Simplify

Co-authored-by: Felipe Oliveira Carvalho <felipekde@gmail.com>

cpp/src/arrow/ipc/message.cc

@@ -625,28 +625,20 @@ class MessageDecoder::MessageDecoderImpl {
           case State::METADATA_LENGTH:
             RETURN_NOT_OK(ConsumeMetadataLengthData(data, next_required_size_));
             break;
-          case State::METADATA: {
-            // We need to copy metadata because it's used in
-            // ConsumeBody(). ConsumeBody() may be called from another
-            // ConsumeData(). We can't assume that the given data for
-            // the current ConsumeData() call is still valid in the
-            // next ConsumeData() call. So we need to copy metadata
-            // here.
-            ARROW_ASSIGN_OR_RAISE(std::shared_ptr<Buffer> buffer,
-                                  AllocateBuffer(next_required_size_, pool_));
-            memcpy(buffer->mutable_data(), data, next_required_size_);
-            RETURN_NOT_OK(ConsumeMetadataBuffer(buffer));
-          } break;
-          case State::BODY: {
+          case State::METADATA:
+            RETURN_NOT_OK(ConsumeMetadataBuffer(
+                std::make_shared<Buffer>(data, next_required_size_)));
+            break;
+          case State::BODY:
             // We don't need to copy the given data for body because
             // we can assume that a decoded record batch should be
             // valid only in a listener_->OnMessageDecoded() call. If
             // the passed message is needed to be valid after the
             // call, it's a listener_'s responsibility. The listener_
             // may copy the data for it.
-            auto buffer = std::make_shared<Buffer>(data, next_required_size_);
-            RETURN_NOT_OK(ConsumeBodyBuffer(buffer));
-          } break;
+            RETURN_NOT_OK(
+                ConsumeBodyBuffer(std::make_shared<Buffer>(data, next_required_size_)));
+            break;
           case State::EOS:
             return Status::OK();
         }
@@ -819,12 +811,13 @@ class MessageDecoder::MessageDecoderImpl {
   }
 
   Status ConsumeMetadataBuffer(const std::shared_ptr<Buffer>& buffer) {
-    if (buffer->is_cpu()) {
-      metadata_ = buffer;
-    } else {
-      ARROW_ASSIGN_OR_RAISE(metadata_,
-                            Buffer::ViewOrCopy(buffer, CPUDevice::memory_manager(pool_)));
-    }
+    // We need to copy metadata because it's used in
+    // ConsumeBody(). ConsumeBody() may be called from another
+    // ConsumeData(). We can't assume that the given data for the
+    // current ConsumeData() call is still valid in the next
+    // ConsumeData() call. So we need to copy metadata here.
+    ARROW_ASSIGN_OR_RAISE(metadata_,
+                          Buffer::ViewOrCopy(buffer, CPUDevice::memory_manager(pool_)));
     return ConsumeMetadata();
   }