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