[英]C++ Bitflaged enum to string
當你將鼠標懸停在一個按位枚舉(或者它被稱為)變量(調試時)時,我試圖通過獲取枚舉並將其轉換為字符串來嘗試Intellisense在visual studio中所做的事情。
例如:
#include <iostream>
enum Color {
White = 0x0000,
Red = 0x0001,
Green = 0x0002,
Blue = 0x0004,
};
int main()
{
Color yellow = Color(Green | Blue);
std::cout << yellow << std::endl;
return 0;
}
如果你將鼠標懸停在yellow
你會看到:
所以我想能夠打電話給:
std::cout << BitwiseEnumToString(yellow) << std::endl;
並輸出打印: Green | Blue
Green | Blue
我寫了以下內容,試圖提供一種打印枚舉的通用方法:
#include <string>
#include <functional>
#include <sstream>
const char* ColorToString(Color color)
{
switch (color)
{
case White:
return "White";
case Red:
return "Red";
case Green:
return "Green";
case Blue:
return "Blue";
default:
return "Unknown Color";
}
}
template <typename T>
std::string BitwiseEnumToString(T flags, const std::function<const char*(T)>& singleFlagToString)
{
if (flags == 0)
{
return singleFlagToString(flags);
}
int index = flags;
int mask = 1;
bool isFirst = true;
std::ostringstream oss;
while (index)
{
if (index % 2 != 0)
{
if (!isFirst)
{
oss << " | ";
}
oss << singleFlagToString((T)(flags & mask));
isFirst = false;
}
index = index >> 1;
mask = mask << 1;
}
return oss.str();
}
所以現在我可以打電話:
int main()
{
Color yellow = Color(Green | Blue);
std::cout << BitwiseEnumToString<Color>(yellow, ColorToString) << std::endl;
return 0;
}
我得到了所需的輸出。
我猜我找不到任何關於它的東西,因為我不知道它是怎么稱呼的,但無論如何 -
std或boost中有什么東西可以用來提供這個嗎?
如果沒有,那么做這種事最有效的方法是什么? (或者我的太多了)
編輯:請參閱下面的通用template
實現...但是請注意,這個template
實現實際上踐踏了所有OVER ostream
的operator <<()
實現! 如果enum
是完整的類,並且template
具有基類實現,那就更好了。 這個通用定義相當於中國商店的原子彈...
我用測試函數編寫了以下示例。 它使用C ++重載來讓你簡單地cout
一個Color
- 如果你想仍然能夠打印簡單的數值,你必須將它轉換為int
:
#include <iostream>
enum Color {
White = 0x0000,
Red = 0x0001,
Green = 0x0002,
Blue = 0x0004,
}; // Color
std::ostream &operator <<(std::ostream &os, Color color) {
static const char *colors[] = { "Red", "Green", "Blue", 0 }; // Synchronise with Color enum!
// For each possible color string...
for (const char * const *ptr = colors;
*ptr != 0;
++ptr) {
// Get whether to print something
bool output = (color & 0x01)!=0;
// Is color bit set?
if (output) {
// Yes! Output that string.
os << *ptr;
} // if
// Next bit in color
color = (Color)(color >> 1);
// All done?
if (color == 0) {
// Yes! Leave
break;
} // if
// No, so show some more...
if (output) {
// If output something, need 'OR'
os << " | ";
} // if
} // for
return os;
} // operator <<(Color)
void PrintColor() {
for (unsigned c = 0; c < 8; ++c) {
Color color = Color(c);
std::cout << color << std::endl;
} // fors
} // PrintColor()
首先,頭文件:
// EnumBitString.h
template <typename ENUM>
const char * const *Strings() {
static const char *strings[] = { "Zero", 0 }; // By default there are no Strings
return strings;
} // Strings<ENUM>()
template <typename ENUM>
std::ostream &operator <<(std::ostream &os, ENUM e) {
const char * const *ptr = Strings<ENUM>();
if (e == 0) {
os.operator <<(*ptr);
return os;
} // if
// For each possible ENUM string...
while (*ptr != 0) {
bool output = (e & 0x01) != 0;
// Is bit set?
if (output) {
// Yes! Output that string.
os.operator <<(*ptr);
} // if
// Next bit in e
e = (ENUM)(e >> 1);
// All done?
if (e == 0) {
// Yes! Leave
break;
} // if
// No, so show some more...
if (output) {
os.operator <<(" | ");
} // if
++ptr;
} // while
return os;
} // operator <<(ENUM)
接下來,您的示例:
// Colors.h
#include "EnumBitString.h"
enum Colors {
White = 0x0000,
Red = 0x0001,
Green = 0x0002,
Blue = 0x0004,
NumColors = 4
}; // Colors
template <>
const char * const *Strings<Colors>() {
static const char *strings[] { "White", // Zero case
"Red",
"Green",
"Blue",
0 }; // Don't forget final 0
static_assert((sizeof(strings)/sizeof(strings[0])==NumColors+1, "Colors mismatch!");
return strings;
} // Strings<Colors>()
然后,值中的另一個位示例:
// Flags.h
#include "EnumBitString.h"
enum Flags {
CF = 0x0001,
// Res1 = 0x02,
PF = 0x0004,
// Res2 = 0x08,
AF = 0x0010,
// Res3 = 0x20,
ZF = 0x0040,
NumFlags = 7
}; // Flags
template <>
const char * const *Strings<Flags>() {
static const char *strings[] = { "None",
"Carry",
"",
"Parity",
"",
"Arithmetic",
"",
"Zero",
0 }; // Don't forget final 0
static_assert((sizeof(strings)/sizeof(strings[0])==NumFlags+1, "Flags mismatch!");
return strings;
} // Strings<Flags>()
最后,一個測試程序:
#include <iostream>
#include "Colors.h"
#include "Flags.h"
void TestENUM() {
for (unsigned c = 0; c < 0x0008; ++c) {
Colors color = Colors(c);
std::cout << color << std::endl;
} // for
for (unsigned f = 0; f < 0x0080; ++f) {
Flags flag = Flags(f);
std::cout << flag << std::endl;
} // for
} // TestENUM()
很酷,對吧?
您將不得不維護枚舉的字符串表示列表,無論是在向量中,硬編碼等等。這是一種可能的實現方式。
enum Color : char
{
White = 0x00,
Red = 0x01,
Green = 0x02,
Blue = 0x04,
//any others
}
std::string EnumToStr(Color color)
{
std::string response;
if(color & Color::White)
response += "White | ";
if(color & Color::Red)
response += "Red | ";
if(color & Color::Green)
response += "Green | ";
if(color & Color::Blue)
response += "Blue | ";
//do this for as many colors as you wish
if(response.empty())
response = "Unknown Color";
else
response.erase(response.end() - 3, response.end());
return response;
}
然后按照相同的表單為要執行此操作的每個枚舉創建另一個EnumToStr函數
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