From 69a1b9099d262b3f221f282aeaa71a1f879fa7cd Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Fri, 16 Feb 2024 17:50:21 -0800
Subject: [PATCH] Share common prefix search in addWriteRange

---
 ConflictSet.cpp | 91 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 66 insertions(+), 25 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index e05d084..8b86573 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -1396,46 +1396,87 @@ void destroyTree(Node *root) {
 void addWriteRange(Node *&root, int64_t oldestVersion,
                    const ConflictSet::WriteRange &w) {
 
-  auto *begin = insert(&root, std::span<const uint8_t>(w.begin.p, w.begin.len),
-                       w.writeVersion, true);
+  auto begin = std::span<const uint8_t>(w.begin.p, w.begin.len);
+  auto end = std::span<const uint8_t>(w.end.p, w.end.len);
 
-  const bool insertedBegin = !std::exchange(begin->entryPresent, true);
+  int lcp = longestCommonPrefix(begin.data(), end.data(),
+                                std::min(begin.size(), end.size()));
+  auto remaining = begin.subspan(0, lcp);
+
+  auto *n = root;
+
+  for (;;) {
+    if (int(remaining.size()) < n->partialKeyLen + 1) {
+      break;
+    }
+    int i = 0;
+    for (; i < n->partialKeyLen; ++i) {
+      if (remaining[i] != n->partialKey[i]) {
+        break;
+      }
+    }
+    if (i != n->partialKeyLen) {
+      break;
+    }
+
+    int c = getChildGeq(n, remaining[n->partialKeyLen]);
+    if (c != remaining[n->partialKeyLen]) {
+      break;
+    }
+
+    n = getChildExists(n, c);
+    remaining = remaining.subspan(n->partialKeyLen + 1,
+                                  remaining.size() - (n->partialKeyLen + 1));
+  }
+
+  Node **useAsRoot = n->parent == nullptr
+                         ? &root
+                         : &getChildExists(n->parent, n->parentsIndex);
+
+  int consumed = lcp - remaining.size();
+
+  consumed = 0;
+  useAsRoot = &root;
+
+  begin = begin.subspan(consumed, begin.size() - consumed);
+  end = end.subspan(consumed, end.size() - consumed);
+
+  auto *beginNode = insert(useAsRoot, begin, w.writeVersion, true);
+
+  const bool insertedBegin = !std::exchange(beginNode->entryPresent, true);
 
   if (insertedBegin) {
-    auto *p = nextLogical(begin);
-    begin->entry.rangeVersion =
+    auto *p = nextLogical(beginNode);
+    beginNode->entry.rangeVersion =
         p != nullptr ? p->entry.rangeVersion : oldestVersion;
-    begin->entry.pointVersion = w.writeVersion;
-    begin->maxVersion = w.writeVersion;
+    beginNode->entry.pointVersion = w.writeVersion;
+    beginNode->maxVersion = w.writeVersion;
   }
-  begin->maxVersion = std::max(begin->maxVersion, w.writeVersion);
-  begin->entry.pointVersion =
-      std::max(begin->entry.pointVersion, w.writeVersion);
+  beginNode->maxVersion = std::max(beginNode->maxVersion, w.writeVersion);
+  beginNode->entry.pointVersion =
+      std::max(beginNode->entry.pointVersion, w.writeVersion);
 
-  auto *end = insert(&root, std::span<const uint8_t>(w.end.p, w.end.len),
-                     w.writeVersion, false);
+  auto *endNode = insert(useAsRoot, end, w.writeVersion, false);
 
-  const bool insertedEnd = !std::exchange(end->entryPresent, true);
+  const bool insertedEnd = !std::exchange(endNode->entryPresent, true);
 
   if (insertedEnd) {
-    auto *p = nextLogical(end);
-    end->entry.pointVersion =
+    auto *p = nextLogical(endNode);
+    endNode->entry.pointVersion =
         p != nullptr ? p->entry.rangeVersion : oldestVersion;
-    end->maxVersion = std::max(end->maxVersion, end->entry.pointVersion);
+    endNode->maxVersion =
+        std::max(endNode->maxVersion, endNode->entry.pointVersion);
   }
-  end->entry.rangeVersion = w.writeVersion;
+  endNode->entry.rangeVersion = w.writeVersion;
 
   if (insertedEnd) {
-    // begin may have been invalidated
-    auto iter =
-        firstGeq(root, std::span<const uint8_t>(w.begin.p, w.begin.len));
-    assert(iter.cmp == 0);
-    begin = iter.n;
+    // beginNode may have been invalidated
+    beginNode = insert(useAsRoot, begin, w.writeVersion, true);
   }
 
-  for (begin = nextLogical(begin); begin != end;) {
-    auto *old = begin;
-    begin = nextLogical(begin);
+  for (beginNode = nextLogical(beginNode); beginNode != endNode;) {
+    auto *old = beginNode;
+    beginNode = nextLogical(beginNode);
     old->entryPresent = false;
     if (old->numChildren == 0 && old->parent != nullptr) {
       eraseChild(old->parent, old->parentsIndex);