Faster approach to checking for an all-zero buffer in C?

Question

I am searching for a faster method of accomplishing this:

int is_empty(char * buf, int size) 
{
    int i;
    for(i = 0; i < size; i++) {
        if(buf[         


        

Answer 1

Edit: Bad answer

A novel approach might be

int is_empty(char * buf, int size) {
    char start = buf[0];
    char end = buff[size-1];
    buf[0] = 'x';
    buf[size-1] = '\0';
    int result = strlen(buf) == 0;
    buf[0] = start;
    buff[size-1] = end;
    return result;
}

Why the craziness? because strlen is one of the library function that's more likely to be optimized. Storing and replacing the first character is to prevent the false positive. Storing and replacing the last character is to make sure it terminates.