SQLite4  Check-in [d4c5a3bad7]

int lsmEnvLock(lsm_env *pEnv, lsm_file *pFile, int iLock, int eLock);

int lsmEnvShmMap(lsm_env *, lsm_file *, int, int, void **); 
void lsmEnvShmBarrier(lsm_env *);
void lsmEnvShmUnmap(lsm_env *, lsm_file *, int);

void lsmEnvSleep(lsm_env *, int);

int lsmFsReadSyncedId(lsm_db *db, int, i64 *piVal);

/*
** End of functions from "lsm_file.c".
**************************************************************************/

/* 
** Functions from file "lsm_sorted.c".

    }else{
      p->nData = pFS->nPagesize;
    }
    pFS->nOut += (p->nRef==0);
    p->nRef++;
  }
  *ppPg = p;
  return rc;
}

/*
** Read the 64-bit checkpoint id of the checkpoint currently stored on meta
** page iMeta of the database file. If no error occurs, store the id value
** in *piVal and return LSM_OK. Otherwise, return an LSM error code and leave
** *piVal unmodified.
**
** If a checkpointer connection is currently updating meta-page iMeta, or an
** earlier checkpointer crashed while doing so, the value read into *piVal
** may be garbage. It is the callers responsibility to deal with this.
*/
int lsmFsReadSyncedId(lsm_db *db, int iMeta, i64 *piVal){
  FileSystem *pFS = db->pFS;
  int rc = LSM_OK;

  assert( iMeta==1 || iMeta==2 );
  if( pFS->bUseMmap ){
    fsGrowMapping(pFS, iMeta*LSM_META_PAGE_SIZE, &rc);
    if( rc==LSM_OK ){
      *piVal = (i64)lsmGetU64(&((u8 *)pFS->pMap)[(iMeta-1)*LSM_META_PAGE_SIZE]);
    }
  }else{
    MetaPage *pMeta = 0;
    rc = lsmFsMetaPageGet(pFS, 0, iMeta, &pMeta);
    if( rc==LSM_OK ){
      *piVal = (i64)lsmGetU64(pMeta->aData);
      lsmFsMetaPageRelease(pMeta);
    }
  }

  return rc;
}


static int fsRunEndsBetween(
  Segment *pRun, 
  Segment *pIgnore, 

/*
** If possible, reclaim log file space. Log file space is reclaimed after
** a snapshot that points to the same data in the database file is synced
** into the db header.
*/
static int logReclaimSpace(lsm_db *pDb){
  int rc = LSM_OK;
  int iMeta;

  iMeta = (int)pDb->pShmhdr->iMetaPage;
  if( iMeta==1 || iMeta==2 ){
    DbLog *pLog = &pDb->treehdr.log;
    i64 iSyncedId;

    /* Read the snapshot-id of the snapshot stored on meta-page iMeta. Note
    ** that in theory, the value read is untrustworthy (due to a race 
    ** condition - see comments above lsmFsReadSyncedId()). So it is only 
    ** ever used to conclude that no log space can be reclaimed. If it seems
    ** to indicate that it may be possible to reclaim log space, a
    ** second call to lsmCheckpointSynced() (which does return trustworthy
    ** values) is made below to confirm.  */
    rc = lsmFsReadSyncedId(pDb, iMeta, &iSyncedId);

    if( rc==LSM_OK && pLog->iSnapshotId!=iSyncedId ){
      i64 iSnapshotId = 0;
      i64 iOff = 0;
      rc = lsmCheckpointSynced(pDb, &iSnapshotId, &iOff, 0);
      if( rc==LSM_OK && pLog->iSnapshotId<iSnapshotId ){
        int iRegion;
        for(iRegion=0; iRegion<3; iRegion++){
          LogRegion *p = &pLog->aRegion[iRegion];
          if( iOff>=p->iStart && iOff<=p->iEnd ) break;
          p->iStart = 0;
          p->iEnd = 0;
        }
        assert( iRegion<3 );
        pLog->aRegion[iRegion].iStart = iOff;
        pLog->iSnapshotId = iSnapshotId;
      }
    }
  }
  return rc;
}

/*
** This function is called when a write-transaction is first opened. It

u32 lsmGetU32(u8 *aOut){
  return ((u32)aOut[0] << 24) 
       + ((u32)aOut[1] << 16) 
       + ((u32)aOut[2] << 8) 
       + ((u32)aOut[3]);
}

u64 lsmGetU64(u8 *aOut){
  return ((u64)aOut[0] << 56) 
       + ((u64)aOut[1] << 48) 
       + ((u64)aOut[2] << 40) 
       + ((u64)aOut[3] << 32) 
       + ((u64)aOut[4] << 24)
       + ((u32)aOut[5] << 16) 
       + ((u32)aOut[6] << 8)