与其他类似的问题不同,这个问题是关于如何使用c++的新特性。

2008 c Is there a simple way to convert C++ enum to string? 2008 c Easy way to use variables of enum types as string in C? 2008 c++ How to easily map c++ enums to strings 2008 c++ Making something both a C identifier and a string? 2008 c++ Is there a simple script to convert C++ enum to string? 2009 c++ How to use enums as flags in C++? 2011 c++ How to convert an enum type variable to a string? 2011 c++ Enum to String C++ 2011 c++ How to convert an enum type variable to a string? 2012 c How to convert enum names to string in c 2013 c Stringifying an conditionally compiled enum in C

看了很多答案后,我还没有找到:

优雅的方式使用c++ 11、c++ 14或c++ 17的新特性 或者在Boost中使用一些现成的东西 还有一些东西计划在c++ 20中实现

例子

举例往往比冗长的解释更好。 您可以在Coliru上编译和运行这个代码片段。 (另一个前面的例子也可用)

#include <map>
#include <iostream>

struct MyClass
{
    enum class MyEnum : char {
        AAA = -8,
        BBB = '8',
        CCC = AAA + BBB
    };
};

// Replace magic() by some faster compile-time generated code
// (you're allowed to replace the return type with std::string
// if that's easier for you)
const char* magic (MyClass::MyEnum e)
{
    const std::map<MyClass::MyEnum,const char*> MyEnumStrings {
        { MyClass::MyEnum::AAA, "MyClass::MyEnum::AAA" },
        { MyClass::MyEnum::BBB, "MyClass::MyEnum::BBB" },
        { MyClass::MyEnum::CCC, "MyClass::MyEnum::CCC" }
    };
    auto   it  = MyEnumStrings.find(e);
    return it == MyEnumStrings.end() ? "Out of range" : it->second;
}

int main()
{
   std::cout << magic(MyClass::MyEnum::AAA) <<'\n';
   std::cout << magic(MyClass::MyEnum::BBB) <<'\n';
   std::cout << magic(MyClass::MyEnum::CCC) <<'\n';
}

约束

请不要无价值的重复其他答案或基本链接。 请避免基于宏的臃肿答案,或尽量减少#define开销。 请不要手动enum ->字符串映射。

很高兴有

支持从不同于零的数字开始的enum值 支持负enum值 支持碎片enum值 支持类枚举(c++ 11) 支持类枚举:<类型>有任何允许的<类型> (c++ 11) 编译时(不是运行时)到字符串的转换, 或者至少在运行时快速执行(例如std::map不是一个好主意…) constexpr (c++ 11,然后在c++ 14/17/20中放松) noexcept (C + + 11) c++ 17/ c++ 20友好的代码片段

一个可能的想法是使用c++编译器功能,在编译时使用基于可变参数模板类和constexpr函数的元编程技巧来生成c++代码……


当前回答

我不太喜欢与此相关的所有花哨的框架(宏、模板和类),因为我认为使用它们会使代码更难理解,并且会增加编译时间并隐藏错误。总的来说,我想要一个简单的解决这个问题的方法。添加额外的100行代码并不简单。

最初问题中给出的示例与我实际在生产中使用的代码非常接近。相反,我只想对原来的示例查找函数提出一些小的改进:

const std::string& magic(MyClass::MyEnum e)
{
    static const std::string OUT_OF_RANGE = "Out of range";
    #define ENTRY(v) { MyClass::MyEnum::v, "MyClass::MyEnum::" #v }
    static const std::unordered_map<MyClass::MyEnum, std::string> LOOKUP {
        ENTRY(AAA),
        ENTRY(BBB),
        ENTRY(CCC),
    };
    #undef ENTRY
    auto it  = LOOKUP.find(e);
    return ((it != LOOKUP.end()) ? it->second : OUT_OF_RANGE);
}

具体地说:

Internal data structures are now 'static' and 'const'. These are unchanging, so there is no need to construct these on every call to the function, and to do so would be very inefficient. Instead, these are constructed on the first call to the function only. Return value is now 'const std::string&'. This function will only return references to already-allocated std::string objects with 'static' lifetime, so there is no need to copy them when returning. Map type is now 'std::unordered_map' for O(1) access instead of std::map's O(log(N)) access. Use of the ENTRY macro allows somewhat more concise code and also avoids potential problems from typos made while entering names in the string literals. (If the programmer enters an invalid name, a compiler error will result.)

