C++ std::string字符串格式化

心已赠人 2021-11-02 16:56 915阅读 1赞

很遗憾的是，C++ 标准库 std::string并没有提供类似于sprintf之类的字符串格式化函数，所以就自己来实现咯。

#include <memory>
    #include <cstdio>
    #include <string>
    
    template<typename ... Args>
    static std::string formatString(const std::string &format, Args ... args)
    {
    	auto size = std::snprintf(nullptr, 0, format.c_str(), args ...) + 1; // Extra space for '\0'
    	std::unique_ptr<char[]> buf(new char[size]);
    	std::snprintf(buf.get(), size, format.c_str(), args ...);
    	return std::string(buf.get(), buf.get() + size - 1); // We don't want the '\0' inside
    }
    
    template<typename ... Args>
    static std::wstring formatString(const std::wstring &format, Args ... args)
    {
    	auto size = std::swprintf(nullptr, 0, format.c_str(), args ...) + 1; // Extra space for '\0'
    	std::unique_ptr<wchar_t[]> buf(new wchar_t[size]);
    	std::swprintf(buf.get(), size, format.c_str(), args ...);
    	return std::wstring(buf.get(), buf.get() + size - 1); // We don't want the '\0' inside
    }
    
    
    template<typename ... Args>
    static void formatStringEx(std::string &dst, const std::string &format, Args ... args)
    {
    	auto size = std::snprintf(nullptr, 0, format.c_str(), args ...) + 1; // Extra space for '\0'
    	std::unique_ptr<char[]> buf(new char[size]);
    	std::snprintf(buf.get(), size, format.c_str(), args ...);
    	dst = { buf.get(),  buf.get() + size - 1 };
    }
    
    template<typename ... Args>
    static void formatStringEx(std::wstring &dst, const std::wstring &format, Args ... args)
    {
    	auto size = std::swprintf(nullptr, 0, format.c_str(), args ...) + 1; // Extra space for '\0'
    	std::unique_ptr<wchar_t[]> buf(new wchar_t[size]);
    	std::swprintf(buf.get(), size, format.c_str(), args ...);
    	dst = { buf.get(),  buf.get() + size - 1 };
    }

示例程序：

int main(int argc, char *argv[])
    {
    	std::string str;
    	std::wstring wstr;
    
    	std::string str_1 = formatString("%s, %d, %f, %.2lf", "today", 2, 2.1, 0.1);
    	formatStringEx(str, "%s, %d, %f, %.2lf", "today", 2, 2.1, 0.1);
    
    	std::wstring wstr_1 = formatString(L"%s, %d, %f, %.2lf", L"today", 2, 2.1, 0.1);
    	formatStringEx(wstr, L"%s, %d, %f, %.2lf", L"today", 2, 2.1, 0.1);
    
    	return 0;
    }