/* $XConsortium: Context.c,v 1.4 88/09/06 16:08:12 jim Exp $ */
#ifndef lint
static char *sccsid = "@(#)Context.c	1.5	2/24/87";
#endif				/* lint */


/***********************************************************
Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
and the Massachusetts Institute of Technology, Cambridge, Massachusetts.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Digital or MIT not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/* Created by weissman, Thu Jun 26 15:18:59 1986 */

/*
 * This module implements a simple sparse array.
 * 
 * XSaveContext(a,b,c,d) will store d in position (a,b,c) of the array.
 * XFindContext(a,b,c,&d) will set d to be the value in position (a,b,c).
 * XDeleteContext(a,b,c) will delete the entry in (a,b,c).
 * 
 * a is a display id, b is a window id, and c is a Context.  d is just a
 * caddr_t.  This code will work with any range of parameters, but is geared
 * to be most efficient with very few (one or two) different a's.
 * 
 */

#include <stdio.h>
#include "Xlib.h"
#include "Xutil.h"
#include "Xlibos.h"

#define INITHASHSIZE 1024	/* Number of entries originally in the hash
				 * table. */


typedef struct _TableEntryRec {	/* Stores one entry. */
  Window window;
  XContext context;
  caddr_t data;
  struct _TableEntryRec *next;
} TableEntryRec, *TableEntry;

typedef struct _DspRec {	/* Stores hash table for one display. */
  Display *display;		/* Which display this is a hash for. */
  TableEntry *table;		/* Pointer to array of hash entries. */
  int size;			/* Current size of hash table. */
  int numentries;		/* Number of entries currently in table. */
  int maxentries;		/* How many entries we can take before
				 * increasing table size. */
} DspRec, *Dsp;

static Dsp *DspArray = NULL;	/* Pointer to array of display entries. */
static int numDsp = 0;		/* How many display entries we have. */


/* Assign dsp to be the Dsp entry that contains display. */

static Dsp lastdsp = NULL;
#define FindCorrectDsp \
	if (lastdsp && display == lastdsp->display) dsp = lastdsp; \
	else dsp = lastdsp = FindDsp(display);


/*
 * Given a Window and a context, returns a value between 0 and HashSize-1.
 * Currently, this requires that HashSize be a power of 2.
 */

#define HashValue(window, context, HashSize) \
    ((((int)window << 3) + (int)context) & ((HashSize) - 1))


/* Resize the given dsp to have the given number of hash buckets. */

static int 
ResizeTable (dsp, NewSize)
  Dsp dsp;
  int NewSize;
{
  TableEntry *OldHashTable;
  register TableEntry CurEntry, NextEntry;
  register int i, OldHashSize, CurHash;
  OldHashTable = dsp->table;
  OldHashSize = dsp->size;
  dsp->table = (TableEntry *) Xcalloc ((unsigned) NewSize, sizeof (TableEntry));
  if (dsp->table == NULL) {
    dsp->table = OldHashTable;
    return XCNOMEM;
  }
  dsp->size = NewSize;
  dsp->maxentries = NewSize;	/* When to next resize the hash table. */
  if (OldHashTable != NULL) {
    for (i = 0; i < OldHashSize; i++) {
      CurEntry = OldHashTable[i];
      while (CurEntry != NULL) {
	(void) XDeleteContext (dsp->display,
			       CurEntry->window, CurEntry->context);
	NextEntry = CurEntry->next;
	CurHash = HashValue (CurEntry->window, CurEntry->context,
			     NewSize);
	CurEntry->next = dsp->table[CurHash];
	dsp->table[CurHash] = CurEntry;
	CurEntry = NextEntry;
      }
    }
    Xfree ((char *) OldHashTable);
  }
  return 0;
}


