Add portability support for PThread's TLS API

Summary:
This is the last piece needed to get Folly working on Windows without PThreads.
Updating Folly's test suite to support compiling without PThreads will come next.

Reviewed By: yfeldblum

Differential Revision: D4894048

fbshipit-source-id: 6076317e1364aef82a5d3cb306bea7c2226b3cdc

folly/Makefile.am

@@ -489,6 +489,7 @@ libfolly_la_SOURCES = \
 	portability/Malloc.cpp \
 	portability/Memory.cpp \
 	portability/OpenSSL.cpp \
+	portability/PThread.cpp \
 	portability/Sockets.cpp \
 	portability/Stdio.cpp \
 	portability/Stdlib.cpp \

folly/portability/PThread.cpp

+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.
+ */
+
+#include <folly/portability/PThread.h>
+
+#if !FOLLY_HAVE_PTHREAD && _WIN32
+#include <unordered_map>
+#include <utility>
+
+namespace folly {
+namespace portability {
+namespace pthread {
+static thread_local struct PThreadLocalMap {
+  PThreadLocalMap() = default;
+  ~PThreadLocalMap() {
+    for (auto kv : keyMap) {
+      // Call destruction callbacks if they exist.
+      if (kv.second.second != nullptr) {
+        kv.second.second(kv.second.first);
+      }
+    }
+  }
+
+  int createKey(pthread_key_t* key, void (*destructor)(void*)) {
+    auto ret = TlsAlloc();
+    if (ret == TLS_OUT_OF_INDEXES) {
+      return -1;
+    }
+    *key = ret;
+    keyMap.emplace(*key, std::make_pair(nullptr, destructor));
+    return 0;
+  }
+
+  int deleteKey(pthread_key_t key) {
+    if (!TlsFree(key)) {
+      return -1;
+    }
+    keyMap.erase(key);
+    return 0;
+  }
+
+  void* getKey(pthread_key_t key) {
+    return TlsGetValue(key);
+  }
+
+  int setKey(pthread_key_t key, void* value) {
+    if (!TlsSetValue(key, value)) {
+      return -1;
+    }
+    keyMap[key].first = value;
+    return 0;
+  }
+
+  std::unordered_map<pthread_key_t, std::pair<void*, void (*)(void*)>> keyMap{};
+} s_tls_key_map;
+
+int pthread_key_create(pthread_key_t* key, void (*destructor)(void*)) {
+  return s_tls_key_map.createKey(key, destructor);
+}
+
+int pthread_key_delete(pthread_key_t key) {
+  return s_tls_key_map.deleteKey(key);
+}
+
+void* pthread_getspecific(pthread_key_t key) {
+  return s_tls_key_map.getKey(key);
+}
+
+int pthread_setspecific(pthread_key_t key, const void* value) {
+  // Yes, the PThread API really is this bad -_-...
+  return s_tls_key_map.setKey(key, const_cast<void*>(value));
+}
+}
+}
+}
+#endif

folly/portability/PThread.h

@@ -16,6 +16,34 @@
 
 #pragma once
 
+#include <folly/portability/Config.h>
+
+#if !FOLLY_HAVE_PTHREAD
+
+#ifndef _WIN32
+#error Building Folly without pthreads is only supported on Windows.
+#endif
+
+#include <folly/portability/Windows.h>
+#include <cstdint>
+
+namespace folly {
+namespace portability {
+namespace pthread {
+using pthread_key_t = DWORD;
+
+int pthread_key_create(pthread_key_t* key, void (*destructor)(void*));
+int pthread_key_delete(pthread_key_t key);
+void* pthread_getspecific(pthread_key_t key);
+int pthread_setspecific(pthread_key_t key, const void* value);
+}
+}
+}
+
+/* using override */ using namespace folly::portability::pthread;
+
+#else
+
 #include <pthread.h>
 
 #ifdef _WIN32
@@ -95,3 +123,4 @@ struct hash<pthread_t> {
 };
 }
 #endif
+#endif