| // Copyright 2019 The Pigweed Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| // use this file except in compliance with the License. You may obtain a copy of |
| // the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| // License for the specific language governing permissions and limitations under |
| // the License. |
| |
| #pragma once |
| |
| // Preprocessor boolean operation macros that evaluate to 0 or 1. |
| // |
| // These macros perform boolean operations in the C preprocessor that evaluate |
| // to a literal 1 or 0. They can be used for a few purposes: |
| // |
| // - Generate other macros that evaluate to a 1 or 0, instead of a |
| // parenthesized boolean expression. |
| // - Ensure that the operands are defined and evaluate to 1 or 0 themselves. |
| // - Write macros that conditionally use other macros by token pasting the |
| // resulting 1 or 0 to form a new macro name. |
| // |
| // These macros should not be used outside of macro definitions. Use normal C |
| // operators (&&, ||, !, ==, !=) instead. For example, to check whether two |
| // flags are set, the C operators are the best choice: |
| // |
| // #if RELEASE && OPTIMIZED |
| // |
| // However, there are cases when a literal 0 or 1 is required. For example: |
| // |
| // #define SELECT_ALGORITHM() PW_CONCAT(ALGO_, PW_AND(RELEASE, OPTIMIZED)) |
| // |
| // SELECT_ALGORITHM evaluates to ALGO_0 or ALGO_1, depending on whether RELEASE |
| // and OPTIMIZED are set to 1. |
| |
| // Boolean AND of two preprocessor expressions that evaluate to 0 or 1. |
| #define PW_AND(a, b) _PW_AND(a, b) // Expand the macro an extra time to |
| #define _PW_AND(a, b) _PW_AND_##a##b() // allow macro substitution to occur. |
| #define _PW_AND_00() 0 |
| #define _PW_AND_01() 0 |
| #define _PW_AND_10() 0 |
| #define _PW_AND_11() 1 |
| |
| // Boolean OR of two preprocessor expressions that evaluate to 0 or 1. |
| #define PW_OR(a, b) _PW_OR(a, b) |
| #define _PW_OR(a, b) _PW_OR_##a##b() |
| #define _PW_OR_00() 0 |
| #define _PW_OR_01() 1 |
| #define _PW_OR_10() 1 |
| #define _PW_OR_11() 1 |
| |
| // Boolean NOT of a preprocessor expression that evaluates to 0 or 1. |
| #define PW_NOT(value) _PW_NOT(value) |
| #define _PW_NOT(value) _PW_NOT_##value() |
| #define _PW_NOT_0() 1 |
| #define _PW_NOT_1() 0 |
| |
| // Boolean XOR of two preprocessor expressions that evaluate to 0 or 1. |
| #define PW_XOR(a, b) _PW_XOR(a, b) |
| #define _PW_XOR(a, b) _PW_XOR_##a##b() |
| #define _PW_XOR_00() 0 |
| #define _PW_XOR_01() 1 |
| #define _PW_XOR_10() 1 |
| #define _PW_XOR_11() 0 |
| |
| // Boolean NAND, NOR, and XNOR of expressions that evaluate to 0 or 1. |
| #define PW_NAND(a, b) PW_NOT(PW_AND(a, b)) |
| #define PW_NOR(a, b) PW_NOT(PW_OR(a, b)) |
| #define PW_XNOR(a, b) PW_NOT(PW_XOR(a, b)) |
