SQLite4  Check-in [e97d02f068]

  int bCksum,                     /* If true, include checksums */
  void **ppCkpt,                  /* OUT: Buffer containing checkpoint */
  int *pnCkpt                     /* OUT: Size of checkpoint in bytes */
){
  int rc = LSM_OK;                /* Return Code */
  FileSystem *pFS = pDb->pFS;     /* File system object */
  Snapshot *pSnap = pDb->pWorker; /* Worker snapshot */

  int nLevel = 0;                 /* Number of levels in checkpoint */
  int iLevel;                     /* Used to count out nLevel levels */
  int iOut = 0;                   /* Current offset in aCkpt[] */
  Level *pLevel;                  /* Level iterator */
  int i;                          /* Iterator used while serializing freelist */
  CkptBuffer ckpt;
  int nFree;
 
  nFree = pSnap->freelist.nEntry;

  /* Write the log offset into the checkpoint. */
  ckptExportLog(pDb, bLog, &ckpt, &iOut, &rc);

  /* Write the append-point list */
  ckptExportAppendlist(pDb, &ckpt, &iOut, &rc);

  /* Figure out how many levels will be written to the checkpoint. */
  for(pLevel=lsmDbSnapshotLevel(pSnap); pLevel; pLevel=pLevel->pNext) nLevel++;



  /* Serialize nLevel levels. */
  iLevel = 0;
  for(pLevel=lsmDbSnapshotLevel(pSnap); iLevel<nLevel; pLevel=pLevel->pNext){
    ckptExportLevel(pLevel, &ckpt, &iOut, &rc);
    iLevel++;
  }

  /* Write the freelist */
  if( rc==LSM_OK ){
    ckptSetValue(&ckpt, iOut++, nFree, &rc);

  /* Write the checkpoint header */
  assert( iId>=0 );
  ckptSetValue(&ckpt, CKPT_HDR_ID_MSW, (u32)(iId>>32), &rc);
  ckptSetValue(&ckpt, CKPT_HDR_ID_LSW, (u32)(iId&0xFFFFFFFF), &rc);
  ckptSetValue(&ckpt, CKPT_HDR_NCKPT, iOut+2, &rc);
  ckptSetValue(&ckpt, CKPT_HDR_NBLOCK, pSnap->nBlock, &rc);
  ckptSetValue(&ckpt, CKPT_HDR_BLKSZ, lsmFsBlockSize(pFS), &rc);
  ckptSetValue(&ckpt, CKPT_HDR_NLEVEL, nLevel, &rc);
  ckptSetValue(&ckpt, CKPT_HDR_PGSZ, lsmFsPageSize(pFS), &rc);
  ckptSetValue(&ckpt, CKPT_HDR_OVFL, nOvfl, &rc);

  if( bCksum ){
    ckptAddChecksum(&ckpt, iOut, &rc);
  }else{
    ckptSetValue(&ckpt, iOut, 0, &rc);

      if( rc==LSM_OK ) pShm->iMetaPage = iMeta;
    }
  }

  /* If no error has occured, then the snapshot currently in pDb->aSnapshot
  ** has been synced to disk. This means it may be possible to wrap the
  ** log file. Obtain the WRITER lock and update the relevent tree-header
  ** fields to reflect this. 
  */
  if( rc==LSM_OK ){
    u64 iLogoff = lsmCheckpointLogOffset(pDb->aSnapshot);
    if( pDb->nTransOpen==0 ){
      rc = lsmShmLock(pDb, LSM_LOCK_WRITER, LSM_LOCK_EXCL, 0);
    }
    if( rc==LSM_OK ){
      rc = lsmTreeLoadHeader(pDb);
      if( rc==LSM_OK ) lsmLogCheckpoint(pDb, iLogoff);
      if( rc==LSM_OK ) lsmTreeEndTransaction(pDb, 1);
      if( rc==LSM_BUSY ) rc = LSM_OK;
      if( pDb->nTransOpen==0 ){
        rc = lsmShmLock(pDb, LSM_LOCK_WRITER, LSM_LOCK_UNLOCK, 0);
      }
    }
  }

  lsmShmLock(pDb, LSM_LOCK_CHECKPOINTER, LSM_LOCK_UNLOCK, 0);
  return rc;
}

int lsmBeginWork(lsm_db *pDb){

  /* If there is no read-transaction open, open one now. */
  rc = lsmBeginReadTrans(pDb);

