diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 8bbe452..e98e4b6 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -30,6 +30,9 @@
 
 import errno
 import os
+import re
+import shutil
+import subprocess
 import tempfile
 import zipfile
 
@@ -67,8 +70,10 @@
   block_list = common.MakeTempFile(prefix="system-blocklist-", suffix=".map")
   imgname = BuildSystem(OPTIONS.input_tmp, OPTIONS.info_dict,
                         block_list=block_list)
-  common.ZipWrite(output_zip, imgname, prefix + "system.img")
-  common.ZipWrite(output_zip, block_list, prefix + "system.map")
+  with open(imgname, "rb") as f:
+    common.ZipWriteStr(output_zip, prefix + "system.img", f.read())
+  with open(block_list, "rb") as f:
+    common.ZipWriteStr(output_zip, prefix + "system.map", f.read())
 
 
 def BuildSystem(input_dir, info_dict, block_list=None):
@@ -89,8 +94,10 @@
   block_list = common.MakeTempFile(prefix="vendor-blocklist-", suffix=".map")
   imgname = BuildVendor(OPTIONS.input_tmp, OPTIONS.info_dict,
                      block_list=block_list)
-  common.ZipWrite(output_zip, imgname, prefix + "vendor.img")
-  common.ZipWrite(output_zip, block_list, prefix + "vendor.map")
+  with open(imgname, "rb") as f:
+    common.ZipWriteStr(output_zip, prefix + "vendor.img", f.read())
+  with open(block_list, "rb") as f:
+    common.ZipWriteStr(output_zip, prefix + "vendor.map", f.read())
 
 
 def BuildVendor(input_dir, info_dict, block_list=None):
@@ -289,6 +296,7 @@
   output_zip.close()
 
 def main(argv):
+
   def option_handler(o, a):
     if o in ("-a", "--add_missing"):
       OPTIONS.add_missing = True
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index ed313d9..8941f89 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -781,44 +781,6 @@
     return result
 
 
-def ZipWrite(zip_file, filename, arcname=None, perms=0o644,
-             compress_type=None):
-  import datetime
-
-  # http://b/18015246
-  # Python 2.7's zipfile implementation wrongly thinks that zip64 is required
-  # for files larger than 2GiB. We can work around this by adjusting their
-  # limit. Note that `zipfile.writestr()` will not work for strings larger than
-  # 2GiB. The Python interpreter sometimes rejects strings that large (though
-  # it isn't clear to me exactly what circumstances cause this).
-  # `zipfile.write()` must be used directly to work around this.
-  #
-  # This mess can be avoided if we port to python3.
-  saved_zip64_limit = zipfile.ZIP64_LIMIT
-  zipfile.ZIP64_LIMIT = (1 << 32) - 1
-
-  compress_type = compress_type or zip_file.compression
-  arcname = arcname or filename
-
-  saved_stat = os.stat(filename)
-
-  try:
-    # `zipfile.write()` doesn't allow us to pass ZipInfo, so just modify the
-    # file to be zipped and reset it when we're done.
-    os.chmod(filename, perms)
-
-    # Use a fixed timestamp so the output is repeatable.
-    epoch = datetime.datetime.fromtimestamp(0)
-    timestamp = (datetime.datetime(2009, 1, 1) - epoch).total_seconds()
-    os.utime(filename, (timestamp, timestamp))
-
-    zip_file.write(filename, arcname=arcname, compress_type=compress_type)
-  finally:
-    os.chmod(filename, saved_stat.st_mode)
-    os.utime(filename, (saved_stat.st_atime, saved_stat.st_mtime))
-    zipfile.ZIP64_LIMIT = saved_zip64_limit
-
-
 def ZipWriteStr(zip, filename, data, perms=0644, compression=None):
   # use a fixed timestamp so the output is repeatable.
   zinfo = zipfile.ZipInfo(filename=filename,
@@ -1112,21 +1074,19 @@
                           self.tgt.TotalSha1(), self.partition))
 
   def _WriteUpdate(self, script, output_zip):
-    ZipWrite(output_zip,
-             '{}.transfer.list'.format(self.path),
-             '{}.transfer.list'.format(self.partition))
-    ZipWrite(output_zip,
-             '{}.new.dat'.format(self.path),
-             '{}.new.dat'.format(self.partition))
-    ZipWrite(output_zip,
-             '{}.patch.dat'.format(self.path),
-             '{}.patch.dat'.format(self.partition),
-             compress_type=zipfile.ZIP_STORED)
+    partition = self.partition
+    with open(self.path + ".transfer.list", "rb") as f:
+      ZipWriteStr(output_zip, partition + ".transfer.list", f.read())
+    with open(self.path + ".new.dat", "rb") as f:
+      ZipWriteStr(output_zip, partition + ".new.dat", f.read())
+    with open(self.path + ".patch.dat", "rb") as f:
+      ZipWriteStr(output_zip, partition + ".patch.dat", f.read(),
+                         compression=zipfile.ZIP_STORED)
 
