Write the magic number 0xf5f5dcdc into a script snapshot file and use this to distinguish whether a…

runtime/bin/main.cc

Index: runtime/bin/main.cc
===================================================================
--- runtime/bin/main.cc	(revision 20251)
+++ runtime/bin/main.cc	(working copy)
@@ -29,7 +29,6 @@
 
 
 // Global state that stores a pointer to the application script snapshot.
-static bool use_script_snapshot = false;
 static bool generate_script_snapshot = false;
 static File* snapshot_file = NULL;
 
@@ -154,25 +153,6 @@
 }
 
 
-static bool ProcessUseScriptSnapshotOption(const char* filename) {
-  if (filename != NULL && strlen(filename) != 0) {
-    use_script_snapshot = true;
-    if (generate_script_snapshot) {
-      Log::PrintErr("Incompatible options specified --generate-script-snapshot "
-                    "and --use-script-snapshot\n");
-      return false;
-    }
-    snapshot_file = File::Open(filename, File::kRead);
-    if (snapshot_file == NULL) {
-      Log::PrintErr("Unable to open file %s for reading the snapshot\n",
-                    filename);
-      return false;
-    }
-  }
-  return true;
-}
-
-
 static bool ProcessVmStatsOption(const char* port) {
   ASSERT(port != NULL);
   if (*port == '\0') {
@@ -216,11 +196,6 @@
                     " dart\n");
       return false;
     }
-    if (use_script_snapshot) {
-      Log::PrintErr("Incompatible options specified --use-script-snapshot "
-                    "and --generate-script-snapshot\n");
-      return false;
-    }
     snapshot_file = File::Open(filename, File::kWriteTruncate);
     if (snapshot_file == NULL) {
       Log::PrintErr("Unable to open file %s for writing the snapshot\n",
@@ -249,7 +224,6 @@
   { "--break_at=", ProcessBreakpointOption },
   { "--compile_all", ProcessCompileAllOption },
   { "--debug", ProcessDebugOption },
-  { "--use-script-snapshot=", ProcessUseScriptSnapshotOption },
   { "--generate-script-snapshot=", ProcessGenScriptSnapshotOption },
   { "--stats-root=", ProcessVmStatsRootOption },
   { "--stats", ProcessVmStatsOption },
@@ -476,54 +450,21 @@
   CHECK_RESULT(result);
 
   // Load the specified application script into the newly created isolate.
-  Dart_Handle library;
-  if (use_script_snapshot) {
-    if (snapshot_file == NULL) {
-      use_script_snapshot = false;
-      *error = strdup("Invalid script snapshot file name specified");
-      Dart_ExitScope();
-      Dart_ShutdownIsolate();
-      return false;
-    }
-    size_t len = snapshot_file->Length();
-    uint8_t* buffer = reinterpret_cast<uint8_t*>(malloc(len));
-    if (buffer == NULL) {
-      delete snapshot_file;
-      snapshot_file = NULL;
-      use_script_snapshot = false;
-      *error = strdup("Unable to read contents of script snapshot file");
-      Dart_ExitScope();
-      Dart_ShutdownIsolate();
-      return false;
-    }
-    // Prepare for script loading by setting up the 'print' and 'timer'
-    // closures and setting up 'package root' for URI resolution.
-    Dart_Handle builtin_lib =
-        Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
-    DartUtils::PrepareForScriptLoading(package_root, builtin_lib);
 
-    snapshot_file->ReadFully(buffer, len);
-    library = Dart_LoadScriptFromSnapshot(buffer);
-    free(buffer);
-    delete snapshot_file;
-    snapshot_file = NULL;
-    use_script_snapshot = false;  // No further usage of script snapshots.
-  } else {
-    // Prepare builtin and its dependent libraries for use to resolve URIs.
-    Dart_Handle uri_url = DartUtils::NewString(DartUtils::kUriLibURL);
-    Dart_Handle uri_lib = Dart_LookupLibrary(uri_url);
-    CHECK_RESULT(uri_lib);
-    Dart_Handle builtin_lib =
-        Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
-    CHECK_RESULT(builtin_lib);
+  // Prepare builtin and its dependent libraries for use to resolve URIs.
+  Dart_Handle uri_url = DartUtils::NewString(DartUtils::kUriLibURL);
+  Dart_Handle uri_lib = Dart_LookupLibrary(uri_url);
+  CHECK_RESULT(uri_lib);
+  Dart_Handle builtin_lib =
+      Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);

[Ivan Posva, 2013/03/20 06:18:00]

Isn't this library also part of the script snapshot? Will it be loaded twice in
this case? Once here and once from the script snapshot, further below when we
determine to be loading a script snapshot.

I understand that this was already happening before, but I would like to make
sure this is correct.

[siva, 2013/03/20 20:57:20]

This library is part of the core snapshot, It will not end up in the script
snapshot.
We should find it already here when we lookup. I will add a comment to that
effect.

On 2013/03/20 06:18:00, Ivan Posva wrote:

+  CHECK_RESULT(builtin_lib);
 
-    // Prepare for script loading by setting up the 'print' and 'timer'
-    // closures and setting up 'package root' for URI resolution.
-    result = DartUtils::PrepareForScriptLoading(package_root, builtin_lib);
-    CHECK_RESULT(result);
+  // Prepare for script loading by setting up the 'print' and 'timer'
+  // closures and setting up 'package root' for URI resolution.
+  result = DartUtils::PrepareForScriptLoading(package_root, builtin_lib);
+  CHECK_RESULT(result);
 
-    library = DartUtils::LoadScript(script_uri, builtin_lib);
-  }
+  Dart_Handle library = DartUtils::LoadScript(script_uri, builtin_lib);
   CHECK_RESULT(library);
   if (!Dart_IsLibrary(library)) {
     char errbuf[256];
@@ -825,6 +766,9 @@
       return kErrorExitCode;  // Indicates we encountered an error.
     }
 
+    // Write the magic number to indicate file is a script snapshot.
+    DartUtils::WriteMagicNumber(snapshot_file);
+
     // Now write the snapshot out to specified file.
     bool bytes_written = snapshot_file->WriteFully(buffer, size);
     ASSERT(bytes_written);