C++ 如何获得指向 std::vector 中第一个元素的指针？
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How can I get a pointer to the first element in an std::vector?
提问by Luc Danton
I want to write data from an std::vector<char>to a socket, using the writefunction, which has this prototype:
我想std::vector<char>使用write具有以下原型的函数将数据从 an 写入套接字：
ssize_t write(int, const void *, size_t);
The second argument to this function must be a pointer to the first element in the std::vector<char>. How can I get a pointer to this element?
此函数的第二个参数必须是指向std::vector<char>. 如何获得指向该元素的指针？
I tried std::vector::frontbut this returns a reference, while I need a pointer.
我试过了，std::vector::front但这会返回一个引用，而我需要一个指针。
采纳答案by Oliver Charlesworth
&mv_vec[0]
or
或者
&my_vec.front()
回答by Luc Danton
C++11 has vec.data()which has the benefit that the call is valid even if the vector is empty.
C++11vec.data()的好处是即使向量为空，调用也是有效的。
回答by Armen Tsirunyan
my_vec.empty() ? 0 : &my_vec.front()
If you would like an std::out_of_rangeto be thrown if vector is empty, you could use
如果您希望std::out_of_range在 vector 为空时抛出an ，您可以使用
&my_vec.at(0)
回答by B?ови?
&*my_vec.begin()
or
或者
&mv_vec[0]
回答by Christian Rau
By taking the address of the first element, with &vec[0], as the standard (since C++03, I think) demands continous storage of std::vectorelements.
通过获取第一个元素的地址&vec[0]，作为标准（我认为是 C++03 起）需要std::vector元素的连续存储。