-    call = ('block_image_update("{device}", '
-            'package_extract_file("{partition}.transfer.list"), '
-            '"{partition}.new.dat", "{partition}.patch.dat");\n'.format(
-                device=self.device, partition=self.partition))
+    call = (('block_image_update("%s", '
+             'package_extract_file("%s.transfer.list"), '
+             '"%s.new.dat", "%s.patch.dat");\n') %
+            (self.device, partition, partition, partition))
     script.AppendExtra(script._WordWrap(call))
 
   def _CheckFirstBlock(self, script):
diff --git a/tools/releasetools/img_from_target_files.py b/tools/releasetools/img_from_target_files.py
index a9d4cbe..4b88e73 100755
--- a/tools/releasetools/img_from_target_files.py
+++ b/tools/releasetools/img_from_target_files.py
@@ -88,13 +88,11 @@
       # and all we have to do is copy them to the output zip.
       images = os.listdir(images_path)
       if images:
-        for image in images:
-          if bootable_only and image not in ("boot.img", "recovery.img"):
-            continue
-          if not image.endswith(".img"):
-            continue
-          common.ZipWrite(
-              output_zip, os.path.join(images_path, image), image)
+        for i in images:
+          if bootable_only and i not in ("boot.img", "recovery.img"): continue
+          if not i.endswith(".img"): continue
+          with open(os.path.join(images_path, i), "r") as f:
+            common.ZipWriteStr(output_zip, i, f.read())
         done = True
 
     if not done:
diff --git a/tools/releasetools/ota_from_target_files b/tools/releasetools/ota_from_target_files
index 6517bf3..945f11a 100755
--- a/tools/releasetools/ota_from_target_files
+++ b/tools/releasetools/ota_from_target_files
@@ -646,8 +646,10 @@
   WriteMetadata(metadata, output_zip)
 
 
-def WritePolicyConfig(file_name, output_zip):
-  common.ZipWrite(output_zip, file_name, os.path.basename(file_name))
+def WritePolicyConfig(file_context, output_zip):
+  f = open(file_context, 'r');
+  basename = os.path.basename(file_context)
+  common.ZipWriteStr(output_zip, basename, f.read())
 
 
 def WriteMetadata(metadata, output_zip):
diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
deleted file mode 100644
index f163f92..0000000
--- a/tools/releasetools/test_common.py
+++ /dev/null
@@ -1,108 +0,0 @@
-#
-# Copyright (C) 2015 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-import os
-import tempfile
-import time
-import unittest
-import zipfile
-
-import common
-
-
-def random_string_with_holes(size, block_size, step_size):
-  data = ["\0"] * size
-  for begin in range(0, size, step_size):
-    end = begin + block_size
-    data[begin:end] = os.urandom(block_size)
-  return "".join(data)
-
-
-class CommonZipTest(unittest.TestCase):
-  def _test_ZipWrite(self, contents, extra_zipwrite_args=None):
-    extra_zipwrite_args = dict(extra_zipwrite_args or {})
-
-    test_file = tempfile.NamedTemporaryFile(delete=False)
-    zip_file = tempfile.NamedTemporaryFile(delete=False)
-
-    test_file_name = test_file.name
-    zip_file_name = zip_file.name
-
-    # File names within an archive strip the leading slash.
-    arcname = extra_zipwrite_args.get("arcname", test_file_name)
-    if arcname[0] == "/":
-      arcname = arcname[1:]
-
-    zip_file.close()
-    zip_file = zipfile.ZipFile(zip_file_name, "w")
-
-    try:
-      test_file.write(contents)
-      test_file.close()
-
-      old_stat = os.stat(test_file_name)
-      expected_mode = extra_zipwrite_args.get("perms", 0o644)
-
-      time.sleep(5)  # Make sure the atime/mtime will change measurably.
-
-      common.ZipWrite(zip_file, test_file_name, **extra_zipwrite_args)
-
-      new_stat = os.stat(test_file_name)
-      self.assertEqual(int(old_stat.st_mode), int(new_stat.st_mode))
-      self.assertEqual(int(old_stat.st_mtime), int(new_stat.st_mtime))
-
-      zip_file.close()
-      zip_file = zipfile.ZipFile(zip_file_name, "r")
-      info = zip_file.getinfo(arcname)
-
-      self.assertEqual(info.date_time, (2009, 1, 1, 0, 0, 0))
-      mode = (info.external_attr >> 16) & 0o777
-      self.assertEqual(mode, expected_mode)
-      self.assertEqual(zip_file.read(arcname), contents)
-    finally:
-      os.remove(test_file_name)
-      os.remove(zip_file_name)
-
-  def test_ZipWrite(self):
-    file_contents = os.urandom(1024)
-    self._test_ZipWrite(file_contents)
-
-  def test_ZipWrite_with_opts(self):
-    file_contents = os.urandom(1024)
-    self._test_ZipWrite(file_contents, {
-        "arcname": "foobar",
-        "perms": 0o777,
-        "compress_type": zipfile.ZIP_DEFLATED,
-    })
-
-  def test_ZipWrite_large_file(self):
-    kilobytes = 1024
-    megabytes = 1024 * kilobytes
-    gigabytes = 1024 * megabytes
-
-    size = int(2 * gigabytes + 1)
-    block_size = 4 * kilobytes
-    step_size = 4 * megabytes
-    file_contents = random_string_with_holes(
-        size, block_size, step_size)
-    self._test_ZipWrite(file_contents, {
-        "compress_type": zipfile.ZIP_DEFLATED,
-    })
-
-  def test_ZipWrite_resets_ZIP64_LIMIT(self):
-    default_limit = (1 << 31) - 1
-    self.assertEqual(default_limit, zipfile.ZIP64_LIMIT)
-    self._test_ZipWrite('')
-    self.assertEqual(default_limit, zipfile.ZIP64_LIMIT)