Segmentation fault while inserting into a hash table - c

Question

I want to be able to use my getNextWord function to return a pointer to the next word in the file. I think I'm getting the seg fault while inserting but I just can't figure it out. Any help on this would be excellent. Also, I should probably find a better way of getting my hash_table_size than increasing a count for the total number of words in the file then rewinding. How can I make the size grow automatically?
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
int hash_table_size;
char* getNextWord(FILE* fd) {
char c;
char buffer[256];
int putChar = 0;
while((c = fgetc(fd)) != EOF) {
if(isalnum(c)) break;
}
if(c == EOF) return NULL;
buffer[putChar++] = c;
while((c = fgetc(fd)) != EOF) {
if(isspace(c) || putChar >= 256 -1) break;
if(isalnum(c))
buffer[putChar++] = c;
}
buffer[putChar] = '\0';
return strdup(buffer);
}
struct node {
struct node *next;
int count;
char* key;
};
struct list {
struct node *head;
int count;
};
struct list *hashTable = NULL;
/*
* djb2 hash function
*/
unsigned int hash(unsigned char *str) {
unsigned int hash = 5381;
int c;
while(c == *str++)
hash = ((hash << 5) + hash) + c;
return (hash % hash_table_size);
}
struct node* createNode(char *key) {
struct node *new_node;
new_node = (struct node *)malloc(sizeof(struct node));
strcpy(new_node->key, key);
new_node->next = NULL;
return new_node;
}
void hashInsert(char *str) {
int hash_dex = hash(str);
struct node *new_node = createNode(str);
if(!hashTable[hash_dex].head) {
hashTable[hash_dex].head = new_node;
hashTable[hash_dex].count = 1;
return;
}
new_node->next = (hashTable[hash_dex].head);
hashTable[hash_dex].head = new_node;
hashTable[hash_dex].count++;
return;
}
void display() {
struct node *current;
int i;
while(i < hash_table_size) {
if(hashTable[i].count == 0)
continue;
current = hashTable[i].head;
if(!current)
continue;
while(current != NULL) {
char tmp[256];
strcpy(tmp, current->key);
printf("%s", tmp);
current = current->next;
}
}
return;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
printf("Usage: ./hashFile textfile\n");
}
else {
FILE *file = fopen(argv[1], "r");
if(file == 0) {
printf("Could not open file\n");
}
else {
char *new_word;
while((new_word = getNextWord(file)) != NULL) {
hash_table_size++;
}
rewind(file);
hashTable = (struct list *)calloc(hash_table_size, sizeof(struct list));
while((new_word = getNextWord(file)) != NULL) {
hashInsert(new_word);
}
display();
fclose(file);
}
}
return 0;
}

Answer 1

int c;
while(c == *str++)
hash = ((hash << 5) + hash) + c;
c is not initialized here. As is i in display function. Please enable all the compiler warnings and fix them.
Also:
char c;
char buffer[256];
int putChar = 0;
while((c = fgetc(fd)) != EOF) {
if(isalnum(c)) break;
}
c has to be of type int not char.

Answer 2

change
while(c == *str++)
to
while(c = *str++)