Add engine.Config to encapsulate writing

This change adds an engine.Config type to encapsulate the writing
of config files for container engines.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

pkg/config/engine/config.go

@@ -0,0 +1,53 @@
+/**
+# Copyright (c) NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package engine
+
+import (
+	"fmt"
+	"os"
+)
+
+// Config represents a runtime config
+type Config string
+
+// Write writes the specified contents to a config file.
+func (c Config) Write(output []byte) (int, error) {
+	path := string(c)
+	if path == "" {
+		n, err := os.Stdout.Write(output)
+		if err == nil {
+			os.Stdout.WriteString("\n")
+		}
+		return n, err
+	}
+
+	if len(output) == 0 {
+		err := os.Remove(path)
+		if err != nil {
+			return 0, fmt.Errorf("unable to remove empty file: %v", err)
+		}
+		return 0, nil
+	}
+
+	f, err := os.Create(path)
+	if err != nil {
+		return 0, fmt.Errorf("unable to open %v for writing: %v", path, err)
+	}
+	defer f.Close()
+
+	return f.Write(output)
+}