1 // Copyright 2021 The Dawn Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef COMMON_PREPROCESSOR_H_ 16 #define COMMON_PREPROCESSOR_H_ 17 18 // DAWN_PP_GET_HEAD: get the first element of a __VA_ARGS__ without triggering empty 19 // __VA_ARGS__ warnings. 20 #define DAWN_INTERNAL_PP_GET_HEAD(firstParam, ...) firstParam 21 #define DAWN_PP_GET_HEAD(...) DAWN_INTERNAL_PP_GET_HEAD(__VA_ARGS__, dummyArg) 22 23 // DAWN_PP_CONCATENATE: Concatenate tokens, first expanding the arguments passed in. 24 #define DAWN_PP_CONCATENATE(arg1, arg2) DAWN_PP_CONCATENATE_1(arg1, arg2) 25 #define DAWN_PP_CONCATENATE_1(arg1, arg2) DAWN_PP_CONCATENATE_2(arg1, arg2) 26 #define DAWN_PP_CONCATENATE_2(arg1, arg2) arg1##arg2 27 28 // DAWN_PP_EXPAND: Needed to help expand __VA_ARGS__ out on MSVC 29 #define DAWN_PP_EXPAND(...) __VA_ARGS__ 30 31 // Implementation of DAWN_PP_FOR_EACH, called by concatenating DAWN_PP_FOR_EACH_ with a number. 32 #define DAWN_PP_FOR_EACH_1(func, x) func(x) 33 #define DAWN_PP_FOR_EACH_2(func, x, ...) \ 34 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_1)(func, __VA_ARGS__)) 35 #define DAWN_PP_FOR_EACH_3(func, x, ...) \ 36 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_2)(func, __VA_ARGS__)) 37 #define DAWN_PP_FOR_EACH_4(func, x, ...) \ 38 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_3)(func, __VA_ARGS__)) 39 #define DAWN_PP_FOR_EACH_5(func, x, ...) \ 40 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_4)(func, __VA_ARGS__)) 41 #define DAWN_PP_FOR_EACH_6(func, x, ...) \ 42 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_5)(func, __VA_ARGS__)) 43 #define DAWN_PP_FOR_EACH_7(func, x, ...) \ 44 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_6)(func, __VA_ARGS__)) 45 #define DAWN_PP_FOR_EACH_8(func, x, ...) \ 46 func(x) DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_7)(func, __VA_ARGS__)) 47 48 // Implementation for DAWN_PP_FOR_EACH. Get the number of args in __VA_ARGS__ so we can concat 49 // DAWN_PP_FOR_EACH_ and N. 50 // ex.) DAWN_PP_FOR_EACH_NARG(a, b, c) -> 51 // DAWN_PP_FOR_EACH_NARG(a, b, c, DAWN_PP_FOR_EACH_RSEQ()) -> 52 // DAWN_PP_FOR_EACH_NARG_(a, b, c, 8, 7, 6, 5, 4, 3, 2, 1, 0) -> 53 // DAWN_PP_FOR_EACH_ARG_N(a, b, c, 8, 7, 6, 5, 4, 3, 2, 1, 0) -> 54 // DAWN_PP_FOR_EACH_ARG_N( , , , , , , , , N) -> 55 // 3 56 #define DAWN_PP_FOR_EACH_NARG(...) DAWN_PP_FOR_EACH_NARG_(__VA_ARGS__, DAWN_PP_FOR_EACH_RSEQ()) 57 #define DAWN_PP_FOR_EACH_NARG_(...) \ 58 DAWN_PP_EXPAND(DAWN_PP_EXPAND(DAWN_PP_FOR_EACH_ARG_N)(__VA_ARGS__)) 59 #define DAWN_PP_FOR_EACH_ARG_N(_1, _2, _3, _4, _5, _6, _7, _8, N, ...) N 60 #define DAWN_PP_FOR_EACH_RSEQ() 8, 7, 6, 5, 4, 3, 2, 1, 0 61 62 // Implementation for DAWN_PP_FOR_EACH. 63 // Creates a call to DAWN_PP_FOR_EACH_X where X is 1, 2, ..., etc. 64 #define DAWN_PP_FOR_EACH_(N, func, ...) DAWN_PP_CONCATENATE(DAWN_PP_FOR_EACH_, N)(func, __VA_ARGS__) 65 66 // DAWN_PP_FOR_EACH: Apply |func| to each argument in |x| and __VA_ARGS__ 67 #define DAWN_PP_FOR_EACH(func, ...) \ 68 DAWN_PP_FOR_EACH_(DAWN_PP_FOR_EACH_NARG(__VA_ARGS__), func, __VA_ARGS__) 69 70 #endif // COMMON_PREPROCESSOR_H_ 71