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使用提供的ENUM宏定义enum后，提供函数，可以将enum转换为string，也可以通过string获取对应enum的值，定义和使用过程和直接使用enum关键字差不多。
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提供3个函数，如果不是使用ENUM宏定义的enum无法调用。
enum2Str（）// enum转字符串
str2Enum（） // 字符串转enum，没有返回false
getEnumName（）// 获取enum类的名字
ENUM(Arg1, Arg2, Arg3...)
Arg1: 定义的enum的名称。
Arg2：enum类的类型。
Arg3...：enum类的成员，个数最多为63个。
#include"ENUM/ENUM.hpp"
#include<cstring>
#include<iostream>
// VC++需要选择“配置属性”>“C/C++”>“命令行”属性页。
// 修改“附加选项”属性以包含 /experimental:preprocessor，然后选择“确定”
ENUM(Enum1, char, (idleDown), idle, (idleUp, 2), (idleRight, -3), (idleLeft, 10), IDLE);
structExample {
ENUM(Enum2, char, (enum3), (enum4));
};
classExampleClass {
ENUM(Enum3, char, (enum5), (enum6));
};
intexample()
{
usingnamespace std;
Enum1 x = Enum1::idleRight; // idleRight = -3
char str1[] = "str";
cout << std::boolalpha << str2Enum(str1, strlen(str1), x) << endl; // cout: false
cout << x << endl; // cout: -3
cout << enum2Str(x) << endl; // cout: idleRight
cout << "------------------------" << endl;
string str2 = "idleDown"; // 0
cout << std::boolalpha << str2Enum(str2, x) << endl; // cout: true
cout << x << endl; // cout: 0
cout << enum2Str(x) << endl; // cout: idleDown
cout << "name: " << getEnumName(x) << endl; // cout: name: Enum1
cout << "------------------------" << endl;
Example::Enum2 xx = Example::Enum2::enum3;
char str3[] = "str";
cout << std::boolalpha << Example::str2Enum(str3, strlen(str3), xx) << endl; // cout: false
cout << xx << endl; // cout: 0
cout << Example::enum2Str(xx) << endl; // cout: enum3
cout << "------------------------" << endl;
string str4 = "enum4"; // 1
cout << std::boolalpha << Example::str2Enum(str4, xx) << endl; // cout: true
cout << xx << endl; // cout: 1
cout << Example::enum2Str(xx) << endl; // cout: enum4
cout << "name: " << Example::getEnumName(xx) << endl; // cout: name: Enum2
cout << "------------------------" << endl;
return0;
}
使用宏和和编译期计算功能，在编译期的时候对参数进行展开和计算，自动生成对应的函数，尽量减少运行时的时间和空间复杂度。
运行测试版本 >= C++11。
| 代价 | 运行和使用 | 待改进 |
| :---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :--------------------------------------------------------------------------- |
| 1.增加编译时间，生成的目标文件会增大（可忽略不计）。<br/>2.宏可能会给调试增加难度。<br/>3. 如果两个不同的枚举量的hash相同，编译会报错（简单测试过63个参数，没遇到）。 | 1.运行时，字符串转enum时间复杂度和空间复杂度为n，和字符串的长度有关。enum转字符时间和空间复杂度为常数。<br/>2.线程安全。<br/>3.用ENUM定义枚举类型和直接使用enum差不多,用ENUM定义能得到普通的枚举类型同时，也会得到相应的函数。<br/>4.支持自定义顺序。 | 1.因为是使用宏来展开的，需要自己编写展开的宏，现在支持的最大枚举参数为63个。 |
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首先需要需要获取传进宏的枚举的参数的个数的数量。
