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- /*
- * Copyright 2012-present Facebook, Inc.
- *
- * 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
- *
- * http://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.
- */
- // @author: Andrei Alexandrescu
- #pragma once
- /**
- * Necessarily evil preprocessor-related amenities.
- */
- // MSVC's preprocessor is a pain, so we have to
- // forcefully expand the VA args in some places.
- #define FB_VA_GLUE(a, b) a b
- /**
- * FB_ONE_OR_NONE(hello, world) expands to hello and
- * FB_ONE_OR_NONE(hello) expands to nothing. This macro is used to
- * insert or eliminate text based on the presence of another argument.
- */
- #define FB_ONE_OR_NONE(a, ...) FB_VA_GLUE(FB_THIRD, (a, ##__VA_ARGS__, a))
- #define FB_THIRD(a, b, ...) __VA_ARGS__
- /**
- * Helper macro that extracts the first argument out of a list of any
- * number of arguments.
- */
- #define FB_ARG_1(a, ...) a
- /**
- * Helper macro that extracts the second argument out of a list of any
- * number of arguments. If only one argument is given, it returns
- * that.
- */
- #ifdef _MSC_VER
- // GCC refuses to expand this correctly if this macro itself was
- // called with FB_VA_GLUE :(
- #define FB_ARG_2_OR_1(...) \
- FB_VA_GLUE(FB_ARG_2_OR_1_IMPL, (__VA_ARGS__, __VA_ARGS__))
- #else
- #define FB_ARG_2_OR_1(...) FB_ARG_2_OR_1_IMPL(__VA_ARGS__, __VA_ARGS__)
- #endif
- // Support macro for the above
- #define FB_ARG_2_OR_1_IMPL(a, b, ...) b
- /**
- * Helper macro that provides a way to pass argument with commas in it to
- * some other macro whose syntax doesn't allow using extra parentheses.
- * Example:
- *
- * #define MACRO(type, name) type name
- * MACRO(FB_SINGLE_ARG(std::pair<size_t, size_t>), x);
- *
- */
- #define FB_SINGLE_ARG(...) __VA_ARGS__
- #define FOLLY_PP_DETAIL_APPEND_VA_ARG(...) , ##__VA_ARGS__
- /**
- * Helper macro that just ignores its parameters.
- */
- #define FOLLY_IGNORE(...)
- /**
- * Helper macro that just ignores its parameters and inserts a semicolon.
- */
- #define FOLLY_SEMICOLON(...) ;
- /**
- * FB_ANONYMOUS_VARIABLE(str) introduces an identifier starting with
- * str and ending with a number that varies with the line.
- */
- #ifndef FB_ANONYMOUS_VARIABLE
- #define FB_CONCATENATE_IMPL(s1, s2) s1##s2
- #define FB_CONCATENATE(s1, s2) FB_CONCATENATE_IMPL(s1, s2)
- #ifdef __COUNTER__
- #define FB_ANONYMOUS_VARIABLE(str) FB_CONCATENATE(str, __COUNTER__)
- #else
- #define FB_ANONYMOUS_VARIABLE(str) FB_CONCATENATE(str, __LINE__)
- #endif
- #endif
- /**
- * Use FB_STRINGIZE(x) when you'd want to do what #x does inside
- * another macro expansion.
- */
- #define FB_STRINGIZE(x) #x
- #define FOLLY_PP_DETAIL_NARGS_1(dummy, _7, _6, _5, _4, _3, _2, _1, _0, ...) _0
- #define FOLLY_PP_DETAIL_NARGS(...) \
- FOLLY_PP_DETAIL_NARGS_1(dummy, ##__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_0(fn, ...)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_1(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_0(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_2(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_1(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_3(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_2(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_4(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_3(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_5(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_4(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_6(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_5(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_REC_7(fn, a, ...) \
- fn(a) FOLLY_PP_DETAIL_FOR_EACH_REC_6(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_2(fn, n, ...) \
- FOLLY_PP_DETAIL_FOR_EACH_REC_##n(fn, __VA_ARGS__)
- #define FOLLY_PP_DETAIL_FOR_EACH_1(fn, n, ...) \
- FOLLY_PP_DETAIL_FOR_EACH_2(fn, n, __VA_ARGS__)
- /**
- * FOLLY_PP_FOR_EACH
- *
- * Used to invoke a preprocessor macro, the name of which is passed as the
- * first argument, once for each subsequent variadic argument.
- *
- * At present, supports [0, 8) arguments.
- *
- * This input:
- *
- * #define DOIT(a) go_do_it(a);
- * FOLLY_PP_FOR_EACH(DOIT, 3, 5, 7)
- * #undef DOIT
- *
- * Expands to this output (with whitespace adjusted for clarity):
- *
- * go_do_it(3);
- * go_do_it(5);
- * go_do_it(7);
- */
- #define FOLLY_PP_FOR_EACH(fn, ...) \
- FOLLY_PP_DETAIL_FOR_EACH_1( \
- fn, FOLLY_PP_DETAIL_NARGS(__VA_ARGS__), __VA_ARGS__)
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