/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 2002 Robert James Kaes <rjkaes@users.sourceforge.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* A hashmap implementation.  The keys are case-insensitive NULL terminated
 * strings, and the data is arbitrary lumps of data.  Copies of both the
 * key and the data in the hashmap itself, so you must free the original
 * key and data to avoid a memory leak.  The hashmap returns a pointer
 * to the data when a key is searched for, so take care in modifying the
 * data as it's modifying the data stored in the hashmap.  (In other words,
 * don't try to free the data, or realloc the memory. :)
 */

#include "tinyproxy.h"

#include "hashmap.h"
#include "heap.h"

/*
 * These structures are the storage for the hashmap.  Entries are stored in
 * struct hashentry_s (the key, data, and length), and all the "buckets" are
 * grouped together in hashmap_s.  The hashmap_s.size member is for
 * internal use.  It stores the number of buckets the hashmap was created
 * with.
 */
struct hashentry_s
{
  char *key;
  void *data;
  size_t len;

  struct hashentry_s *prev, *next;
};

struct hashbucket_s
{
  struct hashentry_s *head, *tail;
};

struct hashmap_s
{
  unsigned int size;
  hashmap_iter end_iterator;

  struct hashbucket_s *buckets;
};

/*
 * A NULL terminated string is passed to this function and a "hash" value
 * is produced within the range of [0 .. size)  (In other words, 0 to one
 * less than size.)
 * The contents of the key are converted to lowercase, so this function
 * is not case-sensitive.
 *
 * If any of the arguments are invalid a negative number is returned.
 */
static int
hashfunc (const char *key, unsigned int size)
{
  uint32_t hash;

  if (key == NULL)
    return -EINVAL;
  if (size == 0)
    return -ERANGE;

  for (hash = tolower (*key++); *key != '\0'; key++)
    {
      uint32_t bit = (hash & 1) ? (1 << (sizeof (uint32_t) - 1)) : 0;

      hash >>= 1;

      hash += tolower (*key) + bit;
    }

  /* Keep the hash within the table limits */
  return hash % size;
}

/*
 * Create a hashmap with the requested number of buckets.  If "nbuckets" is
 * not greater than zero a NULL is returned; otherwise, a _token_ to the
 * hashmap is returned.
 *
 * NULLs are also returned if memory could not be allocated for hashmap.
 */
hashmap_t
hashmap_create (unsigned int nbuckets)
{
  struct hashmap_s *ptr;

  if (nbuckets == 0)
    return NULL;

  ptr = safecalloc (1, sizeof (struct hashmap_s));
  if (!ptr)
    return NULL;

  ptr->size = nbuckets;
  ptr->buckets = safecalloc (nbuckets, sizeof (struct hashbucket_s));
  if (!ptr->buckets)
    {
      safefree (ptr);
      return NULL;
    }

  /* This points to "one" past the end of the hashmap. */
  ptr->end_iterator = 0;

  return ptr;
}

/*
 * Follow the chain of hashentries and delete them (including the data and
 * the key.)
 *
 * Returns: 0 if the function completed successfully
 *          negative number is returned if "entry" was NULL
 */
static inline int
delete_hashbucket (struct hashbucket_s *bucket)
{
  struct hashentry_s *nextptr;
  struct hashentry_s *ptr;

  if (bucket == NULL || bucket->head == NULL)
    return -EINVAL;

  ptr = bucket->head;
  while (ptr)
    {
      nextptr = ptr->next;

      safefree (ptr->key);
      safefree (ptr->data);
      safefree (ptr);

      ptr = nextptr;
    }

  return 0;
}

/*
 * Deletes a hashmap.  All the key/data pairs are also deleted.
 *
 * Returns: 0 on success
 *          negative if a NULL "map" was supplied
 */
int
hashmap_delete (hashmap_t map)
{
  unsigned int i;

  if (map == NULL)
    return -EINVAL;