/************************** 获取宏的参数个数 ********************/ #defineARG_N(...) \ ARG_N_(0, ##__VA_ARGS__, ARG_N_RESQ) #defineARG_N_(...) \ ARG_N_M(__VA_ARGS__) #defineARG_N_M( \ _0, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, \ _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, \ _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, \ _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, \ _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, \ _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, \ _61, _62, _63, N, ...) N #define ARG_N_RESQ \ 63, 62, 61, 60, \ 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, \ 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, \ 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, \ 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, \ 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
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展开枚举的参数的宏，宏不支持递归，没想到优雅展开宏参数的写法，直接手动编写。
#defineEXPAND_ARG0() #defineEXPAND_ARG1(MACRO, x) MACRO(x, 0) #defineEXPAND_ARG2(MACRO, x, ...) MACRO(x, 1) EXPAND_ARG1(MACRO, __VA_ARGS__) #defineEXPAND_ARG3(MACRO, x, ...) MACRO(x, 2) EXPAND_ARG2(MACRO, __VA_ARGS__) #defineEXPAND_ARG4(MACRO, x, ...) MACRO(x, 3) EXPAND_ARG3(MACRO, __VA_ARGS__) #defineEXPAND_ARG5(MACRO, x, ...) MACRO(x, 4) EXPAND_ARG4(MACRO, __VA_ARGS__) #defineEXPAND_ARG6(MACRO, x, ...) MACRO(x, 5) EXPAND_ARG5(MACRO, __VA_ARGS__) #defineEXPAND_ARG7(MACRO, x, ...) MACRO(x, 6) EXPAND_ARG6(MACRO, __VA_ARGS__) #defineEXPAND_ARG8(MACRO, x, ...) MACRO(x, 7) EXPAND_ARG7(MACRO, __VA_ARGS__) #defineEXPAND_ARG9(MACRO, x, ...) MACRO(x, 8) EXPAND_ARG8(MACRO, __VA_ARGS__) #defineEXPAND_ARG10(MACRO, x, ...) MACRO(x, 9) EXPAND_ARG9(MACRO, __VA_ARGS__) #defineEXPAND_ARG11(MACRO, x, ...) MACRO(x, 10) EXPAND_ARG10(MACRO, __VA_ARGS__) #defineEXPAND_ARG12(MACRO, x, ...) MACRO(x, 11) EXPAND_ARG11(MACRO, __VA_ARGS__) #defineEXPAND_ARG13(MACRO, x, ...) MACRO(x, 12) EXPAND_ARG12(MACRO, __VA_ARGS__) #defineEXPAND_ARG14(MACRO, x, ...) MACRO(x, 13) EXPAND_ARG13(MACRO, __VA_ARGS__) #defineEXPAND_ARG15(MACRO, x, ...) MACRO(x, 14) EXPAND_ARG14(MACRO, __VA_ARGS__) #defineEXPAND_ARG16(MACRO, x, ...) MACRO(x, 15) EXPAND_ARG15(MACRO, __VA_ARGS__) #defineEXPAND_ARG17(MACRO, x, ...) MACRO(x, 16) EXPAND_ARG16(MACRO, __VA_ARGS__) #defineEXPAND_ARG18(MACRO, x, ...) MACRO(x, 17) EXPAND_ARG17(MACRO, __VA_ARGS__) #defineEXPAND_ARG19(MACRO, x, ...) MACRO(x, 18) EXPAND_ARG18(MACRO, __VA_ARGS__) #defineEXPAND_ARG20(MACRO, x, ...) MACRO(x, 19) EXPAND_ARG19(MACRO, __VA_ARGS__) #defineEXPAND_ARG21(MACRO, x, ...) MACRO(x, 20) EXPAND_ARG20(MACRO, __VA_ARGS__) #defineEXPAND_ARG22(MACRO, x, ...) MACRO(x, 21) EXPAND_ARG21(MACRO, __VA_ARGS__) #defineEXPAND_ARG23(MACRO, x, ...) MACRO(x, 22) EXPAND_ARG22(MACRO, __VA_ARGS__) #defineEXPAND_ARG24(MACRO, x, ...) MACRO(x, 23) EXPAND_ARG23(MACRO, __VA_ARGS__) #defineEXPAND_ARG25(MACRO, x, ...) MACRO(x, 24) EXPAND_ARG24(MACRO, __VA_ARGS__) #defineEXPAND_ARG26(MACRO, x, ...) MACRO(x, 25) EXPAND_ARG25(MACRO, __VA_ARGS__) #defineEXPAND_ARG27(MACRO, x, ...) MACRO(x, 26) EXPAND_ARG26(MACRO, __VA_ARGS__) #defineEXPAND_ARG28(MACRO, x, ...) MACRO(x, 27) EXPAND_ARG27(MACRO, __VA_ARGS__) #defineEXPAND_ARG29(MACRO, x, ...) MACRO(x, 28) EXPAND_ARG28(MACRO, __VA_ARGS__) #defineEXPAND_ARG30(MACRO, x, ...) MACRO(x, 