From 3781f711fb6e71fdfff67714d026a4cc7ca72086 Mon Sep 17 00:00:00 2001
From: Christian Herdtweck <christian.herdtweck@intra2net.com>
Date: Thu, 30 Nov 2017 17:33:39 +0100
Subject: [PATCH] ooxml: implement skipping data in ZipSubFile

---
 oletools/ooxml.py | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/oletools/ooxml.py b/oletools/ooxml.py
index 3de095c..4f299b9 100644
--- a/oletools/ooxml.py
+++ b/oletools/ooxml.py
@@ -198,12 +198,24 @@ class ZipSubFile(object):
 
         only re-positioning to start of file is allowed
         """
+        CHUNK_SIZE = 4096
         if pos == 0 and offset == io.SEEK_SET:
             self.reset()
-        elif pos == -self.pos and offset == io.SEEK_CUR:
-            self.reset()
+        elif offset == io.SEEK_CUR:
+            if pos == -self.pos:
+                self.reset()
+            elif pos == 0:
+                return
+            elif pos > 0:
+                skipped = 0
+                n_chunks, leftover = divmod(pos, CHUNK_SIZE)
+                for _ in range(n_chunks):
+                    self.read(CHUNK_SIZE)    # just read and discard
+                self.read(leftover)
+            else:
+                raise NotImplementedError('could reset() and read()?')
         else:
-            raise NotImplementedError('could reset() and read()')
+            raise NotImplementedError('could reset() and read()?')
 
     def tell(self):
         """ inform about position of next read """
--
libgit2 0.21.4