OS/2 Shareware BBS: 10 Tools/10-Tools.zip/snipps97.zip/DEQUE.C

C/C++ Source or Header | 1997-07-04 | 19KB | 875 lines

/* +++Date last modified: 05-Jul-1997 */


/****************************************************************
 *
 *  File : DEQUE.c
 *
 *  Author: Peter Yard [1993.01.02] -- 02 Jan 1993
 *
 *  Disclaimer: This code is released to the public domain.
 *
 *  Description:
 *      Generic double ended queue (Deque pronounced DEK) for handling
 *      any data types, with sorting.
 *
 *      By use of various functions in this module the caller
 *      can create stacks, queues, lists, doubly linked lists,
 *      sorted lists, indexed lists.  All lists are dynamic.
 *
 *      It is the responsibility of the caller to malloc and free
 *      memory for insertion into the queue. A pointer to the object
 *      is used so that not only can any data be used but various kinds
 *      of data can be pushed on the same queue if one so wished e.g.
 *      various length string literals mixed with pointers to structures
 *      or integers etc.
 *
 *  Enhancements:
 *      A future improvement would be the option of multiple "cursors"
 *      so that multiple locations could occur in the one queue to allow
 *      placemarkers and additional flexibility.  Perhaps even use queue
 *      itself to have a list of cursors.
 *
 * Usage:
 *
 *          /x init queue x/
 *          queue  q;
 *          Q_Init(&q);
 *
 *      To create a stack :
 *
 *          Q_PushHead(&q, &mydata1); /x push x/
 *          Q_PushHead(&q, &mydata2);
 *          .....
 *          data_ptr = Q_PopHead(&q); /x pop x/
 *          .....
 *          data_ptr = Q_First(&q);   /x top of stack x/
 *
 *      To create a FIFO:
 *
 *          Q_PushHead(&q, &mydata1);
 *          .....
 *          data_ptr = Q_PopTail(&q);
 *
 *      To create a double list:
 *
 *          data_ptr = Q_First(&q);
 *          ....
 *          data_ptr = Q_Next(&q);
 *          data_ptr = Q_Last(&q);
 *          if (Q_Empty(&q)) ....
 *          .....
 *          data_ptr = Q_Previous(&q);
 *
 *      To create a sorted list:
 *
 *          Q_PushHead(&q, &mydata1); /x push x/
 *          Q_PushHead(&q, &mydata2);
 *          .....
 *          if (!Q_Sort(&q, MyFunction))
 *              .. error ..
 *
 *          /x fill in key field of mydata1.
 *           * NB: Q_Find does linear search
 *           x/
 *
 *          if (Q_Find(&q, &mydata1, MyFunction))
 *          {
 *              /x found it, queue cursor now at correct record x/
 *              /x can retrieve with x/
 *              data_ptr = Q_Get(&q);
 *
 *              /x alter data , write back with x/
 *              Q_Put(&q, data_ptr);
 *          }
 *
 *          /x Search with binary search x/
 *          if (Q_Seek(&q, &mydata, MyFunction))
 *              /x etc x/
 *
 *
 ****************************************************************/


#include <stdlib.h>

#include "deque.h"


static void QuickSort(void *list[], int low, int high,
                      int (*Comp)(const void *, const void *));
static int  Q_BSearch(queue *q, void *key,
                      int (*Comp)(const void *, const void *));

/* The index: a pointer to pointers */

static  void        **index;
static  datanode    **posn_index;


/***
 *
 ** function    : Q_Init
 *
 ** purpose     : Initialise queue object and pointers.
 *
 ** parameters  : 'queue' pointer.
 *
 ** returns     : True_ if init successful else False_
 *
 ** comments    :
 ***/

int Q_Init(queue  *q)
{
      q->head = q->tail = NULL;
      q->cursor = q->head;
      q->size = 0;
      q->sorted = False_;

      return True_;
}

/***
 *
 ** function    : Q_Start
 *
 ** purpose     : tests if cursor is at head of queue
 *
 ** parameters  : 'queue' pointer.
 *
 ** returns     : boolean - True_ is at head else False_
 *
 ** comments    :
 *
 ***/

int Q_Start(queue *q)
{
      return (q->cursor == q->head);
}


/***
 *
 ** function    : Q_End
 *
 ** purpose     : boolean test if cursor at tail of queue
 *
 ** parameters  : 'queue' pointer to test.
 *
 ** returns     : True_ or False_
 *
 ** comments    :
 *
 ***/

