Mojo cpp bindings: report the reason of validation failure.

mojo/public/cpp/bindings/lib/validation_errors.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_VALIDATION_ERRORS_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_VALIDATION_ERRORS_H_
+
+#include "mojo/public/cpp/system/macros.h"
+
+namespace mojo {
+namespace internal {
+
+enum ValidationError {
+  // There is no validation error.
+  VALIDATION_ERROR_NONE,
+  // An object (struct or array) is not 8-byte aligned.
+  VALIDATION_ERROR_MISALIGNED_OBJECT,
+  // An object is not contained inside the message data, or it overlaps other
+  // objects.
+  VALIDATION_ERROR_ILLEGAL_MEMORY_RANGE,
+  // A struct header doesn't make sense, for example:
+  // - |num_bytes| is smaller than the size of the oldest version that we
+  // support.
+  // - |num_fields| is smaller than the field number of the oldest version that
+  // we support.
+  // - |num_bytes| and |num_fields| don't match.
+  VALIDATION_ERROR_UNEXPECTED_STRUCT_HEADER,
+  // An array header doesn't make sense, for example:
+  // - |num_bytes| is smaller than the size of the header plus the size required
+  // to store |num_elements| elements.
+  VALIDATION_ERROR_UNEXPECTED_ARRAY_HEADER,
+  // An encoded handle is illegal.
+  VALIDATION_ERROR_ILLEGAL_HANDLE,
+  // An encoded pointer is illegal.
+  VALIDATION_ERROR_ILLEGAL_POINTER,
+  // |flags| in the message header is an invalid flag combination.
+  VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINAION,
+  // |flags| in the message header indicates that a request ID is required but
+  // there isn't one.
+  VALIDATION_ERROR_MESSAGE_HEADER_MISSING_REQUEST_ID,
+};
+
+const char* ValidationErrorToString(ValidationError error);
+
+void ReportValidationError(ValidationError error);
+
+// Only used by validation tests and when there is only one thread doing message
+// validation.
+class ValidationErrorObserverForTesting {
+ public:
+  ValidationErrorObserverForTesting();
+  ~ValidationErrorObserverForTesting();
+
+  ValidationError last_error() const { return last_error_; }
+  void set_last_error(ValidationError error) { last_error_ = error; }
+
+ private:
+  ValidationError last_error_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(ValidationErrorObserverForTesting);
+};
+
+}  // namespace internal
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_VALIDATION_ERRORS_H_