C++ 如何获取指向原始数据的 std::vector 指针？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/6485496/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to get std::vector pointer to the raw data?
提问by Rookie
I'm trying to use std::vectoras a chararray.
我正在尝试std::vector用作char数组。
My function takes in a void pointer:
我的函数接受一个空指针：
void process_data(const void *data);
Before I simply just used this code:
在我简单地使用此代码之前：
char something[] = "my data here";
process_data(something);
Which worked as expected.
这按预期工作。
But now I need the dynamicity of std::vector, so I tried this code instead:
但是现在我需要 的动态性std::vector，所以我尝试了以下代码：
vector<char> something;
*cut*
process_data(something);
The question is, how do I pass the char vector to my function so I can access the vector raw data (no matter which format it is – floats, etc.)?
问题是，我如何将字符向量传递给我的函数，以便我可以访问向量原始数据（无论它是哪种格式 - 浮点数等）？
I tried this:
我试过这个：
process_data(&something);
And this:
和这个：
process_data(&something.begin());
But it returned a pointer to gibberish data, and the latter gave warning: warning C4238: nonstandard extension used : class rvalue used as lvalue.
但是它返回了一个指向乱码数据的指针，后者给出了警告：warning C4238: nonstandard extension used : class rvalue used as lvalue。
回答by James McNellis
&somethinggives you the address of the std::vectorobject, not the address of the data it holds. &something.begin()gives you the address of the iterator returned by begin()(as the compiler warns, this is not technically allowed because something.begin()is an rvalue expression, so its address cannot be taken).
&something给你std::vector对象的地址，而不是它保存的数据的地址。 &something.begin()给你返回的迭代器的地址begin()（正如编译器警告的那样，这在技术上是不允许的，因为它something.begin()是一个右值表达式，所以它的地址不能被采用）。
Assuming the container has at least one element in it, you need to get the address of the initial element of the container, which you can get via
假设容器中至少有一个元素，则需要获取容器的初始元素的地址，可以通过
&something[0]or&something.front()(the address of the element at index 0), or&*something.begin()(the address of the element pointed to by the iterator returned bybegin()).
&something[0]或&something.front()（索引 0 处元素的地址），或&*something.begin()（由 返回的迭代器指向的元素的地址begin()）。
In C++11, a new member function was added to std::vector: data(). This member function returns the address of the initial element in the container, just like &something.front(). The advantage of this member function is that it is okay to call it even if the container is empty.
在 C++11 中，一个新的成员函数被添加到std::vector: data()。这个成员函数返回容器中初始元素的地址，就像&something.front(). 这个成员函数的优点是即使容器为空也可以调用它。
回答by Chris Dodd
something.data()will return a pointer to the data space of the vector.
something.data()将返回一个指向向量数据空间的指针。
回答by Steven Don
Take a pointer to the first element instead:
取一个指向第一个元素的指针：
process_data (&something [0]);
