add bit flip helper for recover tests

diff --git a/testing/test_recover.py b/testing/test_recover.py
index 206f02b..b85b6dc 100644 (file)
--- a/testing/test_recover.py
+++ b/testing/test_recover.py
@@ -3,9 +3,25 @@ import os
 import shutil
 
 import deltatar.deltatar as deltatar
+import deltatar.crypto   as crypto
 
 from . import BaseTest
 
+def flip_bits (fname, off, b=0x01, n=1):
+    """
+    Open file *fname* at offset *off*, replacing the next *n* bytes with
+    their values xor’ed with *b*.
+    """
+    fd = os.open (fname, os.O_RDWR)
+    try:
+        pos = os.lseek (fd, off, os.SEEK_SET)
+        assert pos == off
+        chunk = os.read (fd, n)
+        chunk = bytes (map (lambda v: v ^ b, chunk))
+        os.write (fd, chunk)
+    finally:
+        os.close (fd)
+
 class RecoverTest (BaseTest):
     """
     Disaster recovery: restore corrupt backups.
@@ -45,10 +61,21 @@ class RecoverTest (BaseTest):
         Expects the extraction to fail in normal mode. With disaster recovery,
         extraction must succeed, and exactly one file must be missing.
         """
-        src_path = "source_dir2"
+        src_path       = "source_dir2"
+        dst_path       = "backup_dir"
+        backup_file    = "the_full_backup.gz"
+        backup_full    = "%s/%s" % (dst_path, backup_file)
+
+        fulldiff = lambda f: f and "full" or "diff"
+
+        def vname (*a, **kwa):
+            return backup_file
 
         dtar = deltatar.DeltaTar (mode="#gz",
-                                  logger=self.consoleLogger)
+                                  logger=self.consoleLogger,
+                                  index_name_func=lambda f: \
+                                    "the_%s_index" % fulldiff (f),
+                                  volume_name_func=vname)
 
         self.hash = dict ()
         os.makedirs (src_path)
@@ -57,6 +84,9 @@ class RecoverTest (BaseTest):
             self.hash [f] = self.create_file (f, i)
 
         dtar.create_full_backup \
-            (source_path="source_dir2", backup_path="backup_dir")
+            (source_path=src_path, backup_path=dst_path)
+
+        # damage byte just after first object header
+        flip_bits (backup_full, crypto.PDTCRYPT_HDR_SIZE + 1)
         shutil.rmtree (src_path)