Mojo: Factor MessageInTransit secondary buffer stuff out into a separate class.

mojo/system/message_in_transit.cc

Index: mojo/system/message_in_transit.cc
diff --git a/mojo/system/message_in_transit.cc b/mojo/system/message_in_transit.cc
index a38ac1ce7a62888e8e32b40f9321b0d097a7b87d..79f1184d9f686bd42f27cff78c34116d5de7c2c2 100644
--- a/mojo/system/message_in_transit.cc
+++ b/mojo/system/message_in_transit.cc
@@ -6,11 +6,10 @@
 
 #include <string.h>
 
-#include <new>
-
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "mojo/system/constants.h"
+#include "mojo/system/transport_data.h"
 
 namespace mojo {
 namespace system {
@@ -32,10 +31,6 @@ STATIC_CONST_MEMBER_DEFINITION const MessageInTransit::Subtype
 STATIC_CONST_MEMBER_DEFINITION const MessageInTransit::EndpointId
     MessageInTransit::kInvalidEndpointId;
 STATIC_CONST_MEMBER_DEFINITION const size_t MessageInTransit::kMessageAlignment;
-STATIC_CONST_MEMBER_DEFINITION const size_t
-    MessageInTransit::kMaxSerializedDispatcherSize;
-STATIC_CONST_MEMBER_DEFINITION const size_t
-    MessageInTransit::kMaxSerializedDispatcherPlatformHandles;
 
 struct MessageInTransit::PrivateStructForCompileAsserts {
   // The size of |Header| must be a multiple of the alignment.
@@ -51,26 +46,8 @@ struct MessageInTransit::PrivateStructForCompileAsserts {
   // size is a multiple of the alignment.
   COMPILE_ASSERT(kMaxMessageNumBytes % kMessageAlignment == 0,
                  kMessageAlignment_not_a_multiple_of_alignment);
-
-  // The maximum serialized dispatcher size must be a multiple of the alignment.
-  COMPILE_ASSERT(kMaxSerializedDispatcherSize % kMessageAlignment == 0,
-                 kMaxSerializedDispatcherSize_not_a_multiple_of_alignment);
-
-  // The size of |HandleTableEntry| must be a multiple of the alignment.
-  COMPILE_ASSERT(sizeof(HandleTableEntry) % kMessageAlignment == 0,
-                 sizeof_MessageInTransit_HandleTableEntry_invalid);
 };
 
-// For each attached (Mojo) handle, there'll be a handle table entry and
-// serialized dispatcher data.
-// static
-const size_t MessageInTransit::kMaxSecondaryBufferSize = kMaxMessageNumHandles *
-    (sizeof(HandleTableEntry) + kMaxSerializedDispatcherSize);
-
-// static
-const size_t MessageInTransit::kMaxPlatformHandles =
-    kMaxMessageNumHandles * kMaxSerializedDispatcherPlatformHandles;
-
 MessageInTransit::View::View(size_t message_size, const void* buffer)
     : buffer_(buffer) {
   size_t next_message_size = 0;
@@ -89,11 +66,13 @@ bool MessageInTransit::View::IsValid(const char** error_message) const {
     return false;
   }
 
-  if (const char* secondary_buffer_error_message =
-          ValidateSecondaryBuffer(num_handles(), secondary_buffer(),
-                                  secondary_buffer_size())) {
-    *error_message = secondary_buffer_error_message;
-    return false;
+  if (transport_data_buffer_size() > 0) {
+    const char* e = TransportData::ValidateBuffer(transport_data_buffer(),
+                                                  transport_data_buffer_size());
+    if (e) {
+      *error_message = e;
+      return false;
+    }
   }
 
   return true;
@@ -102,14 +81,11 @@ bool MessageInTransit::View::IsValid(const char** error_message) const {
 MessageInTransit::MessageInTransit(Type type,
                                    Subtype subtype,
                                    uint32_t num_bytes,
-                                   uint32_t num_handles,
                                    const void* bytes)
     : main_buffer_size_(RoundUpMessageAlignment(sizeof(Header) + num_bytes)),
       main_buffer_(static_cast<char*>(base::AlignedAlloc(main_buffer_size_,
-                                                         kMessageAlignment))),
-      secondary_buffer_size_(0) {
+                                                         kMessageAlignment))) {
   DCHECK_LE(num_bytes, kMaxMessageNumBytes);
-  DCHECK_LE(num_handles, kMaxMessageNumHandles);
 
