From ddca6e85118298734754bb5797d2616e33031385 Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Fri, 9 Feb 2024 18:14:07 -0800
Subject: [PATCH] Rely on bitSet for child existence in Node48

---
 ConflictSet.cpp | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index aae7186..4994e6b 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -152,10 +152,7 @@ struct Node48 : Node {
   Node *children[48] = {};
   int8_t nextFree = 0;
   int8_t index[256];
-  Node48() {
-    this->type = Type::Node48;
-    memset(index, -1, 256);
-  }
+  Node48() { this->type = Type::Node48; }
 };
 
 struct Node256 : Node {
@@ -241,10 +238,8 @@ Node *&getChildExists(Node *self, uint8_t index) {
     return self16->children[getNodeIndex(self16, index)];
   } else if (self->type == Type::Node48) {
     auto *self48 = static_cast<Node48 *>(self);
-    int secondIndex = self48->index[index];
-    if (secondIndex >= 0) {
-      return self48->children[secondIndex];
-    }
+    assert(self48->bitSet.test(index));
+    return self48->children[self48->index[index]];
   } else {
     auto *self256 = static_cast<Node256 *>(self);
     return self256->children[index];
@@ -416,15 +411,14 @@ Node *&getOrCreateChild(Node *&self, uint8_t index) {
   } else if (self->type == Type::Node48) {
   insert48:
     auto *self48 = static_cast<Node48 *>(self);
-    int secondIndex = self48->index[index];
-    if (secondIndex >= 0) {
-      return self48->children[secondIndex];
+    if (self48->bitSet.test(index)) {
+      return self48->children[self48->index[index]];
     }
     if (self->numChildren == 48) {
       auto *newSelf = new (safe_malloc(sizeof(Node256))) Node256;
       memcpy((void *)newSelf, self, offsetof(Node, type));
       for (int i = 0; i < 256; ++i) {
-        if (self48->index[i] >= 0) {
+        if (self48->bitSet.test(i)) {
           newSelf->bitSet.set(i);
           newSelf->children[i] = self48->children[self48->index[i]];
         }
@@ -475,7 +469,7 @@ void eraseChild(Node *self, uint8_t index) {
   } else if (self->type == Type::Node48) {
     auto *self48 = static_cast<Node48 *>(self);
     self48->bitSet.reset(index);
-    int8_t toRemoveChildrenIndex = std::exchange(self48->index[index], -1);
+    int8_t toRemoveChildrenIndex = self48->index[index];
     int8_t lastChildrenIndex = --self48->nextFree;
     assert(toRemoveChildrenIndex >= 0);
     assert(lastChildrenIndex >= 0);