Revert of Mojo: Eliminate duplicate C API symbols

mojo/public/platform/native/system_thunks.h

Index: mojo/public/platform/native/system_thunks.h
diff --git a/mojo/public/platform/native/system_thunks.h b/mojo/public/platform/native/system_thunks.h
new file mode 100644
index 0000000000000000000000000000000000000000..f3b5e8a9d4fc9a4577c8f353300d2c64105efabc
--- /dev/null
+++ b/mojo/public/platform/native/system_thunks.h
@@ -0,0 +1,213 @@
+// Copyright 2014 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.
+
+// Note: This header should be compilable as C.
+
+#ifndef MOJO_PUBLIC_PLATFORM_NATIVE_SYSTEM_THUNKS_H_
+#define MOJO_PUBLIC_PLATFORM_NATIVE_SYSTEM_THUNKS_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "mojo/public/c/system/core.h"
+
+// The embedder needs to bind the basic Mojo Core functions of a DSO to those of
+// the embedder when loading a DSO that is dependent on mojo_system.
+// The typical usage would look like:
+// base::ScopedNativeLibrary app_library(
+//     base::LoadNativeLibrary(app_path_, &error));
+// typedef MojoResult (*MojoSetSystemThunksFn)(MojoSystemThunks*);
+// MojoSetSystemThunksFn mojo_set_system_thunks_fn =
+//     reinterpret_cast<MojoSetSystemThunksFn>(app_library.GetFunctionPointer(
+//         "MojoSetSystemThunks"));
+// MojoSystemThunks system_thunks = MojoMakeSystemThunks();
+// size_t expected_size = mojo_set_system_thunks_fn(&system_thunks);
+// if (expected_size > sizeof(MojoSystemThunks)) {
+//   LOG(ERROR)
+//       << "Invalid DSO. Expected MojoSystemThunks size: "
+//       << expected_size;
+//   break;
+// }
+
+// Structure used to bind the basic Mojo Core functions of a DSO to those of
+// the embedder.
+// This is the ABI between the embedder and the DSO. It can only have new
+// functions added to the end. No other changes are supported.
+#pragma pack(push, 8)
+struct MojoSystemThunks {
+  size_t size;  // Should be set to sizeof(MojoSystemThunks).
+  MojoTimeTicks (*GetTimeTicksNow)();
+  MojoResult (*Close)(MojoHandle handle);
+  MojoResult (*Wait)(MojoHandle handle,
+                     MojoHandleSignals signals,
+                     MojoDeadline deadline,
+                     struct MojoHandleSignalsState* signals_state);
+  MojoResult (*WaitMany)(const MojoHandle* handles,
+                         const MojoHandleSignals* signals,
+                         uint32_t num_handles,
+                         MojoDeadline deadline,
+                         uint32_t* result_index,
+                         struct MojoHandleSignalsState* signals_states);
+  MojoResult (*CreateMessagePipe)(
+      const struct MojoCreateMessagePipeOptions* options,
+      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 struct 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_elements,
+                          MojoWriteDataFlags flags);
+  MojoResult (*BeginWriteData)(MojoHandle data_pipe_producer_handle,
+                               void** buffer,
+                               uint32_t* buffer_num_elements,
+                               MojoWriteDataFlags flags);
+  MojoResult (*EndWriteData)(MojoHandle data_pipe_producer_handle,
+                             uint32_t num_elements_written);
+  MojoResult (*ReadData)(MojoHandle data_pipe_consumer_handle,
+                         void* elements,
+                         uint32_t* num_elements,
+                         MojoReadDataFlags flags);
+  MojoResult (*BeginReadData)(MojoHandle data_pipe_consumer_handle,
+                              const void** buffer,
+                              uint32_t* buffer_num_elements,
+                              MojoReadDataFlags flags);
+  MojoResult (*EndReadData)(MojoHandle data_pipe_consumer_handle,
+                            uint32_t num_elements_read);
+  MojoResult (*CreateSharedBuffer)(
+      const struct MojoCreateSharedBufferOptions* options,
+      uint64_t num_bytes,
+      MojoHandle* shared_buffer_handle);
+  MojoResult (*DuplicateBufferHandle)(
+      MojoHandle buffer_handle,
+      const struct 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);
+
+  MojoResult (*CreateWaitSet)(MojoHandle* wait_set);
+  MojoResult (*AddHandle)(MojoHandle wait_set,
+                          MojoHandle handle,
+                          MojoHandleSignals signals);
+  MojoResult (*RemoveHandle)(MojoHandle wait_set,
+                             MojoHandle handle);
+  MojoResult (*GetReadyHandles)(MojoHandle wait_set,
+                                uint32_t* count,
+                                MojoHandle* handles,
+                                MojoResult* results,
+                                struct MojoHandleSignalsState* signals_states);
+  MojoResult (*Watch)(MojoHandle handle,
