Update our benchmarks in README

This seems to benchmark better

.gitignore

@@ -1,2 +1,3 @@
 .cache
+__pycache__
 build

.pre-commit-config.yaml

@@ -1,11 +1,11 @@
 repos:
   - repo: https://github.com/pre-commit/mirrors-clang-format
-    rev: 6d365699efc33b1b432eab5b4ae331a19e1857de  # frozen: v18.1.2
+    rev: 6d365699efc33b1b432eab5b4ae331a19e1857de # frozen: v18.1.2
     hooks:
       - id: clang-format
         exclude: ".*third_party/.*"
   - repo: https://github.com/cheshirekow/cmake-format-precommit
-    rev: e2c2116d86a80e72e7146a06e68b7c228afc6319  # frozen: v0.6.13
+    rev: e2c2116d86a80e72e7146a06e68b7c228afc6319 # frozen: v0.6.13
     hooks:
       - id: cmake-format
   - repo: local
@@ -13,7 +13,7 @@ repos:
       - id: debug verbose check
         name: disallow checking in DEBUG_VERBOSE=1
         description: disallow checking in DEBUG_VERBOSE=1
-        entry: '^#define DEBUG_VERBOSE 1$'
+        entry: "^#define DEBUG_VERBOSE 1$"
         language: pygrep
         types: [c++]
   - repo: local
@@ -21,10 +21,14 @@ repos:
       - id: debug verbose check
         name: disallow checking in SHOW_MEMORY=1
         description: disallow checking in SHOW_MEMORY=1
-        entry: '^#define SHOW_MEMORY 1$'
+        entry: "^#define SHOW_MEMORY 1$"
         language: pygrep
         types: [c++]
   - repo: https://github.com/shellcheck-py/shellcheck-py
-    rev: a23f6b85d0fdd5bb9d564e2579e678033debbdff  # frozen: v0.10.0.1
+    rev: a23f6b85d0fdd5bb9d564e2579e678033debbdff # frozen: v0.10.0.1
     hooks:
-    -   id: shellcheck
+      - id: shellcheck
+  - repo: https://github.com/psf/black
+    rev: 552baf822992936134cbd31a38f69c8cfe7c0f05 # frozen: 24.3.0
+    hooks:
+      - id: black

Bench.cpp

@@ -258,4 +258,107 @@ void benchConflictSet() {
   }
 }
 
-int main(void) { benchConflictSet(); }
+constexpr int kKeyLenForWorstCase = 50;
+
+ConflictSet worstCaseConflictSetForRadixRangeRead(int cardinality) {
+  ConflictSet cs{0};
+
+  for (int i = 0; i < kKeyLenForWorstCase; ++i) {
+    for (int j = 0; j < cardinality; ++j) {
+      auto b = std::vector<uint8_t>(i, 0);
+      b.push_back(j);
+      auto e = std::vector<uint8_t>(i, 255);
+      e.push_back(255 - j);
+      weaselab::ConflictSet::WriteRange w[] = {{
+                                                   {b.data(), int(b.size())},
+                                                   {nullptr, 0},
+                                               },
+                                               {
+                                                   {e.data(), int(e.size())},
+                                                   {nullptr, 0},
+                                               }};
+      std::sort(std::begin(w), std::end(w),
+                [](const auto &lhs, const auto &rhs) {
+                  int cl = std::min(lhs.begin.len, rhs.begin.len);
+                  if (cl > 0) {
+                    int c = memcmp(lhs.begin.p, rhs.begin.p, cl);
+                    if (c != 0) {
+                      return c < 0;
+                    }
+                  }
+                  return lhs.begin.len < rhs.begin.len;
+                });
+      cs.addWrites(w, sizeof(w) / sizeof(w[0]), 0);
+    }
+  }
+
+  // Defeat short-circuiting on the left
+  {
+    auto k = std::vector<uint8_t>(kKeyLenForWorstCase, 0);
+    weaselab::ConflictSet::WriteRange w[] = {
+        {
+            {k.data(), int(k.size())},
+            {nullptr, 0},
+        },
+    };
+    cs.addWrites(w, sizeof(w) / sizeof(w[0]), 1);
+  }
+
+  // Defeat short-circuiting on the right
+  {
+    auto k = std::vector<uint8_t>(kKeyLenForWorstCase, 255);
+    weaselab::ConflictSet::WriteRange w[] = {
+        {
+            {k.data(), int(k.size())},
+            {nullptr, 0},
+        },
+    };
+    cs.addWrites(w, sizeof(w) / sizeof(w[0]), 1);
+  }
+
+  return cs;
+}
+
+void benchWorstCaseForRadixRangeRead() {
+  ankerl::nanobench::Bench bench;
+
+  std::unique_ptr<ConflictSet> cs[256];
+  for (int i = 0; i < 256; ++i) {
+    cs[i] =
+        std::make_unique<ConflictSet>(worstCaseConflictSetForRadixRangeRead(i));
+  }
+
+  auto begin = std::vector<uint8_t>(kKeyLenForWorstCase - 1, 0);
+  begin.push_back(1);
+  auto end = std::vector<uint8_t>(kKeyLenForWorstCase - 1, 255);
+  end.push_back(254);
+
+  weaselab::ConflictSet::Result result;
+  weaselab::ConflictSet::ReadRange r{
+      {begin.data(), int(begin.size())}, {end.data(), int(end.size())}, 0};
+
+  bench.run("worst case for radix tree", [&]() {
+    for (int i = 0; i < 256; ++i) {
+      result = weaselab::ConflictSet::TooOld;
+      cs[i]->check(&r, &result, 1);
+      if (result != weaselab::ConflictSet::Commit) {
+        abort();
+      }
+    }
+  });
+
+  // for (int i = 0; i < 256; ++i) {
+  //   bench.run("worst case for radix tree, span " + std::to_string(i), [&]() {
+  //     result = weaselab::ConflictSet::TooOld;
+  //     cs[i]->check(&r, &result, 1);
+  //     if (result != weaselab::ConflictSet::Commit) {
+  //       abort();
+  //     }
+  //   });
+  // }
+}
+
+int main(void) {
+  benchConflictSet();
+  benchWorstCaseForRadixRangeRead();
+}

CMakeLists.txt

@@ -1,13 +1,17 @@
 cmake_minimum_required(VERSION 3.18)
 project(
   conflict-set
-  VERSION 0.0.2
+  VERSION 0.0.7
   DESCRIPTION
     "A data structure for optimistic concurrency control on ranges of bitwise-lexicographically-ordered keys."
   HOMEPAGE_URL "https://git.weaselab.dev/weaselab/conflict-set"
   LANGUAGES C CXX)
 set(CMAKE_CXX_STANDARD 20)
 
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/version.txt ${PROJECT_VERSION})
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/version.txt.in
+               ${CMAKE_CURRENT_SOURCE_DIR}/paper/version.txt)
+
 include(CMakePushCheckState)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFileCXX)
@@ -45,7 +49,8 @@ if(HAS_FULL_RELRO)
 endif()
 cmake_pop_check_state()
 
-set(version_script_flags LINKER:--version-script=${CMAKE_SOURCE_DIR}/linker.map)
+set(version_script_flags
+    LINKER:--version-script=${CMAKE_CURRENT_SOURCE_DIR}/linker.map)
 cmake_push_check_state()
 list(APPEND CMAKE_REQUIRED_LINK_OPTIONS ${version_script_flags})
 check_cxx_source_compiles("int main(){}" HAS_VERSION_SCRIPT FAIL_REGEX
@@ -57,7 +62,7 @@ option(USE_SIMD_FALLBACK
 
 # This is encouraged according to
 # https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq
-include_directories(SYSTEM ${CMAKE_SOURCE_DIR}/third_party/valgrind)
+include_directories(SYSTEM ${CMAKE_CURRENT_SOURCE_DIR}/third_party/valgrind)
 
 add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-Wno-invalid-offsetof>)
 
@@ -104,19 +109,20 @@ add_library(${PROJECT_NAME}-object OBJECT ConflictSet.cpp)
 target_compile_options(${PROJECT_NAME}-object PRIVATE -fno-exceptions
                                                       -fvisibility=hidden)
 target_include_directories(${PROJECT_NAME}-object
-                           PRIVATE ${CMAKE_SOURCE_DIR}/include)
+                           PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
 
 add_library(${PROJECT_NAME} SHARED $<TARGET_OBJECTS:${PROJECT_NAME}-object>)
 set_target_properties(
   ${PROJECT_NAME} PROPERTIES LIBRARY_OUTPUT_DIRECTORY
-                             "${CMAKE_BINARY_DIR}/radix_tree")
+                             "${CMAKE_CURRENT_BINARY_DIR}/radix_tree")
 if(NOT CMAKE_BUILD_TYPE STREQUAL Debug)
   set_target_properties(${PROJECT_NAME} PROPERTIES LINKER_LANGUAGE C)
 endif()
 
 if(HAS_VERSION_SCRIPT)
-  target_link_options(${PROJECT_NAME} PRIVATE
-                      LINKER:--version-script=${CMAKE_SOURCE_DIR}/linker.map)
+  target_link_options(
+    ${PROJECT_NAME} PRIVATE
+    LINKER:--version-script=${CMAKE_CURRENT_SOURCE_DIR}/linker.map)
 endif()
 
 add_library(${PROJECT_NAME}-static STATIC
@@ -128,8 +134,8 @@ endif()
 if(APPLE)
   add_custom_command(
     TARGET ${PROJECT_NAME}-static
-    PRE_BUILD
-    COMMAND ${CMAKE_SOURCE_DIR}/privatize_symbols_macos.sh
+    PRE_LINK
+    COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/privatize_symbols_macos.sh
             $<TARGET_OBJECTS:${PROJECT_NAME}-object>)
 else()
   add_custom_command(
@@ -137,21 +143,22 @@ else()
     POST_BUILD
     COMMAND
       ${CMAKE_OBJCOPY}
-      --keep-global-symbols=${CMAKE_SOURCE_DIR}/symbol-exports.txt
+      --keep-global-symbols=${CMAKE_CURRENT_SOURCE_DIR}/symbol-exports.txt
       $<TARGET_FILE:${PROJECT_NAME}-static> || echo
       "Proceeding with all symbols global in static library")
 endif()
 
-set(TEST_FLAGS -Wall -Wextra -Wunreachable-code -Wpedantic -UNDEBUG)
-
 include(CTest)
 
-if(BUILD_TESTING)
+# disable tests if this is being used through e.g. FetchContent
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
+
+  set(TEST_FLAGS -Wall -Wextra -Wunreachable-code -Wpedantic -UNDEBUG)
 
   # corpus tests, which are tests curated by libfuzzer. The goal is to get broad
   # coverage with a small number of tests.
 
-  file(GLOB CORPUS_TESTS ${CMAKE_SOURCE_DIR}/corpus/*)
+  file(GLOB CORPUS_TESTS ${CMAKE_CURRENT_SOURCE_DIR}/corpus/*)
 
   # extra testing that relies on shared libraries, which aren't available with
   # wasm
@@ -160,9 +167,11 @@ if(BUILD_TESTING)
     add_library(skip_list SHARED SkipList.cpp)
     target_compile_options(skip_list PRIVATE -fno-exceptions
                                              -fvisibility=hidden)
-    target_include_directories(skip_list PUBLIC ${CMAKE_SOURCE_DIR}/include)
-    set_target_properties(skip_list PROPERTIES LIBRARY_OUTPUT_DIRECTORY
-                                               "${CMAKE_BINARY_DIR}/skip_list")
+    target_include_directories(skip_list
+                               PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
+    set_target_properties(
+      skip_list PROPERTIES LIBRARY_OUTPUT_DIRECTORY
+                           "${CMAKE_CURRENT_BINARY_DIR}/skip_list")
     set_target_properties(skip_list PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
     set_target_properties(
       skip_list PROPERTIES VERSION ${PROJECT_VERSION} SOVERSION
@@ -173,10 +182,11 @@ if(BUILD_TESTING)
     add_library(hash_table SHARED HashTable.cpp)
     target_compile_options(hash_table PRIVATE -fno-exceptions
                                               -fvisibility=hidden)
-    target_include_directories(hash_table PUBLIC ${CMAKE_SOURCE_DIR}/include)
+    target_include_directories(hash_table
+                               PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
     set_target_properties(
       hash_table PROPERTIES LIBRARY_OUTPUT_DIRECTORY
-                            "${CMAKE_BINARY_DIR}/hash_table")
+                            "${CMAKE_CURRENT_BINARY_DIR}/hash_table")
     set_target_properties(hash_table PROPERTIES OUTPUT_NAME ${PROJECT_NAME})
     set_target_properties(
       hash_table PROPERTIES VERSION ${PROJECT_VERSION} SOVERSION
@@ -259,14 +269,26 @@ if(BUILD_TESTING)
 
   # scripted tests. Written manually to fill in anything libfuzzer couldn't
   # find.
-  add_executable(script_test ScriptTest.cpp)
-  target_compile_options(script_test PRIVATE ${TEST_FLAGS})
-  target_link_libraries(script_test PRIVATE ${PROJECT_NAME})
-  file(GLOB SCRIPT_TESTS ${CMAKE_SOURCE_DIR}/script_tests/*)
-  foreach(TEST ${SCRIPT_TESTS})
-    get_filename_component(name ${TEST} NAME)
-    add_test(NAME conflict_set_script_${name} COMMAND script_test ${TEST})
-  endforeach()
+  if(NOT CMAKE_CROSSCOMPILING)
+    find_package(Python3 REQUIRED COMPONENTS Interpreter)
+    set_property(
+      DIRECTORY
+      APPEND
+      PROPERTY CMAKE_CONFIGURE_DEPENDS
+               ${CMAKE_CURRENT_SOURCE_DIR}/test_conflict_set.py)
+    execute_process(
+      COMMAND ${Python3_EXECUTABLE}
+              ${CMAKE_CURRENT_SOURCE_DIR}/test_conflict_set.py list
+      OUTPUT_VARIABLE SCRIPT_TESTS)
+    foreach(TEST ${SCRIPT_TESTS})
+      add_test(
+        NAME script_test_${TEST}
+        COMMAND
+          ${Python3_EXECUTABLE}
+          ${CMAKE_CURRENT_SOURCE_DIR}/test_conflict_set.py test ${TEST}
+          --build-dir ${CMAKE_CURRENT_BINARY_DIR})
+    endforeach()
+  endif()
 
   find_program(VALGRIND_EXE valgrind)
   if(VALGRIND_EXE AND NOT CMAKE_CROSSCOMPILING)
@@ -298,25 +320,26 @@ if(BUILD_TESTING)
   # symbol visibility tests
   if(NOT WASM AND NOT CMAKE_BUILD_TYPE STREQUAL Debug)
     if(APPLE)
-      set(symbol_exports ${CMAKE_SOURCE_DIR}/apple-symbol-exports.txt)
-      set(symbol_imports ${CMAKE_SOURCE_DIR}/apple-symbol-imports.txt)
+      set(symbol_exports ${CMAKE_CURRENT_SOURCE_DIR}/apple-symbol-exports.txt)
+      set(symbol_imports ${CMAKE_CURRENT_SOURCE_DIR}/apple-symbol-imports.txt)
     else()
-      set(symbol_exports ${CMAKE_SOURCE_DIR}/symbol-exports.txt)
+      set(symbol_exports ${CMAKE_CURRENT_SOURCE_DIR}/symbol-exports.txt)
       if(CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64)
-        set(symbol_imports ${CMAKE_SOURCE_DIR}/aarch64-symbol-imports.txt)
+        set(symbol_imports
+            ${CMAKE_CURRENT_SOURCE_DIR}/aarch64-symbol-imports.txt)
       else()
-        set(symbol_imports ${CMAKE_SOURCE_DIR}/symbol-imports.txt)
+        set(symbol_imports ${CMAKE_CURRENT_SOURCE_DIR}/symbol-imports.txt)
       endif()
     endif()
     add_test(
       NAME conflict_set_shared_symbols
       COMMAND
-        ${CMAKE_SOURCE_DIR}/test_symbols.sh $<TARGET_FILE:${PROJECT_NAME}>
-        ${symbol_exports} ${symbol_imports})
+        ${CMAKE_CURRENT_SOURCE_DIR}/test_symbols.sh
+        $<TARGET_FILE:${PROJECT_NAME}> ${symbol_exports} ${symbol_imports})
     add_test(
       NAME conflict_set_static_symbols
       COMMAND
-        ${CMAKE_SOURCE_DIR}/test_symbols.sh
+        ${CMAKE_CURRENT_SOURCE_DIR}/test_symbols.sh
         $<TARGET_FILE:${PROJECT_NAME}-static> ${symbol_exports}
         ${symbol_imports})
   endif()
@@ -333,6 +356,7 @@ endif()
 # packaging
 
 set(CPACK_PACKAGE_CONTACT andrew@weaselab.dev)
+set(CMAKE_INSTALL_DEFAULT_COMPONENT_NAME all)
 
 set(CPACK_PACKAGE_VENDOR "Weaselab")
 set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/LICENSE")
@@ -353,6 +377,20 @@ else()
   set(CPACK_DEBIAN_PACKAGE_DEPENDS "libc6 (>= 2.14)")
 endif()
 
+# macos
+set(CMAKE_OSX_DEPLOYMENT_TARGET 11.0)
+if(APPLE)
+  find_program(PANDOC_EXE pandoc)
+  if(PANDOC_EXE)
+    execute_process(COMMAND ${PANDOC_EXE} ${CMAKE_CURRENT_SOURCE_DIR}/README.md
+                            -o ${CMAKE_CURRENT_BINARY_DIR}/README.txt)
+    set(CPACK_RESOURCE_FILE_README ${CMAKE_CURRENT_BINARY_DIR}/README.txt)
+  endif()
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/LICENSE
+                 ${CMAKE_CURRENT_BINARY_DIR}/LICENSE.txt COPYONLY)
+  set(CPACK_RESOURCE_FILE_LICENSE ${CMAKE_CURRENT_BINARY_DIR}/LICENSE.txt)
+endif()
+
 include(CPack)
 
 include(GNUInstallDirs)
@@ -377,8 +415,11 @@ install(
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
+
 install(DIRECTORY include/
         DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME})
 
 install(EXPORT ${PROJECT_NAME}Config
         DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake)
+
+cpack_add_component(all)

