diff --git a/atrcopy/ataridos.py b/atrcopy/ataridos.py
index ef30602..ae34895 100644
--- a/atrcopy/ataridos.py
+++ b/atrcopy/ataridos.py
@@ -62,7 +62,7 @@ class AtariDosDirectory(Directory):
             num += 1
 
 
-class AtariDosDirent(object):
+class AtariDosDirent(Dirent):
     # ATR Dirent structure described at http://atari.kensclassics.org/dos.htm
     format = np.dtype([
         ('FLAG', 'u1'),
@@ -73,7 +73,7 @@ class AtariDosDirent(object):
         ])
 
     def __init__(self, image, file_num=0, bytes=None):
-        self.file_num = file_num
+        Dirent.__init__(self, file_num)
         self.flag = 0
         self.opened_output = False
         self.dos_2 = False
@@ -95,6 +95,9 @@ class AtariDosDirent(object):
     def __str__(self):
         return "File #%-2d (%s) %03d %-8s%-3s  %03d" % (self.file_num, self.summary, self.starting_sector, self.basename, self.ext, self.num_sectors)
 
+    def __eq__(self, other):
+        return self.__class__ == other.__class__ and self.filename == other.filename and self.starting_sector == other.starting_sector and self.num_sectors == other.num_sectors
+
     @property
     def filename(self):
         ext = ("." + self.ext) if self.ext else ""
diff --git a/atrcopy/diskimages.py b/atrcopy/diskimages.py
index 58b195c..bcf16cb 100644
--- a/atrcopy/diskimages.py
+++ b/atrcopy/diskimages.py
@@ -282,8 +282,11 @@ class DiskImageBase(object):
         return []
     
     def find_dirent(self, filename):
+        # check if we've been passed a dirent instead of a filename
+        if hasattr(filename, "filename"):
+            return filename
         for dirent in self.files:
-            if filename == dirent.filename:
+            if filename_or_dirent == dirent.filename:
                 return dirent
         raise FileNotFound("%s not found on disk" % filename)
     
diff --git a/atrcopy/dos33.py b/atrcopy/dos33.py
index 488005d..287457a 100644
--- a/atrcopy/dos33.py
+++ b/atrcopy/dos33.py
@@ -1,7 +1,8 @@
 import numpy as np
 
 from errors import *
-from diskimages import BaseHeader, DiskImageBase, Directory, VTOC, WriteableSector, BaseSectorList
+from diskimages import BaseHeader, DiskImageBase
+from utils import Directory, VTOC, WriteableSector, BaseSectorList, Dirent
 from segments import DefaultSegment, EmptySegment, ObjSegment, RawTrackSectorSegment, SegmentSaver
 
 import logging
@@ -143,7 +144,7 @@ class Dos33Directory(Directory):
             current_sector = next_sector
 
 
-class Dos33Dirent(object):
+class Dos33Dirent(Dirent):
     format = np.dtype([
         ('track', 'u1'),
         ('sector', 'u1'),
@@ -153,7 +154,7 @@ class Dos33Dirent(object):
         ])
 
     def __init__(self, image, file_num=0, bytes=None):
-        self.file_num = file_num
+        Dirent.__init__(self, file_num)
         self._file_type = 0
         self.locked = False
         self.deleted = False
@@ -170,6 +171,9 @@ class Dos33Dirent(object):
     
     def __str__(self):
         return "File #%-2d (%s) %03d %-30s %03d %03d" % (self.file_num, self.summary, self.num_sectors, self.filename, self.track, self.sector)
+
+    def __eq__(self, other):
+        return self.__class__ == other.__class__ and self.filename == other.filename and self.track == other.track and self.sector == other.sector and self.num_sectors == other.num_sectors
     
     type_map = {
         0x0: "T",  # text
diff --git a/atrcopy/utils.py b/atrcopy/utils.py
index 6495426..0071ad8 100644
--- a/atrcopy/utils.py
+++ b/atrcopy/utils.py
@@ -133,6 +133,35 @@ class BaseSectorList(object):
         self.sectors.extend(sectors)
 
 
+class Dirent(object):
+    """Abstract base class for a directory entry
+
+    """
+    def __init__(self, file_num=0):
+        self.file_num = file_num
+
+    def __eq__(self, other):
+        raise NotImplementedError
+
+    def mark_deleted(self):
+        raise NotImplementedError
+
+    def parse_raw_dirent(self, image, bytes):
+        raise NotImplementedError
+
+    def encode_dirent(self):
+        raise NotImplementedError
+
+    def get_sectors_in_vtoc(self, image):
+        raise NotImplementedError
+
+    def start_read(self, image):
+        raise NotImplementedError
+
+    def read_sector(self, image):
+        raise NotImplementedError
+
+
 class Directory(BaseSectorList):
     def __init__(self, header, num_dirents=-1, sector_class=WriteableSector):
         BaseSectorList.__init__(self, header)
@@ -167,9 +196,15 @@ class Directory(BaseSectorList):
         return dirent
 
     def find_dirent(self, filename):
-        for dirent in self.dirents.values():
-            if filename == dirent.filename:
-                return dirent
+        if hasattr(filename, "filename"):
+            # we've been passed a dirent instead of a filename
+            for dirent in self.dirents.values():
+                if dirent == filename:
+                    return dirent
+        else:
+            for dirent in self.dirents.values():
+                if filename == dirent.filename:
+                    return dirent
         raise FileNotFound("%s not found on disk" % filename)
 
     def save_dirent(self, image, dirent, vtoc, sector_list):