29) EXPAND_ARG29(MACRO, __VA_ARGS__) #defineEXPAND_ARG31(MACRO, x, ...) MACRO(x, 30) EXPAND_ARG30(MACRO, __VA_ARGS__) #defineEXPAND_ARG32(MACRO, x, ...) MACRO(x, 31) EXPAND_ARG31(MACRO, __VA_ARGS__) #defineEXPAND_ARG33(MACRO, x, ...) MACRO(x, 32) EXPAND_ARG32(MACRO, __VA_ARGS__) #defineEXPAND_ARG34(MACRO, x, ...) MACRO(x, 33) EXPAND_ARG33(MACRO, __VA_ARGS__) #defineEXPAND_ARG35(MACRO, x, ...) MACRO(x, 34) EXPAND_ARG34(MACRO, __VA_ARGS__) #defineEXPAND_ARG36(MACRO, x, ...) MACRO(x, 35) EXPAND_ARG35(MACRO, __VA_ARGS__) #defineEXPAND_ARG37(MACRO, x, ...) MACRO(x, 36) EXPAND_ARG36(MACRO, __VA_ARGS__) #defineEXPAND_ARG38(MACRO, x, ...) MACRO(x, 37) EXPAND_ARG37(MACRO, __VA_ARGS__) #defineEXPAND_ARG39(MACRO, x, ...) MACRO(x, 38) EXPAND_ARG38(MACRO, __VA_ARGS__) #defineEXPAND_ARG40(MACRO, x, ...) MACRO(x, 39) EXPAND_ARG39(MACRO, __VA_ARGS__) #defineEXPAND_ARG41(MACRO, x, ...) MACRO(x, 40) EXPAND_ARG40(MACRO, __VA_ARGS__) #defineEXPAND_ARG42(MACRO, x, ...) MACRO(x, 41) EXPAND_ARG41(MACRO, __VA_ARGS__) #defineEXPAND_ARG43(MACRO, x, ...) MACRO(x, 42) EXPAND_ARG42(MACRO, __VA_ARGS__) #defineEXPAND_ARG44(MACRO, x, ...) MACRO(x, 43) EXPAND_ARG43(MACRO, __VA_ARGS__) #defineEXPAND_ARG45(MACRO, x, ...) MACRO(x, 44) EXPAND_ARG44(MACRO, __VA_ARGS__) #defineEXPAND_ARG46(MACRO, x, ...) MACRO(x, 45) EXPAND_ARG45(MACRO, __VA_ARGS__) #defineEXPAND_ARG47(MACRO, x, ...) MACRO(x, 46) EXPAND_ARG46(MACRO, __VA_ARGS__) #defineEXPAND_ARG48(MACRO, x, ...) MACRO(x, 47) EXPAND_ARG47(MACRO, __VA_ARGS__) #defineEXPAND_ARG49(MACRO, x, ...) MACRO(x, 48) EXPAND_ARG48(MACRO, __VA_ARGS__) #defineEXPAND_ARG50(MACRO, x, ...) MACRO(x, 49) EXPAND_ARG49(MACRO, __VA_ARGS__) #defineEXPAND_ARG51(MACRO, x, ...) MACRO(x, 50) EXPAND_ARG50(MACRO, __VA_ARGS__) #defineEXPAND_ARG52(MACRO, x, ...) MACRO(x, 51) EXPAND_ARG51(MACRO, __VA_ARGS__) #defineEXPAND_ARG53(MACRO, x, ...) MACRO(x, 52) EXPAND_ARG52(MACRO, __VA_ARGS__) #defineEXPAND_ARG54(MACRO, x, ...) MACRO(x, 53) EXPAND_ARG53(MACRO, __VA_ARGS__) #defineEXPAND_ARG55(MACRO, x, ...) MACRO(x, 54) EXPAND_ARG54(MACRO, __VA_ARGS__) #defineEXPAND_ARG56(MACRO, x, ...) MACRO(x, 55) EXPAND_ARG55(MACRO, __VA_ARGS__) #defineEXPAND_ARG57(MACRO, x, ...) MACRO(x, 56) EXPAND_ARG56(MACRO, __VA_ARGS__) #defineEXPAND_ARG58(MACRO, x, ...) MACRO(x, 57) EXPAND_ARG57(MACRO, __VA_ARGS__) #defineEXPAND_ARG59(MACRO, x, ...) MACRO(x, 58) EXPAND_ARG58(MACRO, __VA_ARGS__) #defineEXPAND_ARG60(MACRO, x, ...) MACRO(x, 59) EXPAND_ARG59(MACRO, __VA_ARGS__) #defineEXPAND_ARG61(MACRO, x, ...) MACRO(x, 60) EXPAND_ARG60(MACRO, __VA_ARGS__) #defineEXPAND_ARG62(MACRO, x, ...) MACRO(x, 61) EXPAND_ARG61(MACRO, __VA_ARGS__) #defineEXPAND_ARG63(MACRO, x, ...) MACRO(x, 62) EXPAND_ARG62(MACRO, __VA_ARGS__)
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使用上边写的宏，根据宏传入的参数个数获取对应的展开参数的宏
#defineARG_CONCAT_(l, r) l##r #defineARG_CONCAT(l, r) ARG_CONCAT_(l, r) #defineEXPAND(MACRO, ...) ARG_CONCAT(EXPAND_ARG, ARG_N(__VA_ARGS__))(MACRO, __VA_ARGS__)
在编译期将字符串转换为hash值，并且在运行将字符串转变为hash值去匹配。
