Move runtime config code from config to config/engine

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

internal/config/engine/docker/docker.go

@@ -0,0 +1,117 @@
+/**
+# Copyright (c) 2021-2022, 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 docker
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// LoadConfig loads the docker config from disk
+func LoadConfig(configFilePath string) (map[string]interface{}, error) {
+	log.Infof("Loading docker config from %v", configFilePath)
+
+	info, err := os.Stat(configFilePath)
+	if os.IsExist(err) && info.IsDir() {
+		return nil, fmt.Errorf("config file is a directory")
+	}
+
+	cfg := make(map[string]interface{})
+
+	if os.IsNotExist(err) {
+		log.Infof("Config file does not exist, creating new one")
+		return cfg, nil
+	}
+
+	readBytes, err := ioutil.ReadFile(configFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("unable to read config: %v", err)
+	}
+
+	reader := bytes.NewReader(readBytes)
+	if err := json.NewDecoder(reader).Decode(&cfg); err != nil {
+		return nil, err
+	}
+
+	log.Infof("Successfully loaded config")
+	return cfg, nil
+}
+
+// UpdateConfig updates the docker config to include the nvidia runtimes
+func UpdateConfig(config map[string]interface{}, runtimeName string, runtimePath string, setAsDefault bool) error {
+	// Read the existing runtimes
+	runtimes := make(map[string]interface{})
+	if _, exists := config["runtimes"]; exists {
+		runtimes = config["runtimes"].(map[string]interface{})
+	}
+
+	// Add / update the runtime definitions
+	runtimes[runtimeName] = map[string]interface{}{
+		"path": runtimePath,
+		"args": []string{},
+	}
+
+	// Update the runtimes definition
+	if len(runtimes) > 0 {
+		config["runtimes"] = runtimes
+	}
+
+	if setAsDefault {
+		config["default-runtime"] = runtimeName
+	}
+
+	return nil
+}
+
+// FlushConfig flushes the updated/reverted config out to disk
+func FlushConfig(cfg map[string]interface{}, configFilePath string) error {
+	log.Infof("Flushing docker config to %v", configFilePath)
+
+	output, err := json.MarshalIndent(cfg, "", "    ")
+	if err != nil {
+		return fmt.Errorf("unable to convert to JSON: %v", err)
+	}
+
+	switch len(output) {
+	case 0:
+		err := os.Remove(configFilePath)
+		if err != nil {
+			return fmt.Errorf("unable to remove empty file: %v", err)
+		}
+		log.Infof("Config empty, removing file")
+	default:
+		f, err := os.Create(configFilePath)
+		if err != nil {
+			return fmt.Errorf("unable to open %v for writing: %v", configFilePath, err)
+		}
+		defer f.Close()
+
+		_, err = f.WriteString(string(output))
+		if err != nil {
+			return fmt.Errorf("unable to write output: %v", err)
+		}
+	}
+
+	log.Infof("Successfully flushed config")
+
+	return nil
+}