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

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_debugger_api.h"
@@ skipping 11 matching lines @@
 #include "bin/process.h"
 #include "bin/vmstats_impl.h"
 #include "platform/globals.h"
 
 // snapshot_buffer points to a snapshot if we link in a snapshot otherwise
 // it is initialized to NULL.
 extern const uint8_t* snapshot_buffer;
 
 
 // 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;
 
 
 // Global state that indicates whether there is a debug breakpoint.
 // This pointer points into an argv buffer and does not need to be
 // free'd.
 static const char* breakpoint_at = NULL;
 
 
@@ skipping 104 matching lines @@
     Log::PrintErr("unrecognized --debug option syntax. "
                     "Use --debug[:<port number>]\n");
     return false;
   }
   breakpoint_at = "main";
   start_debugger = true;
   return true;
 }
 
 
-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') {
     vmstats_port = 0;  // Dynamically assigned port number.
   } else {
     if ((*port == '=') || (*port == ':')) {
       vmstats_port = atoi(port + 1);
     }
   }
   if (vmstats_port < 0) {
@@ skipping 23 matching lines @@
 
 
 static bool ProcessGenScriptSnapshotOption(const char* filename) {
   if (filename != NULL && strlen(filename) != 0) {
     // Ensure that are already running using a full snapshot.
     if (snapshot_buffer == NULL) {
       Log::PrintErr("Script snapshots cannot be generated in this version of"
                     " 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",
                     filename);
       return false;
     }
     generate_script_snapshot = true;
   }
   return true;
 }
 
 
 static struct {
   const char* option_name;
   bool (*process)(const char* option);
 } main_options[] = {
   // Standard options shared with dart2js.
   { "--version", ProcessVersionOption },
   { "--help", ProcessHelpOption },
   { "-h", ProcessHelpOption },
   { "--verbose", ProcessVerboseOption },
   { "-v", ProcessVerboseOption },
   { "--package-root=", ProcessPackageRootOption },
   { "-p", ProcessPackageRootOption },
   // VM specific options to the standalone dart program.
   { "--break_at=", ProcessBreakpointOption },
   { "--compile_all", ProcessCompileAllOption },
   { "--debug", ProcessDebugOption },
-  { "--use-script-snapshot=", ProcessUseScriptSnapshotOption },
   { "--generate-script-snapshot=", ProcessGenScriptSnapshotOption },
   { "--stats-root=", ProcessVmStatsRootOption },
   { "--stats", ProcessVmStatsOption },
   { "--print-script", ProcessPrintScriptOption },
   { NULL, NULL }
 };
 
 
 static bool ProcessMainOptions(const char* option) {
   int i = 0;
@@ skipping 206 matching lines @@
     // Setup the native resolver as the snapshot does not carry it.
     Builtin::SetNativeResolver(Builtin::kBuiltinLibrary);
     Builtin::SetNativeResolver(Builtin::kIOLibrary);
   }
 
   // Set up the library tag handler for this isolate.
   Dart_Handle result = Dart_SetLibraryTagHandler(DartUtils::LibraryTagHandler);
   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.
+  // The builtin library is part of the core snapshot and would already be
+  // available here in the case of script snapshot loading.
+  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 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];
     snprintf(errbuf, sizeof(errbuf),
              "Expected a library when loading script: %s",
              script_uri);
     *error = strdup(errbuf);
     Dart_ExitScope();
     Dart_ShutdownIsolate();
     return false;
@@ skipping 281 matching lines @@
     uint8_t* buffer = NULL;
     intptr_t size = 0;
     result = Dart_CreateScriptSnapshot(&buffer, &size);
     if (Dart_IsError(result)) {
       Log::PrintErr("%s\n", Dart_GetError(result));
       Dart_ExitScope();
       Dart_ShutdownIsolate();
       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);
     delete snapshot_file;
   } else {
     if (has_compile_all) {
       result = Dart_CompileAll();
       if (Dart_IsError(result)) {
         return ErrorExit("%s\n", Dart_GetError(result));
       }
@@ skipping 47 matching lines @@
   Dart_ShutdownIsolate();
   // Terminate process exit-code handler.
   Process::TerminateExitCodeHandler();
   // Free copied argument strings if converted.
   if (argv_converted) {
     for (int i = 0; i < argc; i++) free(argv[i]);
   }
 
   return Process::GlobalExitCode();
 }