  /* Attempt to take the WRITER lock */
  if( rc==LSM_OK ){
    rc = lsmShmLock(pDb, LSM_LOCK_WRITER, LSM_LOCK_EXCL, 0);
  assert( rc!=LSM_BUSY );
  }

  /* If the previous writer failed mid-transaction, run emergency rollback. */
  if( rc==LSM_OK && pShm->bWriter ){
    /* TODO: This! */
    assert( 0 );
    rc = LSM_CORRUPT_BKPT;

  }
  lsmMutexLeave(db->pEnv, p->pClientMutex);

  return rc;
}

#ifdef LSM_DEBUG

int shmLockType(lsm_db *db, int iLock){
  const u32 me = (1 << (iLock-1));
  const u32 ms = (1 << (iLock+16-1));

  if( db->mLock & me ) return LSM_LOCK_EXCL;
  if( db->mLock & ms ) return LSM_LOCK_SHARED;
  return LSM_LOCK_UNLOCK;
}

/*
** The arguments passed to this function are similar to those passed to
** the lsmShmLock() function. However, instead of obtaining a new lock 
** this function returns true if the specified connection already holds 
** (or does not hold) such a lock, depending on the value of eOp. As
** follows:
**
**   (eOp==LSM_LOCK_UNLOCK) -> true if db has no lock on iLock
**   (eOp==LSM_LOCK_SHARED) -> true if db has at least a SHARED lock on iLock.
**   (eOp==LSM_LOCK_EXCL)   -> true if db has an EXCLUSIVE lock on iLock.
*/
int lsmShmAssertLock(lsm_db *db, int iLock, int eOp){
  const u32 me = (1 << (iLock-1));
  const u32 ms = (1 << (iLock+16-1));
  int ret;
  int eHave;

  assert( iLock>=1 && iLock<=LSM_LOCK_READER(LSM_LOCK_NREADER-1) );
  assert( iLock<=16 );
  assert( eOp==LSM_LOCK_UNLOCK || eOp==LSM_LOCK_SHARED || eOp==LSM_LOCK_EXCL );

  eHave = shmLockType(db, iLock);

  switch( eOp ){
    case LSM_LOCK_UNLOCK:
      ret = (eHave==LSM_LOCK_UNLOCK);
      break;
    case LSM_LOCK_SHARED:
      ret = (eHave!=LSM_LOCK_UNLOCK);
      break;
    case LSM_LOCK_EXCL:
      ret = (eHave==LSM_LOCK_EXCL);
      break;
    default:
      assert( !"bad eOp value passed to lsmShmAssertLock()" );
      break;
  }

  return ret;
}

int lsmShmAssertWorker(lsm_db *db){
  return lsmShmAssertLock(db, LSM_LOCK_WORKER, LSM_LOCK_EXCL) && db->pWorker;
}

/*
** This function does not contribute to library functionality, and is not
** included in release builds. It is intended to be called from within
** an interactive debugger.
**
** When called, this function prints a single line of human readable output
** to stdout describing the locks currently held by the connection. For 
** example:
**
**     (gdb) call print_db_locks(pDb)
**     (shared on dms2) (exclusive on writer) 
*/
void print_db_locks(lsm_db *db){
  int iLock;
  for(iLock=0; iLock<16; iLock++){
    int bOne = 0;
    const char *azLock[] = {0, "shared", "exclusive"};
    const char *azName[] = {
      0, "dms1", "dms2", "writer", "worker", "checkpointer",
      "reader0", "reader1", "reader2", "reader3", "reader4", "reader5"
    };
    int eHave = shmLockType(db, iLock);
    if( azLock[eHave] ){
      printf("%s(%s on %s)", (bOne?" ":""), azLock[eHave], azName[iLock]);
      bOne = 1;
    }
  }
  printf("\n");
}
#endif

void lsmShmBarrier(lsm_db *db){
  /* TODO */
}