Use a pool of native ports for file operations

runtime/bin/file.cc

 // Copyright (c) 2012, 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 "bin/file.h"
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
+#include "bin/thread.h"
 
 #include "include/dart_api.h"
 
+dart::Mutex File::mutex_;
+int File::service_ports_size_ = 0;
+Dart_Port* File::service_ports_ = NULL;
+int File::service_ports_index_ = 0;
 
 bool File::ReadFully(void* buffer, int64_t num_bytes) {
   int64_t remaining = num_bytes;
   char* current_buffer = reinterpret_cast<char*>(buffer);
   while (remaining > 0) {
     int bytes_read = Read(current_buffer, remaining);
     if (bytes_read <= 0) {
       return false;
     }
     remaining -= bytes_read;  // Reduce the number of remaining bytes.
@@ skipping 696 matching lines @@
         default:
           UNREACHABLE();
       }
     }
   }
 
   Dart_PostCObject(reply_port_id, response->AsApiCObject());
 }
 
 
+Dart_Port File::GetServicePort() {
+  MutexLocker lock(&mutex_);
+  if (service_ports_size_ == 0) {
+    ASSERT(service_ports_ == NULL);
+    service_ports_size_ = 16;
+    service_ports_ = new Dart_Port[service_ports_size_];
+    service_ports_index_ = 0;
+    for (int i = 0; i < service_ports_size_; i++) {
+      service_ports_[i] = kIllegalPort;
+    }
+  }
+
+  Dart_Port result = service_ports_[service_ports_index_];
+  if (result == kIllegalPort) {
+    result = Dart_NewNativePort("FileService",
+                                FileService,
+                                true);
+    ASSERT(result != kIllegalPort);
+    service_ports_[service_ports_index_] = result;
+  }
+  service_ports_index_ = (service_ports_index_ + 1) % service_ports_size_;
+  return result;
+}
+
+
 void FUNCTION_NAME(File_NewServicePort)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Dart_SetReturnValue(args, Dart_Null());
-  Dart_Port service_port = kIllegalPort;
-  service_port = Dart_NewNativePort("FileService",
-                                    FileService,
-                                    true);
+  Dart_Port service_port = File::GetServicePort();
   if (service_port != kIllegalPort) {
     // Return a send port for the service port.
     Dart_Handle send_port = Dart_NewSendPort(service_port);
     Dart_SetReturnValue(args, send_port);
   }
   Dart_ExitScope();
 }