ConflictSet.cpp

@@ -294,6 +294,12 @@ struct Node48 : Node {
   int8_t nextFree;
   int8_t index[256];
   Child children[kMaxNodes];
+  uint8_t reverseIndex[kMaxNodes];
+  constexpr static int kMaxOfMaxPageSize = 8;
+  constexpr static int kMaxOfMaxShift =
+      std::countr_zero(uint32_t(kMaxOfMaxPageSize));
+  constexpr static int kMaxOfMaxTotalPages = kMaxNodes / kMaxOfMaxPageSize;
+  int64_t maxOfMax[kMaxOfMaxTotalPages];
 
   uint8_t *partialKey() { return (uint8_t *)(this + 1); }
 
@@ -308,6 +314,11 @@ struct Node256 : Node {
   constexpr static auto kType = Type_Node256;
   BitSet bitSet;
   Child children[256];
+  constexpr static int kMaxOfMaxPageSize = 8;
+  constexpr static int kMaxOfMaxShift =
+      std::countr_zero(uint32_t(kMaxOfMaxPageSize));
+  constexpr static int kMaxOfMaxTotalPages = 256 / kMaxOfMaxPageSize;
+  int64_t maxOfMax[kMaxOfMaxTotalPages];
   uint8_t *partialKey() { return (uint8_t *)(this + 1); }
   void copyChildrenAndKeyFrom(const Node48 &other);
   void copyChildrenAndKeyFrom(const Node256 &other);
@@ -405,6 +416,7 @@ inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
          kNodeCopySize);
   assert(numChildren == Node16::kMaxNodes);
   memset(index, -1, sizeof(index));
+  memset(children, 0, sizeof(children));
   memcpy(partialKey(), &other + 1, partialKeyLen);
   bitSet.init();
   nextFree = Node16::kMaxNodes;
@@ -415,6 +427,9 @@ inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
     children[i] = other.children[i];
     assert(children[i].child->parent == &other);
     children[i].child->parent = this;
+    reverseIndex[i] = x;
+    maxOfMax[i >> Node48::kMaxOfMaxShift] = std::max(
+        maxOfMax[i >> Node48::kMaxOfMaxShift], children[i].childMaxVersion);
     ++i;
   }
 }
@@ -422,13 +437,17 @@ inline void Node48::copyChildrenAndKeyFrom(const Node16 &other) {
 inline void Node48::copyChildrenAndKeyFrom(const Node48 &other) {
   memcpy((char *)this + kNodeCopyBegin, (char *)&other + kNodeCopyBegin,
          kNodeCopySize);
-  memcpy(&bitSet, &other.bitSet,
-         sizeof(*this) - sizeof(Node) - sizeof(children));
+  bitSet = other.bitSet;
+  nextFree = other.nextFree;
+  memcpy(index, other.index, sizeof(index));
+  memset(children, 0, sizeof(children));
   for (int i = 0; i < numChildren; ++i) {
     children[i] = other.children[i];
     assert(children[i].child->parent == &other);
     children[i].child->parent = this;
   }
+  memcpy(reverseIndex, other.reverseIndex, sizeof(reverseIndex));
+  memcpy(maxOfMax, other.maxOfMax, sizeof(maxOfMax));
   memcpy(partialKey(), &other + 1, partialKeyLen);
 }
 
@@ -436,6 +455,7 @@ inline void Node48::copyChildrenAndKeyFrom(const Node256 &other) {
   memcpy((char *)this + kNodeCopyBegin, (char *)&other + kNodeCopyBegin,
          kNodeCopySize);
   memset(index, -1, sizeof(index));
+  memset(children, 0, sizeof(children));
   nextFree = other.numChildren;
   bitSet = other.bitSet;
   int i = 0;
@@ -448,6 +468,9 @@ inline void Node48::copyChildrenAndKeyFrom(const Node256 &other) {
         children[i] = other.children[c];
         assert(children[i].child->parent == &other);
         children[i].child->parent = this;
+        reverseIndex[i] = c;
+        maxOfMax[i >> Node48::kMaxOfMaxShift] = std::max(
+            maxOfMax[i >> Node48::kMaxOfMaxShift], children[i].childMaxVersion);
         ++i;
       },
       0, 256);
@@ -457,13 +480,17 @@ inline void Node48::copyChildrenAndKeyFrom(const Node256 &other) {
 inline void Node256::copyChildrenAndKeyFrom(const Node48 &other) {
   memcpy((char *)this + kNodeCopyBegin, (char *)&other + kNodeCopyBegin,
          kNodeCopySize);
-  memset(children, 0, sizeof(children));
   bitSet = other.bitSet;
+  memset(children, 0, sizeof(children));
+  memset(maxOfMax, 0, sizeof(maxOfMax));
   bitSet.forEachInRange(
       [&](int c) {
         children[c] = other.children[other.index[c]];
         assert(children[c].child->parent == &other);
         children[c].child->parent = this;
+        maxOfMax[c >> Node256::kMaxOfMaxShift] =
+            std::max(maxOfMax[c >> Node256::kMaxOfMaxShift],
+                     children[c].childMaxVersion);
       },
       0, 256);
   memcpy(partialKey(), &other + 1, partialKeyLen);
@@ -481,6 +508,7 @@ inline void Node256::copyChildrenAndKeyFrom(const Node256 &other) {
         children[c].child->parent = this;
       },
       0, 256);
+  memcpy(maxOfMax, other.maxOfMax, sizeof(maxOfMax));
   memcpy(partialKey(), &other + 1, partialKeyLen);
 }
 
@@ -532,7 +560,7 @@ template <class T> struct BoundedFreeListAllocator {
   static_assert(std::derived_from<T, Node>);
   static_assert(std::is_trivial_v<T>);
 
-  T *allocate(int partialKeyCapacity) {
+  T *allocate_helper(int partialKeyCapacity) {
     if (freeList != nullptr) {
       T *n = (T *)freeList;
       VALGRIND_MAKE_MEM_DEFINED(freeList, sizeof(freeList));
@@ -560,6 +588,17 @@ template <class T> struct BoundedFreeListAllocator {
     return result;
   }
 
+  T *allocate(int partialKeyCapacity) {
+    T *result = allocate_helper(partialKeyCapacity);
+    if constexpr (!std::is_same_v<T, Node0>) {
+      memset(result->children, 0, sizeof(result->children));
+    }
+    if constexpr (std::is_same_v<T, Node48> || std::is_same_v<T, Node256>) {
+      memset(result->maxOfMax, 0, sizeof(result->maxOfMax));
+    }
+    return result;
+  }
+
   void release(T *p) {
     if (freeListBytes >= kFreeListMaxMemory) {
       removeNode(p);
@@ -732,8 +771,9 @@ Node *&getChildExists(Node *self, uint8_t index) {
   }
 }
 
-// Precondition - an entry for index must exist in the node
-int64_t &maxVersion(Node *n, ConflictSet::Impl *);
+int64_t maxVersion(Node *n, ConflictSet::Impl *);
+
+void setMaxVersion(Node *n, ConflictSet::Impl *, int64_t maxVersion);
 
 Node *&getInTree(Node *n, ConflictSet::Impl *);
 
@@ -770,7 +810,7 @@ template <class NodeT> int getChildGeqSimd(NodeT *self, int child) {
 
   // cachegrind says the plain loop is fewer instructions and more mis-predicted
   // branches. Microbenchmark says plain loop is faster. It's written in this
-  // weird "generic" way though in case someday we can use the simd
+  // weird "generic" way though so that someday we can use the simd
   // implementation easily if we want.
   if constexpr (std::is_same_v<NodeT, Node3>) {
     Node3 *n = (Node3 *)self;
@@ -1025,6 +1065,7 @@ Node *&getOrCreateChild(Node *&self, uint8_t index,
     assert(self48->nextFree < 48);
     int nextFree = self48->nextFree++;
     self48->index[index] = nextFree;
+    self48->reverseIndex[nextFree] = index;
     auto &result = self48->children[nextFree].child;
     result = nullptr;
     return result;
@@ -1146,8 +1187,14 @@ void freeAndMakeCapacityAtLeast(Node *&self, int capacity,
 // capacity.
 void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
                            ConflictSet::Impl *impl) {
+
   const int maxCapacity =
       (self->numChildren + int(self->entryPresent)) * (self->partialKeyLen + 1);
+#if DEBUG_VERBOSE && !defined(NDEBUG)
+  fprintf(stderr, "maybeDecreaseCapacity: current: %d, max: %d, key: %s\n",
+          self->getCapacity(), maxCapacity,
+          getSearchPathPrintable(self).c_str());
+#endif
   if (self->getCapacity() <= maxCapacity) {
     return;
   }
@@ -1204,7 +1251,7 @@ void maybeDownsize(Node *self, NodeAllocators *allocators,
 
       // Max versions are stored in the parent, so we need to update it now
       // that we have a new parent.
-      maxVersion(child, impl) = childMaxVersion;
+      setMaxVersion(child, impl, childMaxVersion);
 
       getInTree(self, impl) = child;
       allocators->node3.release(self3);
@@ -1318,9 +1365,12 @@ Node *erase(Node *self, NodeAllocators *allocators, ConflictSet::Impl *impl,
     if (toRemoveChildrenIndex != lastChildrenIndex) {
       parent48->children[toRemoveChildrenIndex] =
           parent48->children[lastChildrenIndex];
-      parent48->index[parent48->children[toRemoveChildrenIndex]
-                          .child->parentsIndex] = toRemoveChildrenIndex;
+      auto parentIndex =
+          parent48->children[toRemoveChildrenIndex].child->parentsIndex;
+      parent48->index[parentIndex] = toRemoveChildrenIndex;
+      parent48->reverseIndex[toRemoveChildrenIndex] = parentIndex;
     }
+    parent48->children[lastChildrenIndex].childMaxVersion = 0;
 
     --parent->numChildren;
 
