Reduce copying in sending service responses.

runtime/vm/json_stream.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 
+#include "include/dart_native_api.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/json_stream.h"
 #include "vm/message.h"
 #include "vm/metrics.h"
 #include "vm/object.h"
+#include "vm/safepoint.h"
 #include "vm/service.h"
 #include "vm/service_event.h"
 #include "vm/timeline.h"
 #include "vm/unicode.h"
 
 
 namespace dart {
 
 #ifndef PRODUCT
 
@@ skipping 163 matching lines @@
       va_start(args2, details_format);
       OS::VSNPrint(buffer, (len + 1), details_format, args2);
       va_end(args2);
 
       data.AddProperty("details", buffer);
     }
   }
 }
 
 
-static uint8_t* allocator(uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
-  void* new_ptr = realloc(reinterpret_cast<void*>(ptr), new_size);
-  return reinterpret_cast<uint8_t*>(new_ptr);
-}
-
-
 void JSONStream::PostNullReply(Dart_Port port) {
   PortMap::PostMessage(new Message(
       port, Object::null(), Message::kNormalPriority));
 }
 
 
+static void Finalizer(void* isolate_callback_data,
+                      Dart_WeakPersistentHandle handle,
+                      void* buffer) {
+  free(buffer);
+}
+
+
 void JSONStream::PostReply() {
   Dart_Port port = reply_port();
   ASSERT(port != ILLEGAL_PORT);
   set_reply_port(ILLEGAL_PORT);  // Prevent double replies.
   ASSERT(seq_ != NULL);
   if (seq_->IsString()) {
     const String& str = String::Cast(*seq_);
     PrintProperty("id", str.ToCString());
   } else if (seq_->IsInteger()) {
     const Integer& integer = Integer::Cast(*seq_);
     PrintProperty64("id", integer.AsInt64Value());
   } else if (seq_->IsDouble()) {
     const Double& dbl = Double::Cast(*seq_);
     PrintProperty("id", dbl.value());
   } else if (seq_->IsNull()) {
     // JSON-RPC 2.0 says that a request with a null ID shouldn't get a reply.
     PostNullReply(port);
     return;
   }
   buffer_.AddChar('}');
 
-  const String& reply = String::Handle(String::New(ToCString()));
-  ASSERT(!reply.IsNull());
+  char* cstr;
+  intptr_t length;
+  Steal(&cstr, &length);
 
-  uint8_t* data = NULL;
-  MessageWriter writer(&data, &allocator, false);
-  writer.WriteMessage(reply);
-  bool result = PortMap::PostMessage(new Message(port, data,
-                                                 writer.BytesWritten(),
-                                                 Message::kNormalPriority));
+  bool result;
+  {
+    TransitionVMToNative transition(Thread::Current());
+    Dart_CObject bytes;
+    bytes.type = Dart_CObject_kExternalTypedData;
+    bytes.value.as_external_typed_data.type = Dart_TypedData_kUint8;
+    bytes.value.as_external_typed_data.length = length;
+    bytes.value.as_external_typed_data.data = reinterpret_cast<uint8_t*>(cstr);
+    bytes.value.as_external_typed_data.peer = cstr;
+    bytes.value.as_external_typed_data.callback = Finalizer;
+    Dart_CObject* elements[1];
+    elements[0] = &bytes;
+    Dart_CObject message;
+    message.type = Dart_CObject_kArray;
+    message.value.as_array.length = 1;
+    message.value.as_array.values = elements;
+    result = Dart_PostCObject(port, &message);
+  }
+
+  if (!result) {
+    free(cstr);
+  }
+
   if (FLAG_trace_service) {
     Isolate* isolate = Isolate::Current();
     ASSERT(isolate != NULL);
     const char* isolate_name = isolate->name();
     int64_t total_time = OS::GetCurrentTimeMicros() - setup_time_micros_;
     if (result) {
       OS::Print("[+%" Pd64 "ms] Isolate %s processed service request %s "
                 "(%" Pd64 "us)\n",
                 Dart::timestamp(), isolate_name, method_, total_time);
     } else {
@@ skipping 417 matching lines @@
   intptr_t len2 = OS::VSNPrint(p, len+1, format, args);
   va_end(args);
   ASSERT(len == len2);
   buffer_.AddChar('"');
   AddEscapedUTF8String(p);
   buffer_.AddChar('"');
   free(p);
 }
 
 
-void JSONStream::Steal(const char** buffer, intptr_t* buffer_length) {
+void JSONStream::Steal(char** buffer, intptr_t* buffer_length) {
   ASSERT(buffer != NULL);
   ASSERT(buffer_length != NULL);
   *buffer_length = buffer_.length();
   *buffer = buffer_.Steal();
 }
 
 
 void JSONStream::set_reply_port(Dart_Port port) {
   reply_port_ = port;
 }
@@ skipping 276 matching lines @@
   ASSERT(len == len2);
   stream_->buffer_.AddChar('"');
   stream_->AddEscapedUTF8String(p);
   stream_->buffer_.AddChar('"');
   free(p);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart