传递 std::vector<int>可变参数函数的项目

So passing vector items to one of those functions can work by allocating enough memory for the vector items and copy them over prior to the call.

话虽如此，这里是动态分配堆栈的方法:

#include <iostream>
#include <stdio.h>
#include <stdarg.h>
#include <string>
#include <vector>
#include <alloca.h>

using namespace std;


class Format
{
    typedef vector<unsigned long> ULVector;
    ULVector _args;
    string _format;

    public:
        Format(const char* format) : _format(format)
        {}

        Format &operator<<(int arg) {
            _args.push_back((unsigned long)arg);
            return *this;
        }

        Format &operator<<(const char* arg) {
            _args.push_back((unsigned long)arg);
            return *this;
        }

        string format() {
            union {
                va_list varargs;
                unsigned long* packedArray;
            } fake_va_list;

            // malloc would do it as well!
            // but alloca frees the mem after leaving this method
            unsigned long *p = (unsigned long*)alloca(_args.size() * sizeof(unsigned long));
            fake_va_list.packedArray = p;

            ULVector::iterator i = _args.begin();
            for (int n=0; i != _args.end(); i++, n++) {
                p[n] = *i;
            }

            char buffer[512];
            const char* fmt = _format.c_str();
            vsprintf(buffer, fmt, fake_va_list.varargs);

            // place a free(p) here if you used malloc
            return string(buffer);
        }
};


ostream& operator <<=(ostream &os, Format &obj) {
      os << obj.format();
      return os;
}


int main()
{
    // we use '<<=' operator here which has lower precedence than '<<'
    // otherwise we have to write
    // cout << ( Format("
%x %s %x %c
") <<  etc. );
    cout <<= Format("
%x %s %x %c
") << 0x11223344 << "VectorToVarArg" << 0xAABBCCDD << '!';
    return 0;
}

猜猜它的作用是什么?它允许使用向量中收集的参数进行 printf(..) 样式格式化.是的，它并不完美，但它可以满足我的需求.此外，它涵盖了两个主要平台:D