reverse: resolve long names in Open and GetAttr

The last patch added functionality for generating gocryptfs.longname.*
files, this patch adds support for mapping them back to the full
filenames.

Note that resolving a long name needs a full readdir. A cache
will be implemented later on to improve performance.

1 files changed, 57 insertions, 0 deletions

diff --git a/internal/fusefrontend_reverse/virtualfile.go b/internal/fusefrontend_reverse/virtualfile.go
new file mode 100644
index 0000000..5373b48
--- /dev/null
+++ b/internal/fusefrontend_reverse/virtualfile.go
@@ -0,0 +1,57 @@
+package fusefrontend_reverse
+
+import (
+	"fmt"
+	"syscall"
+
+	"github.com/hanwen/go-fuse/fuse"
+	"github.com/hanwen/go-fuse/fuse/nodefs"
+)
+
+type virtualFile struct {
+	// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
+	nodefs.File
+	// file content
+	content []byte
+	// absolute path to a parent file
+	parentFile string
+	// inode number
+	ino uint64
+}
+
+func (rfs *reverseFS) NewVirtualFile(content []byte, parentFile string) (nodefs.File, fuse.Status) {
+	return &virtualFile{
+		File:       nodefs.NewDefaultFile(),
+		content:    content,
+		parentFile: parentFile,
+		ino:        rfs.inoGen.next(),
+	}, fuse.OK
+}
+
+// Read - FUSE call
+func (f *virtualFile) Read(buf []byte, off int64) (resultData fuse.ReadResult, status fuse.Status) {
+	if off >= int64(len(f.content)) {
+		return nil, fuse.OK
+	}
+	end := int(off) + len(buf)
+	if end > len(f.content) {
+		end = len(f.content)
+	}
+	return fuse.ReadResultData(f.content[off:end]), fuse.OK
+}
+
+// GetAttr - FUSE call
+func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
+	var st syscall.Stat_t
+	err := syscall.Lstat(f.parentFile, &st)
+	if err != nil {
+		fmt.Printf("Lstat %q: %v\n", f.parentFile, err)
+		return fuse.ToStatus(err)
+	}
+	st.Ino = f.ino
+	st.Size = int64(len(f.content))
+	st.Mode = syscall.S_IFREG | 0400
+	st.Nlink = 1
+	a.FromStat(&st)
+	return fuse.OK
+}