From 2cc2dffab56e3784d7b9b292ae5855f12371cd58 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Thu, 20 Aug 2020 11:05:14 +0100
Subject: [PATCH] [thin_check (rust)] Make NodeVisitor::visit non mut.

Preparation for making btree_walk multithreaded
---
 src/pdata/btree.rs | 18 +++++++++---------
 src/thin/check.rs  |  4 ++--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/pdata/btree.rs b/src/pdata/btree.rs
index 38adeae..a928927 100644
--- a/src/pdata/btree.rs
+++ b/src/pdata/btree.rs
@@ -147,7 +147,8 @@ pub fn unpack_node<V: Unpack>(
 //------------------------------------------
 
 pub trait NodeVisitor<V: Unpack> {
-    fn visit(&mut self, header: &NodeHeader, keys: &[u64], values: &[V]) -> Result<()>;
+    // &self is deliberately non mut to allow the walker to use multiple threads.
+    fn visit(&self, header: &NodeHeader, keys: &[u64], values: &[V]) -> Result<()>;
 }
 
 #[derive(Clone)]
@@ -274,23 +275,22 @@ impl BTreeWalker {
 //------------------------------------------
 
 struct ValueCollector<V> {
-    values: BTreeMap<u64, V>,
+    values: Mutex<BTreeMap<u64, V>>,
 }
 
 impl<V> ValueCollector<V> {
     fn new() -> ValueCollector<V> {
         ValueCollector {
-            values: BTreeMap::new(),
+            values: Mutex::new(BTreeMap::new()),
         }
     }
 }
 
 impl<V: Unpack + Clone> NodeVisitor<V> for ValueCollector<V> {
-    fn visit(&mut self, _h: &NodeHeader, keys: &[u64], values: &[V]) -> Result<()> {
+    fn visit(&self, _h: &NodeHeader, keys: &[u64], values: &[V]) -> Result<()> {
+        let mut vals = self.values.lock().unwrap();
         for n in 0..keys.len() {
-            let k = keys[n];
-            let v = values[n].clone();
-            self.values.insert(k, v);
+            vals.insert(keys[n], values[n].clone());
         }
 
         Ok(())
@@ -306,7 +306,7 @@ pub fn btree_to_map<V: Unpack + Clone>(
     let mut visitor = ValueCollector::<V>::new();
 
     walker.walk(&mut visitor, root)?;
-    Ok(visitor.values)
+    Ok(visitor.values.into_inner().unwrap())
 }
 
 pub fn btree_to_map_with_sm<V: Unpack + Clone>(
@@ -319,7 +319,7 @@ pub fn btree_to_map_with_sm<V: Unpack + Clone>(
     let mut visitor = ValueCollector::<V>::new();
 
     walker.walk(&mut visitor, root)?;
-    Ok(visitor.values)
+    Ok(visitor.values.into_inner().unwrap())
 }
 
 //------------------------------------------
diff --git a/src/thin/check.rs b/src/thin/check.rs
index 9fcd33f..c38fddc 100644
--- a/src/thin/check.rs
+++ b/src/thin/check.rs
@@ -50,7 +50,7 @@ struct BottomLevelVisitor {
 //------------------------------------------
 
 impl NodeVisitor<BlockTime> for BottomLevelVisitor {
-    fn visit(&mut self, _h: &NodeHeader, _k: &[u64], values: &[BlockTime]) -> Result<()> {
+    fn visit(&self, _h: &NodeHeader, _k: &[u64], values: &[BlockTime]) -> Result<()> {
         // FIXME: do other checks
 
         if values.len() == 0 {
@@ -124,7 +124,7 @@ impl<'a> OverflowChecker<'a> {
 }
 
 impl<'a> NodeVisitor<u32> for OverflowChecker<'a> {
-    fn visit(&mut self, _h: &NodeHeader, keys: &[u64], values: &[u32]) -> Result<()> {
+    fn visit(&self, _h: &NodeHeader, keys: &[u64], values: &[u32]) -> Result<()> {
         for n in 0..keys.len() {
             let k = keys[n];
             let v = values[n];