ISMIndex.h

Classes

ISMIndex -- The Index of the Incremental Storage Manager (full description)

class ISMIndex

Interface

Public Members
explicit ISMIndex (ISMBase* parent)
~ISMIndex()
void addRow (uInt nrrow)
Int removeRow (uInt rownr)
uInt getBucketNr (uInt rownr, uInt& bucketStartRow, uInt& bucketNrrow) const
void get (AipsIO& os)
void put (AipsIO& os)
void addBucketNr (uInt rownr, uInt bucketNr)
Bool nextBucketNr (uInt& cursor, uInt& bucketStartRow, uInt& bucketNrrow, uInt& bucketNr) const
Private Members
ISMIndex (const ISMIndex&)
ISMIndex& operator= (const ISMIndex&)
uInt getIndex (uInt rownr) const

Description

Prerequisite

Etymology

ISMIndex represents the index in the Incremental Storage Manager.

Synopsis

ISMIndex maintains an index of all buckets in an ISM (Incremental Storage Manager). The index consists of the starting row number and the bucket number of each bucket in the BucketCache object of the ISM. When the ISM is opened, the entire index is read in and kept in memory. When the ISM is closed or flushed, the index is written back after all buckets in the file. A little header at the beginning of the file indicates the starting offset of the index.

Motivation

ISMIndex encapsulates all operations on the ISM index.

Member Description

explicit ISMIndex (ISMBase* parent)

Create a ISMIndex object with the given parent for a new table. It keeps the pointer to its parent (but does not own it).

~ISMIndex()

The destructor closes the file (if opened).

void addRow (uInt nrrow)

Add a row.

Int removeRow (uInt rownr)

Remove a row from the index. If the result of this is that the entire bucket gets empty, that bucketnr is returned. Otherwise -1 is returned.

uInt getBucketNr (uInt rownr, uInt& bucketStartRow, uInt& bucketNrrow) const

Get the bucket number for the given row. Also return the start row of the bucket and the number of rows in it.

void get (AipsIO& os)

Read the bucket index from the AipsIO object.

void put (AipsIO& os)

Write the bucket index into the AipsIO object.

void addBucketNr (uInt rownr, uInt bucketNr)

Add a bucket number to the index. Argument rownr gives the starting row of the bucket. It is used to add the bucket number at the correct place (such that the row numbers are kept in ascending order).

Bool nextBucketNr (uInt& cursor, uInt& bucketStartRow, uInt& bucketNrrow, uInt& bucketNr) const

Get the number of the next bucket from the index and return it in bucketNr. The starting row of that bucket and the number of rows in the bucket are also returned. Return status False indicates that no more buckets are available.
The start of the iteration is indicated by cursor=0. The first bucket returned is the bucket containing the rownr given in bucketStartRow (thus set bucketStartRow to 0 if you to start at the first bucket).
The next iterations return the next bucket number and fill the starting row and number of rows.

ISMIndex (const ISMIndex&)

Forbid copy constructor.

ISMIndex& operator= (const ISMIndex&)

Forbid assignment.

uInt getIndex (uInt rownr) const

Get the index of the bucket containing the given row.