其他回答

(better_enum库的方法)

在当前的c++中,有一种方法是这样做的:

ENUM(Channel, char, Red = 1, Green, Blue)

// "Same as":
// enum class Channel : char { Red = 1, Green, Blue };

用法:

Channel     c = Channel::_from_string("Green");  // Channel::Green (2)
c._to_string();                                  // string "Green"

for (Channel c : Channel::_values())
    std::cout << c << std::endl;

// And so on...

所有操作都可以写成constexpr。你也可以实现@ecatmur回答中提到的c++ 17反射提议。

There is only one macro. I believe this is the minimum possible, because preprocessor stringization (#) is the only way to convert a token to a string in current C++. The macro is pretty unobtrusive – the constant declarations, including initializers, are pasted into a built-in enum declaration. This means they have the same syntax and meaning as in a built-in enum. Repetition is eliminated. The implementation is most natural and useful in at least C++11, due to constexpr. It can also be made to work with C++98 + __VA_ARGS__. It is definitely modern C++.


宏的定义有些复杂,所以我将从几个方面回答这个问题。

The bulk of this answer is an implementation that I think is suitable for the space constraints on StackOverflow. There is also a CodeProject article describing the basics of the implementation in a long-form tutorial. [Should I move it here? I think it's too much for a SO answer]. There is a full-featured library "Better Enums" that implements the macro in a single header file. It also implements N4428 Type Property Queries, the current revision of the C++17 reflection proposal N4113. So, at least for enums declared through this macro, you can have the proposed C++17 enum reflection now, in C++11/C++14.

将这个答案扩展到库的特性是很简单的——这里没有遗漏任何“重要”的东西。然而,这是相当乏味的,并且存在编译器可移植性问题。

免责声明:我是CodeProject文章和该库的作者。

您可以尝试这个答案中的代码、库以及在Wandbox中在线实现N4428。标准库文档还包含如何将其作为N4428使用的概述,其中解释了该建议的enumums部分。


解释

下面的代码实现了枚举和字符串之间的转换。然而,它也可以扩展到做其他事情,比如迭代。此答案将枚举包装在结构体中。你也可以在枚举旁边生成一个trait结构体。

策略是生成如下内容:

struct Channel {
    enum _enum : char { __VA_ARGS__ };
    constexpr static const Channel          _values[] = { __VA_ARGS__ };
    constexpr static const char * const     _names[] = { #__VA_ARGS__ };

    static const char* _to_string(Channel v) { /* easy */ }
    constexpr static Channel _from_string(const char *s) { /* easy */ }
};

问题是:

We will end up with something like {Red = 1, Green, Blue} as the initializer for the values array. This is not valid C++, because Red is not an assignable expression. This is solved by casting each constant to a type T that has an assignment operator, but will drop the assignment: {(T)Red = 1, (T)Green, (T)Blue}. Similarly, we will end up with {"Red = 1", "Green", "Blue"} as the initializer for the names array. We will need to trim off the " = 1". I am not aware of a great way to do this at compile time, so we will defer this to run time. As a result, _to_string won't be constexpr, but _from_string can still be constexpr, because we can treat whitespace and equals signs as terminators when comparing with untrimmed strings. Both the above need a "mapping" macro that can apply another macro to each element in __VA_ARGS__. This is pretty standard. This answer includes a simple version that can handle up to 8 elements. If the macro is to be truly self-contained, it needs to declare no static data that requires a separate definition. In practice, this means arrays need special treatment. There are two possible solutions: constexpr (or just const) arrays at namespace scope, or regular arrays in non-constexpr static inline functions. The code in this answer is for C++11 and takes the former approach. The CodeProject article is for C++98 and takes the latter.