/* Given a display, find the corresponding dsp. */

static Dsp 
FindDsp (display)
  Display *display;
{
  int i;
  Dsp dsp;
  for (i = 0; i < numDsp; i++)
    if (DspArray[i]->display == display)
      return DspArray[i];
  numDsp++;
  if (DspArray == NULL)
    DspArray = (Dsp *) Xmalloc (sizeof (Dsp));
  else
    DspArray = (Dsp *) Xrealloc (
		       (char *) DspArray, (unsigned) sizeof (Dsp) * numDsp);
  dsp = DspArray[numDsp - 1] = (Dsp) Xmalloc (sizeof (DspRec));
  dsp->display = display;
  dsp->table = NULL;
  dsp->size = INITHASHSIZE / 2;
  dsp->numentries = 0;
  dsp->maxentries = -1;
  (void) ResizeTable (dsp, dsp->size * 2);
  return dsp;
}



/* Public routines. */

/*
 * Save the given value of data to correspond with the keys Window and
 * context. If an entry with the given Window and context already exists,
 * this one will override it; however, such an override has costs in time and
 * space.  It is better to call XDeleteContext first if you know the entry
 * already exists. Returns nonzero error code if an error has occured, 0
 * otherwise. Possible errors are Out-of-memory.
 */

int 
XSaveContext (display, window, context, data)
  register Display *display;
  register Window window;
  register XContext context;
  caddr_t data;
{
  register int CurHash;
  register TableEntry CurEntry;
  register Dsp dsp;
  FindCorrectDsp;
  if (++(dsp->numentries) > dsp->maxentries)
    if (ResizeTable (dsp, dsp->size * 2) == XCNOMEM)
      return XCNOMEM;
  CurEntry = (TableEntry) Xmalloc (sizeof (TableEntryRec));
  if (CurEntry == NULL)
    return XCNOMEM;
  CurEntry->window = window;
  CurEntry->context = context;
  CurEntry->data = data;
  CurHash = HashValue (window, context, dsp->size);
  CurEntry->next = dsp->table[CurHash];
  dsp->table[CurHash] = CurEntry;
  return 0;
}



/*
 * Given a window and context, returns the associated data.  Note that data
 * here is a pointer since it is a return value.  Returns nonzero error code
 * if an error has occured, 0 otherwise.  Possible errors are
 * Entry-not-found.
 */

int 
XFindContext (display, window, context, data)
  register Display *display;
  register Window window;
  register XContext context;
  caddr_t *data;		/* RETURN */
{
  register TableEntry CurEntry;
  register Dsp dsp;
  FindCorrectDsp;
  for (CurEntry = dsp->table[HashValue (window, context, dsp->size)];
       CurEntry != NULL;
       CurEntry = CurEntry->next) {
    if (CurEntry->window == window && CurEntry->context == context) {
      *data = CurEntry->data;
      return 0;
    }
  }
  return XCNOENT;
}



/*
 * Deletes all entries for the given window and context from the
 * datastructure. This returns the same thing that FindContext would have
 * returned if called with the same arguments.
 */

int 
XDeleteContext (display, window, context)
  register Display *display;
  register Window window;
  register XContext context;
{
  register int CurHash;
  int Result;
  register TableEntry CurEntry, PrevEntry, NextEntry;
  register Dsp dsp;

  FindCorrectDsp;
  Result = XCNOENT;
  CurHash = HashValue (window, context, dsp->size);
  PrevEntry = NULL;
  CurEntry = dsp->table[CurHash];
  while (CurEntry != NULL) {
    if (CurEntry->window == window && CurEntry->context == context) {
      dsp->numentries--;
      Result = 0;
      NextEntry = CurEntry->next;
      if (PrevEntry == NULL) {
	dsp->table[CurHash] = NextEntry;
      }
      else {
	PrevEntry->next = NextEntry;
      }
      Xfree ((char *) CurEntry);
      CurEntry = NextEntry;
    }
    else {
      PrevEntry = CurEntry;
      CurEntry = CurEntry->next;
    }
  }
  return Result;
}