Buffered writer for file descriptors.

Wraps a file descriptor with an internal buffer for efficient writes. Reduces the number of system calls by batching small writes together.

Example

{ BufWriter } :: import "std/sys/bufio/buf_writer";

writer := BufWriter.new(fd);
io.await(writer.write_string(`hello\n`, io));
io.await(writer.flush(io));