  for (i = 0; i != map->size; i++)
    {
      if (map->buckets[i].head != NULL)
        {
          delete_hashbucket (&map->buckets[i]);
        }
    }

  safefree (map->buckets);
  safefree (map);

  return 0;
}

/*
 * Inserts a NULL terminated string (as the key), plus any arbitrary "data"
 * of "len" bytes.  Both the key and the data are copied, so the original
 * key/data must be freed to avoid a memory leak.
 * The "data" must be non-NULL and "len" must be greater than zero.  You
 * cannot insert NULL data in association with the key.
 *
 * Returns: 0 on success
 *          negative number if there are errors
 */
int
hashmap_insert (hashmap_t map, const char *key, const void *data, size_t len)
{
  struct hashentry_s *ptr;
  int hash;
  char *key_copy;
  void *data_copy;

  assert (map != NULL);
  assert (key != NULL);
  assert (data != NULL);
  assert (len > 0);

  if (map == NULL || key == NULL)
    return -EINVAL;
  if (!data || len < 1)
    return -ERANGE;

  hash = hashfunc (key, map->size);
  if (hash < 0)
    return hash;

  /*
   * First make copies of the key and data in case there is a memory
   * problem later.
   */
  key_copy = safestrdup (key);
  if (!key_copy)
    return -ENOMEM;

  data_copy = safemalloc (len);
  if (!data_copy)
    {
      safefree (key_copy);
      return -ENOMEM;
    }
  memcpy (data_copy, data, len);

  ptr = safemalloc (sizeof (struct hashentry_s));
  if (!ptr)
    {
      safefree (key_copy);
      safefree (data_copy);
      return -ENOMEM;
    }

  ptr->key = key_copy;
  ptr->data = data_copy;
  ptr->len = len;

  /*
   * Now add the entry to the end of the bucket chain.
   */
  ptr->next = NULL;
  ptr->prev = map->buckets[hash].tail;
  if (map->buckets[hash].tail)
    map->buckets[hash].tail->next = ptr;

  map->buckets[hash].tail = ptr;
  if (!map->buckets[hash].head)
    map->buckets[hash].head = ptr;

  map->end_iterator++;
  return 0;
}

/*
 * Get an iterator to the first entry.
 *
 * Returns: an negative value upon error.
 */
hashmap_iter
hashmap_first (hashmap_t map)
{
  assert (map != NULL);

  if (!map)
    return -EINVAL;

  if (map->end_iterator == 0)
    return -1;
  else
    return 0;
}

/*
 * Checks to see if the iterator is pointing at the "end" of the entries.
 *
 * Returns: 1 if it is the end
 *          0 otherwise
 */
int
hashmap_is_end (hashmap_t map, hashmap_iter iter)
{
  assert (map != NULL);
  assert (iter >= 0);

  if (!map || iter < 0)
    return -EINVAL;

  if (iter == map->end_iterator)
    return 1;
  else
    return 0;
}

/*
 * Return a "pointer" to the first instance of the particular key.  It can
 * be tested against hashmap_is_end() to see if the key was not found.
 *
 * Returns: negative upon an error
 *          an "iterator" pointing at the first key
 *          an "end-iterator" if the key wasn't found
 */
hashmap_iter
hashmap_find (hashmap_t map, const char *key)
{
  unsigned int i;
  hashmap_iter iter = 0;
  struct hashentry_s *ptr;

  assert (map != NULL);
  assert (key != NULL);

  if (!map || !key)
    return -EINVAL;

