Replace port_posix with port_stdcxx.

The porting layer implements threading primitives: atomic pointers,
condition variables, mutexes, thread-safe initialization. These are all
specified in C++11, so the reference open source port implementation can
become platform-independent.

The porting layer will remain in place to allow the use of other
implementations with more features, such as the built-in deadlock
detection in abseil's Mutex.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=193245934

CMakeLists.txt

@@ -79,33 +79,10 @@ if(BUILD_SHARED_LIBS)
   add_compile_options(-fvisibility=hidden)
 endif(BUILD_SHARED_LIBS)
 
-# POSIX code is specified separately so we can leave it out in the future.
-add_library(leveldb_port_posix OBJECT "")
-target_sources(leveldb_port_posix
-  PRIVATE
-    "${PROJECT_SOURCE_DIR}/port/port_posix.cc"
-
-  PUBLIC
-    # The headers below are dependencies for leveldb, but aren't needed by users
-    # that link to the installed version of leveldb and rely on its public API.
-    $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h>
-    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/port/atomic_pointer.h>
-    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/port/port_posix.h>
-    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/port/port.h>
-)
-if (NOT HAVE_CXX17_HAS_INCLUDE)
-  target_compile_definitions(leveldb_port_posix
-    PRIVATE
-      LEVELDB_HAS_PORT_CONFIG_H=1
-  )
-endif(NOT HAVE_CXX17_HAS_INCLUDE)
-if(BUILD_SHARED_LIBS)
-  set_property(TARGET leveldb_port_posix PROPERTY POSITION_INDEPENDENT_CODE ON)
-endif(BUILD_SHARED_LIBS)
-
 add_library(leveldb "")
 target_sources(leveldb
   PRIVATE
+    "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"
     "${PROJECT_SOURCE_DIR}/db/builder.cc"
     "${PROJECT_SOURCE_DIR}/db/builder.h"
     "${PROJECT_SOURCE_DIR}/db/c.cc"
@@ -136,6 +113,8 @@ target_sources(leveldb
     "${PROJECT_SOURCE_DIR}/db/version_set.h"
     "${PROJECT_SOURCE_DIR}/db/write_batch_internal.h"
     "${PROJECT_SOURCE_DIR}/db/write_batch.cc"
+    "${PROJECT_SOURCE_DIR}/port/atomic_pointer.h"
+    "${PROJECT_SOURCE_DIR}/port/port_stdcxx.h"
     "${PROJECT_SOURCE_DIR}/port/port.h"
     "${PROJECT_SOURCE_DIR}/port/thread_annotations.h"
     "${PROJECT_SOURCE_DIR}/table/block_builder.cc"
@@ -163,7 +142,6 @@ target_sources(leveldb
     "${PROJECT_SOURCE_DIR}/util/comparator.cc"
     "${PROJECT_SOURCE_DIR}/util/crc32c.cc"
     "${PROJECT_SOURCE_DIR}/util/crc32c.h"
-    "${PROJECT_SOURCE_DIR}/util/env_posix.cc"
     "${PROJECT_SOURCE_DIR}/util/env.cc"
     "${PROJECT_SOURCE_DIR}/util/filter_policy.cc"
     "${PROJECT_SOURCE_DIR}/util/hash.cc"
@@ -172,10 +150,8 @@ target_sources(leveldb
     "${PROJECT_SOURCE_DIR}/util/logging.h"
     "${PROJECT_SOURCE_DIR}/util/mutexlock.h"
     "${PROJECT_SOURCE_DIR}/util/options.cc"
-    "${PROJECT_SOURCE_DIR}/util/posix_logger.h"
     "${PROJECT_SOURCE_DIR}/util/random.h"
     "${PROJECT_SOURCE_DIR}/util/status.cc"
-    $<TARGET_OBJECTS:leveldb_port_posix>
 