   // |total_size| is updated below, from the other values.
   header()->type = type;
@@ -117,9 +93,8 @@ MessageInTransit::MessageInTransit(Type type,
   header()->source_id = kInvalidEndpointId;
   header()->destination_id = kInvalidEndpointId;
   header()->num_bytes = num_bytes;
-  header()->num_handles = num_handles;
-  // Note: If dispatchers are subsequently attached (in particular, if
-  // |num_handles| is nonzero), then |total_size| will have to be adjusted.
+  // Note: If dispatchers are subsequently attached, then |total_size| will have
+  // to be adjusted.
   UpdateTotalSize();
 
   if (bytes) {
@@ -131,24 +106,14 @@ MessageInTransit::MessageInTransit(Type type,
   }
 }
 
-// TODO(vtl): Do I really want/need to copy the secondary buffer here, or should
-// I just create (deserialize) the dispatchers right away?
 MessageInTransit::MessageInTransit(const View& message_view)
     : main_buffer_size_(message_view.main_buffer_size()),
       main_buffer_(static_cast<char*>(base::AlignedAlloc(main_buffer_size_,
-                                                         kMessageAlignment))),
-      secondary_buffer_size_(message_view.secondary_buffer_size()),
-      secondary_buffer_(secondary_buffer_size_ ?
-                            static_cast<char*>(
-                                base::AlignedAlloc(secondary_buffer_size_,
-                                                   kMessageAlignment)) : NULL) {
+                                                         kMessageAlignment))) {
   DCHECK_GE(main_buffer_size_, sizeof(Header));
   DCHECK_EQ(main_buffer_size_ % kMessageAlignment, 0u);
 
   memcpy(main_buffer_.get(), message_view.main_buffer(), main_buffer_size_);
-  memcpy(secondary_buffer_.get(), message_view.secondary_buffer(),
-         secondary_buffer_size_);
-
   DCHECK_EQ(main_buffer_size_,
             RoundUpMessageAlignment(sizeof(Header) + num_bytes()));
 }
@@ -163,17 +128,6 @@ MessageInTransit::~MessageInTransit() {
       (*dispatchers_)[i]->Close();
     }
   }
-
-  if (platform_handles_) {
-    for (size_t i = 0; i < platform_handles_->size(); i++)
-      (*platform_handles_)[i].CloseIfNecessary();
-  }
-
-#ifndef NDEBUG
-  secondary_buffer_size_ = 0;
-  dispatchers_.reset();
-  platform_handles_.reset();
-#endif
 }
 
 // static
@@ -210,206 +164,24 @@ void MessageInTransit::SetDispatchers(
 
 void MessageInTransit::SerializeAndCloseDispatchers(Channel* channel) {
   DCHECK(channel);
-  DCHECK(!secondary_buffer_);
+  DCHECK(!transport_data_);
 
-  const size_t num_handles = dispatchers_ ? dispatchers_->size() : 0;
-  if (!num_handles)
+  if (!dispatchers_ || !dispatchers_->size())
     return;
 