@@ -1615,75 +1665,113 @@ downLeftSpine:
   }
 }
 
-// Return the max version among all keys starting with the search path of n +
-// [child], where child in (begin, end). Does not account for the range version
-// of firstGt(searchpath(n) + [end - 1])
-int64_t maxBetweenExclusive(Node *n, int begin, int end) {
+// Return whether or not the max version among all keys starting with the search
+// path of n + [child], where child in (begin, end) is <= readVersion. Does not
+// account for the range version of firstGt(searchpath(n) + [end - 1])
+bool checkMaxBetweenExclusive(Node *n, int begin, int end,
+                              int64_t readVersion) {
   assume(-1 <= begin);
   assume(begin <= 256);
   assume(-1 <= end);
   assume(end <= 256);
   assume(begin < end);
-  int64_t result = std::numeric_limits<int64_t>::lowest();
   {
     int c = getChildGeq(n, begin + 1);
     if (c >= 0 && c < end) {
       auto *child = getChildExists(n, c);
       if (child->entryPresent) {
-        result = std::max(result, child->entry.rangeVersion);
+        if (!(child->entry.rangeVersion <= readVersion)) {
+          return false;
+        };
       }
       begin = c;
     } else {
-      return result;
+      return true;
     }
   }
+
+  // [begin, end) is now the half-open interval of children we're interested in.
+
+  const unsigned shiftUpperBound = end - begin;
+  const unsigned shiftAmount = begin;
+  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };
+
   switch (n->getType()) {
   case Type_Node0: // GCOVR_EXCL_LINE
     // We would have returned above, after not finding a child
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   case Type_Node3: {
     auto *self = static_cast<Node3 *>(n);
-    for (int i = 0; i < self->numChildren && self->index[i] < end; ++i) {
-      if (begin <= self->index[i]) {
-        result = std::max(result, self->children[i].childMaxVersion);
-      }
+    bool result = true;
+    for (int i = 0; i < 3; ++i) {
+      result &= !((self->children[i].childMaxVersion > readVersion) &
+                  inBounds(self->index[i]));
     }
+    return result;
   } break;
   case Type_Node16: {
     auto *self = static_cast<Node16 *>(n);
-    for (int i = 0; i < self->numChildren && self->index[i] < end; ++i) {
-      if (begin <= self->index[i]) {
-        result = std::max(result, self->children[i].childMaxVersion);
-      }
+    bool result = true;
+    for (int i = 0; i < 16; ++i) {
+      result &= !((self->children[i].childMaxVersion > readVersion) &
+                  inBounds(self->index[i]));
     }
+    return result;
   } break;
   case Type_Node48: {
     auto *self = static_cast<Node48 *>(n);
-    self->bitSet.forEachInRange(
-        [&](int i) {
-          result =
-              std::max(result, self->children[self->index[i]].childMaxVersion);
-        },
-        begin, end);
-    break;
+    // Check all pages
+    bool result = true;
+    for (int i = 0; i < Node48::kMaxOfMaxTotalPages; ++i) {
+      if (self->maxOfMax[i] > readVersion) {
+        for (int j = 0; j < Node48::kMaxOfMaxPageSize; ++j) {
+          int k = (i << Node48::kMaxOfMaxShift) + j;
+          result &= !(self->children[k].childMaxVersion > readVersion &&
+                      inBounds(self->reverseIndex[k]));
+        }
+      }
+    }
+    return result;
   }
   case Type_Node256: {
     auto *self = static_cast<Node256 *>(n);
-    self->bitSet.forEachInRange(
-        [&](int i) {
-          result = std::max(result, self->children[i].childMaxVersion);
-        },
-        begin, end);
-    break;
+    // Check the first page
+    if (self->maxOfMax[begin >> Node256::kMaxOfMaxShift] > readVersion) {
+      bool result = true;
+      for (int i = 0; i < Node256::kMaxOfMaxPageSize; ++i) {
+        int j = (begin & ~(Node256::kMaxOfMaxPageSize - 1)) + i;
+        result &=
+            !((self->children[j].childMaxVersion > readVersion) & inBounds(j));
+      }
+      if (!result) {
+        return result;
+      }
+    }
+    // Check the last page
+    if (end >= 1 &&
+        self->maxOfMax[(end - 1) >> Node256::kMaxOfMaxShift] > readVersion) {
+      bool result = true;
+      for (int i = 0; i < Node256::kMaxOfMaxPageSize; ++i) {
+        int j = ((end - 1) & ~(Node256::kMaxOfMaxPageSize - 1)) + i;
+        result &=
+            !((self->children[j].childMaxVersion > readVersion) & inBounds(j));
+      }
+      if (!result) {
+        return result;
+      }
+    }
+    // Check inner pages
+    bool result = true;
+    for (int i = (begin >> Node256::kMaxOfMaxShift) + 1;
+         i < ((end - 1) >> Node256::kMaxOfMaxShift); ++i) {
+      result &= self->maxOfMax[i] <= readVersion;
+    }
+    return result;
   }
   default:                   // GCOVR_EXCL_LINE
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   }
-#if DEBUG_VERBOSE && !defined(NDEBUG)
-  fprintf(stderr, "At `%s', max version in (%02x, %02x) is %" PRId64 "\n",
-          getSearchPathPrintable(n).c_str(), begin, end, result);
-#endif
-  return result;
+  return true;
 }
 
 Vector<uint8_t> getSearchPath(Arena &arena, Node *n) {
@@ -1716,7 +1804,7 @@ bool checkRangeStartsWith(Node *n, std::span<const uint8_t> key, int begin,
 #endif
   auto remaining = key;
   if (remaining.size() == 0) {
-    return maxBetweenExclusive(n, begin, end) <= readVersion;
+    return checkMaxBetweenExclusive(n, begin, end, readVersion);
   }
 
   auto *child = getChild(n, remaining[0]);
@@ -1815,7 +1903,7 @@ struct CheckRangeLeftSide {
       }
 
       if (searchPathLen >= prefixLen) {
-        if (maxBetweenExclusive(n, remaining[0], 256) > readVersion) {
+        if (!checkMaxBetweenExclusive(n, remaining[0], 256, readVersion)) {
           ok = false;
           return true;
         }
@@ -1957,7 +2045,7 @@ struct CheckRangeRightSide {
           return true;
         }
 
-        if (maxBetweenExclusive(n, -1, remaining[0]) > readVersion) {
+        if (!checkMaxBetweenExclusive(n, -1, remaining[0], readVersion)) {
           ok = false;
           return true;
         }
@@ -2168,7 +2256,7 @@ template <bool kBegin>
                          allocators) = old;
         old->parent = *self;
         old->parentsIndex = old->partialKey()[partialKeyIndex];
-        maxVersion(old, impl) = oldMaxVersion;
+        setMaxVersion(old, impl, oldMaxVersion);
 
         memmove(old->partialKey(), old->partialKey() + partialKeyIndex + 1,
                 old->partialKeyLen - (partialKeyIndex + 1));
@@ -2192,9 +2280,8 @@ template <bool kBegin>
     }
 
     if constexpr (kBegin) {
-      auto &m = maxVersion(*self, impl);
-      assert(writeVersion >= m);
-      m = writeVersion;
+      assert(maxVersion(*self, impl) <= writeVersion);
+      setMaxVersion(*self, impl, writeVersion);
     }
 
     if (key.size() == 0) {
@@ -2202,9 +2289,8 @@ template <bool kBegin>
     }
 
     if constexpr (!kBegin) {
-      auto &m = maxVersion(*self, impl);
-      assert(writeVersion >= m);
-      m = writeVersion;
+      assert(maxVersion(*self, impl) <= writeVersion);
+      setMaxVersion(*self, impl, writeVersion);
     }
 
     auto &child = getOrCreateChild(*self, key.front(), allocators);
@@ -2215,8 +2301,7 @@ template <bool kBegin>
       child->partialKeyLen = 0;
       child->parent = *self;
       child->parentsIndex = key.front();
-      maxVersion(child, impl) =
-          kBegin ? writeVersion : std::numeric_limits<int64_t>::lowest();
+      setMaxVersion(child, impl, kBegin ? writeVersion : 0);
     }
 
     self = &child;
@@ -2261,7 +2346,7 @@ void addPointWrite(Node *&root, int64_t oldestVersion,
     n->entryPresent = true;
 
     n->entry.pointVersion = writeVersion;
-    maxVersion(n, impl) = writeVersion;
+    setMaxVersion(n, impl, writeVersion);
     n->entry.rangeVersion =
         p != nullptr ? p->entry.rangeVersion : oldestVersion;
   } else {
@@ -2302,9 +2387,8 @@ void addWriteRange(Node *&root, int64_t oldestVersion,
       break;
     }
 
-    auto &m = maxVersion(n, impl);
-    assert(writeVersion >= m);
-    m = writeVersion;
+    assert(maxVersion(n, impl) <= writeVersion);
+    setMaxVersion(n, impl, writeVersion);
 
     remaining = remaining.subspan(n->partialKeyLen + 1,
                                   remaining.size() - (n->partialKeyLen + 1));
@@ -2331,11 +2415,10 @@ void addWriteRange(Node *&root, int64_t oldestVersion,
     beginNode->entry.rangeVersion =
         p != nullptr ? p->entry.rangeVersion : oldestVersion;
     beginNode->entry.pointVersion = writeVersion;
-    maxVersion(beginNode, impl) = writeVersion;
+    assert(maxVersion(beginNode, impl) <= writeVersion);
+    setMaxVersion(beginNode, impl, writeVersion);
   }
-  auto &m = maxVersion(beginNode, impl);
-  assert(writeVersion >= m);
-  m = writeVersion;
+  setMaxVersion(beginNode, impl, writeVersion);
   assert(writeVersion >= beginNode->entry.pointVersion);
   beginNode->entry.pointVersion = writeVersion;
 