Code

#include <cstddef>      // For size_t.
#include <cstring>      // For strcspn, strncpy.
#include <stdexcept>    // For runtime_error.



// A "typical" mapping macro. MAP(macro, a, b, c, ...) expands to
// macro(a) macro(b) macro(c) ...
// The helper macro COUNT(a, b, c, ...) expands to the number of
// arguments, and IDENTITY(x) is needed to control the order of
// expansion of __VA_ARGS__ on Visual C++ compilers.
#define MAP(macro, ...) \
    IDENTITY( \
        APPLY(CHOOSE_MAP_START, COUNT(__VA_ARGS__)) \
            (macro, __VA_ARGS__))

#define CHOOSE_MAP_START(count) MAP ## count

#define APPLY(macro, ...) IDENTITY(macro(__VA_ARGS__))

#define IDENTITY(x) x

#define MAP1(m, x)      m(x)
#define MAP2(m, x, ...) m(x) IDENTITY(MAP1(m, __VA_ARGS__))
#define MAP3(m, x, ...) m(x) IDENTITY(MAP2(m, __VA_ARGS__))
#define MAP4(m, x, ...) m(x) IDENTITY(MAP3(m, __VA_ARGS__))
#define MAP5(m, x, ...) m(x) IDENTITY(MAP4(m, __VA_ARGS__))
#define MAP6(m, x, ...) m(x) IDENTITY(MAP5(m, __VA_ARGS__))
#define MAP7(m, x, ...) m(x) IDENTITY(MAP6(m, __VA_ARGS__))
#define MAP8(m, x, ...) m(x) IDENTITY(MAP7(m, __VA_ARGS__))

#define EVALUATE_COUNT(_1, _2, _3, _4, _5, _6, _7, _8, count, ...) \
    count

#define COUNT(...) \
    IDENTITY(EVALUATE_COUNT(__VA_ARGS__, 8, 7, 6, 5, 4, 3, 2, 1))



// The type "T" mentioned above that drops assignment operations.
template <typename U>
struct ignore_assign {
    constexpr explicit ignore_assign(U value) : _value(value) { }
    constexpr operator U() const { return _value; }

    constexpr const ignore_assign& operator =(int dummy) const
        { return *this; }

    U   _value;
};



// Prepends "(ignore_assign<_underlying>)" to each argument.
#define IGNORE_ASSIGN_SINGLE(e) (ignore_assign<_underlying>)e,
#define IGNORE_ASSIGN(...) \
    IDENTITY(MAP(IGNORE_ASSIGN_SINGLE, __VA_ARGS__))

// Stringizes each argument.
#define STRINGIZE_SINGLE(e) #e,
#define STRINGIZE(...) IDENTITY(MAP(STRINGIZE_SINGLE, __VA_ARGS__))



// Some helpers needed for _from_string.
constexpr const char    terminators[] = " =\t\r\n";

// The size of terminators includes the implicit '\0'.
constexpr bool is_terminator(char c, size_t index = 0)
{
    return
        index >= sizeof(terminators) ? false :
        c == terminators[index] ? true :
        is_terminator(c, index + 1);
}

constexpr bool matches_untrimmed(const char *untrimmed, const char *s,
                                 size_t index = 0)
{
    return
        is_terminator(untrimmed[index]) ? s[index] == '\0' :
        s[index] != untrimmed[index] ? false :
        matches_untrimmed(untrimmed, s, index + 1);
}



