Use hash of key as priority. Vendor xxhash v0.8.2

CMakeLists.txt

@@ -63,10 +63,11 @@ add_subdirectory(third_party)
 add_executable(versioned_map_main VersionedMap.cpp)
 target_include_directories(versioned_map_main
                            PRIVATE ${CMAKE_SOURCE_DIR}/include)
-target_link_libraries(versioned_map_main PRIVATE nanobench)
+target_link_libraries(versioned_map_main PRIVATE nanobench xxhash)
 target_compile_definitions(versioned_map_main PRIVATE ENABLE_MAIN)
 
 add_library(versioned_map VersionedMap.cpp)
+target_link_libraries(versioned_map PRIVATE xxhash)
 target_compile_options(versioned_map PRIVATE -fno-exceptions)
 target_include_directories(versioned_map PUBLIC ${CMAKE_SOURCE_DIR}/include)
 set_target_properties(versioned_map PROPERTIES LINKER_LANGUAGE C)

VersionedMap.cpp

@@ -7,6 +7,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <unordered_set>
+#include <xxhash.h>
 
 void *mmapSafe(void *addr, size_t len, int prot, int flags, int fd,
                off_t offset) {
@@ -86,7 +87,7 @@ struct Entry {
     e->keyLen = keyLen;
     e->valLen = valLen;
     e->refCount = 1;
-    e->priority = rand(); // TODO
+    e->priority = XXH3_64bits(key, keyLen);
     e->clearTo = clearTo;
     memcpy((uint8_t *)e->getKey(), key, keyLen);
     ((uint8_t *)e->getKey())[keyLen] = 0;

third_party/CMakeLists.txt

@@ -1,3 +1,7 @@
 add_library(nanobench ${CMAKE_CURRENT_SOURCE_DIR}/nanobench.cpp)
-target_include_directories(nanobench
+target_include_directories(nanobench SYSTEM
                            PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include/nanobench)
+
+add_library(xxhash ${CMAKE_CURRENT_SOURCE_DIR}/xxhash.c)
+target_include_directories(xxhash SYSTEM
+                           PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include/xxhash)

third_party/xxhash.c

@@ -0,0 +1,43 @@
+/*
+ * xxHash - Extremely Fast Hash algorithm
+ * Copyright (C) 2012-2021 Yann Collet
+ *
+ * BSD 2-Clause License (https://www.opensource.org/licenses/bsd-license.php)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following disclaimer
+ *      in the documentation and/or other materials provided with the
+ *      distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * You can contact the author at:
+ *   - xxHash homepage: https://www.xxhash.com
+ *   - xxHash source repository: https://github.com/Cyan4973/xxHash
+ */
+
+
+/*
+ * xxhash.c instantiates functions defined in xxhash.h
+ */
+
+#define XXH_STATIC_LINKING_ONLY   /* access advanced declarations */
+#define XXH_IMPLEMENTATION   /* access definitions */
+
+#include "xxhash.h"