Use a pool of native ports for file operations

runtime/bin/file.cc

Index: runtime/bin/file.cc
diff --git a/runtime/bin/file.cc b/runtime/bin/file.cc
index 7cbf4db7f6dfec3934242118c844df6b48f86ea1..093ff4d4655fa7d49f9f64d5a08a1ac85e838c2c 100644
--- a/runtime/bin/file.cc
+++ b/runtime/bin/file.cc
@@ -6,9 +6,14 @@
 
 #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;
@@ -725,13 +730,35 @@ void FileService(Dart_Port dest_port_id,
 }
 
 
+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);