   # Only CMake 3.3+ supports PUBLIC sources in targets exported by "install".
   $<$<VERSION_GREATER:CMAKE_VERSION,3.2>:PUBLIC>
@@ -195,12 +171,21 @@ target_sources(leveldb
     "${LEVELDB_PUBLIC_INCLUDE_DIR}/table.h"
     "${LEVELDB_PUBLIC_INCLUDE_DIR}/write_batch.h"
 )
+
+# POSIX code is specified separately so we can leave it out in the future.
+target_sources(leveldb
+  PRIVATE
+    "${PROJECT_SOURCE_DIR}/util/env_posix.cc"
+    "${PROJECT_SOURCE_DIR}/util/posix_logger.h"
+)
+
 # MemEnv is not part of the interface and could be pulled to a separate library.
 target_sources(leveldb
   PRIVATE
     "${PROJECT_SOURCE_DIR}/helpers/memenv/memenv.cc"
     "${PROJECT_SOURCE_DIR}/helpers/memenv/memenv.h"
 )
+
 target_include_directories(leveldb
   PUBLIC
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
@@ -234,11 +219,6 @@ if(HAVE_CLANG_THREAD_SAFETY)
       -Werror -Wthread-safety)
 endif(HAVE_CLANG_THREAD_SAFETY)
 
-# TODO(costan): This is only needed for port_posix.
-set(THREADS_PREFER_PTHREAD_FLAG ON)
-find_package(Threads REQUIRED)
-target_link_libraries(leveldb Threads::Threads)
-
 if(HAVE_CRC32C)
   target_link_libraries(leveldb crc32c)
 endif(HAVE_CRC32C)
@@ -249,6 +229,10 @@ if(HAVE_TCMALLOC)
   target_link_libraries(leveldb tcmalloc)
 endif(HAVE_TCMALLOC)
 
+# Needed by port_stdcxx.h
+find_package(Threads REQUIRED)
+target_link_libraries(leveldb Threads::Threads)
+
 add_executable(leveldbutil
   "${PROJECT_SOURCE_DIR}/db/leveldbutil.cc"
 )
@@ -271,14 +255,6 @@ if(LEVELDB_BUILD_TESTS)
 
         "${test_file}"
     )
-    if(BUILD_SHARED_LIBS)
-      # Port functions aren't exposed in the shared library build.
-      target_sources("${test_target_name}"
-        PRIVATE
-          $<TARGET_OBJECTS:leveldb_port_posix>
-      )
-    endif(BUILD_SHARED_LIBS)
-
     target_link_libraries("${test_target_name}" leveldb)
     target_compile_definitions("${test_target_name}"
       PRIVATE
@@ -351,14 +327,6 @@ if(LEVELDB_BUILD_BENCHMARKS)
 
         "${bench_file}"
     )
-    if(BUILD_SHARED_LIBS)
-      # Port functions aren't exposed in the shared library build.
-      target_sources("${bench_target_name}"
-        PRIVATE
-          $<TARGET_OBJECTS:leveldb_port_posix>
-      )
-    endif(BUILD_SHARED_LIBS)
-
     target_link_libraries("${bench_target_name}" leveldb)
     target_compile_definitions("${bench_target_name}"
       PRIVATE

port/README

@@ -5,6 +5,6 @@ Code in the rest of the package includes "port.h" from this directory.
 "port.h" in turn includes a platform specific "port_<platform>.h" file
 that provides the platform specific implementation.
 
-See port_posix.h for an example of what must be provided in a platform
+See port_stdcxx.h for an example of what must be provided in a platform
 specific header file.
 

port/port.h

@@ -11,7 +11,7 @@
 // porting to a new platform, see "port_example.h" for documentation
 // of what the new port_<platform>.h file must provide.
 #if defined(LEVELDB_PLATFORM_POSIX)
-#  include "port/port_posix.h"
+#  include "port/port_stdcxx.h"
 #elif defined(LEVELDB_PLATFORM_CHROMIUM)
 #  include "port/port_chromium.h"
 #endif

port/port_posix.h → port/port_stdcxx.h

@@ -1,11 +1,9 @@
-// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
-//
-// See port_example.h for documentation for the following types/functions.
 
-#ifndef STORAGE_LEVELDB_PORT_PORT_POSIX_H_
-#define STORAGE_LEVELDB_PORT_PORT_POSIX_H_
+#ifndef STORAGE_LEVELDB_PORT_PORT_STDCXX_H_
+#define STORAGE_LEVELDB_PORT_PORT_STDCXX_H_
 
 // port/port_config.h availability is automatically detected via __has_include
 // in newer compilers. If LEVELDB_HAS_PORT_CONFIG_H is defined, it overrides the
@@ -24,62 +22,75 @@
 
 #endif  // defined(LEVELDB_HAS_PORT_CONFIG_H)
 
