From b893a6c8ee0027981642e0c5152b18d6417ced30 Mon Sep 17 00:00:00 2001
From: Ignotus Peverell <igno.peverell@protonmail.com>
Date: Tue, 28 Nov 2017 18:43:02 -0500
Subject: [PATCH] Back up the removed log before truncating in memory

Without a backup, the in-memory data structure stays truncated
even if the rewind is abandoned. Also add some logging on our
most problematic block in case it still is problematic.
---
 chain/src/sumtree.rs |  6 +++++-
 store/src/sumtree.rs | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/chain/src/sumtree.rs b/chain/src/sumtree.rs
index 1db758c59..090887797 100644
--- a/chain/src/sumtree.rs
+++ b/chain/src/sumtree.rs
@@ -239,9 +239,13 @@ impl<'a> Extension<'a> {
 	pub fn apply_block(&mut self, b: &Block) -> Result<(), Error> {
 
 		// doing inputs first guarantees an input can't spend an output in the
-  // same block, enforcing block cut-through
+		// same block, enforcing block cut-through
 		for input in &b.inputs {
 			let pos_res = self.commit_index.get_output_pos(&input.commitment());
+			if b.hash().to_string() == "f697a877" {
+				debug!(LOGGER, "input pos: {:?}, commit: {} {:?}",
+							 pos_res, input.commitment().hash(), input.commitment());
+			}
 			if let Ok(pos) = pos_res {
 				match self.output_pmmr.prune(pos, b.header.height as u32) {
 					Ok(true) => {
diff --git a/store/src/sumtree.rs b/store/src/sumtree.rs
index 17454da7c..7d57bbd49 100644
--- a/store/src/sumtree.rs
+++ b/store/src/sumtree.rs
@@ -163,6 +163,8 @@ struct RemoveLog {
 	removed: Vec<(u64, u32)>,
 	// Holds positions temporarily until flush is called.
 	removed_tmp: Vec<(u64, u32)>,
+	// Holds truncated removed temporarily until discarded or committed
+	removed_bak: Vec<(u64, u32)>,
 }
 
 impl RemoveLog {
@@ -174,6 +176,7 @@ impl RemoveLog {
 			path: path,
 			removed: removed,
 			removed_tmp: vec![],
+			removed_bak: vec![],
 		})
 	}
 
@@ -181,10 +184,14 @@ impl RemoveLog {
 	fn truncate(&mut self, last_offs: u32) -> io::Result<()> {
 		// simplifying assumption: we always remove older than what's in tmp
 		self.removed_tmp = vec![];
+		// DEBUG
+		let _ = self.flush_truncate(last_offs);
 
 		if last_offs == 0 {
 			self.removed = vec![];
 		} else {
+			// backing it up before truncating
+			self.removed_bak = self.removed.clone();
 			self.removed = self.removed
 				.iter()
 				.filter(|&&(_, idx)| idx < last_offs)
@@ -194,6 +201,15 @@ impl RemoveLog {
 		Ok(())
 	}
 
+	// DEBUG: saves the remove log to the side before each truncate
+	fn flush_truncate(&mut self, last_offs: u32) -> io::Result<()> {
+		let mut file = File::create(format!("{}.{}", self.path.clone(), last_offs))?;
+		for elmt in &self.removed {
+			file.write_all(&ser::ser_vec(&elmt).unwrap()[..])?;
+		}
+		file.sync_data()
+	}
+
 	/// Append a set of new positions to the remove log. Both adds those
 	/// positions the ordered in-memory set and to the file.
 	fn append(&mut self, elmts: Vec<u64>, index: u32) -> io::Result<()> {
@@ -223,11 +239,16 @@ impl RemoveLog {
 			file.write_all(&ser::ser_vec(&elmt).unwrap()[..])?;
 		}
 		self.removed_tmp = vec![];
+		self.removed_bak = vec![];
 		file.sync_data()
 	}
 
 	/// Discard pending changes
 	fn discard(&mut self) {
+		if self.removed_bak.len() > 0 {
+			self.removed = self.removed_bak.clone();
+			self.removed_bak = vec![];
+		}
 		self.removed_tmp = vec![];
 	}