C++ Build an array of data by repeating a vector many times

C++ Build an array of data by repeating a vector many times

I have a sequence of numbers that I need to repeat many times and get the
repeated data as a pointer to the data along the size (actually element
count). I need that data to pass it on to an API.
What would be the most efficient way to allocate the memory, pass on the
repeated data and then free it again. I currently have the sequence that
needs to be repeated stored in a std::vector
A couple of thoughts I had were along the lines of:
// Setup code
unsigned int repeat = 30000;
std::vector<int> datavector(5, 0); // assume this would contain arbitrary
numbers that needed to be repeated
// Idea 1:
{
unsigned int byte_size_step = datavector.size() * sizeof(int);
unsigned int byte_full_size = byte_size_step * repeat;
int *ptr = malloc(byte_full_size);
for(unsigned int i=0; i<repeat; i++)
{
memcpy(ptr+(i*byte_size_step), datavector.data(), byte_size_step);
}
apiFunc(ptr); // apiFunc copies the data
free(ptr)
}
// Idea 2:
{
std::vector datarepeated(datavector.size()*repeat);
for(unsigned int i=0; i<repeat; i++)
{
datarepeated.insert(datarepeated.begin()+(i*size_step),
datavector.begin(), datavector.end());
}
apiFunc(datarepeated.data());
}
Though I felt that there would be a function or easy-to-go method laying
around to quickly repeat the sequence in memory. I'm probably missing
something. I personally don't know if something like this could benefit
from a multithreaded solution.
Any tips to do this (most) efficiently are welcome.