int Q_End(queue *q)
{
      return (q->cursor == q->tail);
}


/***
 *
 ** function    : Q_Empty
 *
 ** purpose     : test if queue has nothing in it.
 *
 ** parameters  : 'queue' pointer
 *
 ** returns     : True_ if empty queue, else False_
 *
 ** comments    :
 *
 ***/

int Q_Empty(queue *q)
{
      return (q->size == 0);
}

/***
 *
 ** function    : Q_Size
 *
 ** purpose     : return the number of elements in the queue
 *
 ** parameters  : queue pointer
 *
 ** returns     : number of elements
 *
 ** comments    :
 *
 ***/

int Q_Size(queue *q)
{
      return q->size;
}


/***
 *
 ** function    : Q_First
 *
 ** purpose     : position queue cursor to first element (head) of queue.
 *
 ** parameters  : 'queue' pointer
 *
 ** returns     : pointer to data at head. If queue is empty returns NULL
 *
 ** comments    :
 *
 ***/

void *Q_First(queue *q)
{
      if (Q_Empty(q))
            return NULL;

      q->cursor = q->head;

      return  q->cursor->data;
}


/***
 *
 ** function    : Q_Last
 *
 ** purpose     : locate cursor at tail of queue.
 *
 ** parameters  : 'queue' pointer
 *
 ** returns     : pointer to data at tail , if queue empty returns NULL
 *
 ** comments    :
 *
 ***/

void *Q_Last(queue *q)
{
      if (Q_Empty(q))
            return NULL;

      q->cursor = q->tail;

      return  q->cursor->data;
}


/***
 *
 ** function    : Q_PushHead
 *
 ** purpose     : put a data pointer at the head of the queue
 *
 ** parameters  : 'queue' pointer, void pointer to the data.
 *
 ** returns     : True_ if success else False_ if unable to push data.
 *
 ** comments    :
 *
 ***/

int Q_PushHead(queue *q, void *d)
{
      node    *n;
      datanode *p;

      q->head->prev = malloc(sizeof(datanode));
      if (q->head->prev == NULL)
            return False_;

      n = q->head;

      p = q->head->prev;
      q->head = (node*)p;
      q->head->prev = NULL;

      if (q->size == 0)
      {
            q->head->next = NULL;
            q->tail = q->head;
      }
      else  q->head->next = (datanode*)n;

      q->head->data = d;
      q->size++;

      q->cursor = q->head;

      q->sorted = False_;

      return True_;
}



/***
 *
 ** function    : Q_PushTail
 *
 ** purpose     : put a data element pointer at the tail of the queue
 *
 ** parameters  : queue pointer, pointer to the data
 *
 ** returns     : True_ if data pushed, False_ if data not inserted.
 *
 ** comments    :
 *
 ***/

int Q_PushTail(queue *q, void *d)
{
      node        *p;
      datanode    *n;

      q->tail->next = malloc(sizeof(datanode));
      if (q->tail->next == NULL)
            return False_;

      p = q->tail;
      n = q->tail->next;
      q->tail = (node *)n;

      if (q->size == 0)
      {
            q->tail->prev = NULL;
            q->head = q->tail;
      }
      else  q->tail->prev = (datanode *)p;

      q->tail->next = NULL;

      q->tail->data =  d;
      q->cursor = q->tail;
      q->size++;

      q->sorted = False_;

      return True_;
}



/***
 *
 ** function    : Q_PopHead
 *
 ** purpose     : remove and return the top element at the head of the
 *                queue.
 *
 ** parameters  : queue pointer
 *
 ** returns     : pointer to data element or NULL if queue is empty.
 *
 ** comments    :
 *
 ***/

void *Q_PopHead(queue *q)
{
      datanode    *n;
      void        *d;

      if (Q_Empty(q))
            return NULL;

      d = q->head->data;
      n = q->head->next;
      free(q->head);

      q->size--;

      if (q->size == 0)
            q->head = q->tail = q->cursor = NULL;
      else
      {
            q->head = (node *)n;
            q->head->prev = NULL;
            q->cursor = q->head;
      }

      q->sorted = False_;

      return d;
}


/***
 *
 ** function    : Q_PopTail
 *
 ** purpose     : remove element from tail of queue and return data.
 *
 ** parameters  : queue pointer
 *
 ** returns     : pointer to data element that was at tail. NULL if queue
 *                empty.
 *
 ** comments    :
 *
 ***/

void *Q_PopTail(queue *q)
{
      datanode    *p;
      void        *d;

      if (Q_Empty(q))
            return NULL;

      d = q->tail->data;
      p = q->tail->prev;
      free(q->tail);
      q->size--;

