Cloning a bunch of stuff from the native_client repository at r6528

ppapi/native_client/src/shared/ppapi_proxy/plugin_callback.h

Index: ppapi/native_client/src/shared/ppapi_proxy/plugin_callback.h
===================================================================
--- ppapi/native_client/src/shared/ppapi_proxy/plugin_callback.h	(revision 0)
+++ ppapi/native_client/src/shared/ppapi_proxy/plugin_callback.h	(revision 0)
@@ -0,0 +1,65 @@
+// Copyright (c) 2011 The Native Client Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PLUGIN_CALLBACK_H_
+#define NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PLUGIN_CALLBACK_H_
+
+#include <pthread.h>
+#include <map>
+#include "native_client/src/shared/ppapi_proxy/plugin_globals.h"
+#include "ppapi/c/pp_completion_callback.h"
+
+namespace ppapi_proxy {
+
+// Skips callback invocation and returns |result| if callback function is NULL
+// or PP_COMPLETIONCALLBACK_FLAG_OPTIONAL is set. Otherwise, schedules the
+// callback with |result| as an argument and returns PP_OK_COMPLETIONPENDING.
+int32_t MayForceCallback(PP_CompletionCallback callback, int32_t result);
+
+// Maintains a table of PP_CompletionCallback objects and their respective
+// identifiers that can be used to retrieve the objects.
+class CompletionCallbackTable {
+ public:
+  // Return a singleton instance.
+  static CompletionCallbackTable* Get() {
+    static CompletionCallbackTable table;
+    return &table;
+  }
+
+  // Adds the given |callback| and optionally the associated |read_buffer|,
+  // generating and returning an identifier for it.
+  // If |callback| is NULL, then returns 0.
+  int32_t AddCallback(const PP_CompletionCallback& callback);
+  int32_t AddCallback(const PP_CompletionCallback& callback, void* read_buffer);
+  // Removes and returns the callback and optionally the associated
+  // |read_buffer| corresponding to the given |callback_id|.
+  // If no callback is found, returns a NULL callback.
+  PP_CompletionCallback RemoveCallback(int32_t callback_id, void** read_buffer);
+
+ private:
+  // Currently implemented as singleton, so use a private constructor.
+  CompletionCallbackTable() : next_id_(1) { }
+  ~CompletionCallbackTable() { }
+
+  struct CallbackInfo {
+    PP_CompletionCallback callback;
+    void* read_buffer;  // To be used with callbacks invoked on byte reads.
+  };
+
+  typedef std::map<int32_t, CallbackInfo> CallbackTable;
+  CallbackTable table_;
+  int32_t next_id_;
+
+  // Single static mutex used as critical section for all callback tables.
+  static pthread_mutex_t mutex_;
+  class CallbackTableCriticalSection {
+   public:
+    CallbackTableCriticalSection() { pthread_mutex_lock(&mutex_); }
+    ~CallbackTableCriticalSection() { pthread_mutex_unlock(&mutex_); }
+  };
+};
+
+}  // namespace ppapi_proxy
+
+#endif  // NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PLUGIN_CALLBACK_H_