fread can't read an object from file - c

Question

Task is to read a map from a file and then display it. The binary file begins with 2 floats and continues with objects of this format:
struct Node {
float height;
int terrainType;
float visitsCount;
struct Node *next;
}Node;
And the function doing the reading:
void showMapTerrain(struct Node Node)
{
FILE *fp;
if ((fp = fopen("map.bin", "rb")) == NULL) {
puts("Unable to open file.");
exit(7);
}
float mapLenght, alt;
if (fread(&mapLenght, sizeof(float), 1, fp) != 1) {
puts("Unable to read from file.");
exit(18);
}
if (fread(&alt, sizeof(float), 1, fp) != 1) {
puts("Unable to read from file.");
exit(20);
}
/*Idea with this is to get the 2 floats out of the way so I can start reading the objects with a single fread.*/
char *mapTerrain = (char *)calloc(mapLenght, sizeof(char));
while (1) {
if (fread(&Node, sizeof(struct Node), 1, fp) != 1) {
//But this bit right here fails, it reads 0 objects.
printf("fread: %d\n", fread(&Node, sizeof(struct Node), 1, fp));
puts("Unable to read from file.");
exit(30);
}
*mapTerrain = Node.terrainType;
}
puts("Terrain type map: ");
while (*mapTerrain) {
printf("[%c]", *mapTerrain);
}
free(mapTerrain);
}
The 2 floats are only in the beginning, so they're outside the loop, that reads objects. I'm pretty sure the syntax for the fread is correct, it's unclear to me what the problem is.
Also, it's not required to make a linked list in this function, we're creating an array of numbers (ranging 1-4, hence char*) and then displaying it.
Edit: the function doing the writing:
void addToFile(struct Node Node)
{
FILE *fp;
float mapLenght, alt;
if ((fp = fopen("map.bin", "rb")) == NULL) {
if ((fp = fopen("map.bin", "wb")) == NULL) {
//2 fopens to check if the file exists. If it doesn't, the user has to input the //2 floats in the beginning. Otherwise we skip straight to adding objects in the //file
puts("Unable to open the file.");
exit(7);
}
puts("How long is the map?");
scanf("%f", &mapLenght);
if (fwrite(&mapLenght, sizeof(float), 1, fp) != 1) {
puts("Unable to write to file.");
exit(6);
}
puts("What's the map's altitude?");
scanf("%f", &alt);
if (fwrite(&alt, sizeof(float), 1, fp) != 1) {
puts("Unable to write to file.");
}
fclose(fp);
}
else {
fclose(fp);
}
if ((fp = fopen("map.bin", "ab")) == NULL){
puts("Unable to open file for further writing.");
exit(7);
}
int c = 0;
while (1) {
puts("Inputting data for individual square meters of the map:");
printf("How high is square meter %d?", ++c);
puts("('-1' to stop.)");
scanf("%f", &Node.height);
if (Node.height == -1) {
system("cls");
puts("You've decided to stop adding data.");
break;
}
printf("What's the terrain type of square meter %d?\n", c);
puts("Values allowed: ");
puts("0 - flora");
puts("1 - waste");
puts("2 - water");
puts("3 - road");
puts("4 - building");
Node.terrainType = 7;
while (1) {
scanf("%d", &Node.terrainType);
if (Node.terrainType < 0 || Node.terrainType>4) {
puts("Invalid data.");
}
else {
break;
}
}
printf("What's the daily visit count for square meter %d?", c);
scanf("%f", &Node.visitsCount);
if (fwrite(&Node, sizeof(Node), 1, fp) != 1) {
//Unlike the other function, everything here works properly, even this fwrite
puts("Error writing data to file.");
exit(6);
}
}
}

Answer 1

My apologies, but I made a very dumb mistake. fread was reading objects just fine, it returned 0 when it got to EOF. I assumed it returned 0 on the first iteration. Fix is bellow:
int *mapTerrain = (int *)calloc(mapLenght, sizeof(int));
int i = 0;
while (1) {
if (fread(&Node, sizeof(struct Node), 1, fp) != 1) {
break;
}
mapTerrain[i] = Node.terrainType;
i++;
}
puts("Map by terrain type: ");
int n;
for (n = 0; n < i; n++) {
printf("[%d]", mapTerrain[n]);
}
puts("");
free(mapTerrain);