Inserting into a Hash Table - c

Question

I am trying to get words inserted into a hash table. When I run the code, it's supposed to give me a list of the frequency of each word, but it just gives me nothing.
I'm sure it's either to do with my print function, or my insert function, probably more my insert function. I know it's isn't mylib.h, but I'm just not sure where I'm going wrong.
It doesn't insert anything into my table or print it. I'm not really sure what's going on.
hashtable.c:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "htable.h"
struct htablerec {
char **key;
int *frequencies;
int num_keys;
int capacity;
};
void *emalloc(size_t s) {
void *result = malloc(s);
if (NULL == result) {
fprintf(stderr, "Memory allocation failed!\n");
exit(EXIT_FAILURE);
}
return result;
}
htable htable_new(int capacity) {
int i;
htable h = emalloc(sizeof * h);
h->capacity = capacity;
h->num_keys = 0;
h->frequencies = emalloc(h->capacity * sizeof h->frequencies[0]);
h->key = emalloc(h->capacity * sizeof h->key[0]);
for (i = 0; i < h->capacity; i++) {
h->frequencies[i] = 0;
h->key[i] = NULL;
}
return h;
}
void htable_free(htable h) {
free(h->frequencies);
free(h->key);
free(h);
}
static unsigned int htable_word_to_int(char *word) {
unsigned int result = 0;
while (*word != '\0') {
result = (*word++ + 31 * result);
}
return result;
}
int htable_insert(htable h, char *str) {
int i;
/*convert string to integer*/
unsigned int index = htable_word_to_int(str);
/*calculate index to insert into hash table*/
int remainder = index%h->capacity;
/*once calculated position in the hash table, 3 possibilities occur*/
/*no string in this positon, copy string to that position, increment number of keys, return 1*/
if (h->key[remainder] == NULL) {
h->frequencies[remainder] = 1;
h->num_keys++;
return 1;
}
/*the exact same string is at the position, increment frequency at that position, return frequency*/
if (strcmp(str, h->key[remainder]) == 0) {
h->frequencies[remainder]++;
return h->frequencies[remainder];
}/*a string is at that position, but it isnt the rightone, keep moving along the array
until you find either an open space or the string you are looking for*/
if (h->key[remainder] != NULL && strcmp(str, h->key[remainder]) != 0) {
/*you may need to wrap back around to the beginning of the table, so each time you add
to the position you should also mod by the table capacity.*/
for (i = 0; i <= h->capacity; i++) {
if (h->key[remainder] != NULL && h->capacity == i) {
i = 0;
}
/*no string in this positon, copy string to that position, increment number of keys*/
if (h->key[remainder] == NULL) {
h->frequencies[remainder] = 1;
h->num_keys++;
}
/*if you find the string you were looking for, increment the frequecny at the position
and return the frequency*/
if (strcmp(str, h->key[remainder]) == 0) {
h->frequencies[remainder]++;
return h->frequencies[remainder];
}
}
}
/*if you have kept looking for an open space but there isnt one, the hash table must be full so return 0*/
return 0;
}
void htable_print(htable h, FILE *stream) {
int i;
for(i = 0; i < h->capacity; i++) {
if(h->key[i] != NULL) {
fprintf(stream, "%d%s\n", h->frequencies[i], h->key[i]);
}
}
}
htable.h:
#ifndef HTABLE_H_
#define HTABLE_H_
#include <stdio.h>
typedef struct htablerec *htable;
extern void htable_free(htable h);
extern int htable_insert(htable h, char *str);
extern htable htable_new(int capacity);
extern void htable_print(htable h, FILE *stream);
extern int htable_search(htable h, char *str);
#endif
mylib.c:
#include <stdio.h>
#include <stdlib.h>
#include "mylib.h"
#include "htable.h"
int main(void) {
htable h = htable_new(18143);
char word[256];
while (getword(word, sizeof word, stdin) !=EOF) {
htable_insert(h, word);
}
htable_print(h, stdout);
htable_free(h);
return EXIT_SUCCESS;
}
mylib.h:
#include <assert.h>
#include <ctype.h>
#include <stdio.h>
int getword(char *s, int limit, FILE *stream) {
int c;
char *w = s;
assert(limit > 0 && s != NULL && stream != NULL);
/*skip to the start fo the word */
while (!isalnum(c = getc(stream)) && EOF != c)
;
if(EOF == c) {
return EOF;
} else if (--limit > 0) { /*reduce limit by 1 to allow for the \0 */
*w++ = tolower(c);
}
while(--limit > 0) {
if(isalnum(c = getc(stream))) {
*w++ = tolower(c);
} else if ('\'' == c) {
limit++;
} else {
break;
}
}
*w = '\0';
return w - s;
}

Answer 1

You never set h->key[remainder] to anything in htable_insert, so h->key[i] is still NULL for all i when you call htable_print.

Answer 2

/*no string in this positon, copy string to that position, increment number of keys, return 1*/
if (h->key[remainder] == NULL) {
h->frequencies[remainder] = 1;
h->num_keys++;
return 1;
}
...
/*no string in this positon, copy string to that position, increment number of keys*/
if (h->key[remainder] == NULL) {
h->frequencies[remainder] = 1;
h->num_keys++;
}
You never copy the string. Try something like...
char *key = emalloc(strlen(str) + 1);
strcpy(str, key);
h->key[remainder] = key;