-  // The offset to the start of the (Mojo) handle table.
-  // TODO(vtl): Add a header to the secondary buffer.
-  const size_t handle_table_start_offset = 0;
-  // The offset to the start of the serialized dispatcher data.
-  const size_t serialized_dispatcher_start_offset =
-      handle_table_start_offset + num_handles * sizeof(HandleTableEntry);
-  // The estimated size of the secondary buffer. We compute this estimate below.
-  // It must be at least as big as the (eventual) actual size.
-  size_t estimated_size = serialized_dispatcher_start_offset;
-  size_t num_platform_handles = 0;
-#if DCHECK_IS_ON
-  std::vector<size_t> all_max_sizes(num_handles);
-  std::vector<size_t> all_max_platform_handles(num_handles);
-#endif
-  for (size_t i = 0; i < num_handles; i++) {
-    if (Dispatcher* dispatcher = (*dispatchers_)[i].get()) {
-      size_t max_size = 0;
-      size_t max_platform_handles = 0;
-      Dispatcher::MessageInTransitAccess::StartSerialize(
-              dispatcher, channel, &max_size, &max_platform_handles);
-
-      DCHECK_LE(max_size, kMaxSerializedDispatcherSize);
-      estimated_size += RoundUpMessageAlignment(max_size);
-      DCHECK_LE(estimated_size, kMaxSecondaryBufferSize);
-
-      DCHECK_LE(max_platform_handles,
-                kMaxSerializedDispatcherPlatformHandles);
-      num_platform_handles += max_platform_handles;
-      DCHECK_LE(num_platform_handles, kMaxPlatformHandles);
-
-#if DCHECK_IS_ON
-      all_max_sizes[i] = max_size;
-      all_max_platform_handles[i] = max_platform_handles;
-#endif
-    }
-  }
-
-  secondary_buffer_.reset(static_cast<char*>(
-      base::AlignedAlloc(estimated_size, kMessageAlignment)));
-  // Entirely clear out the secondary buffer, since then we won't have to worry
-  // about clearing padding or unused space (e.g., if a dispatcher fails to
-  // serialize).
-  memset(secondary_buffer_.get(), 0, estimated_size);
-
-  if (num_platform_handles > 0) {
-    DCHECK(!platform_handles_);
-    platform_handles_.reset(new std::vector<embedder::PlatformHandle>());
-  }
-
-  HandleTableEntry* handle_table = reinterpret_cast<HandleTableEntry*>(
-      secondary_buffer_.get() + handle_table_start_offset);
-  size_t current_offset = serialized_dispatcher_start_offset;
-  for (size_t i = 0; i < num_handles; i++) {
-    Dispatcher* dispatcher = (*dispatchers_)[i].get();
-    if (!dispatcher) {
-      COMPILE_ASSERT(Dispatcher::kTypeUnknown == 0,
-                     value_of_Dispatcher_kTypeUnknown_must_be_zero);
-      continue;
-    }
-
-#if DCHECK_IS_ON
-    size_t old_platform_handles_size =
-        platform_handles_ ? platform_handles_->size() : 0;
-#endif
-
-    void* destination = secondary_buffer_.get() + current_offset;
-    size_t actual_size = 0;
-    if (Dispatcher::MessageInTransitAccess::EndSerializeAndClose(
-            dispatcher, channel, destination, &actual_size,
-            platform_handles_.get())) {
-      handle_table[i].type = static_cast<int32_t>(dispatcher->GetType());
-      handle_table[i].offset = static_cast<uint32_t>(current_offset);
-      handle_table[i].size = static_cast<uint32_t>(actual_size);
-
-#if DCHECK_IS_ON
-      DCHECK_LE(actual_size, all_max_sizes[i]);
-      DCHECK_LE(platform_handles_ ? (platform_handles_->size() -
-                                         old_platform_handles_size) : 0,
-                all_max_platform_handles[i]);
-#endif
-    } else {
-      // Nothing to do on failure, since |secondary_buffer_| was cleared, and
-      // |kTypeUnknown| is zero. The handle was simply closed.
-      LOG(ERROR) << "Failed to serialize handle to remote message pipe";
-    }
-
-    current_offset += RoundUpMessageAlignment(actual_size);
-    DCHECK_LE(current_offset, estimated_size);
-    DCHECK_LE(platform_handles_ ? platform_handles_->size() : 0,
-              num_platform_handles);
-  }
-
-  // There's no aligned realloc, so it's no good way to release unused space (if
-  // we overshot our estimated space requirements).
-  secondary_buffer_size_ = current_offset;
-
-  // The dispatchers (which we "owned") were closed. We can dispose of them now.
-  dispatchers_.reset();
+  transport_data_.reset(new TransportData(dispatchers_.Pass(), channel));
 
