Break large blobs into multiple ipcs during creation.

content/common/webblob_messages.h

 // Copyright (c) 2011 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.
 
 // IPC messages for HTML5 Blob.
 // Multiply-included message file, hence no include guard.
 
 #include "content/common/common_param_traits.h"
 #include "content/common/webkit_param_traits.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START BlobMsgStart
 
+IPC_ENUM_TRAITS(webkit_blob::BlobData::Type)
+
+IPC_STRUCT_TRAITS_BEGIN(webkit_blob::BlobData::Item)
+  IPC_STRUCT_TRAITS_MEMBER(type)
+  IPC_STRUCT_TRAITS_MEMBER(data)
+  IPC_STRUCT_TRAITS_MEMBER(file_path)
+  IPC_STRUCT_TRAITS_MEMBER(blob_url)
+  IPC_STRUCT_TRAITS_MEMBER(offset)
+  IPC_STRUCT_TRAITS_MEMBER(length)
+  IPC_STRUCT_TRAITS_MEMBER(expected_modification_time)
+IPC_STRUCT_TRAITS_END()
+
 // Blob messages sent from the renderer to the browser.
 
-// Registers a blob URL referring to the specified blob data.
-IPC_MESSAGE_CONTROL2(BlobHostMsg_RegisterBlobUrl,
+
+// Registers a blob as being built.
+IPC_MESSAGE_CONTROL1(BlobHostMsg_StartBuildingBlob,
+                     GURL /* url */)
+
+// Appends data to a blob being built.
+IPC_MESSAGE_CONTROL2(BlobHostMsg_AppendBlobDataItem,
                      GURL /* url */,
-                     scoped_refptr<webkit_blob::BlobData> /* blob_data */)
+                     webkit_blob::BlobData::Item)
 
-// Registers a blob URL referring to the blob data identified by the specified
-// source URL.
-IPC_MESSAGE_CONTROL2(BlobHostMsg_RegisterBlobUrlFrom,
+// Asks the browser to create a block of shared memory for the renderer to
+// fill in and pass back to the browser.
+IPC_SYNC_MESSAGE_CONTROL1_1(BlobHostMsg_SyncAllocateSharedMemory,

[jam, 2011/10/11 01:56:51]

no need to duplicate this. you can reuse the existing message in view_messages.h
(ViewHostMsg_AllocateSharedMemoryBuffer)

[jam, 2011/10/11 02:02:18]

just to be clear, we should reuse not just the message but also the dispatching
function. so if this blob code is used in both renderer+worker, the impl of the
function can move to ChildProcessHost from RenderMessageFilter, and it can be a
ChildHostMsg instead

+                            size_t /* buffer size */,
+                            base::SharedMemoryHandle)
+
+// Appends data to a blob being built.
+IPC_SYNC_MESSAGE_CONTROL3_0(BlobHostMsg_SyncAppendSharedMemory,
+                            GURL /* url */,
+                            base::SharedMemoryHandle,
+                            size_t /* buffer size */)
+
+// Finishes building a blob.
+IPC_MESSAGE_CONTROL2(BlobHostMsg_FinishBuildingBlob,
+                     GURL /* url */,
+                     std::string /* content_type */)
+
+// Creates a new blob that's a clone of an existing src blob.
+// The source blob must be fully built.
+IPC_MESSAGE_CONTROL2(BlobHostMsg_CloneBlob,
                      GURL /* url */,
                      GURL /* src_url */)
 
-// Unregister a blob URL.
-IPC_MESSAGE_CONTROL1(BlobHostMsg_UnregisterBlobUrl,
+// Removes a blob.
+IPC_MESSAGE_CONTROL1(BlobHostMsg_RemoveBlob,
                      GURL /* url */)