!=3){
FrameBuffer[a]=temp[i];
i++;
a++;
}
FrameBuffer[a]=temp[i];
printf(" Framebuffer: %s ", FrameBuffer);
result=layer1(FrameBuffer,PacketAction);
i++;
a=0;
}
The problem is that I want FrameBuffer to be reset each time it goes through the inner while loop (Size of FrameBuffer is 0 at start of loop). I've tried using free(FrameBuffer) but I get an error because I free the array more than once. I also tried writing FrameBuffer=NULL, but that did not work. Any help would be greatly appreciated. Thank you!

Answer 1

If you just need to initialise FrameBuffer before the start of each inner loop, memset can be used-:
while(temp[i]!=0) {
memset(FrameBuffer, 0, sizeof(FrameBuffer));
while(temp[i]!=3) {

Answer 2

Since you don't show the declarations or give a particularly good description of the input string, temp, it is a bit hard to know what you're up to.
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
extern int somefunc(const char *fb, int pa);
extern int layer1(const char *fb, int pa);
int somefunc(const char *temp, int PacketAction)
{
int rc = 0;
char *FrameBuffer = calloc(2048, sizeof(char));
if (FrameBuffer != 0)
{
int i = 0;
while (temp[i] != '\0')
{
int a = 0;
while (temp[i] != 3)
FrameBuffer[a++] = temp[i++];
FrameBuffer[a++] = temp[i++];
FrameBuffer[a] = '\0';
assert(a < 2048);
printf("Framebuffer: %.*s\n", a, FrameBuffer);
int result = layer1(FrameBuffer, PacketAction);
if (rc == 0)
rc = result;
}
}
return rc;
}
This is probably sufficient. The function layer1 gets a null terminated string in FrameBuffer (it has no other visible way of determining how long the data is).
Note that by declaring a in the scope of the outer loop, I don't need to reinitialize it at the end of the loop. I've used a++ and i++ to increment the counters; it allows for compact notation with no loss of readability to the experienced C programmer — though I concede it can be a little more difficult for novice programmers to handle. Nevertheless, the idiom is worth learning.
I wonder if the inner loop should check for '\0' as well as 3 (aka '\3' or '\003'); I would need to know whether nulls can ever appear in temp other than at the very end. The code shown takes a lazy way out of validating for no overflow of the FrameBuffer. It would be better still if the function was told the length of the input temp:
void somefunc(const char *temp, size_t templen, int PacketAction)
The code could be written more resiliently. It could probably use strlen(temp), but it isn't absolutely clear from the available information.