Add truncate operation to File API.

runtime/bin/file.cc

 // Copyright (c) 2011, 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 "include/dart_api.h"
@@ skipping 200 matching lines @@
   if (file != NULL) {
     return_value = file->Position();
   }
   Dart_SetReturnValue(args, Dart_NewInteger(return_value));
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(File_SetPosition)(Dart_NativeArguments args) {
   Dart_EnterScope();
-  intptr_t return_value = -1;
+  bool return_value = false;
   intptr_t value =
       DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 0));
   File* file = reinterpret_cast<File*>(value);
   if (file != NULL) {
     int64_t position =
         DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
     return_value = file->SetPosition(position);
   }
-  Dart_SetReturnValue(args, Dart_NewInteger(return_value));
+  Dart_SetReturnValue(args, Dart_NewBoolean(return_value));
   Dart_ExitScope();
 }
 
+
+void FUNCTION_NAME(File_Truncate)(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  bool return_value = false;
+  intptr_t value =
+      DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 0));
+  File* file = reinterpret_cast<File*>(value);
+  if (file != NULL) {
+    int64_t length =
+        DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
+    return_value = file->Truncate(length);
+  }
+  Dart_SetReturnValue(args, Dart_NewBoolean(return_value));
+  Dart_ExitScope();
+}
+
 
 void FUNCTION_NAME(File_Length)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t return_value = -1;
   intptr_t value =
       DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 0));
   File* file = reinterpret_cast<File*>(value);
   if (file != NULL) {
     return_value = file->Length();
   }
@@ skipping 41 matching lines @@
   Dart_EnterScope();
   const char* str =
       DartUtils::GetStringValue(Dart_GetNativeArgument(args, 0));
   char* path = File::GetCanonicalPath(str);
   if (path != NULL) {
     Dart_SetReturnValue(args, Dart_NewString(path));
     free(path);
   }
   Dart_ExitScope();
 }