How to Get a Raw Data Pointer from a std::vector?

Retrieving std::vector Raw Data Pointer

In programming, it is often necessary to pass data to functions that expect a raw pointer to the data itself. This task can be challenging when working with dynamic containers like std::vector.

Consider a scenario where you have a function process_data() that takes a const void pointer as input. Previously, you could simply pass a char array by reference:

char something[] = "my data here";
process_data(something);

However, when converting this logic to use a std::vector, attempts to pass the vector directly:

vector<char> something;
process_data(something);

or taking the address of its begin iterator:

process_data(&something.begin());

result in nonsensical data or compiler warnings.

The challenge lies in obtaining a pointer to the actual data within the std::vector. To do so, several options are available:

1. Accessing the First Element:

You can retrieve the address of the first element in the vector:

process_data(&something[0]); // or &something.front()

2. Using the data() Member Function (C 11 and later):

In C 11, std::vector introduced the data() member function:

process_data(something.data());

This function is preferred since it is safe to call even when the vector is empty.

Note: &something provides the address of the vector object itself, not its data. Hence, it should not be used for this purpose.

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