From 2037d37c6608863f49ccdb6cc003a2d07736f32d Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Wed, 4 Sep 2024 12:11:16 -0700
Subject: [PATCH] checkRangeLeftSide

---
 ConflictSet.cpp | 148 +++++++++++++++++++++++-------------------------
 1 file changed, 71 insertions(+), 77 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 98b2b74..0d62e65 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -2510,104 +2510,99 @@ downLeftSpine:
 namespace {
 // Return true if the max version among all keys that start with key[:prefixLen]
 // that are >= key is <= readVersion
-struct CheckRangeLeftSide {
+bool checkRangeLeftSide(Node *n, std::span<const uint8_t> key, int prefixLen,
+                        InternalVersionT readVersion, ReadContext *tls) {
   bool ok;
+  auto remaining = key;
+  int searchPathLen = 0;
+  for (;; ++tls->range_read_iterations_accum) {
+    if (remaining.size() == 0) {
+      assert(searchPathLen >= prefixLen);
+      ok = maxVersion(n) <= readVersion;
+      return ok;
+    }
 
-  bool step(Node *n, std::span<const uint8_t> key, int prefixLen,
-            InternalVersionT readVersion, ReadContext *tls) {
-    auto remaining = key;
-    int searchPathLen = 0;
-    for (;; ++tls->range_read_iterations_accum) {
-      if (remaining.size() == 0) {
-        assert(searchPathLen >= prefixLen);
-        ok = maxVersion(n) <= readVersion;
-        return true;
+    if (searchPathLen >= prefixLen) {
+      if (!checkMaxBetweenExclusive(n, remaining[0], 256, readVersion, tls)) {
+        ok = false;
+        return ok;
       }
+    }
 
-      if (searchPathLen >= prefixLen) {
-        if (!checkMaxBetweenExclusive(n, remaining[0], 256, readVersion, tls)) {
-          ok = false;
-          return true;
+    auto [child, maxV] = getChildAndMaxVersion(n, remaining[0]);
+    if (child == nullptr) {
+      auto c = getChildGeq(n, remaining[0]);
+      if (c != nullptr) {
+        if (searchPathLen < prefixLen) {
+          n = c;
+          goto downLeftSpine;
         }
+        n = c;
+        ok = maxVersion(n) <= readVersion;
+        return ok;
+      } else {
+        n = nextSibling(n);
+        if (n == nullptr) {
+          ok = true;
+          return ok;
+        }
+        goto downLeftSpine;
       }
+    }
 
-      auto [child, maxV] = getChildAndMaxVersion(n, remaining[0]);
-      if (child == nullptr) {
-        auto c = getChildGeq(n, remaining[0]);
-        if (c != nullptr) {
+    n = child;
+    remaining = remaining.subspan(1, remaining.size() - 1);
+    ++searchPathLen;
+
+    if (n->partialKeyLen > 0) {
+      int commonLen = std::min<int>(n->partialKeyLen, remaining.size());
+      int i = longestCommonPrefix(n->partialKey(), remaining.data(), commonLen);
+      searchPathLen += i;
+      if (i < commonLen) {
+        auto c = n->partialKey()[i] <=> remaining[i];
+        if (c > 0) {
           if (searchPathLen < prefixLen) {
-            n = c;
             goto downLeftSpine;
           }
-          n = c;
+          if (n->entryPresent && n->entry.rangeVersion > readVersion) {
+            ok = false;
+            return ok;
+          }
           ok = maxVersion(n) <= readVersion;
-          return true;
+          return ok;
         } else {
           n = nextSibling(n);
           if (n == nullptr) {
             ok = true;
-            return true;
+            return ok;
           }
           goto downLeftSpine;
         }
       }
-
-      n = child;
-      remaining = remaining.subspan(1, remaining.size() - 1);
-      ++searchPathLen;
-
-      if (n->partialKeyLen > 0) {
-        int commonLen = std::min<int>(n->partialKeyLen, remaining.size());
-        int i =
-            longestCommonPrefix(n->partialKey(), remaining.data(), commonLen);
-        searchPathLen += i;
-        if (i < commonLen) {
-          auto c = n->partialKey()[i] <=> remaining[i];
-          if (c > 0) {
-            if (searchPathLen < prefixLen) {
-              goto downLeftSpine;
-            }
-            if (n->entryPresent && n->entry.rangeVersion > readVersion) {
-              ok = false;
-              return true;
-            }
-            ok = maxVersion(n) <= readVersion;
-            return true;
-          } else {
-            n = nextSibling(n);
-            if (n == nullptr) {
-              ok = true;
-              return true;
-            }
-            goto downLeftSpine;
-          }
+      if (commonLen == n->partialKeyLen) {
+        // partial key matches
+        remaining = remaining.subspan(commonLen, remaining.size() - commonLen);
+      } else if (n->partialKeyLen > int(remaining.size())) {
+        assert(searchPathLen >= prefixLen);
+        if (n->entryPresent && n->entry.rangeVersion > readVersion) {
+          ok = false;
+          return ok;
         }
-        if (commonLen == n->partialKeyLen) {
-          // partial key matches
-          remaining =
-              remaining.subspan(commonLen, remaining.size() - commonLen);
-        } else if (n->partialKeyLen > int(remaining.size())) {
-          assert(searchPathLen >= prefixLen);
-          if (n->entryPresent && n->entry.rangeVersion > readVersion) {
-            ok = false;
-            return true;
-          }
-          ok = maxVersion(n) <= readVersion;
-          return true;
-        }
-      }
-      if (maxV <= readVersion) {
-        ok = true;
-        return true;
+        ok = maxVersion(n) <= readVersion;
+        return ok;
       }
     }
-  downLeftSpine:
-    for (; !n->entryPresent; n = getFirstChildExists(n)) {
+    if (maxV <= readVersion) {
+      ok = true;
+      return ok;
     }
-    ok = n->entry.rangeVersion <= readVersion;
-    return true;
   }
-};
+downLeftSpine:
+  for (; !n->entryPresent; n = getFirstChildExists(n)) {
+  }
+  ok = n->entry.rangeVersion <= readVersion;
+  return ok;
+}
 
 // Return true if the max version among all keys that start with key[:prefixLen]
 // that are < key is <= readVersion
@@ -2816,13 +2811,12 @@ bool checkRangeRead(Node *n, std::span<const uint8_t> begin,
   // This makes it safe to check maxVersion within CheckRangeLeftSide. If this
   // were false, then we would have returned above since lcp == begin.size().
   assert(!(n->parent == nullptr && begin.size() == 0));
-  CheckRangeLeftSide checkRangeLeftSide{};
-  checkRangeLeftSide.step(n, begin, lcp + 1, readVersion, tls);
+  bool lhsOk = checkRangeLeftSide(n, begin, lcp + 1, readVersion, tls);
   CheckRangeRightSide checkRangeRightSide{n, end, lcp + 1, readVersion, tls};
   for (; !checkRangeRightSide.step(); ++tls->range_read_iterations_accum)
     ;
 
-  return checkRangeLeftSide.ok && checkRangeRightSide.ok;
+  return lhsOk && checkRangeRightSide.ok;
 }
 
 #ifdef __x86_64__