// The macro proper.
//
// There are several "simplifications" in this implementation, for the
// sake of brevity. First, we have only one viable option for declaring
// constexpr arrays: at namespace scope. This probably should be done
// two namespaces deep: one namespace that is likely to be unique for
// our little enum "library", then inside it a namespace whose name is
// based on the name of the enum to avoid collisions with other enums.
// I am using only one level of nesting.
//
// Declaring constexpr arrays inside the struct is not viable because
// they will need out-of-line definitions, which will result in
// duplicate symbols when linking. This can be solved with weak
// symbols, but that is compiler- and system-specific. It is not
// possible to declare constexpr arrays as static variables in
// constexpr functions due to the restrictions on such functions.
//
// Note that this prevents the use of this macro anywhere except at
// namespace scope. Ironically, the C++98 version of this, which can
// declare static arrays inside static member functions, is actually
// more flexible in this regard. It is shown in the CodeProject
// article.
//
// Second, for compilation performance reasons, it is best to separate
// the macro into a "parametric" portion, and the portion that depends
// on knowing __VA_ARGS__, and factor the former out into a template.
//
// Third, this code uses a default parameter in _from_string that may
// be better not exposed in the public interface.

#define ENUM(EnumName, Underlying, ...)                               \
namespace data_ ## EnumName {                                         \
    using _underlying = Underlying;                                   \
    enum { __VA_ARGS__ };                                             \
                                                                      \
    constexpr const size_t           _size =                          \
        IDENTITY(COUNT(__VA_ARGS__));                                 \
                                                                      \
    constexpr const _underlying      _values[] =                      \
        { IDENTITY(IGNORE_ASSIGN(__VA_ARGS__)) };                     \
                                                                      \
    constexpr const char * const     _raw_names[] =                   \
        { IDENTITY(STRINGIZE(__VA_ARGS__)) };                         \
}                                                                     \
                                                                      \
struct EnumName {                                                     \
    using _underlying = Underlying;                                   \
    enum _enum : _underlying { __VA_ARGS__ };                         \
                                                                      \
    const char * _to_string() const                                   \
    {                                                                 \
        for (size_t index = 0; index < data_ ## EnumName::_size;      \
             ++index) {                                               \
                                                                      \
            if (data_ ## EnumName::_values[index] == _value)          \
                return _trimmed_names()[index];                       \
        }                                                             \
                                                                      \
        throw std::runtime_error("invalid value");                    \
    }                                                                 \
                                                                      \
    constexpr static EnumName _from_string(const char *s,             \
                                           size_t index = 0)          \
    {                                                                 \
        return                                                        \
            index >= data_ ## EnumName::_size ?                       \
                    throw std::runtime_error("invalid identifier") :  \
            matches_untrimmed(                                        \
                data_ ## EnumName::_raw_names[index], s) ?            \
                    (EnumName)(_enum)data_ ## EnumName::_values[      \
                                                            index] :  \
            _from_string(s, index + 1);                               \
    }                                                                 \
                                                                      \
    EnumName() = delete;                                              \
    constexpr EnumName(_enum value) : _value(value) { }               \
    constexpr operator _enum() const { return (_enum)_value; }        \
                                                                      \
  private:                                                            \
    _underlying     _value;                                           \
                                                                      \
    static const char * const * _trimmed_names()                      \
    {                                                                 \
        static char     *the_names[data_ ## EnumName::_size];         \
        static bool     initialized = false;                          \
                                                                      \
        if (!initialized) {                                           \
            for (size_t index = 0; index < data_ ## EnumName::_size;  \
                 ++index) {                                           \
                                                                      \
                size_t  length =                                      \
                    std::strcspn(data_ ## EnumName::_raw_names[index],\
                                 terminators);                        \
                                                                      \
                the_names[index] = new char[length + 1];              \
                                                                      \
                std::strncpy(the_names[index],                        \
                             data_ ## EnumName::_raw_names[index],    \
                             length);                                 \
                the_names[index][length] = '\0';                      \
            }                                                         \
                                                                      \
            initialized = true;                                       \
        }                                                             \
                                                                      \
        return the_names;                                             \
    }                                                                 \
};

and

// The code above was a "header file". This is a program that uses it.
#include <iostream>
#include "the_file_above.h"

