/* Emacs style mode select   -*- C++ -*-
 *-----------------------------------------------------------------------------
 *
 *
 *  PrBoom: a Doom port merged with LxDoom and LSDLDoom
 *  based on BOOM, a modified and improved DOOM engine
 *  Copyright (C) 2001 by
 *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
 *  Copyright 2005, 2006 by
 *  Florian Schulze, Colin Phipps, Neil Stevens, Andrey Budko
 *
 *  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., 59 Temple Place - Suite 330, Boston, MA
 *  02111-1307, USA.
 *
 * DESCRIPTION:
 *      Transparent access to data in WADs using mmap
 *
 *-----------------------------------------------------------------------------
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "doomstat.h"
#include "doomtype.h"

#ifdef __GNUG__
#pragma implementation "w_wad.h"
#endif
#include "w_wad.h"
#include "z_zone.h"
#include "lprintf.h"
#include "i_system.h"

#define RANGECHECK

static struct {
  void *cache;
  void *mmapadr;
#ifdef TIMEDIAG
  int locktic;
#endif
  int locks;
} *cachelump;



#ifdef HEAPDUMP
void W_PrintLump(FILE* fp, void* p) {
  int i;
  for (i=0; i<numlumps; i++)
    if (cachelump[i].cache == p) {
      fprintf(fp, " %8.8s %6u %2d %6d", lumpinfo[i].name,
        W_LumpLength(i), cachelump[i].locks, gametic - cachelump[i].locktic);
      return;
    }
  fprintf(fp, " not found");
}
#endif

#ifdef TIMEDIAG
static void W_ReportLocks(void)
{
  int i;
  lprintf(LO_DEBUG, "W_ReportLocks:\nLump     Size   Locks  Tics\n");
  for (i=0; i<numlumps; i++) {
    if (cachelump[i].locks > 0)
      lprintf(LO_DEBUG, "%8.8s %6u %2d   %6d\n", lumpinfo[i].name,
        W_LumpLength(i), cachelump[i].locks, gametic - cachelump[i].locktic);
  }
}
#endif

void W_InitCache(void)
{
  // set up caching
  cachelump = calloc(numlumps, sizeof *cachelump);
  if (!cachelump)
    I_Error ("W_Init: Couldn't allocate lumpcache");


  for (int i=0; i<numlumps; i++)  cachelump[i].locks = -1;

#ifdef TIMEDIAG
  atexit(W_ReportLocks);
#endif

}


void W_DoneCache(void)
{
    //ToDo... if we ever unload a wad
}

/*
As far as I can see, the lump scheme is reference counted... W_CacheLumpNum loads up a lump, W_LockLumpNum increases the lock count,
W_UnlockLumpNum decreases it and if it's -1 it can un-mmap the lump. NOTE: W_LockLumpNum is not used in the current code.
*/


const void* W_CacheLumpNum(int lump)
{
#ifdef RANGECHECK
  if ((unsigned)lump >= (unsigned)numlumps)
    I_Error ("W_CacheLumpNum: %i >= numlumps",lump);
#endif
	cachelump[lump].mmapadr=I_Mmap(NULL, W_LumpLength(lump), 0, 0, lumpinfo[lump].wadfile->handle, lumpinfo[lump].position);
	return (char*)cachelump[lump].mmapadr;
}

/*
 * W_LockLumpNum
 *
 * This copies the lump into a malloced memory region and returns its address
 * instead of returning a pointer into the memory mapped area
 *
 */
const void* W_LockLumpNum(int lump)
{
  size_t len = W_LumpLength(lump);
  const void *data = W_CacheLumpNum(lump);

  if (!cachelump[lump].cache) {
    // read the lump in
    Z_Malloc(len, PU_CACHE, &cachelump[lump].cache);
    memcpy(cachelump[lump].cache, data, len);
  }

  /* cph - if wasn't locked but now is, tell z_zone to hold it */
  if (cachelump[lump].locks <= 0) {
    Z_ChangeTag(cachelump[lump].cache,PU_STATIC);
#ifdef TIMEDIAG
    cachelump[lump].locktic = gametic;
#endif
    // reset lock counter
    cachelump[lump].locks = 1;
  } else {
    // increment lock counter
    cachelump[lump].locks += 1;
  }

#ifdef SIMPLECHECKS
  if (!((cachelump[lump].locks+1) & 0xf))
    lprintf(LO_DEBUG, "W_CacheLumpNum: High lock on %8s (%d)\n",
      lumpinfo[lump].name, cachelump[lump].locks);
#endif

  return cachelump[lump].cache;
}

void W_UnlockLumpNum(int lump) {
  if (cachelump[lump].locks == -1) {
    // this lump is memory mapped
    I_Munmap(cachelump[lump].mmapadr, W_LumpLength(lump));
    return;
  }
#ifdef SIMPLECHECKS
  if (cachelump[lump].locks == 0)
    lprintf(LO_DEBUG, "W_UnlockLumpNum: Excess unlocks on %8s\n",
      lumpinfo[lump].name);
#endif
  cachelump[lump].locks -= 1;
  /* cph - Note: must only tell z_zone to make purgeable if currently locked,
   * else it might already have been purged
   */
  if (cachelump[lump].locks == 0)
    Z_ChangeTag(cachelump[lump].cache, PU_CACHE);
}

