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/** @file
Utility functions for performing basic math operations constrained within a
modulus.
These functions are intended to simplify small changes to a value which much
remain within a specified modulus.
NOTE: Changes must be less than or equal to the modulus specified by MaxVal.
Copyright (c) 2012, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available
under the terms and conditions of the BSD License which accompanies this
distribution. The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php.
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
#include <Uefi.h>
#include <LibConfig.h>
#include <assert.h>
/** Counter = (Counter + 1) % MaxVal;
Counter is always expected to be LESS THAN MaxVal.
0 <= Counter < MaxVal
@param[in] Counter The value to be incremented.
@param[in] MaxVal Modulus of the operation.
@return Returns the result of incrementing Counter, modulus MaxVal.
If Counter >= MaxVal, returns -1.
**/
INT32
EFIAPI
ModuloIncrement(
UINT32 Counter,
UINT32 MaxVal
)
{
INT32 Temp;
if(Counter < MaxVal) {
Temp = (INT32)(Counter + 1);
if(Temp >= (INT32)MaxVal) {
Temp = 0;
}
}
else {
Temp = -1;
}
return Temp;
}
/** Counter = (Counter - 1) % MaxVal;
Counter is always expected to be LESS THAN MaxVal.
0 <= Counter < MaxVal
@param[in] Counter The value to be decremented.
@param[in] MaxVal Modulus of the operation.
@return Returns the result of decrementing Counter, modulus MaxVal.
If Counter >= MaxVal, returns -1.
**/
INT32
EFIAPI
ModuloDecrement(
UINT32 Counter,
UINT32 MaxVal
)
{
INT32 Temp;
if(Counter < MaxVal) {
Temp = (INT32)Counter - 1;
// If Counter is zero, Temp will become -1.
if(Temp < 0) {
Temp = (INT32)MaxVal - 1;
}
}
else {
Temp = -1;
}
return Temp;
}
/** Decrement Counter but don't decrement past zero.
@param[in] Counter The value to be decremented.
@return Returns the result of decrementing Counter.
**/
UINT32
EFIAPI
BoundDecrement(
UINT32 Counter
)
{
return ((Counter > 0) ? (Counter - 1) : 0);
}
/** Increment Counter but don't increment past MaxVal.
Counter should be maintained in the range (0 <= Counter < MaxVal).
@param[in] Counter The value to be decremented.
@param[in] MaxVal The upper bound for Counter.
@return Returns the result of incrementing Counter.
**/
UINT32
EFIAPI
BoundIncrement(
UINT32 Counter,
UINT32 MaxVal
)
{
return ((Counter < (MaxVal - 1)) ? (Counter + 1) : (MaxVal - 1));
}
/** Counter = (Counter + Increment) % MaxVal;
@param[in] Counter The value to be incremented.
@param[in] Increment The value to add to Counter.
@param[in] MaxVal Modulus of the operation.
@return Returns the result of adding Increment to Counter, modulus MaxVal,
or -1 if Increment is larger than MaxVal.
**/
INT32
EFIAPI
ModuloAdd (
UINT32 Counter,
UINT32 Increment,
UINT32 MaxVal
)
{
UINT32 Temp;
if(Increment > MaxVal) {
return -1;
}
Temp = (Counter + Increment);
while(Temp >= MaxVal) {
Temp -= MaxVal;
}
return Temp;
}
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