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

4 files changed, 44 insertions, 87 deletions

diff --git a/port/README b/port/README
index 422563e..8b17153 100644
--- a/port/README
+++ b/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.
 
diff --git a/port/port.h b/port/port.h
index e667db4..0975fed 100644
--- a/port/port.h
+++ b/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
diff --git a/port/port_posix.cc b/port/port_posix.cc
deleted file mode 100644
index 04095bb..0000000
--- a/port/port_posix.cc
+++ /dev/null
@@ -1,53 +0,0 @@
-// Copyright (c) 2011 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.
-
-#include "port/port_posix.h"
-
-#include <cstdlib>
-#include <stdio.h>
-#include <string.h>
-
-namespace leveldb {
-namespace port {
-
-static void PthreadCall(const char* label, int result) {
-  if (result != 0) {
-    fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
-    abort();
-  }
-}
-
-Mutex::Mutex() { PthreadCall("init mutex", pthread_mutex_init(&mu_, nullptr)); }
-
-Mutex::~Mutex() { PthreadCall("destroy mutex", pthread_mutex_destroy(&mu_)); }
-
-void Mutex::Lock() { PthreadCall("lock", pthread_mutex_lock(&mu_)); }
-
-void Mutex::Unlock() { PthreadCall("unlock", pthread_mutex_unlock(&mu_)); }
-
-CondVar::CondVar(Mutex* mu)
-    : mu_(mu) {
-    PthreadCall("init cv", pthread_cond_init(&cv_, nullptr));
-}
-
-CondVar::~CondVar() { PthreadCall("destroy cv", pthread_cond_destroy(&cv_)); }
-
-void CondVar::Wait() {
-  PthreadCall("wait", pthread_cond_wait(&cv_, &mu_->mu_));
-}
-
-void CondVar::Signal() {
-  PthreadCall("signal", pthread_cond_signal(&cv_));
-}
-
-void CondVar::SignalAll() {
-  PthreadCall("broadcast", pthread_cond_broadcast(&cv_));
-}
-
-void InitOnce(OnceType* once, void (*initializer)()) {
-  PthreadCall("once", pthread_once(once, initializer));
-}
-
-}  // namespace port
-}  // namespace leveldb
diff --git a/port/port_posix.h b/port/port_stdcxx.h
index 54b07b6..4e58cba 100644
--- a/port/port_posix.h
+++ b/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
@@ -24,22 +22,22 @@
 
 #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 {
 
@@ -47,39 +45,52 @@ 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_