#include <sys/types.h>
#include <unistd.h>
+#include <sys/uio.h>
// Mock system functions for testing.
ssize_t read(int fd, void *buf, size_t count);
ssize_t write(int fd, const void *buf, size_t count);
+ssize_t writev (int fd, const struct iovec *iovec, int count);
}