bundle: Implement a DirectoryLoader for fs.FS (#3493)

To make it possible to create a DirectoryLoader based on the fs.FS interface.
This interface requires go version 1.16 or above.

Fixes: #3489

Signed-off-by: Simon Gottschlag <simon.gottschlag@xenit.se>

bundle/filefs.go

@@ -0,0 +1,73 @@
+// +build go1.16
+
+package bundle
+
+import (
+	"fmt"
+	"io"
+	"io/fs"
+	"sync"
+)
+
+const (
+	defaultFSLoaderRoot = "."
+)
+
+type dirLoaderFS struct {
+	sync.Mutex
+	filesystem fs.FS
+	files      []string
+	idx        int
+}
+
+// NewFSLoader returns a basic DirectoryLoader implementation
+// that will load files from a fs.FS interface
+func NewFSLoader(filesystem fs.FS) (DirectoryLoader, error) {
+	d := dirLoaderFS{
+		filesystem: filesystem,
+	}
+
+	err := fs.WalkDir(d.filesystem, defaultFSLoaderRoot, d.walkDir)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list files: %w", err)
+	}
+
+	return &d, nil
+}
+
+func (d *dirLoaderFS) walkDir(path string, dirEntry fs.DirEntry, err error) error {
+	if err != nil {
+		return err
+	}
+
+	if dirEntry != nil && dirEntry.Type().IsRegular() {
+		d.files = append(d.files, path)
+	}
+
+	return nil
+}
+
+// NextFile iterates to the next file in the directory tree
+// and returns a file Descriptor for the file.
+func (d *dirLoaderFS) NextFile() (*Descriptor, error) {
+	d.Lock()
+	defer d.Unlock()
+
+	// If done reading files then just return io.EOF
+	// errors for each NextFile() call
+	if d.idx >= len(d.files) {
+		return nil, io.EOF
+	}
+
+	fileName := d.files[d.idx]
+	d.idx++
+
+	fh, err := d.filesystem.Open(fileName)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open file %s: %w", fileName, err)
+	}
+
+	fileNameWithSlash := fmt.Sprintf("/%s", fileName)
+	f := newDescriptor(fileNameWithSlash, fileNameWithSlash, fh).withCloser(fh)
+	return f, nil
+}

bundle/filefs_test.go

@@ -0,0 +1,26 @@
+// +build go1.16
+
+package bundle
+
+import (
+	"strings"
+	"testing"
+	"testing/fstest"
+)
+
+func TestFSLoader(t *testing.T) {
+	archiveFS := make(fstest.MapFS)
+	for k, v := range archiveFiles {
+		file := strings.TrimPrefix(k, "/")
+		archiveFS[file] = &fstest.MapFile{
+			Data: []byte(v),
+		}
+	}
+
+	loader, err := NewFSLoader(archiveFS)
+	if err != nil {
+		t.Fatalf("Unexpected error: %s", err)
+	}
+
+	testLoader(t, loader, "", archiveFiles)
+}