Add 'zcash_history/' from commit 'e2c131fdc308265adcab774e54d4d5804c23b368'

git-subtree-dir: zcash_history
git-subtree-mainline: be0ee9eb82
git-subtree-split: e2c131fdc3

zcash_history/examples/long.rs

@@ -0,0 +1,109 @@
+use zcash_mmr::{Entry, EntryLink, NodeData, Tree};
+
+#[path= "lib/shared.rs"]
+mod share;
+
+fn draft(into: &mut Vec<(u32, Entry)>, vec: &Vec<NodeData>, peak_pos: usize, h: u32) {
+    let node_data = vec[peak_pos-1].clone();
+    let peak: Entry = match h {
+        0 => node_data.into(),
+        _ => Entry::new(
+            node_data,
+            EntryLink::Stored((peak_pos - (1 << h) - 1) as u32),
+            EntryLink::Stored((peak_pos - 2) as u32),
+        ),
+    };
+
+    println!("Entry #{}: {}", into.len(), peak);
+
+    into.push(((peak_pos-1) as u32, peak));
+}
+
+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();
+
+    // used later
+    let mut last_peak_pos = 0;
+    let mut last_peak_h = 0;
+
+    loop {
+
+        if peak_pos > vec.len() {
+            // left child, -2^h
+            peak_pos = peak_pos - (1<<h);
+            h = h - 1;
+        }
+
+        if peak_pos <= vec.len() {
+            draft(&mut nodes, vec, peak_pos, h);
+
+            // save to be used in next loop
+            last_peak_pos = peak_pos;
+            last_peak_h = h;
+
+            // right sibling
+            peak_pos = peak_pos + (1 << (h+1)) - 1;
+        }
+
+        if h == 0 {
+            break;
+        }
+    }
+
+    // for deletion, everything on the right slope of the last peak should be pre-loaded
+    let mut extra = Vec::new();
+    let mut h = last_peak_h;
+    let mut peak_pos = last_peak_pos;
+
+    while h > 0 {
+        let left_pos = peak_pos - (1<<h);
+        let right_pos = peak_pos - 1;
+        h = h - 1;
+
+        // drafting left child
+        draft(&mut extra, vec, left_pos, h);
+
+        // drafting right child
+        draft(&mut extra, vec, right_pos, h);
+
+        // continuing on right slope
+        peak_pos = right_pos;
+    }
+
+    println!("Total extra of {} required for deletion!", extra.len());
+
+    Tree::new(vec.len() as u32, nodes, extra)
+}
+
+fn main() {
+    let number= match std::env::args().skip(1).next() {
+        None => { eprintln!("writer <number of nodes> [<out_file>]"); std::process::exit(1); },
+        Some(number) => {
+            number.parse::<usize>().expect("invalid number")
+        }
+    };
+
+    let long_vec = share::NodeDataIterator::new().take(number)
+        .collect::<Vec<NodeData>>();
+
+    let now = std::time::Instant::now();
+
+    let tree = prepare_tree(&long_vec);
+    let elapsed = now.elapsed();
+
+    println!("Tree final root: {}-{}",
+        tree.root_node().expect("root").data().start_height,
+        tree.root_node().expect("root").data().end_height,
+    );
+
+    println!("Prepare tree of {} length: {} ns / {} mcs / {} ms",
+        number,
+        elapsed.as_nanos(), elapsed.as_micros(), elapsed.as_millis()
+    );
+}