/************************************计算HASH值********************************************/
/************************************计算HASH值********************************************/
#pragmaonce
// 返回字符串长度
#define STR_SIZE(STR)(sizeof(STR)-1)
// Hash计算公式
#define COMPUTE(SEED,STR,N)((unsigned int)(SEED ^STR[N]+0x9e3779b9+(SEED <<6)+(SEED >>2)))
// 字符串计算hash值
constexprunsignedintcompute(unsignedint&&seed, constchar*val, intNUM)
{
return NUM > 0 ? compute(COMPUTE(seed, val, NUM - 1), val, NUM - 1) : seed;
}
自动生成转换代码的ENUM宏。enum转字符串，展开时用E2S宏替换，返回字符串。字符串转enum时，展开是用S2E替换，将传入字符串转换为hash，然后匹配编译期生成的hash值，匹配到返回true。
#pragmaonce
#include"PP.hpp"
#include"computeHash.hpp"
#include"expandMacro.h"
#include<string>
// GCC 的宏不支持和‘(’连接， VC通过
// 选择“配置属性”>“C/C++”>“命令行”属性页。
// 修改“附加选项”属性以包含 /experimental:preprocessor，然后选择“确定”
#define PARAM_ENUM_1(X) X,
#define PARAM_ENUM_2(X,Y) X = Y,
#define PARAM_ENUM_END_1(X) X
#define PARAM_ENUM_END_2(X,Y) X = Y
// 元组处理
#define CALL_FUN(FUN,X) FUN X
#define COUNT_BRACKET(...)ARG_N(__VA_ARGS__)
#define PP_BRACKET(...) __VA_ARGS__
#define PP_IF(FREE,THEN,ELSE)ARG_CONCAT(PP_IF_,PP_BOOL(FREE))(THEN, ELSE)
#define PP_IF_0(THEN,ELSE) ELSE
#define PP_IF_1(THEN,ELSE) THEN
#define PARAM_ENUM_IMPL_1(X,NUM)PP_IF(NUM, \
(CALL_FUN(ARG_CONCAT(PARAM_ENUM_,CALL_FUN(COUNT_BRACKET, X)), X)),\
(CALL_FUN(ARG_CONCAT(PARAM_ENUM_END_,CALL_FUN(COUNT_BRACKET, X)), X)))
#define PARAM_ENUM_IMPL_2(X,NUM)PP_IF(NUM,(PARAM_ENUM_1(X)),(PARAM_ENUM_END_1(X)))
#define PARAM_ENUM_IMPL(X,NUM)PP_IF(PP_IS_PARENS(X),(PARAM_ENUM_IMPL_1(X, NUM)),(PARAM_ENUM_IMPL_2(X, NUM)))
#define PARAM_ENUM(X,NUM)CALL_FUN(PP_BRACKET,CALL_FUN(PP_BRACKET,PARAM_ENUM_IMPL(X, NUM)))
#define GET_PAR_1(X) X
#define GET_PAR_2(X,Y) X
#define GET_PAR(X)CALL_FUN(ARG_CONCAT(GET_PAR_,CALL_FUN(COUNT_BRACKET, X)), X)
#define TO_STR_(X)#X
#define TO_STR(X)TO_STR_(X)
#define TUPLE_STR(X)TO_STR(GET_PAR(X))
#define E2S_(X,NUM) \
case(PP_IF(PP_IS_PARENS(X),GET_PAR(X), X)): { \
returnPP_IF(PP_IS_PARENS(X),TUPLE_STR(X),#X);\
}
#define S2E_(X,NUM) \
case(compute(0,PP_IF(PP_IS_PARENS(X),TUPLE_STR(X),#X),STR_SIZE(PP_IF(PP_IS_PARENS(X),TUPLE_STR(X),#X)))): {\
Enum =PP_IF(PP_IS_PARENS(X),GET_PAR(X), X); \
ret = true; \
break; \
}
#define ENUM(ENUM_NAME,TYPE,...) \
enum ENUM_NAME: TYPE { EXPAND(PARAM_ENUM, __VA_ARGS__) }; \
static const char* enum2Str(ENUM_NAMEEnum) \
{ \
switch(Enum){ \
EXPAND(E2S_, __VA_ARGS__) \
default:{ \
break; \
} \
} \
return nullptr; \
} \
static bool str2Enum(const char* str, const unsigned int& size,ENUM_NAME& Enum)\
{ \
bool ret = false; \
unsigned int s =compute(0, str, size); \
switch(s){ \
EXPAND(S2E_, __VA_ARGS__) \
default:{ \
break; \
} \
} \
return ret; \
} \
static bool str2Enum(const std::string& str,ENUM_NAME& Enum) \
{ \
returnstr2Enum(str.c_str(),str.length(), Enum); \
} \
static const char* getEnumName(ENUM_NAME& Enum) \
{ \
return#ENUM_NAME; \
}
《C++标准库（第二版）》
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