ENUM(Channel, char, Red = 1, Green, Blue)

constexpr Channel   channel = Channel::_from_string("Red");

int main()
{
    std::cout << channel._to_string() << std::endl;

    switch (channel) {
        case Channel::Red:   return 0;
        case Channel::Green: return 1;
        case Channel::Blue:  return 2;
    }
}

static_assert(sizeof(Channel) == sizeof(char), "");

如您所料,上面的程序输出红色。这里有一定程度的类型安全,因为您不能在没有初始化的情况下创建枚举,并且从开关中删除其中一个情况将导致编译器发出警告(取决于您的编译器和标志)。另外,请注意“Red”在编译过程中被转换为枚举。

我的答案在这里。

你可以同时获得枚举值名称和这些索引,如deque of string。

这种方法只需要少量的复制粘贴和编辑。

当需要枚举类类型值时,需要将获得的结果从size_t类型转换为枚举类类型,但我认为这是一种非常可移植和强大的处理枚举类的方法。

enum class myenum
{
  one = 0,
  two,
  three,
};

deque<string> ssplit(const string &_src, boost::regex &_re)
{
  boost::sregex_token_iterator it(_src.begin(), _src.end(), _re, -1);
  boost::sregex_token_iterator e;
  deque<string> tokens;
  while (it != e)
    tokens.push_back(*it++);
  return std::move(tokens);
}

int main()
{
  regex re(",");
  deque<string> tokens = ssplit("one,two,three", re);
  for (auto &t : tokens) cout << t << endl;
    getchar();
  return 0;
}
#define ENUM_MAKE(TYPE, ...) \
        enum class TYPE {__VA_ARGS__};\
        struct Helper_ ## TYPE { \
            static const String& toName(TYPE type) {\
                int index = static_cast<int>(type);\
                return splitStringVec()[index];}\
            static const TYPE toType(const String& name){\
                static std::unordered_map<String,TYPE> typeNameMap;\
                if( typeNameMap.empty() )\
                {\
                    const StringVector& ssVec = splitStringVec();\
                    for (size_t i = 0; i < ssVec.size(); ++i)\
                        typeNameMap.insert(std::make_pair(ssVec[i], static_cast<TYPE>(i)));\
                }\
                return typeNameMap[name];}\
            static const StringVector& splitStringVec() {\
                static StringVector typeNameVector;\
                if(typeNameVector.empty()) \
                {\
                    typeNameVector = StringUtil::split(#__VA_ARGS__, ",");\
                    for (auto& name : typeNameVector)\
                    {\
                        name.erase(std::remove(name.begin(), name.end(), ' '),name.end()); \
                        name = String(#TYPE) + "::" + name;\
                    }\
                }\
                return typeNameVector;\
            }\
        };


using String = std::string;
using StringVector = std::vector<String>;

   StringVector StringUtil::split( const String& str, const String& delims, unsigned int maxSplits, bool preserveDelims)
    {
        StringVector ret;
        // Pre-allocate some space for performance
        ret.reserve(maxSplits ? maxSplits+1 : 10);    // 10 is guessed capacity for most case

        unsigned int numSplits = 0;

        // Use STL methods 
        size_t start, pos;
        start = 0;
        do 
        {
            pos = str.find_first_of(delims, start);
            if (pos == start)
            {
                // Do nothing
                start = pos + 1;
            }
            else if (pos == String::npos || (maxSplits && numSplits == maxSplits))
            {
                // Copy the rest of the string
                ret.push_back( str.substr(start) );
                break;
            }
            else
            {
                // Copy up to delimiter
                ret.push_back( str.substr(start, pos - start) );

                if(preserveDelims)
                {
                    // Sometimes there could be more than one delimiter in a row.
                    // Loop until we don't find any more delims
                    size_t delimStart = pos, delimPos;
                    delimPos = str.find_first_not_of(delims, delimStart);
                    if (delimPos == String::npos)
                    {
                        // Copy the rest of the string
                        ret.push_back( str.substr(delimStart) );
                    }
                    else
                    {
                        ret.push_back( str.substr(delimStart, delimPos - delimStart) );
                    }
                }

                start = pos + 1;
            }
            // parse up to next real data
            start = str.find_first_not_of(delims, start);
            ++numSplits;

