diff --git a/CMakeLists.txt b/CMakeLists.txt
index 88997295fa..48ee15e8a1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,7 +14,7 @@ HunterGate(
     SHA1 "1b94f895831f76e5a63e0537dd366ae142543c02"
 )
 
-project(leveldb VERSION 0.1.0 LANGUAGES C CXX)
+project(leveldb VERSION 1.20 LANGUAGES C CXX)
 
 option(LEVELDB_BUILD_TESTS "Build LevelDB's unit tests" ON)
 option(LEVELDB_BUILD_BENCHMARKS "Build LevelDB's benchmarks" ON)
@@ -42,6 +42,11 @@ if(LEVELDB_WITH_SNAPPY)
 endif()
 
 include(CheckSymbolExists)
+foreach(file_operation read write flush)
+  set(func "f${file_operation}_unlocked")
+  string(TOUPPER "HAVE_${func}" config_var)
+  check_symbol_exists("${func}" "unistd.h" ${config_var})
+endforeach()
 check_symbol_exists(fdatasync "unistd.h" HAVE_FDATASYNC)
 
 configure_file(
diff --git a/port/port_config.h.in b/port/port_config.h.in
index af27823911..b90894719a 100644
--- a/port/port_config.h.in
+++ b/port/port_config.h.in
@@ -5,10 +5,25 @@
 #ifndef STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
 #define STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
 
+// Define to 1 if you have a definition for fread_unlocked() in <unistd.h>.
+#if !defined(HAVE_FREAD_UNLOCKED)
+#cmakedefine01 HAVE_FREAD_UNLOCKED
+#endif  // !defined(HAVE_FREAD_UNLOCKED)
+
+// Define to 1 if you have a definition for fwrite_unlocked() in <unistd.h>.
+#if !defined(HAVE_FWRITE_UNLOCKED)
+#cmakedefine01 HAVE_FWRITE_UNLOCKED
+#endif  // !defined(HAVE_FWRITE_UNLOCKED)
+
+// Define to 1 if you have a definition for fflush_unlocked() in <unistd.h>.
+#if !defined(HAVE_FFLUSH_UNLOCKED)
+#cmakedefine01 HAVE_FFLUSH_UNLOCKED
+#endif  // !defined(HAVE_FFLUSH_UNLOCKED)
+
 // Define to 1 if you have a definition for fdatasync() in <unistd.h>.
-#if !defined(HAVE_FUNC_FDATASYNC)
-#cmakedefine01 HAVE_FUNC_FDATASYNC
-#endif  // !defined(HAVE_FUNC_FDATASYNC)
+#if !defined(HAVE_FDATASYNC)
+#cmakedefine01 HAVE_FDATASYNC
+#endif  // !defined(HAVE_FDATASYNC)
 
 // Define to 1 if you have Google CRC32C.
 #if !defined(HAVE_CRC32C)
diff --git a/port/port_posix.h b/port/port_posix.h
index cb6dae7c17..869567d371 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -41,6 +41,21 @@
 #define fdatasync fsync
 #endif  // !HAVE_FDATASYNC
 
+#if !HAVE_FREAD_UNLOCKED
+// Use fread() on platforms without fread_unlocked()
+#define fread_unlocked fread
+#endif  // !HAVE_FREAD_UNLOCKED
+
+#if !HAVE_FWRITE_UNLOCKED
+// Use fwrite() on platforms without fwrite_unlocked()
+#define fwrite_unlocked fwrite
+#endif  // !HAVE_FWRITE_UNLOCKED
+
+#if !HAVE_FFLUSH_UNLOCKED
+// Use fflush() on platforms without fflush_unlocked()
+#define fflush_unlocked fflush
+#endif  // !HAVE_FFLUSH_UNLOCKED
+
 namespace leveldb {
 namespace port {