@@ -2350,8 +2433,8 @@ void addWriteRange(Node *&root, int64_t oldestVersion,
     auto *p = nextLogical(endNode);
     endNode->entry.pointVersion =
         p != nullptr ? p->entry.rangeVersion : oldestVersion;
-    auto &m = maxVersion(endNode, impl);
-    m = std::max(m, endNode->entry.pointVersion);
+    auto m = maxVersion(endNode, impl);
+    setMaxVersion(endNode, impl, std::max(m, endNode->entry.pointVersion));
   }
   endNode->entry.rangeVersion = writeVersion;
 
@@ -2389,7 +2472,11 @@ Iterator firstGeq(Node *n, const std::span<const uint8_t> key) {
       } else {
         n = nextSibling(n);
         if (n == nullptr) {
-          return {nullptr, 1};
+          //  This line is genuinely unreachable from any entry point of the
+          //  final library, since we can't remove a key without introducing a
+          //  key after it, and the only production caller of firstGeq is for
+          //  resuming the setOldestVersion scan.
+          return {nullptr, 1}; // GCOVR_EXCL_LINE
         }
         goto downLeftSpine;
       }
@@ -2510,6 +2597,10 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   }
 
   explicit Impl(int64_t oldestVersion) : oldestVersion(oldestVersion) {
+#if DEBUG_VERBOSE
+    fprintf(stderr, "radix_tree: create\n");
+#endif
+
     // Insert ""
     root = allocators.node0.allocate(0);
     root->numChildren = 0;
@@ -2524,7 +2615,12 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     root->entry.pointVersion = oldestVersion;
     root->entry.rangeVersion = oldestVersion;
   }
-  ~Impl() { destroyTree(root); }
+  ~Impl() {
+#if DEBUG_VERBOSE
+    fprintf(stderr, "radix_tree: destroy\n");
+#endif
+    destroyTree(root);
+  }
 
   NodeAllocators allocators;
 
@@ -2538,8 +2634,7 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   int64_t totalBytes = 0;
 };
 
-// Precondition - an entry for index must exist in the node
-int64_t &maxVersion(Node *n, ConflictSet::Impl *impl) {
+int64_t maxVersion(Node *n, ConflictSet::Impl *impl) {
   int index = n->parentsIndex;
   n = n->parent;
   if (n == nullptr) {
@@ -2573,22 +2668,65 @@ int64_t &maxVersion(Node *n, ConflictSet::Impl *impl) {
   }
 }
 
+void setMaxVersion(Node *n, ConflictSet::Impl *impl, int64_t newMax) {
+  int index = n->parentsIndex;
+  n = n->parent;
+  if (n == nullptr) {
+    impl->rootMaxVersion = newMax;
+    return;
+  }
+  switch (n->getType()) {
+  case Type_Node0:           // GCOVR_EXCL_LINE
+    __builtin_unreachable(); // GCOVR_EXCL_LINE
+  case Type_Node3: {
+    auto *n3 = static_cast<Node3 *>(n);
+    int i = getNodeIndex(n3, index);
+    n3->children[i].childMaxVersion = newMax;
+    return;
+  }
+  case Type_Node16: {
+    auto *n16 = static_cast<Node16 *>(n);
+    int i = getNodeIndex(n16, index);
+    n16->children[i].childMaxVersion = newMax;
+    return;
+  }
+  case Type_Node48: {
+    auto *n48 = static_cast<Node48 *>(n);
+    assert(n48->bitSet.test(index));
+    int i = n48->index[index];
+    n48->children[i].childMaxVersion = newMax;
+    n48->maxOfMax[i >> Node48::kMaxOfMaxShift] =
+        std::max(n48->maxOfMax[i >> Node48::kMaxOfMaxShift], newMax);
+    return;
+  }
+  case Type_Node256: {
+    auto *n256 = static_cast<Node256 *>(n);
+    assert(n256->bitSet.test(index));
+    n256->children[index].childMaxVersion = newMax;
+    n256->maxOfMax[index >> Node256::kMaxOfMaxShift] =
+        std::max(n256->maxOfMax[index >> Node256::kMaxOfMaxShift], newMax);
+    return;
+  }
+  default:                   // GCOVR_EXCL_LINE
+    __builtin_unreachable(); // GCOVR_EXCL_LINE
+  }
+}
+
 Node *&getInTree(Node *n, ConflictSet::Impl *impl) {
   return n->parent == nullptr ? impl->root
                               : getChildExists(n->parent, n->parentsIndex);
 }
 
-// ==================== END IMPLEMENTATION ====================
+// Internal entry points. Public entry points should just delegate to these
 
-// GCOVR_EXCL_START
-
-void ConflictSet::check(const ReadRange *reads, Result *results,
-                        int count) const {
-  return impl->check(reads, results, count);
+void internal_check(ConflictSet::Impl *impl,
+                    const ConflictSet::ReadRange *reads,
+                    ConflictSet::Result *results, int count) {
+  impl->check(reads, results, count);
 }
-
-void ConflictSet::addWrites(const WriteRange *writes, int count,
-                            int64_t writeVersion) {
+void internal_addWrites(ConflictSet::Impl *impl,
+                        const ConflictSet::WriteRange *writes, int count,
+                        int64_t writeVersion) {
   mallocBytesDelta = 0;
   impl->addWrites(writes, count, writeVersion);
   impl->totalBytes += mallocBytesDelta;
@@ -2599,7 +2737,7 @@ void ConflictSet::addWrites(const WriteRange *writes, int count,
 #endif
 }
 
-void ConflictSet::setOldestVersion(int64_t oldestVersion) {
+void internal_setOldestVersion(ConflictSet::Impl *impl, int64_t oldestVersion) {
   mallocBytesDelta = 0;
   impl->setOldestVersion(oldestVersion);
   impl->totalBytes += mallocBytesDelta;
@@ -2609,19 +2747,47 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
   }
 #endif
 }
+ConflictSet::Impl *internal_create(int64_t oldestVersion) {
+  mallocBytesDelta = 0;
+  auto *result = new (safe_malloc(sizeof(ConflictSet::Impl)))
+      ConflictSet::Impl{oldestVersion};
+  result->totalBytes += mallocBytesDelta;
+  return result;
+}
 
-int64_t ConflictSet::getBytes() const { return impl->totalBytes; }
+void internal_destroy(ConflictSet::Impl *impl) {
+  impl->~Impl();
+  safe_free(impl, sizeof(ConflictSet::Impl));
+}
+
+int64_t internal_getBytes(ConflictSet::Impl *impl) { return impl->totalBytes; }
+
+// ==================== END IMPLEMENTATION ====================
+
+// GCOVR_EXCL_START
+
+void ConflictSet::check(const ReadRange *reads, Result *results,
+                        int count) const {
+  internal_check(impl, reads, results, count);
+}
+
+void ConflictSet::addWrites(const WriteRange *writes, int count,
+                            int64_t writeVersion) {
+  internal_addWrites(impl, writes, count, writeVersion);
+}
+
+void ConflictSet::setOldestVersion(int64_t oldestVersion) {
+  internal_setOldestVersion(impl, oldestVersion);
+}
+
+int64_t ConflictSet::getBytes() const { return internal_getBytes(impl); }
 
 ConflictSet::ConflictSet(int64_t oldestVersion)
-    : impl((mallocBytesDelta = 0,
-            new(safe_malloc(sizeof(Impl))) Impl{oldestVersion})) {
-  impl->totalBytes += mallocBytesDelta;
-}
+    : impl(internal_create(oldestVersion)) {}
 
 ConflictSet::~ConflictSet() {
   if (impl) {
-    impl->~Impl();
-    safe_free(impl, sizeof(*impl));
+    internal_destroy(impl);
   }
 }
 
@@ -2642,40 +2808,27 @@ extern "C" {
 __attribute__((__visibility__("default"))) void
 ConflictSet_check(void *cs, const ConflictSet_ReadRange *reads,
                   ConflictSet_Result *results, int count) {
-  ((ConflictSet::Impl *)cs)->check(reads, results, count);
+  internal_check((ConflictSet::Impl *)cs, reads, results, count);
 }
 __attribute__((__visibility__("default"))) void
 ConflictSet_addWrites(void *cs, const ConflictSet_WriteRange *writes, int count,
                       int64_t writeVersion) {
-  auto *impl = ((ConflictSet::Impl *)cs);
-  mallocBytesDelta = 0;
-  impl->addWrites(writes, count, writeVersion);
-  impl->totalBytes += mallocBytesDelta;
+  internal_addWrites((ConflictSet::Impl *)cs, writes, count, writeVersion);
 }
 __attribute__((__visibility__("default"))) void
 ConflictSet_setOldestVersion(void *cs, int64_t oldestVersion) {
-  auto *impl = ((ConflictSet::Impl *)cs);
-  mallocBytesDelta = 0;
-  impl->setOldestVersion(oldestVersion);
-  impl->totalBytes += mallocBytesDelta;
+  internal_setOldestVersion((ConflictSet::Impl *)cs, oldestVersion);
 }
 __attribute__((__visibility__("default"))) void *
 ConflictSet_create(int64_t oldestVersion) {
-  mallocBytesDelta = 0;
-  auto *result = new (safe_malloc(sizeof(ConflictSet::Impl)))
-      ConflictSet::Impl{oldestVersion};
-  result->totalBytes += mallocBytesDelta;
-  return result;
+  return internal_create(oldestVersion);
 }
 __attribute__((__visibility__("default"))) void ConflictSet_destroy(void *cs) {
-  using Impl = ConflictSet::Impl;
-  ((Impl *)cs)->~Impl();
-  safe_free(cs, sizeof(Impl));
+  internal_destroy((ConflictSet::Impl *)cs);
 }
 __attribute__((__visibility__("default"))) int64_t
 ConflictSet_getBytes(void *cs) {
-  using Impl = ConflictSet::Impl;
-  return ((Impl *)cs)->totalBytes;
+  return internal_getBytes((ConflictSet::Impl *)cs);
 }
 }
 
