Adding an element to a struct that contains a char pointer - c

Question

Okay so I am sure this is not too difficult a question but I am lost after trying to figure it out for so long so here is the code first the declaration for my structs.
struct GraphicElement {
char* fileName;
struct GraphicElement* pNext;
};
struct RasterGraphic {
struct GraphicElement* GraphicElements;
};
Then I call a function that takes care of the initialization which I believe is working properly.
int main(void)
{
char response;
BOOL RUNNING = TRUE;
struct RasterGraphic RG;
_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
InitRasterGraphic(&RG);
The init function is as follows
void InitRasterGraphic(struct RasterGraphic* pA)
{
pA->GraphicElements = malloc(sizeof(struct GraphicElement));
if (pA->GraphicElements == NULL) return;
//pA->GraphicElements = 0;
//pA->GraphicElements->pNext = NULL;
//pA->GraphicElements->fileName = NULL;
pA->GraphicElements->fileName = (char*)malloc(sizeof(char));
return;
}
So the next part of code is where I am going to ask my question. I have a function that takes a user input of some sort of string. Id like to take that input and add it to the next element. So every time the user calls the function they put in their input and its added to the next element. My code right now is a mess and I know it definitely is probably way off I've tried a bunch of things already. I believe I need to use realloc. What I am not able to wrap my head around here is how to take the input and add it so that later on I can printf all the elements in order. so for example user calls function 3 times and puts in inputs "hello" "world". Later I would like to cycle through and print
graphic 1 is "hello"
graphic 2 is "world"
void InsertGraphicElement(struct RasterGraphic* pA)
{
char response[256];
printf("Insert a GraphicElement in the RasterGraphic\nPlease enter the GraphicElement filename: ");
scanf("%s", &response[0]);
pA->GraphicElements->fileName = realloc(pA->GraphicElements, 256*sizeof(char));
pA->GraphicElements++;
strcpy(pA->GraphicElements->fileName, &response);
if (pA->GraphicElements == 1){
printf("\nThis is the first GraphicElement in the list\n");
}
return;
}

Answer 1

Here are the few issues in your code.
I believe InitRasterGraphic should just initialize the pA->GraphicElements = NULL instead of mallocing it. Since same should be handled in InsertGraphicElement function.
pA->GraphicElements->fileName = (char*)malloc(sizeof(char)); this will just allocate the memory of size single char and there is no point in allocing and reallocing.
scanf("%s", &response[0]); should be scanf("%s", &response[0]);.
pA->GraphicElements++; This is wrong instead use one more member to maintain the number of nodes in the list.
Hence after correcting the above issues your code will look like below.
your RasterGraphic will look like below.
struct RasterGraphic {
int numNodes;
struct GraphicElement* GraphicElements;
};
Your InitRasterGraphic will look like below.
void InitRasterGraphic(struct RasterGraphic* pA)
{
pA->GraphicElements = NULL;
pA->numNodes = 0;
return;
}
Your InsertGraphicElement will look like below.
void InsertGraphicElement(struct RasterGraphic* pA)
{
struct GraphicElement *newNode = malloc(sizeof(*newNode));
if (newNode == NULL) return;
newNode->fileName = malloc(256*sizeof(char));
if (newNode->fileName == NULL) return;
newNode->pNext = NULL;
printf("Insert a GraphicElement in the RasterGraphic\nPlease enter the GraphicElement filename: ");
scanf("%s", newNode->fileName);
if (pA->GraphicElements == NULL)
{
pA->GraphicElements = newNode;
}
else
{
struct GraphicElement *tempHead = pA->GraphicElements;
while(tempHead->pNext != NULL)
{
tempHead = tempHead->pNext;
}
tempHead->pNext = newNode;
}
pA->numNodes++;
if (pA->numNodes == 1){
printf("\nThis is the first GraphicElement in the list\n");
}
return;
}