[mojo-edk] Expose portable API for platform handle wrapping

mojo/public/cpp/system/platform_handle.h

+// Copyright 2016 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.
+
+// This file provides a C++ wrapping around the Mojo C API for platform handles,
+// replacing the prefix of "Mojo" with a "mojo" namespace.
+//
+// Please see "mojo/public/c/system/buffer.h" for complete documentation of the

[Anand Mistry (off Chromium), 2016/05/23 07:16:53]

s/buffer/platform_handle

[Ken Rockot(use gerrit already), 2016/05/23 17:17:54]

done

+// API.
+
+#ifndef MOJO_PUBLIC_CPP_SYSTEM_PLATFORM_HANDLE_H_
+#define MOJO_PUBLIC_CPP_SYSTEM_PLATFORM_HANDLE_H_
+
+#include <stdint.h>
+
+#include "base/compiler_specific.h"
+#include "base/files/file.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/memory/shared_memory_handle.h"
+#include "base/process/process_handle.h"
+#include "mojo/public/c/system/platform_handle.h"
+#include "mojo/public/cpp/system/buffer.h"
+#include "mojo/public/cpp/system/handle.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+namespace mojo {
+
+#if defined(OS_POSIX)
+
+const MojoPlatformHandleType kPlatformFileHandleType =
+    MOJO_PLATFORM_HANDLE_TYPE_FILE_DESCRIPTOR;
+const base::PlatformFile kInvalidPlatformFile = -1;
+
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+const MojoPlatformHandleType kPlatformSharedBufferHandleType =
+    MOJO_PLATFORM_HANDLE_TYPE_MACH_PORT;
+#else
+const MojoPlatformHandleType kPlatformSharedBufferHandleType =
+    MOJO_PLATFORM_HANDLE_TYPE_FILE_DESCRIPTOR;
+#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
+
+#elif defined(OS_WIN)
+const MojoPlatformHandleType kPlatformFileHandleType =
+    MOJO_PLATFORM_HANDLE_TYPE_WINDOWS_HANDLE;
+const base::PlatformFile kInvalidPlatformFile = INVALID_HANDLE_VALUE;
+
+const MojoPlatformHandleType kPlatformSharedBufferHandleType =
+    MOJO_PLATFORM_HANDLE_TYPE_WINDOWS_HANDLE;
+#else
+#error Unsupported platform.

[Anand Mistry (off Chromium), 2016/05/23 07:16:53]

Hmmm. We don't support platforms that are non-posix and non-windows. Should we
even bother with this case? I'm pretty sure we don't consistently handle it.

[Ken Rockot(use gerrit already), 2016/05/23 17:17:54]

Fair point - removed all these

+#endif

[Anand Mistry (off Chromium), 2016/05/23 07:16:53]

#endif  // defined(OS_POSIX)

[Ken Rockot(use gerrit already), 2016/05/23 17:17:54]

done

+
+inline uint64_t PlatformHandleValueFromPlatformFile(base::PlatformFile file) {

[Anand Mistry (off Chromium), 2016/05/23 07:16:53]

Shouldn't these two be in an anonymous or internal namespace?

[Ken Rockot(use gerrit already), 2016/05/23 17:17:54]

Done

+#if defined(OS_WIN)
+  return reinterpret_cast<uint64_t>(file);
+#else
+  return static_cast<uint64_t>(file);
+#endif
+}
+
+inline base::PlatformFile PlatformFileFromPlatformHandleValue(uint64_t value) {
+#if defined(OS_WIN)
+  return reinterpret_cast<base::PlatformFile>(value);
+#else
+  return static_cast<base::PlatformFile>(value);
+#endif
+}
+
+// Wraps a PlatformFile as a Mojo handle. Takes ownership of the file object.
+inline ScopedHandle WrapPlatformFile(base::PlatformFile platform_file) {

[Anand Mistry (off Chromium), 2016/05/23 07:16:53]

These implementations are non-trivial and not performance sensitive. Please move
to a .cc file.

[Ken Rockot(use gerrit already), 2016/05/23 17:17:54]

