1 /** @file 2 Utility functions for performing basic math operations constrained within a 3 modulus. 4 5 These functions are intended to simplify small changes to a value which much 6 remain within a specified modulus. Changes must be less than or equal to 7 the modulus specified by MaxVal. 8 9 Copyright (c) 2012, Intel Corporation. All rights reserved.<BR> 10 This program and the accompanying materials are licensed and made available 11 under the terms and conditions of the BSD License which accompanies this 12 distribution. The full text of the license may be found at 13 http://opensource.org/licenses/bsd-license.php. 14 15 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 16 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 17 **/ 18 #ifndef _MODULO_UTIL_H 19 #define _MODULO_UTIL_H 20 #include <Uefi.h> 21 #include <sys/EfiCdefs.h> 22 23 __BEGIN_DECLS 24 25 /** Counter = (Counter + 1) % MaxVal; 26 27 Counter is always expected to be LESS THAN MaxVal. 28 0 <= Counter < MaxVal 29 30 @param[in] Counter The value to be incremented. 31 @param[in] MaxVal Modulus of the operation. 32 33 @return Returns the result of incrementing Counter, modulus MaxVal. 34 If Counter >= MaxVal, returns -1. 35 **/ 36 INT32 37 EFIAPI 38 ModuloIncrement( 39 UINT32 Counter, 40 UINT32 MaxVal 41 ); 42 43 /** Counter = (Counter - 1) % MaxVal; 44 45 Counter is always expected to be LESS THAN MaxVal. 46 0 <= Counter < MaxVal 47 48 @param[in] Counter The value to be decremented. 49 @param[in] MaxVal Modulus of the operation. 50 51 @return Returns the result of decrementing Counter, modulus MaxVal. 52 If Counter >= MaxVal, returns -1. 53 **/ 54 INT32 55 EFIAPI 56 ModuloDecrement( 57 UINT32 Counter, 58 UINT32 MaxVal 59 ); 60 61 /** Counter = (Counter + Increment) % MaxVal; 62 63 @param[in] Counter The value to be incremented. 64 @param[in] Increment The value to add to Counter. 65 @param[in] MaxVal Modulus of the operation. 66 67 @return Returns the result of adding Increment to Counter, modulus MaxVal, 68 or -1 if Increment is larger than MaxVal. 69 **/ 70 INT32 71 EFIAPI 72 ModuloAdd ( 73 UINT32 Counter, 74 UINT32 Increment, 75 UINT32 MaxVal 76 ); 77 78 /** Increment Counter but don't increment past MaxVal. 79 80 @param[in] Counter The value to be decremented. 81 @param[in] MaxVal The upper bound for Counter. Counter < MaxVal. 82 83 @return Returns the result of incrementing Counter. 84 **/ 85 UINT32 86 EFIAPI 87 BoundIncrement( 88 UINT32 Counter, 89 UINT32 MaxVal 90 ); 91 92 /** Decrement Counter but don't decrement past zero. 93 94 @param[in] Counter The value to be decremented. 95 96 @return Returns the result of decrementing Counter. 97 **/ 98 UINT32 99 EFIAPI 100 BoundDecrement( 101 UINT32 Counter 102 ); 103 104 __END_DECLS 105 #endif /* _MODULO_UTIL_H */ 106