Add code to process Jetpack CSV files

This change adds code to process Jetpack CSV mount specifications.

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

internal/discover/csv/csv.go

@@ -0,0 +1,90 @@
+/**
+# Copyright (c) 2021, 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 csv
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	// DefaultRoot is default location of CSV files that define the modifications required to the OCI spec
+	DefaultRoot = "/etc/nvidia-container-runtime/host-files-for-container.d"
+)
+
+// GetFileList returns the (non-recursive) list of CSV files in the specified
+// folder
+func GetFileList(root string) ([]string, error) {
+	contents, err := os.ReadDir(root)
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		return nil, nil
+	} else if err != nil {
+		return nil, fmt.Errorf("failed to read the contents of %v: %v", root, err)
+	}
+
+	var csvFilePaths []string
+	for _, c := range contents {
+		if c.IsDir() {
+			continue
+		}
+		if c.Name() == ".csv" {
+			continue
+		}
+		ext := strings.ToLower(filepath.Ext(c.Name()))
+		if ext != ".csv" {
+			continue
+		}
+
+		csvFilePaths = append(csvFilePaths, filepath.Join(root, c.Name()))
+	}
+
+	return csvFilePaths, nil
+}
+
+// ParseFile parses the specified file and returns a list of required jetson mounts
+func ParseFile(logger *logrus.Logger, filename string) ([]*MountSpec, error) {
+	csvFile, err := os.Open(filename)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open %v for reading: %v", filename, err)
+	}
+	return parseCSVFromReader(logger, csvFile), nil
+}
+
+// parseCSVFromReader parses the specified file and returns a list of required jetson mounts
+func parseCSVFromReader(logger *logrus.Logger, reader io.Reader) []*MountSpec {
+	var targets []*MountSpec
+
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		line := scanner.Text()
+		target, err := NewMountSpecFromLine(line)
+		if err != nil {
+			logger.Debugf("Skipping invalid mount spec '%v': %v", line, err)
+			continue
+		}
+		targets = append(targets, target)
+	}
+
+	return targets
+}