@@ -2814,7 +2967,7 @@ Iterator firstGeq(Node *n, std::string_view key) {
 [[maybe_unused]] int64_t checkMaxVersion(Node *root, Node *node,
                                          int64_t oldestVersion, bool &success,
                                          ConflictSet::Impl *impl) {
-  int64_t expected = std::numeric_limits<int64_t>::lowest();
+  int64_t expected = 0;
   if (node->entryPresent) {
     expected = std::max(expected, node->entry.pointVersion);
   }
@@ -2911,10 +3064,6 @@ Iterator firstGeq(Node *n, std::string_view key) {
 
 } // namespace
 
-namespace std {
-void __throw_length_error(const char *) { __builtin_unreachable(); }
-} // namespace std
-
 #if SHOW_MEMORY
 
 int64_t nodeBytes = 0;
@@ -2995,6 +3144,7 @@ void removeKey(Node *n) {
 
 struct __attribute__((visibility("default"))) PeakPrinter {
   ~PeakPrinter() {
+    printf("--- radix_tree ---\n");
     printf("malloc bytes: %g\n", double(mallocBytes));
     printf("Peak malloc bytes: %g\n", double(peakMallocBytes));
     printf("Node bytes: %g\n", double(nodeBytes));

Internal.h

@@ -99,8 +99,7 @@ __attribute__((always_inline)) inline void safe_free(void *p, size_t s) {
   mallocBytesDelta -= s;
 #if SHOW_MEMORY
   mallocBytes -= s;
-  free(p);
-#else
+#endif
 #ifndef NDEBUG
   (char *&)p -= kMallocHeaderSize;
   size_t expected;
@@ -108,7 +107,6 @@ __attribute__((always_inline)) inline void safe_free(void *p, size_t s) {
   assert(s == expected);
 #endif
   free(p);
-#endif
 }
 
 // ==================== BEGIN ARENA IMPL ====================
@@ -257,10 +255,65 @@ template <class T> struct ArenaAlloc {
   void deallocate(T *, size_t) noexcept {}
 };
 
-template <class T> using Vector = std::vector<T, ArenaAlloc<T>>;
-template <class T> auto vector(Arena &arena) {
-  return Vector<T>(ArenaAlloc<T>(&arena));
-}
+template <class T> struct Vector {
+  static_assert(std::is_trivially_destructible_v<T>);
+  static_assert(std::is_trivially_copyable_v<T>);
+
+  explicit Vector(Arena *arena)
+      : arena(arena), t(nullptr), size_(0), capacity(0) {}
+
+  void append(std::span<const T> slice) {
+    if (size_ + int(slice.size()) > capacity) {
+      grow(std::max<int>(size_ + slice.size(), capacity * 2));
+    }
+    if (slice.size() > 0) {
+      memcpy(const_cast<std::remove_const_t<T> *>(t) + size_, slice.data(),
+             slice.size() * sizeof(T));
+    }
+    size_ += slice.size();
+  }
+
+  void push_back(const T &t) { append(std::span<const T>(&t, 1)); }
+
+  T *begin() { return t; }
+  T *end() { return t + size_; }
+  T *data() { return t; }
+  T &back() {
+    assert(size_ > 0);
+    return t[size_ - 1];
+  }
+  T &operator[](int i) {
+    assert(i >= 0 && i < size_);
+    return t[i];
+  }
+
+  void pop_back() {
+    assert(size_ > 0);
+    --size_;
+  }
+
+  int size() const { return size_; }
+
+  operator std::span<const T>() const { return std::span(t, size_); }
+
+private:
+  void grow(int newCapacity) {
+    capacity = newCapacity;
+    auto old = std::span<const T>(*this);
+    t = (T *)new (std::align_val_t(alignof(T)), *arena)
+        uint8_t[capacity * sizeof(T)];
+    size_ = 0;
+    append(old);
+  }
+
+  Arena *arena;
+  T *t;
+  int size_;
+  int capacity;
+};
+
+template <class T> auto vector(Arena &arena) { return Vector<T>(&arena); }
+
 template <class T, class C> using Set = std::set<T, C, ArenaAlloc<T>>;
 template <class T, class C = std::less<T>> auto set(Arena &arena) {
   return Set<T, C>(ArenaAlloc<T>(&arena));
@@ -525,15 +578,18 @@ template <class ConflictSetImpl> struct TestDriver {
   explicit TestDriver(const uint8_t *data, size_t size)
       : arbitrary({data, size}) {}
 
-  int64_t writeVersion = 0;
+  int64_t writeVersion = 100;
   int64_t oldestVersion = 0;
   ConflictSetImpl cs{oldestVersion};
   ReferenceImpl refImpl{oldestVersion};
 
-  constexpr static auto kMaxKeyLen = 8;
+  constexpr static auto kMaxKeySuffixLen = 8;
 
   bool ok = true;
 
+  const int prefixLen = arbitrary.bounded(512);
+  const int prefixByte = arbitrary.randT<uint8_t>();
+
   // Call until it returns true, for "done". Check internal invariants etc
   // between calls to next.
   bool next() {
@@ -544,7 +600,7 @@ template <class ConflictSetImpl> struct TestDriver {
     {
       int numPointWrites = arbitrary.bounded(100);
       int numRangeWrites = arbitrary.bounded(100);
-      int64_t v = ++writeVersion;
+      int64_t v = (writeVersion += arbitrary.bounded(10));
       auto *writes =
           new (arena) ConflictSet::WriteRange[numPointWrites + numRangeWrites];
       auto keys = set<std::string_view>(arena);
@@ -552,9 +608,10 @@ template <class ConflictSetImpl> struct TestDriver {
         if (!arbitrary.hasEntropy()) {
           return true;
         }
-        int keyLen = arbitrary.bounded(kMaxKeyLen);
+        int keyLen = prefixLen + arbitrary.bounded(kMaxKeySuffixLen);
         auto *begin = new (arena) uint8_t[keyLen];
-        arbitrary.randomBytes(begin, keyLen);
+        memset(begin, prefixByte, prefixLen);
+        arbitrary.randomBytes(begin + prefixLen, keyLen - prefixLen);
         keys.insert(std::string_view((const char *)begin, keyLen));
       }
 
@@ -603,8 +660,8 @@ template <class ConflictSetImpl> struct TestDriver {
 
       refImpl.addWrites(writes, numPointWrites + numRangeWrites, v);
 
-      oldestVersion = std::max<int64_t>(writeVersion - arbitrary.bounded(10),
-                                        oldestVersion);
+      oldestVersion =
+          std::min(writeVersion - 10, oldestVersion + arbitrary.bounded(10));
       cs.setOldestVersion(oldestVersion);
       refImpl.setOldestVersion(oldestVersion);
     }
@@ -619,9 +676,10 @@ template <class ConflictSetImpl> struct TestDriver {
         if (!arbitrary.hasEntropy()) {
           return true;
         }
-        int keyLen = arbitrary.bounded(kMaxKeyLen);
+        int keyLen = prefixLen + arbitrary.bounded(kMaxKeySuffixLen);
         auto *begin = new (arena) uint8_t[keyLen];
-        arbitrary.randomBytes(begin, keyLen);
+        memset(begin, prefixByte, prefixLen);
+        arbitrary.randomBytes(begin + prefixLen, keyLen - prefixLen);
         keys.insert(std::string_view((const char *)begin, keyLen));
       }
 

Jenkinsfile

@@ -111,6 +111,9 @@ pipeline {
                 gcovr -f ConflictSet.cpp --cobertura > build/coverage.xml
                 '''
                 cobertura autoUpdateHealth: false, autoUpdateStability: false, coberturaReportFile: 'build/coverage.xml', conditionalCoverageTargets: '70, 0, 0', failUnhealthy: false, failUnstable: false, lineCoverageTargets: '80, 0, 0', maxNumberOfBuilds: 0, methodCoverageTargets: '80, 0, 0', onlyStable: false, sourceEncoding: 'ASCII', zoomCoverageChart: false
+                sh '''
+                gcovr -f ConflictSet.cpp --fail-under-line 100 > /dev/null
+                '''
             }
         }
     }

README.md

@@ -60,25 +60,27 @@ Performance counters:
 
 |               ns/op |                op/s |    err% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------:|:----------
-|              246.99 |        4,048,700.59 |    0.2% |      0.01 | `point reads`
-|              260.16 |        3,843,784.65 |    0.1% |      0.01 | `prefix reads`
-|              493.35 |        2,026,953.19 |    0.1% |      0.01 | `range reads`
-|              462.05 |        2,164,289.23 |    0.6% |      0.01 | `point writes`
-|              448.19 |        2,231,205.25 |    0.9% |      0.01 | `prefix writes`
-|              255.83 |        3,908,845.72 |    1.5% |      0.02 | `range writes`
-|              582.63 |        1,716,349.02 |    1.3% |      0.01 | `monotonic increasing point writes`
+|              256.89 |        3,892,784.92 |    0.3% |      0.01 | `point reads`
+|              272.90 |        3,664,395.04 |    0.2% |      0.01 | `prefix reads`
+|              507.22 |        1,971,549.50 |    0.7% |      0.01 | `range reads`
+|              452.66 |        2,209,181.91 |    0.5% |      0.01 | `point writes`
+|              438.09 |        2,282,619.96 |    0.4% |      0.01 | `prefix writes`
+|              253.33 |        3,947,420.36 |    2.5% |      0.02 | `range writes`
+|              574.07 |        1,741,936.71 |    0.3% |      0.01 | `monotonic increasing point writes`
+|          151,562.50 |            6,597.94 |    1.5% |      0.01 | `worst case for radix tree`
 
