arrange data generator example properly

examples/write.rs

@@ -0,0 +1,41 @@
+#[path= "producer/share.rs"]
+mod share;
+
+// Test data generator
+// $ cargo run --example writer -- 16 nodes.dat
+// or
+// $ cargo run --example writer -- 16
+// to preview
+
+fn main() {
+    let mut args = std::env::args().skip(1);
+
+    let (number, out_file) = match args.next() {
+        None => { eprintln!("writer <number of nodes> [<out_file>]"); std::process::exit(1); },
+        Some(number) => {
+            (number.parse::<usize>().expect("invalid number"), args.next())
+        }
+    };
+
+    let iterator = share::NodeDataIterator::new().take(number);
+
+    if let Some(out_file_path) = out_file {
+        use std::io::Write;
+
+        let mut buf = Vec::new();
+
+        for node in iterator{
+            node.write(&mut buf).expect("Failed to write data");
+        }
+
+        let mut file = std::fs::File::create(&out_file_path)
+            .expect("Failed to create output file");
+
+        file.write_all(&buf[..])
+            .expect("Failed to write data to file");
+    } else {
+        for n in iterator {
+            println!("{:?}", n);
+        }
+    }
+}