initial commit

filesystem.go

@@ -0,0 +1,65 @@
+// Copyright (C) 2019 Marius Schellenberger
+
+package authdav
+
+import (
+	"context"
+	"errors"
+	"golang.org/x/net/webdav"
+	"os"
+)
+
+// ErrWonly indicates forbidden operation
+var ErrWonly = errors.New("authdav: only file write once operations permitted")
+
+const writeFlag = os.O_RDWR | os.O_CREATE | os.O_TRUNC
+
+// WriteOnlyOnceFileSystem is a file write only wrapper for a webdav.FileSystem
+type WriteOnlyOnceFileSystem struct {
+	fs webdav.FileSystem
+}
+
+// NewWriteOnlyOnceFileSystem returns a new WriteOnlyOnceFileSystem wrapping a webdav.FileSystem
+func NewWriteOnlyOnceFileSystem(fs webdav.FileSystem) *WriteOnlyOnceFileSystem {
+	return &WriteOnlyOnceFileSystem{fs}
+}
+
+// Mkdir is not permitted
+func (fs *WriteOnlyOnceFileSystem) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	return ErrWonly
+}
+
+// OpenFile allows write only once operations
+func (fs *WriteOnlyOnceFileSystem) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
+	fi, err := fs.Stat(ctx, name)
+	if err == nil && fi.Mode().IsRegular() {
+		f, ok := fi.(*FileInfo)
+		if ok && flag == writeFlag && f.RealSize() > 0 {
+			return nil, ErrWonly
+		}
+	}
+	f, err := fs.fs.OpenFile(ctx, name, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return &File{f}, nil
+}
+
+// RemoveAll is not permitted
+func (fs *WriteOnlyOnceFileSystem) RemoveAll(ctx context.Context, name string) error {
+	return ErrWonly
+}
+
+// Rename is not permitted
+func (fs *WriteOnlyOnceFileSystem) Rename(ctx context.Context, oldName, newName string) error {
+	return ErrWonly
+}
+
+// Stat returns os.FileInfo wrapped in FileInfo
+func (fs *WriteOnlyOnceFileSystem) Stat(ctx context.Context, name string) (os.FileInfo, error) {
+	fi, err := fs.fs.Stat(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	return &FileInfo{fi}, nil
+}