Done

+  MojoPlatformHandle platform_handle;
+  platform_handle.struct_size = sizeof(MojoPlatformHandle);
+  platform_handle.type = kPlatformFileHandleType;
+  platform_handle.value = PlatformHandleValueFromPlatformFile(platform_file);
+
+  MojoHandle mojo_handle;
+  MojoResult result = MojoWrapPlatformHandle(&platform_handle, &mojo_handle);
+  CHECK_EQ(result, MOJO_RESULT_OK);
+
+  return ScopedHandle(Handle(mojo_handle));
+}
+
+// Unwraps a PlatformFile from a Mojo handle.
+inline MojoResult UnwrapPlatformFile(ScopedHandle handle,
+                                     base::PlatformFile* file) {
+  MojoPlatformHandle platform_handle;
+  platform_handle.struct_size = sizeof(MojoPlatformHandle);
+  MojoResult result = MojoUnwrapPlatformHandle(handle.release().value(),
+                                               &platform_handle);
+  if (result != MOJO_RESULT_OK)
+    return result;
+
+  if (platform_handle.type == MOJO_PLATFORM_HANDLE_TYPE_INVALID) {
+    *file = kInvalidPlatformFile;
+  } else {
+    CHECK_EQ(platform_handle.type, kPlatformFileHandleType);
+    *file = PlatformFileFromPlatformHandleValue(platform_handle.value);
+  }
+
+  return MOJO_RESULT_OK;
+}
+
+// Wraps a base::SharedMemoryHandle as a Mojo handle. Takes ownership of the
+// SharedMemoryHandle. Note that |read_only| is only an indicator of whether
+// |memory_handle| only supports read-only mapping. It does NOT have any
+// influence on the access control of the shared buffer object.
+inline ScopedSharedBufferHandle WrapSharedMemoryHandle(
+    const base::SharedMemoryHandle& memory_handle,
+    size_t size,
+    bool read_only) {
+  MojoPlatformHandle platform_handle;
+  platform_handle.struct_size = sizeof(MojoPlatformHandle);
+  platform_handle.type = kPlatformSharedBufferHandleType;
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  platform_handle.value =
+      static_cast<uint64_t>(memory_handle.GetMemoryObject());
+#elif defined(OS_POSIX)
+  platform_handle.value = PlatformHandleValueFromPlatformFile(memory_handle.fd);
+#elif defined(OS_WIN)
+  platform_handle.value =
+      PlatformHandleValueFromPlatformFile(memory_handle.GetHandle());
+#else
+#error Unsupported platform.
+#endif
+
+  MojoPlatformSharedBufferHandleFlags flags =
+      MOJO_PLATFORM_SHARED_BUFFER_HANDLE_FLAG_NONE;
+  if (read_only)
+    flags |= MOJO_PLATFORM_SHARED_BUFFER_HANDLE_FLAG_READ_ONLY;
+
+  MojoHandle mojo_handle;
+  MojoResult result = MojoWrapPlatformSharedBufferHandle(
+      &platform_handle, size, flags, &mojo_handle);
+  CHECK_EQ(result, MOJO_RESULT_OK);
+
+  return ScopedSharedBufferHandle(SharedBufferHandle(mojo_handle));
+}
+
+// Unwraps a base::SharedMemoryHandle from a Mojo handle. The caller assumes
+// responsibility for the lifetime of the SharedMemoryHandle.
+inline MojoResult UnwrapSharedMemoryHandle(
+    ScopedSharedBufferHandle handle,
+    base::SharedMemoryHandle* memory_handle,
+    size_t* size,
+    bool* read_only) {
+  MojoPlatformHandle platform_handle;
+  platform_handle.struct_size = sizeof(MojoPlatformHandle);
+
+  MojoPlatformSharedBufferHandleFlags flags;
+  size_t num_bytes;
+  MojoResult result = MojoUnwrapPlatformSharedBufferHandle(
+      handle.release().value(), &platform_handle, &num_bytes, &flags);
+  if (result != MOJO_RESULT_OK)
+    return result;
+
+  if (size)
+    *size = num_bytes;
+
+  if (read_only)
+    *read_only = flags & MOJO_PLATFORM_SHARED_BUFFER_HANDLE_FLAG_READ_ONLY;
+
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  CHECK_EQ(platform_handle.type, MOJO_PLATFORM_HANDLE_TYPE_MACH_PORT);
+  *memory_handle = base::SharedMemoryHandle(
+      static_cast<mach_port_t>(platform_handle.value), num_bytes,
+      base::GetCurrentProcId());
+#elif defined(OS_POSIX)
+  CHECK_EQ(platform_handle.type, MOJO_PLATFORM_HANDLE_TYPE_FILE_DESCRIPTOR);
+  *memory_handle = base::SharedMemoryHandle(
+      static_cast<int>(platform_handle.value), false);
+#elif defined(OS_WIN)
+  CHECK_EQ(platform_handle.type, MOJO_PLATFORM_HANDLE_TYPE_WINDOWS_HANDLE);
+  *memory_handle = base::SharedMemoryHandle(
+      reinterpret_cast<HANDLE>(platform_handle.value),
+      base::GetCurrentProcId());
+#else
+#error Unsupported platform.
+#endif
+
+  return MOJO_RESULT_OK;
+}
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_SYSTEM_PLATFORM_HANDLE_H_