 ## Radix tree (this implementation)
 
 |               ns/op |                op/s |    err% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------:|:----------
-|               19.42 |       51,483,206.67 |    0.3% |      0.01 | `point reads`
-|               58.43 |       17,115,612.57 |    0.1% |      0.01 | `prefix reads`
-|              216.09 |        4,627,766.60 |    0.2% |      0.01 | `range reads`
-|               28.35 |       35,267,567.72 |    0.2% |      0.01 | `point writes`
-|               43.43 |       23,026,226.17 |    0.2% |      0.01 | `prefix writes`
+|               19.83 |       50,420,955.28 |    0.1% |      0.01 | `point reads`
+|               55.95 |       17,872,542.40 |    0.5% |      0.01 | `prefix reads`
+|               88.28 |       11,327,709.50 |    0.4% |      0.01 | `range reads`
+|               29.15 |       34,309,531.64 |    0.5% |      0.01 | `point writes`
+|               42.36 |       23,607,424.27 |    1.1% |      0.01 | `prefix writes`
 |               50.00 |       20,000,000.00 |    0.0% |      0.01 | `range writes`
-|               92.38 |       10,824,863.69 |    4.1% |      0.01 | `monotonic increasing point writes`
+|               93.52 |       10,692,413.79 |    3.3% |      0.01 | `monotonic increasing point writes`
+|        2,388,417.00 |              418.69 |    0.4% |      0.03 | `worst case for radix tree`
 
 # "Real data" test
 

ScriptTest.cpp

@@ -1,155 +0,0 @@
-#include "Internal.h"
-#include <ConflictSet.h>
-
-#include <chrono>
-#include <cstring>
-#include <fcntl.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-#include <unistd.h>
-#include <vector>
-
-inline size_t getPageSize() {
-  static size_t kPageSize = sysconf(_SC_PAGESIZE);
-  return kPageSize;
-}
-
-/// Helper for rounding up to page size (or some other alignment)
-constexpr inline size_t rightAlign(size_t offset, size_t alignment) {
-  return offset % alignment == 0 ? offset
-                                 : ((offset / alignment) + 1) * alignment;
-}
-
-using StringView = std::basic_string_view<uint8_t>;
-
-inline StringView operator"" _v(const char *str, size_t size) {
-  return {reinterpret_cast<const uint8_t *>(str), size};
-}
-
-int main(int argc, const char **argv) {
-
-  ConflictSet cs{0};
-  ReferenceImpl ref{0};
-
-  for (int i = 1; i < argc; ++i) {
-    int fd = open(argv[i], O_RDONLY);
-    struct stat st;
-    if (fstat(fd, &st) == -1) {
-      int err = errno;
-      fprintf(stderr, "stat error %s - %s\n", argv[i], strerror(err));
-      fflush(stderr);
-      abort();
-    }
-
-    int64_t size = rightAlign(st.st_size, getPageSize());
-    const uint8_t *begin =
-        (uint8_t *)mmap(0, size, PROT_READ, MAP_PRIVATE, fd, 0);
-    madvise((void *)begin, size, MADV_SEQUENTIAL);
-    auto *const mapOriginal = begin;
-    const auto sizeOriginal = size;
-
-    StringView b;
-    StringView e;
-    int64_t v = 0;
-    int64_t lastWriteVersion = 0;
-    int64_t lastOldestVersion = 0;
-    std::vector<ConflictSet::WriteRange> writeRanges;
-    std::vector<ConflictSet::ReadRange> readRanges;
-    std::vector<ConflictSet::Result> results;
-
-    for (uint8_t *end = (uint8_t *)memchr(begin, '\n', size); end != nullptr;) {
-      StringView line{begin, static_cast<size_t>(end - begin)};
-      size -= end - begin + 1;
-      begin = end + 1;
-      end = (uint8_t *)memchr(begin, '\n', size);
-
-      if (line.starts_with("begin"_v)) {
-        b = line.substr("begin "_v.size(), line.size());
-        printf("b <- %.*s\n", int(b.size()), b.data());
-      } else if (line.starts_with("end"_v)) {
-        e = line.substr("end "_v.size(), line.size());
-        printf("e <- %.*s\n", int(e.size()), e.data());
-      } else if (line.starts_with("version"_v)) {
-        line = line.substr("version "_v.size(), line.size());
-        v = 0;
-        for (auto c : line) {
-          v = v * 10 + int(c) - int('0');
-        }
-        printf("v <- %" PRId64 "\n", v);
-      } else if (line.starts_with("pointread"_v)) {
-        printf("pointread\n");
-        ConflictSet::ReadRange r;
-        r.begin.p = b.data();
-        r.begin.len = b.size();
-        r.end.len = 0;
-        r.readVersion = v;
-        readRanges.push_back(r);
-      } else if (line.starts_with("pointwrite"_v)) {
-        printf("pointwrite\n");
-        assert(writeRanges.empty() ||
-               (writeRanges.back().end.len == 0 ? writeRanges.back().begin
-                                                : writeRanges.back().end) < b);
-        ConflictSet::WriteRange w;
-        w.begin.p = b.data();
-        w.begin.len = b.size();
-        w.end.len = 0;
-        writeRanges.push_back(w);
-      } else if (line.starts_with("rangeread"_v)) {
-        printf("rangeread\n");
-        ConflictSet::ReadRange r;
-        r.begin.p = b.data();
-        r.begin.len = b.size();
-        r.end.p = e.data();
-        r.end.len = e.size();
-        r.readVersion = v;
-        readRanges.push_back(r);
-      } else if (line.starts_with("rangewrite"_v)) {
-        printf("rangewrite\n");
-        assert(b < e);
-        assert(writeRanges.empty() ||
-               (writeRanges.back().end.len == 0 ? writeRanges.back().begin
-                                                : writeRanges.back().end) < b);
-        ConflictSet::WriteRange w;
-        w.begin.p = b.data();
-        w.begin.len = b.size();
-        w.end.p = e.data();
-        w.end.len = e.size();
-        writeRanges.push_back(w);
-      } else if (line.starts_with("check"_v)) {
-        printf("check\n");
-        Arena arena;
-        auto *expected = new (arena) ConflictSet::Result[readRanges.size()];
-        auto *actual = new (arena) ConflictSet::Result[readRanges.size()];
-        ref.check(readRanges.data(), expected, readRanges.size());
-        cs.check(readRanges.data(), actual, readRanges.size());
-        for (int i = 0; i < int(readRanges.size()); ++i) {
-          if (expected[i] != actual[i]) {
-            fprintf(stderr, "Expected %s, got %s at index %d\n",
-                    resultToStr(expected[i]), resultToStr(actual[i]), i);
-            return 1;
-          }
-        }
-        readRanges = {};
-      } else if (line.starts_with("addwrites"_v)) {
-        printf("addwrites\n");
-        assert(v > lastWriteVersion);
-        lastWriteVersion = v;
-        cs.addWrites(writeRanges.data(), writeRanges.size(), v);
-        ref.addWrites(writeRanges.data(), writeRanges.size(), v);
-        writeRanges = {};
-      } else if (line.starts_with("setoldest"_v)) {
-        printf("setoldest\n");
-        assert(v > lastOldestVersion);
-        lastOldestVersion = v;
-        cs.setOldestVersion(v);
-        ref.setOldestVersion(v);
-      } else if (line.empty() || line.starts_with(";"_v)) {
-        // skip
-      } else {
-        printf("Unrecognized line: %.*s\n", int(line.size()), line.data());
-      }
-    }
-    munmap((void *)mapOriginal, sizeOriginal);
-    close(fd);
-  }
-}

SkipList.cpp

@@ -16,6 +16,8 @@
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
+ *
+ * This source code is modified to compile outside of FoundationDB
  */
 
 #include "ConflictSet.h"
@@ -268,13 +270,21 @@ public:
   }
 
   explicit SkipList(Version version = 0) {
+#if DEBUG_VERBOSE
+    fprintf(stderr, "skip_list: create\n");
+#endif
     header = Node::create(StringRef(), MaxLevels - 1);
     for (int l = 0; l < MaxLevels; l++) {
       header->setNext(l, nullptr);
       header->setMaxVersion(l, version);
     }
   }
-  ~SkipList() { destroy(); }
+  ~SkipList() {
+#if DEBUG_VERBOSE
+    fprintf(stderr, "skip_list: destroy\n");
+#endif
+    destroy();
+  }
   SkipList(SkipList &&other) noexcept : header(other.header) {
     other.header = nullptr;
   }
@@ -603,6 +613,10 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     for (int s = stripes - 1; s >= 0; s--) {
       for (int i = 0; i * 2 < ss; ++i) {
         const auto &w = writes[s * stripeSize / 2 + i];
+#if DEBUG_VERBOSE
+        printf("Write begin: %s\n", printable(w.begin).c_str());
+        fflush(stdout);
+#endif
         values[i * 2] = {w.begin.p, size_t(w.begin.len)};
         values[i * 2 + 1] = w.end.len > 0
                                 ? StringRef{w.end.p, size_t(w.end.len)}
@@ -637,13 +651,16 @@ private:
   SkipList skipList;
 };
 
