c++: Fastest way to fill a buffer with random bytes

Question

I have this big char array that needs to filled with random bytes in high freq. I wonder if there is any faster way other than the naive way (using for loop - fill each cell with random byte) to do this. There is no requirement on the random quality of the values. Any "random" junk will do. Platform is windows

Answer 1

True random (Unix only):

int fd = open("/dev/random", O_RDONLY); read(fd, your_buffer, buffer_size); 

Not completely random (Unix only):

int fd = open("/dev/urandom", O_RDONLY); read(fd, your_buffer, buffer_size); 

Constant random (unless you use srand(time(NULL)), portable):

for(size_t i = 0; i < buffer_size; i++)     your_buffer[i] = rand() % 256; 

Or something like:

memcpy(your_buffer, (void*)memcpy, buffer_size);