diff --git a/tools/releasetools/simg_map.py b/tools/releasetools/simg_map.py
new file mode 100644
index 0000000..22dc863
--- /dev/null
+++ b/tools/releasetools/simg_map.py
@@ -0,0 +1,148 @@
+#! /usr/bin/env python
+
+# Copyright (C) 2012 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.
+
+from __future__ import print_function
+import getopt, posixpath, signal, struct, sys
+
+def main():
+  if len(sys.argv) == 4:
+    print("No sparse_image_file specified")
+    usage(me)
+
+  sparse_fn = sys.argv[1]
+  unsparse_fn = sys.argv[2]
+  map_file = sys.argv[3]
+  mapped_unsparse_fn = sys.argv[4]
+
+  return ComputeMap(sparse_fn, unsparse_fn, map_file, mapped_unsparse_fn)
+
+
+def ComputeMap(sparse_fn, unsparse_fn, map_file, mapped_unsparse_fn):
+  care_map = []
+
+  with open(sparse_fn, "rb") as FH:
+    header_bin = FH.read(28)
+    header = struct.unpack("<I4H4I", header_bin)
+
+    magic = header[0]
+    major_version = header[1]
+    minor_version = header[2]
+    file_hdr_sz = header[3]
+    chunk_hdr_sz = header[4]
+    blk_sz = header[5]
+    total_blks = header[6]
+    total_chunks = header[7]
+    image_checksum = header[8]
+
+    if magic != 0xED26FF3A:
+      print("%s: %s: Magic should be 0xED26FF3A but is 0x%08X"
+            % (me, path, magic))
+      return 1
+    if major_version != 1 or minor_version != 0:
+      print("%s: %s: I only know about version 1.0, but this is version %u.%u"
+            % (me, path, major_version, minor_version))
+      return 1
+    if file_hdr_sz != 28:
+      print("%s: %s: The file header size was expected to be 28, but is %u."
+            % (me, path, file_hdr_sz))
+      return 1
+    if chunk_hdr_sz != 12:
+      print("%s: %s: The chunk header size was expected to be 12, but is %u."
+            % (me, path, chunk_hdr_sz))
+      return 1
+
+    print("%s: Total of %u %u-byte output blocks in %u input chunks."
+          % (sparse_fn, total_blks, blk_sz, total_chunks))
+
+    offset = 0
+    for i in range(total_chunks):
+      header_bin = FH.read(12)
+      header = struct.unpack("<2H2I", header_bin)
+      chunk_type = header[0]
+      reserved1 = header[1]
+      chunk_sz = header[2]
+      total_sz = header[3]
+      data_sz = total_sz - 12
+
+      if chunk_type == 0xCAC1:
+        if data_sz != (chunk_sz * blk_sz):
+          print("Raw chunk input size (%u) does not match output size (%u)"
+                % (data_sz, chunk_sz * blk_sz))
+          return 1
+        else:
+          care_map.append((1, chunk_sz))
+          FH.seek(data_sz, 1)
+
+      elif chunk_type == 0xCAC2:
+        print("Fill chunks are not supported")
+        return 1
+
+      elif chunk_type == 0xCAC3:
+        if data_sz != 0:
+          print("Don't care chunk input size is non-zero (%u)" % (data_sz))
+          return 1
+        else:
+          care_map.append((0, chunk_sz))
+
+      elif chunk_type == 0xCAC4:
+        print("CRC32 chunks are not supported")
+
+      else:
+        print("Unknown chunk type 0x%04X not supported" % (chunk_type,))
+        return 1
+
+      offset += chunk_sz
+
+    if total_blks != offset:
+      print("The header said we should have %u output blocks, but we saw %u"
+            % (total_blks, offset))
+
+    junk_len = len(FH.read())
+    if junk_len:
+      print("There were %u bytes of extra data at the end of the file."
+            % (junk_len))
+      return 1
+
+  last_kind = None
+  new_care_map = []
+  for kind, size in care_map:
+    if kind != last_kind:
+      new_care_map.append((kind, size))
+      last_kind = kind
+    else:
+      new_care_map[-1] = (kind, new_care_map[-1][1] + size)
+
+  if new_care_map[0][0] == 0:
+    new_care_map.insert(0, (1, 0))
+  if len(new_care_map) % 2:
+    new_care_map.append((0, 0))
+
+  with open(map_file, "w") as fmap:
+    fmap.write("%d\n%d\n" % (blk_sz, len(new_care_map)))
+    for _, sz in new_care_map:
+      fmap.write("%d\n" % sz)
+
+  with open(unsparse_fn, "rb") as fin:
+    with open(mapped_unsparse_fn, "wb") as fout:
+      for k, sz in care_map:
+        data = fin.read(sz * blk_sz)
+        if k:
+          fout.write(data)
+        else:
+          assert data == "\x00" * len(data)
+
+if __name__ == "__main__":
+  sys.exit(main())