背景
经常因为打印日志时出现如下情况，导致程序崩溃：
1 | std::string strtest = "this is a simple"; |
方法
为了解决以上的问题，让同事写了个装饰器函数，1
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163#include <stdio.h>
#include <stdint.h>
#include <string>
#include <type_traits>
#include <memory>
class va_in_convert {
public:
template<typename T>
const typename std::enable_if<std::is_pod<typename std::decay<T>::type>::value, T>::type *
operator ()(const T* p) { return p; }
};
class va_out_convert {
public:
const char* operator ()(const std::string& s) { return s.c_str(); }
const wchar_t* operator ()(const std::wstring& s) { return s.c_str(); }
template<typename T>
const typename std::enable_if<std::is_pod<typename std::decay<T>::type>::value, T>::type &
operator ()(const T& p) { return p; }
};
template < typename CONVERT, typename RET, typename... ARGS >
class va_wrapper
{
protected:
RET(__cdecl *func)(ARGS..., ...);
public:
va_wrapper(RET(__cdecl *_func)(ARGS..., ...)) :
func(_func) {}
template < typename... ARGS2 >
RET operator ()(ARGS... args, ARGS2&&... args2) {
return (*func)(std::forward<ARGS>(args)..., CONVERT()(args2)...);
}
};
template < typename CONVERT, typename CLS, typename RET, typename... ARGS >
class va_wrapper2
{
protected:
CLS* cls;
RET(__cdecl CLS::*func)(ARGS..., ...);
public:
va_wrapper2(CLS* _cls, RET(__cdecl CLS::*_func)(ARGS..., ...)) :
cls(_cls), func(_func) {}
template < typename... ARGS2 >
RET operator ()(ARGS... args, ARGS2&&... args2) {
return (cls->*func)(std::forward<ARGS>(args)..., CONVERT()(args2)...);
}
};
template < typename CONVERT, typename RET, typename... ARGS >
va_wrapper<CONVERT, RET, ARGS...> va_analyzer(RET(__cdecl *func)(ARGS..., ...)) {
return va_wrapper<CONVERT, RET, ARGS...>(func);
}
template < typename CONVERT, typename CLS, typename RET, typename... ARGS >
va_wrapper2<CONVERT, CLS, RET, ARGS...> va_analyzer(CLS* cls, RET(__cdecl CLS::*func)(ARGS..., ...)) {
return va_wrapper2<CONVERT, CLS, RET, ARGS...>(cls, func);
}
#define va_in_wrap(func) va_analyzer<va_in_convert>(func)
#define va_in_wrap2(cls, func) va_analyzer<va_in_convert>(cls, func)
#define va_out_wrap(func) va_analyzer<va_out_convert>(func)
#define va_out_wrap2(cls, func) va_analyzer<va_out_convert>(cls, func)
class strscanf_helper
{
protected:
size_t sz;
template < typename T >
class strscanf_pointer {
protected:
T** p;
public:
strscanf_pointer(T*& _v) :p(&_v) {}
~strscanf_pointer() {}
void* operator ()() { return p; }
};
template < typename T >
class strscanf_integer {
protected:
T& v;
intmax_t im;
public:
strscanf_integer(T& _v) :v(_v) {}
~strscanf_integer() { v = (T)im; }
void* operator ()() { return &im; }
};
template < typename T >
class strscanf_float {
protected:
T& v;
long double ld;
public:
strscanf_float(T& _v) :v(_v), ld(0) {}
~strscanf_float() { v = (T)ld; }
void* operator ()() { return &ld; }
};
template < typename T >
class strscanf_string {
protected:
std::basic_string<T>& v;
std::unique_ptr<T[]> p;
public:
strscanf_string(std::basic_string<T>& _v, size_t sz) :v(_v), p(new T[sz + 1]) { p.get()[0] = 0; }
~strscanf_string() { v = p.get(); }
void* operator ()() { return p.get(); }
};
public:
strscanf_helper(size_t _sz) :sz(_sz) { }
~strscanf_helper() { }
template<typename T>
typename std::enable_if<std::is_same<T, char>::value || std::is_same<T, wchar_t>::value, strscanf_string<T>>::type
operator ()(std::basic_string<T>& v) { return strscanf_string<T>(v, sz); }
template<typename T>
typename std::enable_if<std::is_integral<typename std::decay<T>::type>::value, strscanf_integer<T>>::type
operator ()(T& v) { return strscanf_integer<T>(v); }
template<typename T>
typename std::enable_if<std::is_floating_point<typename std::decay<T>::type>::value, strscanf_float<T>>::type
operator ()(T& v) { return strscanf_float<T>(v); }
template<typename T>
strscanf_pointer<T> operator ()(T*& v) { return strscanf_pointer<T>(v); }
};
template < typename... ARGS >
int strscanf(const std::string& src, const std::string& fmt, ARGS&... args)
{
return sscanf(src.c_str(), fmt.c_str(), strscanf_helper(src.size())(args)()...);
}
typedef va_out_convert strprintf_helper;
template < typename... ARGS >
std::string strprintf(const std::string& fmt, const ARGS&... args)
{
std::string s;
int l = _snprintf(nullptr, 0, fmt.c_str(), strprintf_helper()(args)...);
if (l > 0) {
std::unique_ptr<char[]> tmp(new char[l + 1]);
_snprintf(tmp.get(), l + 1, fmt.c_str(), strprintf_helper()(args)...);
s = tmp.get();
}
return s;
}
然后就一劳永逸解决打印std::string 的问题了1
2std::string strtets = "this is a simple";
PRINTF("%s \n", strtets);
