Source code of Windows XP (NT5)
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#include "precomp.h"
#include "fsdiag.h"
DEBUG_FILEZONE(ZONE_T120_MCSNC);
/*
* randchnl.cpp
*
* Copyright (c) 1995 by DataBeam Corporation, Lexington, KY
*
* Abstract:
* This is the implementation file for the RandomChannelGenerator class,
* which inherits from the RandomNumberGenerator class. On instantiation,
* instances of this class will internally generate a random number which
* falls within the allowable range of dynamic channels values. Channel
* assignments are then generated by incrementing this value each time a
* new assignment is requested. Once the maximum allowable value has been
* assigned, the next value to be generated "wraps around" to the minimum
* allowable value.
*
* Obviously, this class does not generate completely random channel
* values for each request. With a completely random generator, it is
* possible to delete a channel in MCS, and then have the random number
* generator assign the same value as the deleted channel before all
* components of the system even know that the channel was deleted to
* start with, thus causing erratic behavior in the system. In this
* class, no channel can be reassigned until all other possible channels
* have been assigned.
*
* This class can be modifed in the future to incorporate additional
* "randomness" into the algorithm and still not reassign any channel
* numbers before all other possible values are used. This, however,
* would be at the expense of performance and/or memory resources.
*
* Caveats:
* None.
*
* Author:
* Alan D. May
*/
#include "randchnl.h"
/*
* These macros define the mimimum and maximum allowable dynamic channel
* values.
*/
#define MINIMUM_DYNAMIC_CHANNEL 1001
#define MAXIMUM_DYNAMIC_CHANNEL 65535
/*
* RandomChannelGenerator ()
*
* Public
*
* Functional Description:
* This version of the constructor is used to create a random channel
* generator object that has been automatically seeded with the current
* time.
*/
RandomChannelGenerator::RandomChannelGenerator()
{
Current_Channel = (GetTickCount() % (MAXIMUM_DYNAMIC_CHANNEL + 1 - MINIMUM_DYNAMIC_CHANNEL)) + MINIMUM_DYNAMIC_CHANNEL;
}
/*
* ~RandomChannelGenerator ()
*
* Public
*
* Functional Description:
* This is the destructor for the RandomChannelGenerator class.
*/
RandomChannelGenerator::~RandomChannelGenerator ()
{
}
/*
* GetRandomChannel ()
*
* Public
*
* Functional Description:
* This method returns a valid dynamic channel number.
*/
RandomValue RandomChannelGenerator::GetRandomChannel (Void)
{
/*
* Increment the current channel value.
*/
++Current_Channel;
/*
* Determine if the current channel value needs to wrap around.
*/ if (Current_Channel > MAXIMUM_DYNAMIC_CHANNEL)
{
Current_Channel = MINIMUM_DYNAMIC_CHANNEL;
}
/*
* Return the current channel value.
*/
return (Current_Channel);
}