      if (q->size == 0)
            q->head = q->tail = q->cursor = NULL;
      else
      {
            q->tail = (node *)p;
            q->tail->next = NULL;
            q->cursor = q->tail;
      }

      q->sorted = False_;

      return d;
}



/***
 *
 ** function    : Q_Next
 *
 ** purpose     : Move to the next element in the queue without popping
 *
 ** parameters  : queue pointer.
 *
 ** returns     : pointer to data element of new element or NULL if end
 *                of the queue.
 *
 ** comments    : This uses the cursor for the current position. Q_Next
 *                only moves in the direction from the head of the queue
 *                to the tail.
 ***/

void *Q_Next(queue *q)
{
      if (q->cursor->next == NULL)
            return NULL;

      q->cursor = (node *)q->cursor->next;

      return  q->cursor->data ;
}



/***
 *
 ** function    : Q_Previous
 *
 ** purpose     : Opposite of Q_Next. Move to next element closer to the
 *                head of the queue.
 *
 ** parameters  : pointer to queue
 *
 ** returns     : pointer to data of new element else NULL if queue empty
 *
 ** comments    : Makes cursor move towards the head of the queue.
 *
 ***/

void *Q_Previous(queue *q)
{
      if (q->cursor->prev == NULL)
            return NULL;

      q->cursor = (node *)q->cursor->prev;

      return q->cursor->data;
}



/***
 *
 ** function    : Q_DelCur
 *
 ** purpose     : Delete the current queue element as pointed to by
 *                the cursor.
 *
 ** parameters  : queue pointer
 *
 ** returns     : pointer to data element.
 *
 ** comments    : WARNING! It is the responsibility of the caller to
 *                free any memory. Queue cannot distinguish between
 *                pointers to literals and malloced memory.
 *
 ***/

void *Q_DelCur(queue *q)
{
      void        *d;
      datanode    *n, *p;

      if (q->cursor == NULL)
            return NULL;

      if (q->cursor == q->head)
            return Q_PopHead(q);

      if (q->cursor == q->tail)
            return Q_PopTail(q);

      n = q->cursor->next;
      p = q->cursor->prev;
      d = q->cursor->data;

      free(q->cursor);
      if (p != NULL)
            q->cursor = p;
      else  q->cursor = n;
      q->size--;

      q->sorted = False_;

      return d;
}



/***
 *
 ** function    : Q_Get
 *
 ** purpose     : get the pointer to the data at the cursor location
 *
 ** parameters  : queue pointer
 *
 ** returns     : data element pointer
 *
 ** comments    :
 *
 ***/

void *Q_Get(queue *q)
{
      if (q->cursor == NULL)
            return NULL;
      return q->cursor->data;
}



/***
 *
 ** function    : Q_Put
 *
 ** purpose     : replace pointer to data with new pointer to data.
 *
 ** parameters  : queue pointer, data pointer
 *
 ** returns     : boolean- True_ if successful, False_ if cursor at NULL
 *
 ** comments    :
 *
 ***/

int Q_Put(queue *q, void *data)
{
      if (q->cursor == NULL)
            return False_;

      q->cursor->data = data;
      return True_;
}


/***
 *
 ** function    : Q_Find
 *
 ** purpose     : Linear search of queue for match with key in *data
 *
 ** parameters  : queue pointer q, data pointer with data containing key
 *                comparison function here called Comp.
 *
 ** returns     : True_ if found , False_ if not in queue.
 *
 ** comments    : Useful for small queues that are constantly changing
 *                and would otherwise need constant sorting with the
 *                Q_Seek function.
 *                For description of Comp see Q_Sort.
 *                Queue cursor left on position found item else at end.
 *
 ***/

int Q_Find(queue *q, void *data,
               int (*Comp)(const void *, const void *))
{
      void *d;
      d = Q_First(q);
      do
      {
            if (Comp(d, data) == 0)
                  return True_;
            d = Q_Next(q);
      } while (!Q_End(q));

      if (Comp(d, data) == 0)
            return True_;

      return False_;
}

/*========  Sorted Queue and Index functions   ========= */


static void QuickSort(void *list[], int low, int high,
                      int (*Comp)(const void *, const void *))
{
      int     flag = 1, i, j;
      void    *key, *temp;

      if (low < high)
      {
            i = low;
            j = high + 1;

            key = list[ low ];

            while (flag)
            {
                  i++;
                  while (Comp(list[i], key) < 0)
                        i++;

                  j--;
                  while (Comp(list[j], key) > 0)
                        j--;

                  if (i < j)
                  {
                        temp = list[i];
                        list[i] = list[j];
                        list[j] = temp;
                  }
                  else  flag = 0;
            }

            temp = list[low];
            list[low] = list[j];
            list[j] = temp;

