diff --git a/examples/producer.rs b/examples/producer.rs
deleted file mode 100644
index 108bc25..0000000
--- a/examples/producer.rs
+++ /dev/null
@@ -1,222 +0,0 @@
-use zcash_mmr::{NodeData, Tree, EntryLink, Entry};
-use std::io::Write;
-
-fn prepare_tree(vec: &Vec<NodeData>) -> Tree {
-
-    assert!(vec.len() > 0);
-
-    // integer log2 of (vec.len()+1), -1
-    let mut h = (32 - ((vec.len()+1) as u32).leading_zeros() - 1)-1;
-    let mut peak_pos = (1 << (h+1)) - 1;
-    let mut nodes = Vec::new();
-
-    loop {
-
-        if peak_pos > vec.len() {
-            // left child, -2^h
-            peak_pos = peak_pos - (1<<h);
-            h = h - 1;
-        }
-
-        if peak_pos <= vec.len() {
-            let mut peak: Entry = vec[peak_pos-1].clone().into();
-            if h != 0 {
-                peak.update_siblings(
-                    EntryLink::Stored((peak_pos - (1<<h) - 1) as u32),
-                    EntryLink::Stored((peak_pos - 2) as u32),
-                );
-            }
-            nodes.push(((peak_pos-1) as u32, peak));
-
-            // right sibling
-            peak_pos = peak_pos + (1 << (h+1)) - 1;
-        }
-
-        if h == 0 {
-            break;
-        }
-    }
-
-    Tree::new(vec.len() as u32, nodes, vec![])
-}
-
-fn main() {
-
-    let mut initial_tree_vec = vec![
-
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 10,
-            end_time: 20,
-            start_target: 100,
-            end_target: 110,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 1,
-            end_height: 1,
-            shielded_tx: 5,
-        },
-
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 21,
-            end_time: 30,
-            start_target: 110,
-            end_target: 120,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 2,
-            end_height: 2,
-            shielded_tx: 4,
-        },
-    ];
-
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[0], &initial_tree_vec[1]));
-
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 31,
-            end_time: 40,
-            start_target: 120,
-            end_target: 130,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 3,
-            end_height: 3,
-            shielded_tx: 6,
-        },
-    );
-
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 41,
-            end_time: 50,
-            start_target: 130,
-            end_target: 140,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 4,
-            end_height: 4,
-            shielded_tx: 7,
-        },
-    );
-
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[3], &initial_tree_vec[4]));
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[2], &initial_tree_vec[5]));
-
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 51,
-            end_time: 60,
-            start_target: 140,
-            end_target: 150,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 5,
-            end_height: 5,
-            shielded_tx: 8,
-        },
-    );
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 61,
-            end_time: 70,
-            start_target: 150,
-            end_target: 160,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 6,
-            end_height: 6,
-            shielded_tx: 9,
-        },
-    );
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[7], &initial_tree_vec[8]));
-
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 71,
-            end_time: 80,
-            start_target: 160,
-            end_target: 170,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 7,
-            end_height: 7,
-            shielded_tx: 10,
-        },
-    );
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 81,
-            end_time: 90,
-            start_target: 170,
-            end_target: 180,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 8,
-            end_height: 8,
-            shielded_tx: 11,
-        },
-    );
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[10], &initial_tree_vec[11]));
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[9], &initial_tree_vec[12]));
-    initial_tree_vec.push(NodeData::combine(&initial_tree_vec[6], &initial_tree_vec[13]));
-
-    initial_tree_vec.push(
-        NodeData {
-            consensus_branch_id: 0,
-            subtree_commitment: [0u8; 32],
-            start_time: 91,
-            end_time: 100,
-            start_target: 180,
-            end_target: 190,
-            start_sapling_root: [0u8; 32],
-            end_sapling_root: [0u8; 32],
-            subtree_total_work: Default::default(),
-            start_height: 9,
-            end_height: 9,
-            shielded_tx: 12,
-        },
-    );
-
-    let tree = prepare_tree(&initial_tree_vec);
-
-    let mut buf = Vec::new();
-    if let Some(out_file_path) = ::std::env::args().nth(1) {
-        for node in initial_tree_vec.into_iter() {
-            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");
-    }
-
-    println!("root: {}", tree.root());
-
-
-}
\ No newline at end of file
diff --git a/examples/producer/main.rs b/examples/producer/main.rs
new file mode 100644
index 0000000..6850079
--- /dev/null
+++ b/examples/producer/main.rs
@@ -0,0 +1,4 @@
+// dummy example
+pub fn main() {
+
+}
\ No newline at end of file
diff --git a/examples/producer/share.rs b/examples/producer/share.rs
new file mode 100644
index 0000000..7ead49d
--- /dev/null
+++ b/examples/producer/share.rs
@@ -0,0 +1,75 @@
+use zcash_mmr:: {NodeData, Tree, Entry, EntryLink};
+
+pub struct NodeDataIterator {
+    return_stack: Vec<NodeData>,
+    tree: Tree,
+    cursor: usize,
+    leaf_cursor: usize,
+}
+
+impl Iterator for NodeDataIterator {
+    type Item = NodeData;
+
+    fn next(&mut self) -> Option<NodeData> {
+        let result = if self.cursor == 1 {
+            self.leaf_cursor = 2;
+            Some(leaf(1))
+        } else if self.cursor == 2 {
+            self.leaf_cursor = 3;
+            Some(leaf(2))
+        } else if self.cursor == 3 {
+            Some(self.tree.root_node().expect("always exists").data().clone())
+        } else if self.return_stack.len() > 0 {
+            self.return_stack.pop()
+        } else {
+            for n_append in
+                self.tree.append_leaf(leaf(self.leaf_cursor as u32))
+                    .expect("full tree cannot fail").into_iter().rev()
+            {
+                self.return_stack.push(self.tree.resolve_link(n_append).expect("just pushed").data().clone())
+            }
+            self.leaf_cursor += 1;
+            self.return_stack.pop()
+        };
+
+        self.cursor += 1;
+        result
+    }
+}
+
+impl NodeDataIterator {
+    pub fn new() -> Self {
+        let mut root: Entry = NodeData::combine(&leaf(1), &leaf(2)).into();
+        root.update_siblings(EntryLink::Stored(0), EntryLink::Stored(1));
+        let tree =
+            Tree::new(
+                3,
+                vec![(2, root)],
+                vec![(0, leaf(1).into()), (1, leaf(2).into())]
+            );
+
+        NodeDataIterator {
+            return_stack: Vec::new(),
+            tree,
+            cursor: 1,
+            leaf_cursor: 1,
+        }
+    }
+}
+
+fn leaf(height: u32) -> NodeData {
+    NodeData {
+        consensus_branch_id: 0,
+        subtree_commitment: [0u8; 32],
+        start_time: height*10+1,
+        end_time: (height+1)*10,
+        start_target: 100 + height*10,
+        end_target: 100 + (height+1)*10,
+        start_sapling_root: [0u8; 32],
+        end_sapling_root: [0u8; 32],
+        subtree_total_work: 0.into(),
+        start_height: height as u64,
+        end_height: height as u64,
+        shielded_tx: 5 + height as u64,
+    }
+}
diff --git a/examples/write.rs b/examples/write.rs
new file mode 100644
index 0000000..f51e2a7
--- /dev/null
+++ b/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);
+        }
+    }
+}
\ No newline at end of file