module io

// new_multi_writer returns a Writer that writes to all writers. The write
// function of the returned Writer writes to all writers of the MultiWriter,
// returns the length of bytes written, and if any writer fails to write the
// full length an error is returned and writing to other writers stops, and if
// any writer returns an error the error is returned immediately and writing to
// other writers stops.
pub fn new_multi_writer(writers ...Writer) Writer {
    return &MultiWriter{
        writers: writers
    }
}

// MultiWriter writes to all its writers.
pub struct MultiWriter {
pub mut:
    writers []Writer
}

// write writes to all writers of the MultiWriter. Returns the length of bytes
// written. If any writer fails to write the full length an error is returned
// and writing to other writers stops. If any writer returns an error the error
// is returned immediately and writing to other writers stops.
pub fn (mut m MultiWriter) write(buf []u8) !int {
    for mut w in m.writers {
        n := w.write(buf)!
        if n != buf.len {
            return error('io: incomplete write to writer of MultiWriter')
        }
    }
    return buf.len
}