-#include <pthread.h>
 #if HAVE_CRC32C
 #include <crc32c/crc32c.h>
 #endif  // HAVE_CRC32C
 #if HAVE_SNAPPY
 #include <snappy.h>
 #endif  // HAVE_SNAPPY
+
+#include <stddef.h>
 #include <stdint.h>
+#include <cassert>
+#include <condition_variable>  // NOLINT
+#include <mutex>               // NOLINT
 #include <string>
 #include "port/atomic_pointer.h"
 #include "port/thread_annotations.h"
 
-#if !HAVE_FDATASYNC
-#define fdatasync fsync
-#endif  // !HAVE_FDATASYNC
-
 namespace leveldb {
 namespace port {
 
 static const bool kLittleEndian = !LEVELDB_IS_BIG_ENDIAN;
 
 class CondVar;
 
+// Thinly wraps std::mutex.
 class LOCKABLE Mutex {
  public:
-  Mutex();
-  ~Mutex();
+  Mutex() = default;
+  ~Mutex() = default;
+
+  Mutex(const Mutex&) = delete;
+  Mutex& operator=(const Mutex&) = delete;
 
-  void Lock() EXCLUSIVE_LOCK_FUNCTION();
-  void Unlock() UNLOCK_FUNCTION();
+  void Lock() EXCLUSIVE_LOCK_FUNCTION() { mu_.lock(); }
+  void Unlock() UNLOCK_FUNCTION() { mu_.unlock(); }
   void AssertHeld() ASSERT_EXCLUSIVE_LOCK() { }
 
  private:
   friend class CondVar;
-  pthread_mutex_t mu_;
-
-  // No copying
-  Mutex(const Mutex&);
-  void operator=(const Mutex&);
+  std::mutex mu_;
 };
 
+// Thinly wraps std::condition_variable.
 class CondVar {
  public:
-  explicit CondVar(Mutex* mu);
-  ~CondVar();
-  void Wait();
-  void Signal();
-  void SignalAll();
+  explicit CondVar(Mutex* mu) : mu_(mu) { assert(mu != nullptr); }
+  ~CondVar() = default;
+
+  CondVar(const CondVar&) = delete;
+  CondVar& operator=(const CondVar&) = delete;
+
+  void Wait() {
+    std::unique_lock<std::mutex> lock(mu_->mu_, std::adopt_lock);
+    cv_.wait(lock);
+    lock.release();
+  }
+  void Signal() { cv_.notify_one(); }
+  void SignalAll() { cv_.notify_all(); }
  private:
-  pthread_cond_t cv_;
-  Mutex* mu_;
+  std::condition_variable cv_;
+  Mutex* const mu_;
 };
 
-typedef pthread_once_t OnceType;
-#define LEVELDB_ONCE_INIT PTHREAD_ONCE_INIT
-void InitOnce(OnceType* once, void (*initializer)());
+using OnceType = std::once_flag;
+#define LEVELDB_ONCE_INIT {}
+
+// Thinly wraps std::call_once.
+inline void InitOnce(OnceType* once, void (*initializer)()) {
+  std::call_once(*once, *initializer);
+}
 
 inline bool Snappy_Compress(const char* input, size_t length,
                             ::std::string* output) {
@@ -103,8 +114,7 @@ inline bool Snappy_GetUncompressedLength(const char* input, size_t length,
 #endif  // HAVE_SNAPPY
 }
 
-inline bool Snappy_Uncompress(const char* input, size_t length,
-                              char* output) {
+inline bool Snappy_Uncompress(const char* input, size_t length, char* output) {
 #if HAVE_SNAPPY
   return snappy::RawUncompress(input, length, output);
 #else
@@ -127,4 +137,4 @@ inline uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size) {
 }  // namespace port
 }  // namespace leveldb
 
-#endif  // STORAGE_LEVELDB_PORT_PORT_POSIX_H_
+#endif  // STORAGE_LEVELDB_PORT_PORT_STDCXX_H_

util/env_posix.cc

@@ -28,6 +28,12 @@
 #include "util/posix_logger.h"
 #include "util/env_posix_test_helper.h"
 
+// HAVE_FDATASYNC is defined in the auto-generated port_config.h, which is
+// included by port_stdcxx.h.
+#if !HAVE_FDATASYNC
+#define fdatasync fsync
+#endif  // !HAVE_FDATASYNC
+
 namespace leveldb {
 
 namespace {