/*---
This software is copyrighted by the Regents of the University of
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each file where they apply.
                                                                                                                                  
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POSSIBILITY OF SUCH DAMAGE.
                                                                                                                                  
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---*/
/*******************************
 * $Id$
 *
 * implementation of the page buffer
 * *************************************************/

#include <config.h>
#include <lladd/common.h>
#include <latches.h>
#include <assert.h>

#include <lladd/bufferManager.h>
#include <lladd/bufferPool.h>

#include <lladd/lockManager.h>
#include "page.h"
#include "blobManager.h"
#include <lladd/pageCache.h>
#include "pageFile.h"
#include <pbl/pbl.h>
#include <lladd/truncation.h>

static pblHashTable_t *activePages; /* page lookup */
/*static Page * activePagePtrs[MAX_BUFFER_SIZE];*/


static pthread_mutex_t loadPagePtr_mutex;

static Page * dummy_page;

int bufInit() {

	pageInit();
	openPageFile();


	pthread_mutex_init(&loadPagePtr_mutex, NULL);

	activePages = pblHtCreate(); 

	dummy_page = pageMalloc();
	pageFree(dummy_page, -1);
	Page *first;
	first = pageMalloc();
	pageFree(first, 0);
	pblHtInsert(activePages, &first->id, sizeof(int), first); 

	openBlobStore();

	pageCacheInit(first);

	assert(activePages);

	return 0;
}

void bufDeinit() {

	closeBlobStore();

	Page *p;
	DEBUG("pageCacheDeinit()");

	for( p = (Page*)pblHtFirst( activePages ); p; p = (Page*)pblHtNext(activePages)) { 

	  pblHtRemove( activePages, 0, 0 );
	  DEBUG("+");
	  pageWrite(p);

	}
	
	pthread_mutex_destroy(&loadPagePtr_mutex);
	
	pblHtDelete(activePages);
	pageCacheDeinit();
	closePageFile();
	
	pageDeInit();

	return;
}
/**
    Just close file descriptors, don't do any other clean up. (For
    testing.)
*/
void simulateBufferManagerCrash() {
  closeBlobStore();
  closePageFile();
}

void releasePage (Page * p) {
  unlock(p->loadlatch);
}

int bufTransCommit(int xid, lsn_t lsn) {
  commitBlobs(xid);
  pageCommit(xid);
  if(globalLockManager.commit) { globalLockManager.commit(xid);} 

  return 0;
}

int bufTransAbort(int xid, lsn_t lsn) {

  abortBlobs(xid);  /* abortBlobs doesn't write any log entries, so it doesn't need the lsn. */
  pageAbort(xid);
  if(globalLockManager.abort) { globalLockManager.abort(xid);} 

  return 0;
}

static Page * getPage(int pageid, int locktype) {
  Page * ret;
  int spin  = 0;

  pthread_mutex_lock(&loadPagePtr_mutex);
  ret = pblHtLookup(activePages, &pageid, sizeof(int));

  if(ret) {
    if(locktype == RW) {
      writelock(ret->loadlatch, 217);
    } else {
      readlock(ret->loadlatch, 217);
    }
  }

  while (ret && (ret->id != pageid)) {
    unlock(ret->loadlatch);
    pthread_mutex_unlock(&loadPagePtr_mutex);
    sched_yield();
    pthread_mutex_lock(&loadPagePtr_mutex);
    ret = pblHtLookup(activePages, &pageid, sizeof(int));

    if(ret) {
      if(locktype == RW) {
	writelock(ret->loadlatch, 217);
      } else {
	readlock(ret->loadlatch, 217);
      }
    }
    spin++;
    if(spin > 10000) {
      printf("GetPage is stuck!");
    }
  } 

  if(ret) { 
    cacheHitOnPage(ret);
    assert(ret->id == pageid);
    pthread_mutex_unlock(&loadPagePtr_mutex);
  } else {

    /* If ret is null, then we know that:

       a) there is no cache entry for pageid
       b) this is the only thread that has gotten this far,
          and that will try to add an entry for pageid
       c) the most recent version of this page has been 
          written to the OS's file cache.                  */
    int oldid = -1;

    if( cache_state == FULL ) {

      /* Select an item from cache, and remove it atomicly. (So it's
	 only reclaimed once) */

      ret = cacheStalePage();
      cacheRemovePage(ret);

      oldid = ret->id;
    
      assert(oldid != pageid);

    } else {

      ret = pageMalloc();
      ret->id = -1;
      ret->inCache = 0;
    }

    writelock(ret->loadlatch, 217); 

    /* Inserting this into the cache before releasing the mutex
       ensures that constraint (b) above holds. */
    pblHtInsert(activePages, &pageid, sizeof(int), ret); 

    pthread_mutex_unlock(&loadPagePtr_mutex); 

    /* Could writelock(ret) go here? */

    assert(ret != dummy_page);
    if(ret->id != -1) { 
      pageWrite(ret);
    }

    pageFree(ret, pageid);

    pageRead(ret);

    writeunlock(ret->loadlatch);
 
    pthread_mutex_lock(&loadPagePtr_mutex);

    pblHtRemove(activePages, &(oldid), sizeof(int)); 

    /* @todo Put off putting this back into cache until we're done with
       it. -- This could cause the cache to empty out if the ratio of
       threads to buffer slots is above ~ 1/3, but it decreases the
       liklihood of thrashing. */
    cacheInsertPage(ret);

    pthread_mutex_unlock(&loadPagePtr_mutex);

    if(locktype == RW) {
      writelock(ret->loadlatch, 217);
    } else {
      readlock(ret->loadlatch, 217);
    }
    if(ret->id != pageid) {
      unlock(ret->loadlatch);
      printf("pageCache.c: Thrashing detected.  Strongly consider increasing LLADD's buffer pool size!\n"); 
      fflush(NULL);
      return getPage(pageid, locktype);
    }

  }
  return ret;
}

compensated_function Page *loadPage(int xid, int pageid) {
  try_ret(NULL) {
    if(globalLockManager.readLockPage) { globalLockManager.readLockPage(xid, pageid); }
  } end_ret(NULL);
  Page * ret = getPage(pageid, RO);
  return ret;
}