+                      MojoHandleSignals signals,
+                      MojoWatchCallback callback,
+                      uintptr_t context);
+  MojoResult (*CancelWatch)(MojoHandle handle, uintptr_t context);
+  MojoResult (*FuseMessagePipes)(MojoHandle handle0, MojoHandle handle1);
+  MojoResult (*WriteMessageNew)(MojoHandle message_pipe_handle,
+                                MojoMessageHandle message,
+                                MojoWriteMessageFlags flags);
+  MojoResult (*ReadMessageNew)(MojoHandle message_pipe_handle,
+                               MojoMessageHandle* message,
+                               uint32_t* num_bytes,
+                               MojoHandle* handles,
+                               uint32_t* num_handles,
+                               MojoReadMessageFlags flags);
+  MojoResult (*AllocMessage)(uint32_t num_bytes,
+                             const MojoHandle* handles,
+                             uint32_t num_handles,
+                             MojoAllocMessageFlags flags,
+                             MojoMessageHandle* message);
+  MojoResult (*FreeMessage)(MojoMessageHandle message);
+  MojoResult (*GetMessageBuffer)(MojoMessageHandle message, void** buffer);
+  MojoResult (*WrapPlatformHandle)(
+      const struct MojoPlatformHandle* platform_handle,
+      MojoHandle* mojo_handle);
+  MojoResult (*UnwrapPlatformHandle)(
+      MojoHandle mojo_handle,
+      struct MojoPlatformHandle* platform_handle);
+  MojoResult (*WrapPlatformSharedBufferHandle)(
+      const struct MojoPlatformHandle* platform_handle,
+      size_t num_bytes,
+      MojoPlatformSharedBufferHandleFlags flags,
+      MojoHandle* mojo_handle);
+  MojoResult (*UnwrapPlatformSharedBufferHandle)(
+      MojoHandle mojo_handle,
+      struct MojoPlatformHandle* platform_handle,
+      size_t* num_bytes,
+      MojoPlatformSharedBufferHandleFlags* flags);
+};
+#pragma pack(pop)
+
+
+#ifdef __cplusplus
+// Intended to be called from the embedder. Returns a |MojoCore| initialized
+// to contain pointers to each of the embedder's MojoCore functions.
+inline MojoSystemThunks MojoMakeSystemThunks() {
+  MojoSystemThunks system_thunks = {sizeof(MojoSystemThunks),
+                                    MojoGetTimeTicksNow,
+                                    MojoClose,
+                                    MojoWait,
+                                    MojoWaitMany,
+                                    MojoCreateMessagePipe,
+                                    MojoWriteMessage,
+                                    MojoReadMessage,
+                                    MojoCreateDataPipe,
+                                    MojoWriteData,
+                                    MojoBeginWriteData,
+                                    MojoEndWriteData,
+                                    MojoReadData,
+                                    MojoBeginReadData,
+                                    MojoEndReadData,
+                                    MojoCreateSharedBuffer,
+                                    MojoDuplicateBufferHandle,
+                                    MojoMapBuffer,
+                                    MojoUnmapBuffer,
+                                    MojoCreateWaitSet,
+                                    MojoAddHandle,
+                                    MojoRemoveHandle,
+                                    MojoGetReadyHandles,
+                                    MojoWatch,
+                                    MojoCancelWatch,
+                                    MojoFuseMessagePipes,
+                                    MojoWriteMessageNew,
+                                    MojoReadMessageNew,
+                                    MojoAllocMessage,
+                                    MojoFreeMessage,
+                                    MojoGetMessageBuffer,
+                                    MojoWrapPlatformHandle,
+                                    MojoUnwrapPlatformHandle,
+                                    MojoWrapPlatformSharedBufferHandle,
+                                    MojoUnwrapPlatformSharedBufferHandle};
+  return system_thunks;
+}
+#endif
+
+
+// Use this type for the function found by dynamically discovering it in
+// a DSO linked with mojo_system. For example:
+// MojoSetSystemThunksFn mojo_set_system_thunks_fn =
+//     reinterpret_cast<MojoSetSystemThunksFn>(app_library.GetFunctionPointer(
+//         "MojoSetSystemThunks"));
+// The expected size of |system_thunks} is returned.
+// The contents of |system_thunks| are copied.
+typedef size_t (*MojoSetSystemThunksFn)(
+    const struct MojoSystemThunks* system_thunks);
+
+#endif  // MOJO_PUBLIC_PLATFORM_NATIVE_SYSTEM_THUNKS_H_