public

clarkgrubb / gist:400762

Created 2010-05-14

#include "hashtable.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
 
void
hashtable_error(char* msg) {
  puts(msg);
}
 
hashtable*
hashtable_create(unsigned int size) {
  if (0 == size) {
    hashtable_error("size must be positive");
    return 0;
  }
  hashtable* retval = malloc(sizeof(hashtable));
  retval->array = calloc(size, sizeof(hashtable_list_item));
  retval->size = size;
  return retval;
}
 
unsigned int
hash_pow(unsigned int base, unsigned int exponent) {
  unsigned int i;
  unsigned int retval = 1;
  for (i=0; i<exponent; i++) {
    retval *= base;
  }
  return retval;
}
 
unsigned int
hash(char* s, unsigned int modulus) {
  unsigned int code = 0;
  unsigned int i;
  int len = strlen(s);
  for(i=0; i<len; i++) {
    code += s[i] * hash_pow(256, i);
  }
  return code % modulus;
}
 
void
hashtable_insert(hashtable* ht, char* key, char* value) {
  if (0 == ht) {
    hashtable_error("first argument is null");
    return;
  }
  unsigned int slot;
  slot = hash(key, ht->size);
  hashtable_list_item* new_item = malloc(sizeof(hashtable_list_item));
  new_item->key = key;
  new_item->value = value;
  new_item->next = ht->array[slot];
  ht->array[slot] = new_item;
}
 
char*
hashtable_search(hashtable* ht, char* key) {
  unsigned int slot;
  slot = hash(key, ht->size);
  hashtable_list_item* hli;
  hli = ht->array[slot];
  while (0 != hli) {
    if (0 == strcmp(hli->key, key)) {
      return hli->value;
    }
    hli = hli->next;
  }
  return 0;
}
 
void
hashtable_delete(hashtable* ht, char* key) {
  unsigned int slot;
  slot = hash(key, ht->size);
  hashtable_list_item **hlip;
  hlip = &(ht->array[slot]);
  while ( *hlip ) {
    if (0 == strcmp((*hlip)->key, key)) {
      (*hlip) = (*hlip)->next;
    }
  }
}