/**
 * hash.c
 *   An implementation of hash tables, based loosely on code from K&R 2nd,
 *   pp. 143-145.
 */

// +---------+--------------------------------------------------------
// | Headers |
// +---------+

#include <stdlib.h>  // For malloc
#include "hash.h"
#include "hashfun.h"


// +-------+----------------------------------------------------------
// | Types |
// +-------+

/**
 * Nodes in a list in one element of the hash table.
 */
struct nlist {          
  struct nlist *next;   // Next entry in the list
  char *key;            // The key
  char *value;          // The value
}; // struct nlist


// +-----------------+------------------------------------------------
// | Local Functions |
// +-----------------+

/**
 * Find an nlist element in a hash table.  (Based on lookup in K&R.)
 */
struct nlist *
lookup (struct hash *hashtab, char *str)
{
  unsigned pos = hash (str) % hashtab->size;
  struct nlist *np;

  for (np = hashtab->contents[pos]; np != NULL; np = np->next)
    if (strcmp (str, np->key) == 0)
      return np;   // found
  return NULL; // not found
} // lookup


// +--------------------+---------------------------------------------
// | Exported Functions |
// +--------------------+

char *
find (struct hash *hashtab, char *key)
{
  struct nlist *np = lookup (hashtab, key);
  if (np == NULL)
    return NULL;
  else
    return np->value;
} // find

struct hash *
new_hash (int size)
{
  struct hash *hashtab = malloc (sizeof (struct hash));

  // Allocate space for the hash table.
  if (hash == NULL)
    return NULL;
  hashtab->size = size;

  // Allocate space for the real part of the hash table.
  hashtab->contents = malloc (size * sizeof (struct nlist *));
  // If we fail, clean up.
  if (hashtab->contents == NULL)
    {
      free (hashtab)
      return NULL;
    }

  // And we're done.
  return hashtab;
} // new_hash (int)