/* 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 vector implementation.  The vector can be of an arbitrary length, and
 * the data for each entry is an lump of data (the size is stored in the
 * vector.)
 */

#include "tinyproxy.h"

#include "heap.h"
#include "vector.h"

/*
 * These structures are the storage for the "vector".  Entries are
 * stored in struct vectorentry_s (the data and the length), and the
 * "vector" structure is implemented as a linked-list.  The struct
 * vector_s stores a pointer to the first vector (vector[0]) and a
 * count of the number of entries (or how long the vector is.)
 */
struct vectorentry_s
{
  void *data;
  size_t len;

  struct vectorentry_s *next;
};

struct vector_s
{
  size_t num_entries;
  struct vectorentry_s *head;
  struct vectorentry_s *tail;
};

/*
 * Create an vector.  The vector initially has no elements and no
 * storage has been allocated for the entries.
 *
 * A NULL is returned if memory could not be allocated for the
 * vector.
 */
vector_t
vector_create (void)
{
  vector_t vector;

  vector = safemalloc (sizeof (struct vector_s));
  if (!vector)
    return NULL;

  vector->num_entries = 0;
  vector->head = vector->tail = NULL;

  return vector;
}

/*
 * Deletes an vector.  All the entries when this function is run.
 *
 * Returns: 0 on success
 *          negative if a NULL vector is supplied
 */
int
vector_delete (vector_t vector)
{
  struct vectorentry_s *ptr, *next;

  if (!vector)
    return -EINVAL;

  ptr = vector->head;
  while (ptr)
    {
      next = ptr->next;
      safefree (ptr->data);
      safefree (ptr);

      ptr = next;
    }

  safefree (vector);

  return 0;
}

/*
 * Appends an entry into the vector.  The entry is an arbitrary
 * collection of bytes of _len_ octets.  The data is copied into the
 * vector, so the original data must be freed to avoid a memory leak.
 * The "data" must be non-NULL and the "len" must be greater than zero.
 * "pos" is either 0 to prepend the data, or 1 to append the data.
 *
 * Returns: 0 on success
 *          negative number if there are errors
 */
#define INSERT_PREPEND 0
#define INSERT_APPEND 1

static int
vector_insert (vector_t vector, void *data, size_t len, int pos)
{
  struct vectorentry_s *entry;

  if (!vector || !data || len <= 0 ||
      (pos != INSERT_PREPEND && pos != INSERT_APPEND))
    return -EINVAL;

  entry = safemalloc (sizeof (struct vectorentry_s));
  if (!entry)
    return -ENOMEM;

  entry->data = safemalloc (len);
  if (!entry->data)
    {
      safefree (entry);
      return -ENOMEM;
    }

  memcpy (entry->data, data, len);
  entry->len = len;
  entry->next = NULL;

  /* If there is no head or tail, create them */
  if (!vector->head && !vector->tail)
    vector->head = vector->tail = entry;
  else if (pos == 0)
    {
      /* prepend the entry */
      entry->next = vector->head;
      vector->head = entry;
    }
  else
    {
      /* append the entry */
      vector->tail->next = entry;
      vector->tail = entry;
    }

  vector->num_entries++;

  return 0;
}

/*
 * The following two function are used to make the API clearer.  As you
 * can see they simply call the vector_insert() function with appropriate
 * arguments.
 */
int
vector_append (vector_t vector, void *data, ssize_t len)
{
  return vector_insert (vector, data, len, INSERT_APPEND);
}

int
vector_prepend (vector_t vector, void *data, ssize_t len)
{
  return vector_insert (vector, data, len, INSERT_PREPEND);
}

/*
 * A pointer to the data at position "pos" (zero based) is returned.
 * If the vector is out of bound, data is set to NULL.
 *
 * Returns: negative upon an error
 *          length of data if position is valid
 */
void *
vector_getentry (vector_t vector, size_t pos, size_t * size)
{
  struct vectorentry_s *ptr;
  size_t loc;

  if (!vector || pos >= vector->num_entries)
    return NULL;

  loc = 0;
  ptr = vector->head;

  while (loc != pos)
    {
      ptr = ptr->next;
      loc++;
    }

  if (size)
    *size = ptr->len;

  return ptr->data;
}

/*
 * Returns the number of entries (or the length) of the vector.
 *
 * Returns: negative if vector is not valid
 *          positive length of vector otherwise
 */
ssize_t
vector_length (vector_t vector)
{
  if (!vector)
    return -EINVAL;

  return vector->num_entries;
}