Implement MojoGetBufferInformation(), part 1.

mojo/edk/system/shared_buffer_dispatcher.cc

 // 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.
 
 #include "mojo/edk/system/shared_buffer_dispatcher.h"
 
 #include <limits>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 214 matching lines @@
   MojoDuplicateBufferHandleOptions validated_options;
   MojoResult result = ValidateDuplicateOptions(options, &validated_options);
   if (result != MOJO_RESULT_OK)
     return result;
 
   // Note: Since this is "duplicate", we keep our ref to |shared_buffer_|.
   *new_dispatcher = CreateInternal(shared_buffer_.Clone());
   return MOJO_RESULT_OK;
 }
 
+MojoResult SharedBufferDispatcher::GetBufferInformationImplNoLock(
+    UserPointer<MojoBufferInformation> info,
+    uint32_t info_num_bytes) {
+  mutex().AssertHeld();
+
+  // Note: If/when |MojoBufferInformation| is extended beyond its initial
+  // definition, more work will be necessary. (See the definition of
+  // |MojoGetBufferInformation()| in mojo/public/c/system/buffer.h.)
+  static_assert(sizeof(MojoBufferInformation) == 16u,
+                "MojoBufferInformation has been extended!");
+
+  if (info_num_bytes < sizeof(MojoBufferInformation))
+    return MOJO_RESULT_INVALID_ARGUMENT;
+
+  MojoBufferInformation model_info = {
+      sizeof(MojoBufferInformation),                         // |struct_size|.
+      MOJO_BUFFER_INFORMATION_FLAG_NONE,                     // |flags|.
+      static_cast<uint64_t>(shared_buffer_->GetNumBytes()),  // |num_bytes|.
+  };
+  info.Put(model_info);
+  return MOJO_RESULT_OK;
+}
+
 MojoResult SharedBufferDispatcher::MapBufferImplNoLock(
     uint64_t offset,
     uint64_t num_bytes,
     MojoMapBufferFlags flags,
     std::unique_ptr<PlatformSharedBufferMapping>* mapping) {
   mutex().AssertHeld();
   DCHECK(shared_buffer_);
 
   if (offset > static_cast<uint64_t>(std::numeric_limits<size_t>::max()))
     return MOJO_RESULT_INVALID_ARGUMENT;
@@ skipping 48 matching lines @@
   platform_handles->push_back(std::move(platform_handle));
   *actual_size = sizeof(SerializedSharedBufferDispatcher);
 
   shared_buffer_ = nullptr;
 
   return true;
 }
 
 }  // namespace system
 }  // namespace mojo