        } while (pos != String::npos);



        return ret;
    }

例子

ENUM_MAKE(MY_TEST, MY_1, MY_2, MY_3)


    MY_TEST s1 = MY_TEST::MY_1;
    MY_TEST s2 = MY_TEST::MY_2;
    MY_TEST s3 = MY_TEST::MY_3;

    String z1 = Helper_MY_TEST::toName(s1);
    String z2 = Helper_MY_TEST::toName(s2);
    String z3 = Helper_MY_TEST::toName(s3);

    MY_TEST q1 = Helper_MY_TEST::toType(z1);
    MY_TEST q2 = Helper_MY_TEST::toType(z2);
    MY_TEST q3 = Helper_MY_TEST::toType(z3);

自动ENUM_MAKE宏生成“枚举类”和“枚举反射函数”辅助类。

为了减少错误,Everything只定义一个ENUM_MAKE。

这种代码的优点是自动创建用于反射和查看宏代码,易于理解的代码。'enum to string', 'string to enum'性能都是算法O(1)。

缺点是第一次使用时,枚举relection的string vector和map的helper类被初始化。 但是如果你想,你也会被预初始化。- - - - - -

只需要生成枚举。为此目的编写一个生成器大约需要5分钟的工作。

生成器代码在java和python,超级容易移植到任何你喜欢的语言,包括c++。

而且非常容易扩展任何你想要的功能。

示例输入:

First = 5
Second
Third = 7
Fourth
Fifth=11

生成头文件:

#include <iosfwd>

enum class Hallo
{
    First = 5,
    Second = 6,
    Third = 7,
    Fourth = 8,
    Fifth = 11
};

std::ostream & operator << (std::ostream &, const Hallo&);

生成的CPP文件

#include <ostream>

#include "Hallo.h"

std::ostream & operator << (std::ostream &out, const Hallo&value)
{
    switch(value)
    {
    case Hallo::First:
        out << "First";
        break;
    case Hallo::Second:
        out << "Second";
        break;
    case Hallo::Third:
        out << "Third";
        break;
    case Hallo::Fourth:
        out << "Fourth";
        break;
    case Hallo::Fifth:
        out << "Fifth";
        break;
    default:
        out << "<unknown>";
    }

    return out;
}

生成器以非常简洁的形式作为移植和扩展的模板。这个示例代码确实试图避免覆盖任何文件,但使用它仍然要自担风险。

package cppgen;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.Charset;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class EnumGenerator
{
    static void fail(String message)
    {
        System.err.println(message);
        System.exit(1);
    }

    static void run(String[] args)
    throws Exception
    {
        Pattern pattern = Pattern.compile("\\s*(\\w+)\\s*(?:=\\s*(\\d+))?\\s*", Pattern.UNICODE_CHARACTER_CLASS);
        Charset charset = Charset.forName("UTF8");
        String tab = "    ";

        if (args.length != 3)
        {
            fail("Required arguments: <enum name> <input file> <output dir>");
        }

        String enumName = args[0];

        File inputFile = new File(args[1]);

        if (inputFile.isFile() == false)
        {
            fail("Not a file: [" + inputFile.getCanonicalPath() + "]");
        }

        File outputDir = new File(args[2]);

        if (outputDir.isDirectory() == false)
        {
            fail("Not a directory: [" + outputDir.getCanonicalPath() + "]");
        }

        File headerFile = new File(outputDir, enumName + ".h");
        File codeFile = new File(outputDir, enumName + ".cpp");

        for (File file : new File[] { headerFile, codeFile })
        {
            if (file.exists())
            {
                fail("Will not overwrite file [" + file.getCanonicalPath() + "]");
            }
        }

        int nextValue = 0;

