IPC: Add attachment brokering support to the message header.

ipc/ipc_message.cc

Index: ipc/ipc_message.cc
diff --git a/ipc/ipc_message.cc b/ipc/ipc_message.cc
index 07d5d254759a23d208829d86d924c5e207a56ce3..6b55d277a8441a7c528cf021514faab40bc119d8 100644
--- a/ipc/ipc_message.cc
+++ b/ipc/ipc_message.cc
@@ -9,6 +9,7 @@
 #include "build/build_config.h"
 #include "ipc/ipc_message_attachment.h"
 #include "ipc/ipc_message_attachment_set.h"
+#include "ipc/placeholder_brokerable_attachment.h"
 
 #if defined(OS_POSIX)
 #include "base/file_descriptor_posix.h"
@@ -46,6 +47,9 @@ Message::~Message() {
 Message::Message() : base::Pickle(sizeof(Header)) {
   header()->routing = header()->type = 0;
   header()->flags = GetRefNumUpper24();
+#if USE_ATTACHMENT_BROKER
+  header()->num_brokered_attachments = 0;
+#endif
 #if defined(OS_POSIX)
   header()->num_fds = 0;
   header()->pad = 0;
@@ -59,6 +63,9 @@ Message::Message(int32 routing_id, uint32 type, PriorityValue priority)
   header()->type = type;
   DCHECK((priority & 0xffffff00) == 0);
   header()->flags = priority | GetRefNumUpper24();
+#if USE_ATTACHMENT_BROKER
+  header()->num_brokered_attachments = 0;
+#endif
 #if defined(OS_POSIX)
   header()->num_fds = 0;
   header()->pad = 0;
@@ -127,10 +134,91 @@ void Message::set_received_time(int64 time) const {
 }
 #endif
 
+Message::NextMessageInfo::NextMessageInfo()
+    : message_found(false), pickle_end(nullptr), message_end(nullptr) {}
+Message::NextMessageInfo::~NextMessageInfo() {}
+
+// static
+Message::NextMessageInfo Message::FindNext(const char* range_start,
+                                           const char* range_end) {
+  NextMessageInfo info;
+  const char* pickle_end =
+      base::Pickle::FindNext(sizeof(Header), range_start, range_end);
+  if (pickle_end == nullptr)
+    return info;
+  info.pickle_end = pickle_end;
+
+#if USE_ATTACHMENT_BROKER
+  // The data is not copied.
+  size_t pickle_len = static_cast<size_t>(pickle_end - range_start);
+  Message message(range_start, static_cast<int>(pickle_len));
+  int num_attachments = message.header()->num_brokered_attachments;
+
+  // Each brokered attachment adds kNonceSize bytes of data to the message. We
+  // want to avoid overflows in our computations, so we limit the number of
+  // brokerable attachments to 100.
+  if (num_attachments > 100)
+    return info;
+
+  // Check whether the range includes the attachments.
+  size_t attachment_length = num_attachments * BrokerableAttachment::kNonceSize;
+  size_t buffer_length = static_cast<size_t>(range_end - range_start);
+  if (buffer_length < attachment_length + pickle_len)
+    return info;
+
+  for (int i = 0; i < num_attachments; ++i) {
+    const char* attachment_start =
+        pickle_end + i * (BrokerableAttachment::kNonceSize);
+    BrokerableAttachment::AttachmentId id(attachment_start,
+                                          BrokerableAttachment::kNonceSize);
+    info.attachment_ids.push_back(id);
+  }
+  info.message_end =
+      pickle_end + num_attachments * BrokerableAttachment::kNonceSize;
+#else
+  info.message_end = pickle_end;
+#endif  // USE_ATTACHMENT_BROKER
+
+  info.message_found = true;
+  return info;
+}
+
+Message::SerializedAttachmentIds
+Message::SerializedIdsOfBrokerableAttachments() {
+  DCHECK(HasBrokerableAttachments());
+  std::vector<const BrokerableAttachment*> attachments =
+      attachment_set_->PeekBrokerableAttachments();
+  size_t size = attachments.size() * BrokerableAttachment::kNonceSize;
+  char* buffer = static_cast<char*>(malloc(size));
+  for (size_t i = 0; i < attachments.size(); ++i) {
+    const BrokerableAttachment* attachment = attachments[i];
+    char* start_range = buffer + i * BrokerableAttachment::kNonceSize;
+    BrokerableAttachment::AttachmentId id = attachment->GetIdentifier();
+    id.SerializeToBuffer(start_range, BrokerableAttachment::kNonceSize);
+  }
+  SerializedAttachmentIds ids;
+  ids.buffer = buffer;
+  ids.size = size;
+  return ids;
+}
+
+bool Message::AddPlaceholderBrokerableAttachmentWithId(
+    BrokerableAttachment::AttachmentId id) {
+  scoped_refptr<PlaceholderBrokerableAttachment> attachment(
+      new PlaceholderBrokerableAttachment(id));
+  return attachment_set()->AddAttachment(attachment);
+}
+
 bool Message::WriteAttachment(scoped_refptr<MessageAttachment> attachment) {
   // We write the index of the descriptor so that we don't have to
   // keep the current descriptor as extra decoding state when deserialising.
   WriteInt(attachment_set()->size());
+
+#if USE_ATTACHMENT_BROKER
+  if (attachment->GetType() == MessageAttachment::TYPE_BROKERABLE_ATTACHMENT)
+    header()->num_brokered_attachments += 1;
+#endif
+
   return attachment_set()->AddAttachment(attachment);
 }