mojo/system/core.h

// Copyright 2013 The Chromium 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 MOJO_SYSTEM_CORE_H_
#define MOJO_SYSTEM_CORE_H_

#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "mojo/system/handle_table.h"
#include "mojo/system/mapping_table.h"
#include "mojo/system/system_impl_export.h"

namespace mojo {
namespace system {

class Dispatcher;

// |Core| is an object that implements the Mojo system calls. All public methods
// are thread-safe.
class MOJO_SYSTEM_IMPL_EXPORT Core {
 public:
  // These methods are only to be used by via the embedder API.
  Core();
  virtual ~Core();
  MojoHandle AddDispatcher(const scoped_refptr<Dispatcher>& dispatcher);

  // System calls implementation.
  MojoTimeTicks GetTimeTicksNow();
  MojoResult Close(MojoHandle handle);
  MojoResult Wait(MojoHandle handle,
                  MojoWaitFlags flags,
                  MojoDeadline deadline);
  MojoResult WaitMany(const MojoHandle* handles,
                      const MojoWaitFlags* flags,
                      uint32_t num_handles,
                      MojoDeadline deadline);
  MojoResult CreateMessagePipe(
      MojoHandle* message_pipe_handle0,
      MojoHandle* message_pipe_handle1);
  MojoResult WriteMessage(MojoHandle message_pipe_handle,
                          const void* bytes,
                          uint32_t num_bytes,
                          const MojoHandle* handles,
                          uint32_t num_handles,
                          MojoWriteMessageFlags flags);
  MojoResult ReadMessage(MojoHandle message_pipe_handle,
                         void* bytes,
                         uint32_t* num_bytes,
                         MojoHandle* handles,
                         uint32_t* num_handles,
                         MojoReadMessageFlags flags);
  MojoResult CreateDataPipe(
      const MojoCreateDataPipeOptions* options,
      MojoHandle* data_pipe_producer_handle,
      MojoHandle* data_pipe_consumer_handle);
  MojoResult WriteData(MojoHandle data_pipe_producer_handle,
                       const void* elements,
                       uint32_t* num_bytes,
                       MojoWriteDataFlags flags);
  MojoResult BeginWriteData(MojoHandle data_pipe_producer_handle,
                            void** buffer,
                            uint32_t* buffer_num_bytes,
                            MojoWriteDataFlags flags);
  MojoResult EndWriteData(MojoHandle data_pipe_producer_handle,
                          uint32_t num_bytes_written);
  MojoResult ReadData(MojoHandle data_pipe_consumer_handle,
                      void* elements,
                      uint32_t* num_bytes,
                      MojoReadDataFlags flags);
  MojoResult BeginReadData(MojoHandle data_pipe_consumer_handle,
                           const void** buffer,
                           uint32_t* buffer_num_bytes,
                           MojoReadDataFlags flags);
  MojoResult EndReadData(MojoHandle data_pipe_consumer_handle,
                         uint32_t num_bytes_read);
  MojoResult CreateSharedBuffer(
      const MojoCreateSharedBufferOptions* options,
      uint64_t num_bytes,
      MojoHandle* shared_buffer_handle);
  MojoResult DuplicateBufferHandle(
      MojoHandle buffer_handle,
      const MojoDuplicateBufferHandleOptions* options,
      MojoHandle* new_buffer_handle);
  MojoResult MapBuffer(MojoHandle buffer_handle,
                       uint64_t offset,
                       uint64_t num_bytes,
                       void** buffer,
                       MojoMapBufferFlags flags);
  MojoResult UnmapBuffer(void* buffer);

 private:
  friend bool internal::ShutdownCheckNoLeaks(Core*);
  // The |busy| member is used only to deal with functions (in particular
  // |WriteMessage()|) that want to hold on to a dispatcher and later remove it
  // from the handle table, without holding on to the handle table lock.
  //
  // For example, if |WriteMessage()| is called with a handle to be sent, (under
  // the handle table lock) it must first check that that handle is not busy (if
  // it is busy, then it fails with |MOJO_RESULT_BUSY|) and then marks it as
  // busy. To avoid deadlock, it should also try to acquire the locks for all
  // the dispatchers for the handles that it is sending (and fail with
  // |MOJO_RESULT_BUSY| if the attempt fails). At this point, it can release the
  // handle table lock.
  //
  // If |Close()| is simultaneously called on that handle, it too checks if the
  // handle is marked busy. If it is, it fails (with |MOJO_RESULT_BUSY|). This
  // prevents |WriteMessage()| from sending a handle that has been closed (or
  // learning about this too late).
  struct HandleTableEntry {
    HandleTableEntry();
    explicit HandleTableEntry(const scoped_refptr<Dispatcher>& dispatcher);
    ~HandleTableEntry();

    scoped_refptr<Dispatcher> dispatcher;
    bool busy;
  };
  typedef base::hash_map<MojoHandle, HandleTableEntry> HandleTableMap;

  // Looks up the dispatcher for the given handle. Returns null if the handle is
  // invalid.
  scoped_refptr<Dispatcher> GetDispatcher(MojoHandle handle);

  // Internal implementation of |Wait()| and |WaitMany()|; doesn't do basic
  // validation of arguments.
  MojoResult WaitManyInternal(const MojoHandle* handles,
                              const MojoWaitFlags* flags,
                              uint32_t num_handles,
                              MojoDeadline deadline);

  // ---------------------------------------------------------------------------

  // TODO(vtl): |handle_table_lock_| should be a reader-writer lock (if only we
  // had them).
  base::Lock handle_table_lock_;  // Protects |handle_table_|.
  HandleTable handle_table_;

  base::Lock mapping_table_lock_;  // Protects |mapping_table_|.
  MappingTable mapping_table_;

  // ---------------------------------------------------------------------------

  DISALLOW_COPY_AND_ASSIGN(Core);
};

}  // namespace system
}  // namespace mojo

#endif  // MOJO_SYSTEM_CORE_H_