Common C pattern, but expressed in C++?

Common C pattern, but expressed in C++?

A common pattern in C programming involves a variable length structure
such as:
typedef struct {
int length;
char data[1];
} MyBuffer;
where data isn't literally an array of [1]. Instead, its variable length
is defined by length.
The structure is allocated like:
MyBuffer* pBuff = malloc(sizeof(MyBuffer) + 100);
I want to use the same pattern, but in C++ code, so using new/delete
instead of malloc/free
Can this same pattern be used in C++ code? How?
EDIT Since several answers and comments are suggesting I switch to
std::vector:
I am supplied with the structure definition MyBuffer from a 3rd party, C
library.
In my C++ app, I need to allocate the buffer and call a function in the C
library.
On "my side" of the boundary, I prefer to keep things C++, and allocate
this structure the C++-way, but I still need to pass it to a C-library
that won't understand anything like a std::vector.