  /*
   * Loop through all the keys and look for the first occurrence
   * of a particular key.
   */
  for (i = 0; i != map->size; i++)
    {
      ptr = map->buckets[i].head;

      while (ptr)
        {
          if (strcasecmp (ptr->key, key) == 0)
            {
              /* Found it, so return the current count */
              return iter;
            }

          iter++;
          ptr = ptr->next;
        }
    }

  return iter;
}

/*
 * Retrieve the data associated with a particular iterator.
 *
 * Returns: the length of the data block upon success
 *          negative upon error
 */
ssize_t
hashmap_return_entry (hashmap_t map, hashmap_iter iter, char **key,
                      void **data)
{
  unsigned int i;
  struct hashentry_s *ptr;
  hashmap_iter count = 0;

  assert (map != NULL);
  assert (iter >= 0);
  assert (iter != map->end_iterator);
  assert (key != NULL);
  assert (data != NULL);

  if (!map || iter < 0 || !key || !data)
    return -EINVAL;

  for (i = 0; i != map->size; i++)
    {
      ptr = map->buckets[i].head;
      while (ptr)
        {
          if (count == iter)
            {
              /* This is the data so return it */
              *key = ptr->key;
              *data = ptr->data;
              return ptr->len;
            }

          ptr = ptr->next;
          count++;
        }
    }

  return -EFAULT;
}

/*
 * Searches for _any_ occurrences of "key" within the hashmap.
 *
 * Returns: negative upon an error
 *          zero if no key is found
 *          count found
 */
ssize_t
hashmap_search (hashmap_t map, const char *key)
{
  int hash;
  struct hashentry_s *ptr;
  ssize_t count = 0;

  if (map == NULL || key == NULL)
    return -EINVAL;

  hash = hashfunc (key, map->size);
  if (hash < 0)
    return hash;

  ptr = map->buckets[hash].head;

  /* All right, there is an entry here, now see if it's the one we want */
  while (ptr)
    {
      if (strcasecmp (ptr->key, key) == 0)
        ++count;

      /* This entry didn't contain the key; move to the next one */
      ptr = ptr->next;
    }

  return count;
}

/*
 * Get the first entry (assuming there is more than one) for a particular
 * key.  The data MUST be non-NULL.
 *
 * Returns: negative upon error
 *          zero if no entry is found
 *          length of data for the entry
 */
ssize_t
hashmap_entry_by_key (hashmap_t map, const char *key, void **data)
{
  int hash;
  struct hashentry_s *ptr;

  if (!map || !key || !data)
    return -EINVAL;

  hash = hashfunc (key, map->size);
  if (hash < 0)
    return hash;

  ptr = map->buckets[hash].head;

  while (ptr)
    {
      if (strcasecmp (ptr->key, key) == 0)
        {
          *data = ptr->data;
          return ptr->len;
        }

      ptr = ptr->next;
    }

  return 0;
}

/*
 * Go through the hashmap and remove the particular key.
 * NOTE: This will invalidate any iterators which have been created.
 *
 * Remove: negative upon error
 *         0 if the key was not found
 *         positive count of entries deleted
 */
ssize_t
hashmap_remove (hashmap_t map, const char *key)
{
  int hash;
  struct hashentry_s *ptr, *next;
  short int deleted = 0;

  if (map == NULL || key == NULL)
    return -EINVAL;

  hash = hashfunc (key, map->size);
  if (hash < 0)
    return hash;

  ptr = map->buckets[hash].head;
  while (ptr)
    {
      if (strcasecmp (ptr->key, key) == 0)
        {
          /*
           * Found the data, now need to remove everything
           * and update the hashmap.
           */
          next = ptr->next;

          if (ptr->prev)
            ptr->prev->next = ptr->next;
          if (ptr->next)
            ptr->next->prev = ptr->prev;

          if (map->buckets[hash].head == ptr)
            map->buckets[hash].head = ptr->next;
          if (map->buckets[hash].tail == ptr)
            map->buckets[hash].tail = ptr->prev;

          safefree (ptr->key);
          safefree (ptr->data);
          safefree (ptr);

          ++deleted;
          --map->end_iterator;

          ptr = next;
          continue;
        }

      /* This entry didn't contain the key; move to the next one */
      ptr = ptr->next;
    }

  /* The key was not found, so return 0 */
  return deleted;
}