![[OPUS]](opus.gif)
This class is available for the OPUS Blackboard API. The initial OPUS 2.0 release is described here
Constructors:
| Absolute_time_bb( ) | |
| ~Absolute_time_bb( ) |
Methods:
| post( ) | no-op |
| erase( ) | no-op |
| replace( ) | no-op |
| search( ) | checks if the time in the search condition is in the past or the future |
| lock_entry( ) | no-op |
| str( ) | gets blackboard name |
| new_time( ) | creates a new Time_entry object that contains an Absolute_time field |
| test_driver( ) | runs the test driver |
Description
This blackboard object is an abstraction of the system clock. That is, the entries stored on the blackboard are clock ticks at one second resolution. It is not possible to manipulate entries on this blackboard. Instead, a Time_entry object containing an Absolute_time field is sent as the "search condition" to the search method. If the Absolute_time embedded time is in the past, the search method returns as if the search was successful (indeed, that time is on the blackboard since all times past are entries on this blackboard) by returning 1 and by placing a clone of the search condition in the results vector. If the time in the search condition is in the future, the search fails. As such, this object acts like a timer that triggers when the absolute time passed to its search method has been reached.
Derived from
Example
#include <iostream>
#include <vector>
#include "absolute_time_bb.h"
#include "entry.h"
#include "time_entry.h"
using namespace std;
// The following example uses the Absolute Time Blackboard to
// determine whether it is past noon yet.
int main(int argc, char* argv[])
{
Absolute_time_bb abb;
Time_entry* t_ent = abb.new_time("12:00:00"); // place noon
// today in new
// time entry
vector<Entry*> results; // results vector
if (abb.search(t_ent, results)) { // it's past noon
cout << "It's past noon." << endl;
delete results[0]; // delete result
} else {
cout << "It's not noon yet." << endl;
}
delete t_ent; // delete search
// condition
return(0);
}
See Also:
Absolute_time_bb::Absolute_time_bb - The Absolute_time_bb constructor.
Synopsis
Absolute_time_bb::Absolute_time_bb()
Description
This method constructs an instance of the absolute time blackboard.
Exceptions Thrown
Absolute_time_bb::~Absolute_time_bb - The Absolute_time_bb destructor.
Synopsis
Absolute_time_bb::~Absolute_time_bb()
Description
This method destroys the object.
Exceptions Thrown
Absolute_time_bb::post - none
Synopsis
void Absolute_time_bb::post(
const Entry* e)
Description
A diagnostic message is produced indicating that this function is a no-op.
Exceptions Thrown
Absolute_time_bb::erase - none
Synopsis
void Absolute_time_bb::erase(
const Entry* e)
Description
A diagnostic message is produced indicating that this function is a no-op.
Exceptions Thrown
Absolute_time_bb::replace - none
Synopsis
void Absolute_time_bb::replace(
const Entry* old_ent,
const Entry* new_ent)
Description
A diagnostic message is produced indicating that this function is a no-op.
Exceptions Thrown
Absolute_time_bb::search - Compare the current system time with the Time_entry time value.
Synopsis
int Absolute_time_bb::search(
const Entry* e, // I - Time_entry with
// Absolute_time
vector<Entry*>& res) // I - results vector
const
Description
A comparison is made between the current system time and the time embedded in the first argument's Absolute_time field. If the time is in the past, the first argument is cloned and the copy is pushed onto the vector second argument. This copy is allocated off the heap and should be deleted by the caller once the object is no longer needed. If the time is in the future, nothing is pushed onto the vector second argument.
Returns
The size of the vector second argument just prior to returning.
Exceptions Thrown
| Bad_val<Entry*> | - if the first argument is null; Bad_val.arg points to the first argument |
| Type<Entry*> | - if the first argument is not of type Time_entry; Type.arg points to the first argument |
Example
Absolute_time_bb abb;
Time_entry* t_ent = abb.new_time("12:00:00"); // place 12:00 PM
// today in new
// time entry
vector<Entry*> results; // results vector
if (abb.search(t_ent, results)) { // it's past noon
cout << "It's past noon." << endl;
delete results[0]; // delete result
} else {
cout << "It's not noon yet." << endl;
}
delete t_ent; // delete search
Absolute_time_bb::new_time - Create a new Time_entry object containing an Absolute_time field.
Synopsis
Time_entry* Absolute_time_bb::new_time() const
Time_entry* Absolute_time_bb::new_time(
const time_t t) // I - seconds since
const // 00:00 Jan. 1,
// 1970
Time_entry* Absolute_time_bb::new_time(
const string& t) // I - string of
const // the form
// YYYY.DDD.HH:MM:SS
// or HH:MM:SS
Description
This method creates a new Time_entry object containing an Absolute_time field. If a string argument is provided,it must be in the format YYYY.DDD.HH:MM:SS, or HH:MM:SS, where YYYY is the year, DDD is the day of the year [0-365], HH is the hour[0-23], MM is the minute [0-59], and SS is the second[0-61] with which to initialize the Absolute_time field. A time_t value (seconds since the epoch) also can be provided as the field initializer. If no argument is provided, the current time is placed in the Absolute_time object.
Returns
A pointer to the new Time_entry object.
Exceptions Thrown
Example
Absolute_time_bb abb;
Time_entry* t_ent = abb.new_time("1998.234.13:34:12");
Absolute_time_bb::lock_entry - none.
Synopsis
Opus_lock* Absolute_time_bb::lock_entry(
const Entry* e)
Description
Locking of entries on the absolute time blackboard is not meaningful, so this method creates a Null_lock object off the heap and returns a pointer to it instead. The caller should delete the object when it is no longer needed.
Returns
A pointer to a Null_lock object.
Exceptions Thrown
Absolute_time_bb::str - Get the blackboard name.
Synopsis
string Absolute_time_bb::str() const
Description
This method returns a string describing the absolute time blackboard.
Returns
string containing the blackboard name
Exceptions Thrown
Example
Absolute_time_bb abb;
cout << "The absolute time blackboard name is: " << abb.str() << endl;
Absolute_time_bb::test_driver - Test the absolute time blackboard implementation.
Synopsis
bool Absolute_time_bb::test_driver()
Description
This method exercises the absolute time blackboard methods. Diagnostic output is sent to cerr. If all of the tests pass, this method returns true. Otherwise, it returns false. All exceptions generated during the test are caught and reported.
Returns
true - if all tests pass
false - if one or more of the tests fail
Exceptions Thrown
Example
Absolute_time_bb atbb;
cout << "Running the Absolute Time Blackboard test driver." << endl;
if (atbb.test_driver()) cout << "Pass." << endl;
else cout << "Fail." << endl;
Copyright © 1997-2000 The Association of Universities for
Research in Astronomy, Inc. All Rights Reserved.
For more information, contact opushelp@stsci.edu
Last modified: 25 April 2000