common/prpc, tools/cmd/cproto: prpc client

common/errors/wrap.go

Index: common/errors/wrap.go
diff --git a/common/errors/wrap.go b/common/errors/wrap.go
new file mode 100644
index 0000000000000000000000000000000000000000..93b78db9a3450da5b739b2a6578b45ceb375fe3d
--- /dev/null
+++ b/common/errors/wrap.go
@@ -0,0 +1,33 @@
+// Copyright 2016 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.
+
+package errors
+
+// Wrapped indicates an error that wraps another error.
+type Wrapped interface {
+	// InnerError returns the wrapped error.
+	InnerError() error
+}
+
+// Unwrap returns the inner error of err.
+// Returns nil if err does not wrap anything or err is nil.
+func Unwrap(err error) error {
+	if wrap, ok := err.(Wrapped); ok {
+		return wrap.InnerError()
+	}
+	return nil
+}
+
+// UnwrapAll unwraps a wrapped error recursively.
+// Returns nil iff err is nil.
+func UnwrapAll(err error) error {
+	for {
+		inner := Unwrap(err)
+		if inner == nil {
+			break
+		}
+		err = inner
+	}
+	return err
+}