Only reload libraries when they may have been modified.

runtime/bin/main.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 <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_tools_api.h"
@@ skipping 1025 matching lines @@
 
 static void ServiceStreamCancelCallback(const char* stream_id) {
   if (strcmp(stream_id, kStdoutStreamId) == 0) {
     SetCaptureStdout(false);
   } else if (strcmp(stream_id, kStderrStreamId) == 0) {
     SetCaptureStderr(false);
   }
 }
 
 
+static bool FileModifiedCallback(const char* url, int64_t since) {
+  if (strncmp(url, "file:///", 8) == 0) {
+    // If it isn't a file on local disk, we don't know if it has been
+    // modified.
+    return true;
+  }
+  int64_t data[File::kStatSize];
+  File::Stat(url + 7, data);
+  if (data[File::kType] == File::kDoesNotExist) {
+    return true;
+  }
+  bool modified = data[File::kModifiedTime] > since;
+  return modified;
+}
+
+
 static void WriteSnapshotFile(const char* snapshot_directory,
                               const char* filename,
                               bool write_magic_number,
                               const uint8_t* buffer,
                               const intptr_t size) {
   char* concat = NULL;
   const char* qualified_filename;
   if ((snapshot_directory != NULL) && (strlen(snapshot_directory) > 0)) {
     intptr_t len = snprintf(NULL, 0, "%s/%s", snapshot_directory, filename);
     concat = new char[len + 1];
@@ skipping 645 matching lines @@
     fprintf(stderr, "VM initialization failed: %s\n", error);
     fflush(stderr);
     free(error);
     Platform::Exit(kErrorExitCode);
   }
 
   Dart_RegisterIsolateServiceRequestCallback(
         "getIO", &ServiceGetIOHandler, NULL);
   Dart_SetServiceStreamCallbacks(&ServiceStreamListenCallback,
                                  &ServiceStreamCancelCallback);
+  Dart_SetFileModifiedCallback(&FileModifiedCallback);
 
   // Run the main isolate until we aren't told to restart.
   while (RunMainIsolate(script_name, &dart_options)) {
     Log::PrintErr("Restarting VM\n");
   }
 
   // Terminate process exit-code handler.
   Process::TerminateExitCodeHandler();
 
   error = Dart_Cleanup();
@@ skipping 24 matching lines @@
   Platform::Exit(Process::GlobalExitCode());
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   dart::bin::main(argc, argv);
   UNREACHABLE();
 }