Add support for file locking

runtime/bin/file.cc

Index: runtime/bin/file.cc
diff --git a/runtime/bin/file.cc b/runtime/bin/file.cc
index a98ff3de909423d1f20b4b52284ecf8e5524c786..709ac252ee7f2b7e2ac6dbb5c74e50a87afcf45e 100644
--- a/runtime/bin/file.cc
+++ b/runtime/bin/file.cc
@@ -391,6 +391,36 @@ void FUNCTION_NAME(File_Flush)(Dart_NativeArguments args) {
 }
 
 
+void FUNCTION_NAME(File_Lock)(Dart_NativeArguments args) {
+  File* file = GetFilePointer(Dart_GetNativeArgument(args, 0));
+  ASSERT(file != NULL);
+  int64_t lock;

[Lasse Reichstein Nielsen, 2015/01/08 11:59:22]

Is this the type on all platforms? There is no lock_t type to use instead?

[Søren Gjesse, 2015/01/09 13:06:19]

The int64_t type is used to get the Dart int argument into C++ code. Below it is
checked to be in the range [0, 2] and then cast to the C++ enum File::LockType
which is then converted to the concrete platform type.

+  // Lock type arguments are checked in Dart code to be legal.

[Lasse Reichstein Nielsen, 2015/01/08 11:59:21]

legal -> valid.
It's not a law.

Don't trust Dart code, always check again in C code.

[Søren Gjesse, 2015/01/09 13:06:19]

I an also checking here. It they are not integers the "Illegal argument" below
will be thrown.

+  if (DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 1), &lock)) {
+    int64_t start;
+    int64_t end;
+    if (lock >= File::kLockMin &&
+        lock <= File::kLockMax &&
+        DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 2), &start) &&
+        DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 3), &end)) {
+      if (file->Lock(static_cast<File::LockType>(lock), start, end)) {
+        Dart_SetReturnValue(args, Dart_True());
+      } else {
+        Dart_Handle err = DartUtils::NewDartOSError();
+        if (Dart_IsError(err)) Dart_PropagateError(err);
+        Dart_SetReturnValue(args, err);
+      }
+      return;
+    }
+  }
+
+  OSError os_error(-1, "Invalid argument", OSError::kUnknown);
+  Dart_Handle err = DartUtils::NewDartOSError(&os_error);
+  if (Dart_IsError(err)) Dart_PropagateError(err);
+  Dart_SetReturnValue(args, err);
+}
+
+
 void FUNCTION_NAME(File_Create)(Dart_NativeArguments args) {
   const char* str =
       DartUtils::GetStringValue(Dart_GetNativeArgument(args, 0));
@@ -1196,5 +1226,30 @@ CObject* File::StatRequest(const CObjectArray& request) {
   return CObject::IllegalArgumentError();
 }
 
+
+CObject* File::LockRequest(const CObjectArray& request) {
+  if (request.Length() == 4 &&
+      request[0]->IsIntptr() &&
+      request[1]->IsInt32OrInt64() &&
+      request[2]->IsInt32OrInt64() &&
+      request[3]->IsInt32OrInt64()) {
+    File* file = CObjectToFilePointer(request[0]);
+    ASSERT(file != NULL);
+    if (!file->IsClosed()) {
+      int64_t lock = CObjectInt32OrInt64ToInt64(request[1]);
+      int64_t start = CObjectInt32OrInt64ToInt64(request[2]);
+      int64_t end = CObjectInt32OrInt64ToInt64(request[3]);
+      if (file->Lock(static_cast<File::LockType>(lock), start, end)) {
+        return CObject::True();
+      } else {
+        return CObject::NewOSError();
+      }
+    } else {
+      return CObject::FileClosedError();
+    }
+  }
+  return CObject::IllegalArgumentError();
+}
+
 }  // namespace bin
 }  // namespace dart