embedfs: Move the embedfs from go-git-fixtures

embedfs/embed.go

@@ -0,0 +1,251 @@
+// embedfs exposes an embed.FS as a read-only billy.Filesystem.
+package embedfs
+
+import (
+	"bytes"
+	"embed"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+
+	"github.com/go-git/go-billy/v6"
+	"github.com/go-git/go-billy/v6/memfs"
+)
+
+type Embed struct {
+	underlying *embed.FS
+}
+
+func New(efs *embed.FS) billy.Filesystem {
+	fs := &Embed{
+		underlying: efs,
+	}
+
+	if efs == nil {
+		fs.underlying = &embed.FS{}
+	}
+
+	return fs
+}
+
+func (fs *Embed) Root() string {
+	return ""
+}
+
+func (fs *Embed) Stat(filename string) (os.FileInfo, error) {
+	f, err := fs.underlying.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	return f.Stat()
+}
+
+func (fs *Embed) Open(filename string) (billy.File, error) {
+	return fs.OpenFile(filename, os.O_RDONLY, 0)
+}
+
+func (fs *Embed) OpenFile(filename string, flag int, _ os.FileMode) (billy.File, error) {
+	if flag&(os.O_CREATE|os.O_WRONLY|os.O_APPEND|os.O_RDWR|os.O_EXCL|os.O_TRUNC) != 0 {
+		return nil, billy.ErrReadOnly
+	}
+
+	f, err := fs.underlying.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	fi, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+
+	if fi.IsDir() {
+		return nil, fmt.Errorf("cannot open directory: %s", filename)
+	}
+
+	data, err := fs.underlying.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	// Only load the bytes to memory if the files is needed.
+	lazyFunc := func() *bytes.Reader { return bytes.NewReader(data) }
+	return toFile(lazyFunc, fi), nil
+}
+
+// Join return a path with all elements joined by forward slashes.
+//
+// This behaviour is OS-agnostic.
+func (fs *Embed) Join(elem ...string) string {
+	for i, el := range elem {
+		if el != "" {
+			clean := filepath.Clean(strings.Join(elem[i:], "/"))
+			return filepath.ToSlash(clean)
+		}
+	}
+	return ""
+}
+
+func (fs *Embed) ReadDir(path string) ([]os.FileInfo, error) {
+	e, err := fs.underlying.ReadDir(path)
+	if err != nil {
+		return nil, err
+	}
+
+	entries := make([]os.FileInfo, 0, len(e))
+	for _, f := range e {
+		fi, _ := f.Info()
+		entries = append(entries, fi)
+	}
+
+	sort.Sort(memfs.ByName(entries))
+
+	return entries, nil
+}
+
+// Chroot is not supported.
+//
+// Calls will always return billy.ErrNotSupported.
+func (fs *Embed) Chroot(_ string) (billy.Filesystem, error) {
+	return nil, billy.ErrNotSupported
+}
+
+// Lstat is not supported.
+//
+// Calls will always return billy.ErrNotSupported.
+func (fs *Embed) Lstat(_ string) (os.FileInfo, error) {
+	return nil, billy.ErrNotSupported
+}
+
+// Readlink is not supported.
+//
+// Calls will always return billy.ErrNotSupported.
+func (fs *Embed) Readlink(_ string) (string, error) {
+	return "", billy.ErrNotSupported
+}
+
+// TempFile is not supported.
+//
+// Calls will always return billy.ErrNotSupported.
+func (fs *Embed) TempFile(_, _ string) (billy.File, error) {
+	return nil, billy.ErrNotSupported
+}
+
+// Symlink is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (fs *Embed) Symlink(_, _ string) error {
+	return billy.ErrReadOnly
+}
+
+// Create is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (fs *Embed) Create(_ string) (billy.File, error) {
+	return nil, billy.ErrReadOnly
+}
+
+// Rename is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (fs *Embed) Rename(_, _ string) error {
+	return billy.ErrReadOnly
+}
+
+// Remove is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (fs *Embed) Remove(_ string) error {
+	return billy.ErrReadOnly
+}
+
+// MkdirAll is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (fs *Embed) MkdirAll(_ string, _ os.FileMode) error {
+	return billy.ErrReadOnly
+}
+
+func toFile(lazy func() *bytes.Reader, fi fs.FileInfo) billy.File {
+	return &file{
+		lazy: lazy,
+		fi:   fi,
+	}
+}
+
+type file struct {
+	lazy   func() *bytes.Reader
+	reader *bytes.Reader
+	fi     fs.FileInfo
+	once   sync.Once
+}
+
+func (f *file) loadReader() {
+	f.reader = f.lazy()
+}
+
+func (f *file) Name() string {
+	return f.fi.Name()
+}
+
+func (f *file) Read(b []byte) (int, error) {
+	f.once.Do(f.loadReader)
+
+	return f.reader.Read(b)
+}
+
+func (f *file) ReadAt(b []byte, off int64) (int, error) {
+	f.once.Do(f.loadReader)
+
+	return f.reader.ReadAt(b, off)
+}
+
+func (f *file) Seek(offset int64, whence int) (int64, error) {
+	f.once.Do(f.loadReader)
+
+	return f.reader.Seek(offset, whence)
+}
+
+func (f *file) Stat() (os.FileInfo, error) {
+	return f.fi, nil
+}
+
+// Close for embedfs file is a no-op.
+func (f *file) Close() error {
+	return nil
+}
+
+// Lock for embedfs file is a no-op.
+func (f *file) Lock() error {
+	return nil
+}
+
+// Unlock for embedfs file is a no-op.
+func (f *file) Unlock() error {
+	return nil
+}
+
+// Truncate is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (f *file) Truncate(_ int64) error {
+	return billy.ErrReadOnly
+}
+
+// Write is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (f *file) Write(_ []byte) (int, error) {
+	return 0, billy.ErrReadOnly
+}
+
+// WriteAt is not supported.
+//
+// Calls will always return billy.ErrReadOnly.
+func (f *file) WriteAt([]byte, int64) (int, error) {
+	return 0, billy.ErrReadOnly
+}