        Map<String, Integer> fields = new LinkedHashMap<>();

        try
        (
            BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(inputFile), charset));
        )
        {
            while (true)
            {
                String line = reader.readLine();

                if (line == null)
                {
                    break;
                }

                if (line.trim().length() == 0)
                {
                    continue;
                }

                Matcher matcher = pattern.matcher(line);

                if (matcher.matches() == false)
                {
                    fail("Syntax error: [" + line + "]");
                }

                String fieldName = matcher.group(1);

                if (fields.containsKey(fieldName))
                {
                    fail("Double fiend name: " + fieldName);
                }

                String valueString = matcher.group(2);

                if (valueString != null)
                {
                    int value = Integer.parseInt(valueString);

                    if (value < nextValue)
                    {
                        fail("Not a monotonous progression from " + nextValue + " to " + value + " for enum field " + fieldName);
                    }

                    nextValue = value;
                }

                fields.put(fieldName, nextValue);

                ++nextValue;
            }
        }

        try
        (
            PrintWriter headerWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(headerFile), charset));
            PrintWriter codeWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(codeFile), charset));
        )
        {
            headerWriter.println();
            headerWriter.println("#include <iosfwd>");
            headerWriter.println();
            headerWriter.println("enum class " + enumName);
            headerWriter.println('{');
            boolean first = true;
            for (Entry<String, Integer> entry : fields.entrySet())
            {
                if (first == false)
                {
                    headerWriter.println(",");
                }

                headerWriter.print(tab + entry.getKey() + " = " + entry.getValue());

                first = false;
            }
            if (first == false)
            {
                headerWriter.println();
            }
            headerWriter.println("};");
            headerWriter.println();
            headerWriter.println("std::ostream & operator << (std::ostream &, const " + enumName + "&);");
            headerWriter.println();

            codeWriter.println();
            codeWriter.println("#include <ostream>");
            codeWriter.println();
            codeWriter.println("#include \"" + enumName + ".h\"");
            codeWriter.println();
            codeWriter.println("std::ostream & operator << (std::ostream &out, const " + enumName + "&value)");
            codeWriter.println('{');
            codeWriter.println(tab + "switch(value)");
            codeWriter.println(tab + '{');
            first = true;
            for (Entry<String, Integer> entry : fields.entrySet())
            {
                codeWriter.println(tab + "case " + enumName + "::" + entry.getKey() + ':');
                codeWriter.println(tab + tab + "out << \"" + entry.getKey() + "\";");
                codeWriter.println(tab + tab + "break;");

                first = false;
            }
            codeWriter.println(tab + "default:");
            codeWriter.println(tab + tab + "out << \"<unknown>\";");
            codeWriter.println(tab + '}');
            codeWriter.println();
            codeWriter.println(tab + "return out;");
            codeWriter.println('}');
            codeWriter.println();
        }
    }

    public static void main(String[] args)
    {
        try
        {
            run(args);
        }
        catch(Exception exc)
        {
            exc.printStackTrace();
            System.exit(1);
        }
    }
}

并将其移植到Python 3.5,因为它的不同可能会有所帮助

import re
import collections
import sys
import io
import os

def fail(*args):
    print(*args)
    exit(1)

pattern = re.compile(r'\s*(\w+)\s*(?:=\s*(\d+))?\s*')
tab = "    "

if len(sys.argv) != 4:
    n=0
    for arg in sys.argv:
        print("arg", n, ":", arg, " / ", sys.argv[n])
        n += 1
    fail("Required arguments: <enum name> <input file> <output dir>")

enumName = sys.argv[1]

inputFile = sys.argv[2]

if not os.path.isfile(inputFile):
    fail("Not a file: [" + os.path.abspath(inputFile) + "]")

outputDir = sys.argv[3]

if not os.path.isdir(outputDir):
    fail("Not a directory: [" + os.path.abspath(outputDir) + "]")

headerFile = os.path.join(outputDir, enumName + ".h")
codeFile = os.path.join(outputDir, enumName + ".cpp")

