Migrate Python code to Python 3.

makecab.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import sys
 import os
@@ -10,7 +10,7 @@ from collections import namedtuple
 CFHEADER_s = struct.Struct("<4sLLLLLBBHHHHH")
 CFHEADER = namedtuple("CFHEADER", "sig res0 size res1 firstfile res2 "
                       "verminor vermajor folders files flags setid icabinet")
-CFHEADER_sig = "MSCF"
+CFHEADER_sig = b"MSCF"
 
 CFFOLDER_s = struct.Struct("<LHH")
 CFFOLDER = namedtuple("CFFOLDER", "firstdata ndata compresstype")
@@ -26,7 +26,7 @@ def mszip(data):
                                   zlib.DEF_MEM_LEVEL, zlib.Z_DEFAULT_STRATEGY)
     compressed = compressor.compress(data)
     compressed += compressor.flush()
-    return "CK" + compressed # add MSZIP header
+    return b"CK" + compressed # add MSZIP header
 
 def packdate(y,m,d):
     return ((y - 1980) << 9) | (m << 5) | d
@@ -34,19 +34,20 @@ def packtime(h,m,s):
     return ((h << 11) | (m << 5) | (s >> 1))
 
 def checksum(data):
-    data_full_words = data[:len(data) & ~3]
-    data_last_word = data[len(data_full_words):]
-    data_last_word = "".join(reversed(data_last_word))
-    data_last_word += "\0" * (3 & -len(data)) # pad to multiple of 4 bytes
-    data = data_full_words + data_last_word
+    data_fullwords_len = len(data) & ~3
+    data_last_word = data[data_fullwords_len:]
+    data_last_word = bytes(reversed(data_last_word))
+    data_last_word += b"\0" * (3 & -len(data)) # pad to multiple of 4 bytes
     toret = 0
-    for offset in xrange(0, len(data), 4):
-        toret ^= struct.unpack_from("<L", data, offset)[0]
+    for part, partlen in ((data, data_fullwords_len),
+                          (data_last_word, len(data_last_word))):
+        for offset in range(0, partlen, 4):
+            toret ^= struct.unpack_from("<L", part, offset)[0]
     return toret
 
 def build_cab(files):
-    uncompressed_data = ""
-    fileheaders = ""
+    uncompressed_data = b""
+    fileheaders = b""
     for name, data, mtime in files:
         mtime_u = time.gmtime(mtime)
         fileheader = CFFILE(
@@ -54,9 +55,10 @@ def build_cab(files):
             date=packdate(mtime_u.tm_year, mtime_u.tm_mon, mtime_u.tm_mday),
             time=packtime(mtime_u.tm_hour, mtime_u.tm_min, mtime_u.tm_sec))
         uncompressed_data += data
-        fileheaders += CFFILE_s.pack(*fileheader) + name + "\0"
+        fileheaders += CFFILE_s.pack(*fileheader)
+        fileheaders += name.encode("ASCII") + b"\0"
 
-    compressed_data = ""
+    compressed_data = b""
     offset = 0
     n_data_blocks = 0
     while offset < len(uncompressed_data):

wrapper.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import sys
 import os