   // Update the sizes in the message header.
   UpdateTotalSize();
 }
 
-// Note: The message's secondary buffer should have been checked by calling
-// |View::IsValid()| (on the |View|) first.
-void MessageInTransit::DeserializeDispatchers(Channel* channel) {
-  DCHECK(!dispatchers_);
-
-  // Already checked by |View::IsValid()|:
-  DCHECK_LE(num_handles(), kMaxMessageNumHandles);
-
-  if (!num_handles())
-    return;
-
-  dispatchers_.reset(
-      new std::vector<scoped_refptr<Dispatcher> >(num_handles()));
-
-  size_t handle_table_size = num_handles() * sizeof(HandleTableEntry);
-  // Already checked by |View::IsValid()|:
-  DCHECK_LE(handle_table_size, secondary_buffer_size_);
-
-  const HandleTableEntry* handle_table =
-      reinterpret_cast<const HandleTableEntry*>(secondary_buffer_.get());
-  for (size_t i = 0; i < num_handles(); i++) {
-    size_t offset = handle_table[i].offset;
-    size_t size = handle_table[i].size;
-    // Already checked by |View::IsValid()|:
-    DCHECK_EQ(offset % kMessageAlignment, 0u);
-    DCHECK_LE(offset, secondary_buffer_size_);
-    DCHECK_LE(offset + size, secondary_buffer_size_);
-
-    const void* source = secondary_buffer_.get() + offset;
-    (*dispatchers_)[i] = Dispatcher::MessageInTransitAccess::Deserialize(
-        channel, handle_table[i].type, source, size);
-  }
-}
-
-// Validates the secondary buffer. Returns null on success, or a human-readable
-// error message on error.
-// static
-const char* MessageInTransit::ValidateSecondaryBuffer(
-    size_t num_handles,
-    const void* secondary_buffer,
-    size_t secondary_buffer_size) {
-  // Always make sure that the secondary buffer size is sane (even if we have no
-  // handles); if it's not, someone's messing with us.
-  if (secondary_buffer_size > kMaxSecondaryBufferSize)
-    return "Message secondary buffer too large";
-
-  // Fast-path for the common case (no handles => no secondary buffer).
-  if (num_handles == 0) {
-    // We shouldn't have a secondary buffer in this case.
-    if (secondary_buffer_size > 0)
-      return "Message has no handles attached, but secondary buffer present";
-    return NULL;
-  }
-
-  // Sanity-check |num_handles| (before multiplying it against anything).
-  if (num_handles > kMaxMessageNumHandles)
-    return "Message handle payload too large";
-
-  if (secondary_buffer_size < num_handles * sizeof(HandleTableEntry))
-    return "Message secondary buffer too small";
-
-  DCHECK(secondary_buffer);
-  const HandleTableEntry* handle_table =
-      static_cast<const HandleTableEntry*>(secondary_buffer);
-
-  static const char kInvalidSerializedDispatcher[] =
-      "Message contains invalid serialized dispatcher";
-  for (size_t i = 0; i < num_handles; i++) {
-    size_t offset = handle_table[i].offset;
-    if (offset % kMessageAlignment != 0)
-      return kInvalidSerializedDispatcher;
-
-    size_t size = handle_table[i].size;
-    if (size > kMaxSerializedDispatcherSize || size > secondary_buffer_size)
-      return kInvalidSerializedDispatcher;
-
-    // Note: This is an overflow-safe check for |offset + size >
-    // secondary_buffer_size()| (we know that |size <= secondary_buffer_size()|
-    // from the previous check).
-    if (offset > secondary_buffer_size - size)
-      return kInvalidSerializedDispatcher;
-  }
-
-  return NULL;
-}
-
 void MessageInTransit::UpdateTotalSize() {
   DCHECK_EQ(main_buffer_size_ % kMessageAlignment, 0u);
-  DCHECK_EQ(secondary_buffer_size_ % kMessageAlignment, 0u);
-  header()->total_size =
-      static_cast<uint32_t>(main_buffer_size_ + secondary_buffer_size_);
+  header()->total_size = static_cast<uint32_t>(main_buffer_size_);
+  if (transport_data_) {
+    header()->total_size +=
+        static_cast<uint32_t>(transport_data_->buffer_size());
+  }
 }
 
 }  // namespace system