ObjectID.h

Classes

ObjectID -- ObjectID: A unique identifier for distributed and other objects. (full description)

class ObjectID

Interface

Public Members

ObjectID(Bool makeNull = False)

ObjectID(Int sequence, Int pid, Int time, const String &hostname)

ObjectID(const ObjectID &other)

ObjectID &operator=(const ObjectID &other)

Bool isNull() const

Bool operator==(const ObjectID &other) const

Bool operator!=(const ObjectID &other) const

Bool fromString(String &error, const String &in)

void toString(String &out) const

Int sequence() const

Int pid() const

Int creationTime() const

const String &hostName() const

static String extractIDs (Block<ObjectID>& objectIDs, const String& command)

Private Members

static Int sequence_number()

Description

Review Status

Reviewed By:

UNKNOWN

Date Reviewed:

before2004/08/25

Programs:

Tests:

tObjectID.cc

Prerequisite

none

Etymology

The ObjectID class name reflects its role as the single identifier for distributed and other user-level objects.

Synopsis

The ObjectID class is used to give a unique identifier to ``high-level'' objects in the system. Internally the ObjectID consists of a sequence number (unique within the creating process), a process id, a creation time, and a host id. Pragmatically the ObjectID should be unique with no dangers of collisions.

A special ``Null'' ObjectID is available.

Motivation

The fundamental purpose for an ObjectID is to provide a unique identifier for persistent objects, or for objects that might be accessed outside the creating processes address space.

To Do

Nothing (hostid -> hostname on this date).

Member Description

ObjectID(Bool makeNull = False)

If makeNull is True, make the null ObjectID, otherwise create a unique ObjectID.

ObjectID(Int sequence, Int pid, Int time, const String &hostname)

Create explicitly from the provided constituents.

ObjectID(const ObjectID &other)
ObjectID &operator=(const ObjectID &other)

Copy other. Note that if the ObjectID is embedded inside an object, the enclosing object probably does not want to copy the ObjectID since generally speaking the identity of the enclosing object should be immutable.

Bool isNull() const

Is this ObjectID set?

Bool operator==(const ObjectID &other) const
Bool operator!=(const ObjectID &other) const

Compare two ObjectID's for (in)equality.

void toString(String &out) const

It is useful to interconvert between strings and ObjecID's, e.g. when saving to FITS or writing to a table. The form of the string is:

    sequence=123 host=hostname pid=pid time=time

with an optional comma between the fields. However, in general user code should not depend on the exact form of the string.

Note that out is zero'd before it is set.

Bool fromString(String &error, const String &in)

It is useful to interconvert between strings and ObjecID's, e.g. when saving to FITS or writing to a table. The form of the string is:

    sequence=123 host=hostname pid=pid time=time

with an optional comma between the fields. However, in general user code should not depend on the exact form of the string.

Int sequence() const
Int pid() const
Int creationTime() const
const String &hostName() const

Ordinarily the user does not need to get at the exact state of the, ObjectID, however it is available for those times when it is necessary.

static String extractIDs (Block<ObjectID>& objectIDs, const String& command)

Extract objectID strings (as set by glish script substitute.g) from a command, convert them to ObjectID objects, store those in the Block, and replace the strings by their Block indices as $OBJ#n#O where n is the index.

static Int sequence_number()

Make a unique sequence number, returns 0 on first call, 1 on next, ...