-void ConflictSet::check(const ReadRange *reads, Result *results,
-                        int count) const {
+// Internal entry points. Public entry points should just delegate to these
+
+void internal_check(ConflictSet::Impl *impl,
+                    const ConflictSet::ReadRange *reads,
+                    ConflictSet::Result *results, int count) {
   impl->check(reads, results, count);
 }
-
-void ConflictSet::addWrites(const WriteRange *writes, int count,
-                            int64_t writeVersion) {
+void internal_addWrites(ConflictSet::Impl *impl,
+                        const ConflictSet::WriteRange *writes, int count,
+                        int64_t writeVersion) {
   mallocBytesDelta = 0;
   impl->addWrites(writes, count, writeVersion);
   impl->totalBytes += mallocBytesDelta;
@@ -654,7 +671,7 @@ void ConflictSet::addWrites(const WriteRange *writes, int count,
 #endif
 }
 
-void ConflictSet::setOldestVersion(int64_t oldestVersion) {
+void internal_setOldestVersion(ConflictSet::Impl *impl, int64_t oldestVersion) {
   mallocBytesDelta = 0;
   impl->setOldestVersion(oldestVersion);
   impl->totalBytes += mallocBytesDelta;
@@ -664,19 +681,43 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
   }
 #endif
 }
+ConflictSet::Impl *internal_create(int64_t oldestVersion) {
+  mallocBytesDelta = 0;
+  auto *result = new (safe_malloc(sizeof(ConflictSet::Impl)))
+      ConflictSet::Impl{oldestVersion};
+  result->totalBytes += mallocBytesDelta;
+  return result;
+}
 
-int64_t ConflictSet::getBytes() const { return impl->totalBytes; }
+void internal_destroy(ConflictSet::Impl *impl) {
+  impl->~Impl();
+  safe_free(impl, sizeof(ConflictSet::Impl));
+}
+
+int64_t internal_getBytes(ConflictSet::Impl *impl) { return impl->totalBytes; }
+
+void ConflictSet::check(const ReadRange *reads, Result *results,
+                        int count) const {
+  internal_check(impl, reads, results, count);
+}
+
+void ConflictSet::addWrites(const WriteRange *writes, int count,
+                            int64_t writeVersion) {
+  internal_addWrites(impl, writes, count, writeVersion);
+}
+
+void ConflictSet::setOldestVersion(int64_t oldestVersion) {
+  internal_setOldestVersion(impl, oldestVersion);
+}
+
+int64_t ConflictSet::getBytes() const { return internal_getBytes(impl); }
 
 ConflictSet::ConflictSet(int64_t oldestVersion)
-    : impl((mallocBytesDelta = 0,
-            new(safe_malloc(sizeof(Impl))) Impl{oldestVersion})) {
-  impl->totalBytes += mallocBytesDelta;
-}
+    : impl(internal_create(oldestVersion)) {}
 
 ConflictSet::~ConflictSet() {
   if (impl) {
-    impl->~Impl();
-    safe_free(impl, sizeof(Impl));
+    internal_destroy(impl);
   }
 }
 
@@ -697,37 +738,34 @@ extern "C" {
 __attribute__((__visibility__("default"))) void
 ConflictSet_check(void *cs, const ConflictSet_ReadRange *reads,
                   ConflictSet_Result *results, int count) {
-  ((ConflictSet::Impl *)cs)->check(reads, results, count);
+  internal_check((ConflictSet::Impl *)cs, reads, results, count);
 }
 __attribute__((__visibility__("default"))) void
 ConflictSet_addWrites(void *cs, const ConflictSet_WriteRange *writes, int count,
                       int64_t writeVersion) {
-  ((ConflictSet::Impl *)cs)->addWrites(writes, count, writeVersion);
+  internal_addWrites((ConflictSet::Impl *)cs, writes, count, writeVersion);
 }
 __attribute__((__visibility__("default"))) void
 ConflictSet_setOldestVersion(void *cs, int64_t oldestVersion) {
-  ((ConflictSet::Impl *)cs)->setOldestVersion(oldestVersion);
+  internal_setOldestVersion((ConflictSet::Impl *)cs, oldestVersion);
 }
 __attribute__((__visibility__("default"))) void *
 ConflictSet_create(int64_t oldestVersion) {
-  return new (safe_malloc(sizeof(ConflictSet::Impl)))
-      ConflictSet::Impl{oldestVersion};
+  return internal_create(oldestVersion);
 }
 __attribute__((__visibility__("default"))) void ConflictSet_destroy(void *cs) {
-  using Impl = ConflictSet::Impl;
-  ((Impl *)cs)->~Impl();
-  safe_free(cs, sizeof(Impl));
+  internal_destroy((ConflictSet::Impl *)cs);
 }
 __attribute__((__visibility__("default"))) int64_t
 ConflictSet_getBytes(void *cs) {
-  using Impl = ConflictSet::Impl;
-  return ((Impl *)cs)->totalBytes;
+  return internal_getBytes((ConflictSet::Impl *)cs);
 }
 }
 
 #if SHOW_MEMORY
 struct __attribute__((visibility("default"))) PeakPrinter {
   ~PeakPrinter() {
+    printf("--- skip_list ---\n");
     printf("malloc bytes: %g\n", double(mallocBytes));
     printf("Peak malloc bytes: %g\n", double(peakMallocBytes));
   }

apple-symbol-imports.txt

@@ -1,7 +1,10 @@
+___stack_chk_fail
+___stack_chk_guard
 __tlv_bootstrap
 _abort
 _bzero
 _free
 _malloc
 _memcpy
-_memmove
+_memmove
+dyld_stub_binder

conflict_set.py

@@ -0,0 +1,138 @@
+import ctypes
+import enum
+import os
+
+from typing import Optional
+
+
+class _Key(ctypes.Structure):
+    _fields_ = [("p", ctypes.POINTER(ctypes.c_ubyte)), ("len", ctypes.c_int)]
+
+
+class ReadRange(ctypes.Structure):
+    _fields_ = [
+        ("begin", _Key),
+        ("end", _Key),
+        ("readVersion", ctypes.c_int64),
+    ]
+
+
+class WriteRange(ctypes.Structure):
+    _fields_ = [("begin", _Key), ("end", _Key)]
+
+
+class Result(enum.Enum):
+    COMMIT = 0
+    CONFLICT = 1
+    TOO_OLD = 2
+
+
+def write(begin: bytes, end: Optional[bytes] = None) -> WriteRange:
+    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
+
+    if end is None:
+        e = (ctypes.c_ubyte * 0)()
+    else:
+        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
+    return WriteRange(_Key(b, len(b)), _Key(e, len(e)))
+
+
+def read(version: int, begin: bytes, end: Optional[bytes] = None) -> ReadRange:
+    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
+    if end is None:
+        e = (ctypes.c_ubyte * 0)()
+    else:
+        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
+    return ReadRange(_Key(b, len(b)), _Key(e, len(e)), version)
+
+
+class ConflictSet:
+    def __init__(
+        self,
+        version: int = 0,
+        build_dir: Optional[str] = None,
+        implementation: Optional[str] = None,
+    ) -> None:
+        self._lib = None
+        if build_dir is None:
+            build_dir = os.path.dirname(__file__) + "/build"
+        if implementation is None:
+            implementation = "radix_tree"
+        for f in (
+            build_dir + "/" + implementation + "/libconflict-set.so.0",
+            os.path.dirname(__file__)
+            + "/build/"
+            + implementation
+            + "/libconflict-set.0.dylib",
+        ):
+            try:
+                self._lib = ctypes.cdll.LoadLibrary(f)
+            except:
+                pass
+
+        if self._lib is None:
+            import sys
+
+            print(
+                "Could not find libconflict-set implementation " + implementation,
+                file=sys.stderr,
+            )
+            sys.exit(1)
+
+        self._lib.ConflictSet_create.argtypes = (ctypes.c_int64,)
+        self._lib.ConflictSet_create.restype = ctypes.c_void_p
+
+        self._lib.ConflictSet_check.argtypes = (
+            ctypes.c_void_p,
+            ctypes.POINTER(ReadRange),
+            ctypes.POINTER(ctypes.c_int),
+            ctypes.c_int,
+        )
+
+        self._lib.ConflictSet_addWrites.argtypes = (
+            ctypes.c_void_p,
+            ctypes.POINTER(WriteRange),
+            ctypes.c_int,
+            ctypes.c_int64,
+        )
+
+        self._lib.ConflictSet_setOldestVersion.argtypes = (
+            ctypes.c_void_p,
+            ctypes.c_int64,
+        )
+
+        self._lib.ConflictSet_destroy.argtypes = (ctypes.c_void_p,)
+
+        self._lib.ConflictSet_getBytes.argtypes = (ctypes.c_void_p,)
+        self._lib.ConflictSet_getBytes.restype = ctypes.c_int64
+
+        self.p = self._lib.ConflictSet_create(version)
+
+    def addWrites(self, version: int, *writes: WriteRange):
+        self._lib.ConflictSet_addWrites(
+            self.p, (WriteRange * len(writes))(*writes), len(writes), version
+        )
+
+    def check(self, *reads: ReadRange) -> list[Result]:
+        r = (ctypes.c_int * len(reads))()
+        self._lib.ConflictSet_check(
+            self.p, (ReadRange * len(reads))(*reads), r, len(reads)
+        )
+        return [Result(x) for x in r]
+
+    def setOldestVersion(self, version: int) -> None:
+        self._lib.ConflictSet_setOldestVersion(self.p, version)
+
+    def getBytes(self) -> int:
+        return self._lib.ConflictSet_getBytes(self.p)
+
+    def __enter__(self):
+        return self
+
+    def close(self) -> None:
+        if self.p is not None:
+            self._lib.ConflictSet_destroy(self.p)
+            self.p = None
+
+    def __exit__(self, exception_type, exception_value, exception_traceback):
+        self.close()