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104 lines
4.1 KiB
C++
104 lines
4.1 KiB
C++
/*
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* SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#pragma once
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/*
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This header contains various general purpose helper macros used across ESP-IDF
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*/
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#include <assert.h>
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#include "esp_assert.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Macro to select different versions of other macros based on whether VA_ARGS has an argument or no argument
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*
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* Some macros (such as in FreeRTOS) have two versions (one that accepts arguments and another that does not). The
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* following "CHOOSE_MACRO_VA_ARG" selector allows automatic selection between two different versions of a macro.
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*
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* "CHOOSE_MACRO_VA_ARG" make use of the fact that "##__VA_ARGS__," will eliminate the trailing comma if there are no
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* arguments, thus allows subsequent arguments in "CHOOSE_MACRO_VA_ARG" to be left shifted in the parameter list.
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*
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* Therefore, if we call the following:
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* - CHOOSE_MACRO_VA_ARG(MACRO_ARGS, MACRO_NO_ARGS, ##__VA_ARGS__)(__VA_ARGS__)
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*
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* The result will be:
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* - MACRO_ARGS(__VA_ARGS__) if __VA_ARGS__ was not empty
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* - MACRO_NO_ARGS() if __VA_ARGS__ was empty
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*
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* @note In the future, we want to become compatible with clang. Hence, we provide two
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* versions of the following macros which are using variadic arguments. One is using the GNU extension ##__VA_ARGS__.
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* The other is using the C++20 feature __VA_OPT__(,). This allows users to compile their code with standard C++20
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* enabled instead of the GNU extension. Below C++20, we haven't found any good alternative to using ##__VA_ARGS__.
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*/
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#if defined(__cplusplus) && (__cplusplus > 201703L)
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#define CHOOSE_MACRO_VA_ARG_INN_IMPL(...) __VA_OPT__(0)
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#define CHOOSE_MACRO_VA_ARG_INN(one, MACRO1, MACRO2, ...) MACRO1
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#define CHOOSE_MACRO_VA_ARG(MACRO_WITH_ARGS, MACRO_WITH_NO_ARGS, ...) CHOOSE_MACRO_VA_ARG_INN(CHOOSE_MACRO_VA_ARG_INN_IMPL(__VA_ARGS__) __VA_OPT__(,) MACRO_WITH_ARGS, MACRO_WITH_NO_ARGS, 0)
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#else
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#define CHOOSE_MACRO_VA_ARG_INN(one, two, MACRO1, MACRO2, ...) MACRO1
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#define CHOOSE_MACRO_VA_ARG(MACRO_WITH_ARGS, MACRO_WITH_NO_ARGS, ...) CHOOSE_MACRO_VA_ARG_INN(0, ##__VA_ARGS__, MACRO_WITH_ARGS, MACRO_WITH_NO_ARGS, 0)
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#endif
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/* Count number of arguments of __VA_ARGS__
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* - reference https://groups.google.com/forum/#!topic/comp.std.c/d-6Mj5Lko_s
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* - __GET_NTH_ARG__() takes args >= N (64) but only expand to Nth one (64th)
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* - __RSEQ_N__() is reverse sequential to N to add padding to have Nth
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* position is the same as the number of arguments
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* - ##__VA_ARGS__ is used to deal with 0 paramerter (swallows comma)
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*/
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#ifndef __VA_NARG__
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# define __VA_NARG__(...) __NARG__(_0, ##__VA_ARGS__, __RSEQ_N__())
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# define __NARG__(...) __GET_NTH_ARG__(__VA_ARGS__)
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# define __GET_NTH_ARG__( \
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_01,_02,_03,_04,_05,_06,_07,_08,_09,_10, \
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_11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \
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_21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \
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_31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \
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_41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \
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_51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \
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_61,_62,_63,N,...) N
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# define __RSEQ_N__() \
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62,61,60, \
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59,58,57,56,55,54,53,52,51,50, \
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49,48,47,46,45,44,43,42,41,40, \
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39,38,37,36,35,34,33,32,31,30, \
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29,28,27,26,25,24,23,22,21,20, \
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19,18,17,16,15,14,13,12,11,10, \
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9, 8, 7, 6, 5, 4, 3, 2, 1, 0
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#endif
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#ifndef ESP_UNUSED
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#define ESP_UNUSED(x) ((void)(x))
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#endif
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/* test macros */
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#define foo_args(...) 1
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#define foo_no_args() 2
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#if defined(__cplusplus) && (__cplusplus > 201703L)
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#define foo(...) CHOOSE_MACRO_VA_ARG(foo_args, foo_no_args __VA_OPT__(,) __VA_ARGS__)(__VA_ARGS__)
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#else
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#define foo(...) CHOOSE_MACRO_VA_ARG(foo_args, foo_no_args, ##__VA_ARGS__)(__VA_ARGS__)
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#endif
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ESP_STATIC_ASSERT(foo() == 2, "CHOOSE_MACRO_VA_ARG() result does not match for 0 arguments");
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ESP_STATIC_ASSERT(foo(42) == 1, "CHOOSE_MACRO_VA_ARG() result does not match for 1 argument");
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#if defined(__cplusplus) && (__cplusplus > 201703L)
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ESP_STATIC_ASSERT(foo(42, 87) == 1, "CHOOSE_MACRO_VA_ARG() result does not match for n arguments");
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#endif
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#undef foo
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#undef foo_args
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#undef foo_no_args
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#ifdef __cplusplus
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}
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#endif
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