From 958ee15cfcf008265130b1cc7af533e2d1981e4e Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Tue, 29 Oct 2024 20:43:58 -0700
Subject: [PATCH] Use forwarding pointers instead of beginIsPrefix

---
 ConflictSet.cpp | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 610de73..203cfc3 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -3108,10 +3108,15 @@ void fixupMaxVersion(Node *node, WriteContext *writeContext) {
   setMaxVersion(node, max);
 }
 
-void addWriteRange(TaggedNodePointer &beginRoot, std::span<const uint8_t> begin,
-                   TaggedNodePointer &endRoot, std::span<const uint8_t> end,
-                   InternalVersionT writeVersion, WriteContext *writeContext,
-                   ConflictSet::Impl *impl, bool beginIsPrefix) {
+struct AddedWriteRange {
+  Node *beginNode;
+  Node *endNode;
+};
+
+AddedWriteRange
+addWriteRange(TaggedNodePointer &beginRoot, std::span<const uint8_t> begin,
+              TaggedNodePointer &endRoot, std::span<const uint8_t> end,
+              InternalVersionT writeVersion, WriteContext *writeContext) {
   ++writeContext->accum.range_writes;
 
   Node *beginNode = *insert(&beginRoot, begin, writeVersion, writeContext);
@@ -3134,15 +3139,18 @@ void addWriteRange(TaggedNodePointer &beginRoot, std::span<const uint8_t> begin,
     endNode->entry.pointVersion =
         p == nullptr ? writeContext->zero
                      : std::max(p->entry.rangeVersion, writeContext->zero);
-    if (beginIsPrefix) {
-      // beginNode may have been invalidated when inserting end
-      beginNode = beginRoot;
-      assert(beginNode->entryPresent);
+    while (beginNode->releaseDeferred) {
+      beginNode = beginNode->forwardTo;
     }
     endNode->entryPresent = true;
   }
   endNode->entry.rangeVersion = writeVersion;
 
+  return {beginNode, endNode};
+}
+
+void eraseInRange(Node *beginNode, Node *endNode, WriteContext *writeContext,
+                  ConflictSet::Impl *impl) {
   // Erase nodes in range
   assert(!beginNode->endOfRange);
   assert(!endNode->endOfRange);
@@ -3172,9 +3180,11 @@ void addWriteRange(TaggedNodePointer &root, std::span<const uint8_t> begin,
   auto useAsRoot =
       insert(&root, begin.subspan(0, lcp), writeVersion, writeContext);
 
-  addWriteRange(*useAsRoot, begin.subspan(lcp, begin.size() - lcp), *useAsRoot,
-                end.subspan(lcp, end.size() - lcp), writeVersion, writeContext,
-                impl, int(begin.size()) == lcp);
+  auto [beginNode, endNode] = addWriteRange(
+      *useAsRoot, begin.subspan(lcp, begin.size() - lcp), *useAsRoot,
+      end.subspan(lcp, end.size() - lcp), writeVersion, writeContext);
+
+  eraseInRange(beginNode, endNode, writeContext, impl);
 }
 
 Node *firstGeqPhysical(Node *n, const std::span<const uint8_t> key) {