            QuickSort(list, low, j-1, Comp);
            QuickSort(list, j+1, high, Comp);
      }
}


/***
 *
 ** function    : Q_Sort
 *
 ** purpose     : sort the queue and allow index style access.
 *
 ** parameters  : queue pointer, comparison function compatible with
 *                with 'qsort'.
 *
 ** returns     : True_ if sort succeeded. False_ if error occurred.
 *
 ** comments    : Comp function supplied by caller must return
 *                  -1 if data1  < data2
 *                   0 if data1 == data2
 *                  +1 if data1  > data2
 *
 *                    for Comp(data1, data2)
 *
 *                If queue is already sorted it frees the memory of the
 *                old index and starts again.
 *
 ***/

int Q_Sort(queue *q, int (*Comp)(const void *, const void *))
{
      int         i;
      void        *d;
      datanode    *dn;

      /* if already sorted free memory for tag array */

      if (q->sorted)
      {
            free(index);
            free(posn_index);
            q->sorted = False_;
      }

      /* Now allocate memory of array, array of pointers */

      index = malloc(q->size * sizeof(q->cursor->data));
      if (index == NULL)
            return False_;

      posn_index = malloc(q->size * sizeof(q->cursor));
      if (posn_index == NULL)
      {
            free(index);
            return False_;
      }

      /* Walk queue putting pointers into array */

      d = Q_First(q);
      for (i=0; i < q->size; i++)
      {
            index[i] = d;
            posn_index[i] = q->cursor;
            d = Q_Next(q);
      }

      /* Now sort the index */

      QuickSort(index, 0, q->size - 1, Comp);

      /* Rearrange the actual queue into correct order */

      dn = q->head;
      i = 0;
      while (dn != NULL)
      {
            dn->data = index[i++];
            dn = dn->next;
      }

      /* Re-position to original element */

      if (d != NULL)
            Q_Find(q, d, Comp);
      else  Q_First(q);

      q->sorted = True_;

      return True_;
}


/***
 *
 ** function    : Q_BSearch
 *
 ** purpose     : binary search of queue index for node containing key
 *
 ** parameters  : queue pointer 'q', data pointer of key 'key',
 *                  Comp comparison function.
 *
 ** returns     : integer index into array of node pointers,
 *                or -1 if not found.
 *
 ** comments    : see Q_Sort for description of 'Comp' function.
 *
 ***/

static int Q_BSearch( queue *q, void *key,
                      int (*Comp)(const void *, const void*))
{
      int low, mid, hi, val;

      low = 0;
      hi = q->size - 1;

      while (low <= hi)
      {
            mid = (low + hi) / 2;
            val = Comp(key, index[ mid ]);

            if (val < 0)
                  hi = mid - 1;

            else if (val > 0)
                  low = mid + 1;

            else /* Success */
                  return mid;
      }

      /* Not Found */

      return -1;
}


/***
 *
 ** function    : Q_Seek
 *
 ** purpose     : use index to locate data according to key in 'data'
 *
 ** parameters  : queue pointer 'q', data pointer 'data', Comp comparison
 *                function.
 *
 ** returns     : pointer to data or NULL if could not find it or could
 *                not sort queue.
 *
 ** comments    : see Q_Sort for description of 'Comp' function.
 *
 ***/

void *Q_Seek(queue *q, void *data, int (*Comp)(const void *, const void *))
{
      int idx;

      if (!q->sorted)
      {
            if (!Q_Sort(q, Comp))
                  return NULL;
      }

      idx = Q_BSearch(q, data, Comp);

      if (idx < 0)
            return NULL;

      q->cursor = posn_index[idx];

      return index[idx];
}



/***
 *
 ** function    : Q_Insert
 *
 ** purpose     : Insert an element into an indexed queue
 *
 ** parameters  : queue pointer 'q', data pointer 'data', Comp comparison
 *                function.
 *
 ** returns     : pointer to data or NULL if could not find it or could
 *                not sort queue.
 *
 ** comments    : see Q_Sort for description of 'Comp' function.
 *                WARNING! This code can be very slow since each new
 *                element means a new Q_Sort.  Should only be used for
 *                the insertion of the odd element ,not the piecemeal
 *                building of an entire queue.
 ***/

int Q_Insert(queue *q, void *data, int (*Comp)(const void *, const void *))
{
      Q_PushHead(q, data);

      if (!Q_Sort(q, Comp))
            return False_;

      return True_;
}