for file in [ headerFile, codeFile ]:
    if os.path.exists(file):
        fail("Will not overwrite file [" + os.path.abspath(file) + "]")

nextValue = 0

fields = collections.OrderedDict()

for line in open(inputFile, 'r'):
    line = line.strip()

    if len(line) == 0:
        continue

    match = pattern.match(line)

    if match == None:
        fail("Syntax error: [" + line + "]")

    fieldName = match.group(1)

    if fieldName in fields:
        fail("Double field name: " + fieldName)

    valueString = match.group(2)

    if valueString != None:
        value = int(valueString)

        if value < nextValue:
            fail("Not a monotonous progression from " + nextValue + " to " + value + " for enum field " + fieldName)

        nextValue = value

    fields[fieldName] = nextValue

    nextValue += 1

headerWriter = open(headerFile, 'w')
codeWriter = open(codeFile, 'w')

try:
    headerWriter.write("\n")
    headerWriter.write("#include <iosfwd>\n")
    headerWriter.write("\n")
    headerWriter.write("enum class " + enumName + "\n")
    headerWriter.write("{\n")
    first = True
    for fieldName, fieldValue in fields.items():
        if not first:
            headerWriter.write(",\n")

        headerWriter.write(tab + fieldName + " = " + str(fieldValue))

        first = False
    if not first:
        headerWriter.write("\n")
    headerWriter.write("};\n")
    headerWriter.write("\n")
    headerWriter.write("std::ostream & operator << (std::ostream &, const " + enumName + "&);\n")
    headerWriter.write("\n")

    codeWriter.write("\n")
    codeWriter.write("#include <ostream>\n")
    codeWriter.write("\n")
    codeWriter.write("#include \"" + enumName + ".h\"\n")
    codeWriter.write("\n")
    codeWriter.write("std::ostream & operator << (std::ostream &out, const " + enumName + "&value)\n")
    codeWriter.write("{\n")
    codeWriter.write(tab + "switch(value)\n")
    codeWriter.write(tab + "{\n")
    for fieldName in fields.keys():
        codeWriter.write(tab + "case " + enumName + "::" + fieldName + ":\n")
        codeWriter.write(tab + tab + "out << \"" + fieldName + "\";\n")
        codeWriter.write(tab + tab + "break;\n")
    codeWriter.write(tab + "default:\n")
    codeWriter.write(tab + tab + "out << \"<unknown>\";\n")
    codeWriter.write(tab + "}\n")
    codeWriter.write("\n")
    codeWriter.write(tab + "return out;\n")
    codeWriter.write("}\n")
    codeWriter.write("\n")
finally:
    headerWriter.close()
    codeWriter.close()

我写了一个库来解决这个问题,所有的事情都发生在编译时,除了获取消息。

用法:

使用宏DEF_MSG定义宏和消息对:

DEF_MSG(CODE_OK,   "OK!")
DEF_MSG(CODE_FAIL, "Fail!")

CODE_OK是要使用的宏,“OK!”是相应的消息。

使用get_message()或gm()来获取消息:

get_message(CODE_FAIL);  // will return "Fail!"
gm(CODE_FAIL);           // works exactly the same as above

使用MSG_NUM查找已经定义了多少个宏。它会自动增加,你不需要做任何事情。

预定义的消息:

MSG_OK:     OK
MSG_BOTTOM: Message bottom

项目:libcodemsg


标准库不会创建额外的数据。一切都发生在编译时。在message_def.h中,它生成一个名为MSG_CODE的enum;在message_def.c中,它生成一个变量,保存静态const char* _g_messages[]中的所有字符串。

在这种情况下,库只能创建一个枚举。这对于返回值非常理想,例如:

MSG_CODE foo(void) {
    return MSG_OK; // or something else
}

MSG_CODE ret = foo();

if (MSG_OK != ret) {
    printf("%s\n", gm(ret););
}

我喜欢这种设计的另一个原因是,您可以在不同的文件中管理消息定义。


我发现这个问题的解看起来好多了。