1 files changed, 141 insertions, 0 deletions
diff --git a/scripts/update_payload/common.py b/scripts/update_payload/common.py
new file mode 100644
index 00000000..16509911
--- /dev/null
+++ b/scripts/update_payload/common.py
@@ -0,0 +1,141 @@
+# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Utilities for update payload processing."""
+
+import ctypes
+import textwrap
+
+from error import PayloadError
+import update_metadata_pb2
+
+
+#
+# Constants.
+#
+PSEUDO_EXTENT_MARKER = ctypes.c_uint64(-1).value
+
+
+#
+# Payload operation types.
+#
+class OpType(object):
+  """Container for operation type constants."""
+  _CLASS = update_metadata_pb2.DeltaArchiveManifest.InstallOperation
+  # pylint: disable=E1101
+  REPLACE = _CLASS.REPLACE
+  REPLACE_BZ = _CLASS.REPLACE_BZ
+  MOVE = _CLASS.MOVE
+  BSDIFF = _CLASS.BSDIFF
+  NAMES = {
+      REPLACE: 'REPLACE',
+      REPLACE_BZ: 'REPLACE_BZ',
+      MOVE: 'MOVE',
+      BSDIFF: 'BSDIFF',
+  }
+
+  def __init__(self):
+    pass
+
+
+#
+# Checker and hashed reading of data.
+#
+def Read(file_obj, length, offset=None, hasher=None):
+  """Reads binary data from a file.
+
+  Args:
+    file_obj: an open file object
+    length: the length of the data to read
+    offset: an offset to seek to prior to reading; this is an absolute offset
+            from either the beginning (non-negative) or end (negative) of the
+            file.  (optional)
+    hasher: a hashing object to pass the read data through (optional)
+  Returns:
+    A string containing the read data.
+  Raises:
+    PayloadError if a read error occurred or not enough data was read.
+
+  """
+  if offset is not None:
+    if offset >= 0:
+      file_obj.seek(offset)
+    else:
+      file_obj.seek(offset, 2)
+
+  try:
+    data = file_obj.read(length)
+  except IOError, e:
+    raise PayloadError('error reading from file (%s): %s' % (file_obj.name, e))
+
+  if len(data) != length:
+    raise PayloadError(
+        'reading from file (%s) too short (%d instead of %d bytes)' %
+        (file_obj.name, len(data), length))
+
+  if hasher:
+    hasher.update(data)
+
+  return data
+
+
+#
+# Formatting functions.
+#
+def FormatExtent(ex, block_size=0):
+  end_block = ex.start_block + ex.num_blocks
+  if block_size:
+    return '%d->%d * %d' % (ex.start_block, end_block, block_size)
+  else:
+    return '%d->%d' % (ex.start_block, end_block)
+
+
+def FormatSha256(digest):
+  """Returns a canonical string representation of a SHA256 digest."""
+  return '\n'.join(textwrap.wrap(digest.encode('hex'), 32))
+
+
+#
+# Useful iterators.
+#
+def _ObjNameIter(items, base_name, reverse=False, name_format_func=None):
+  """A generic (item, name) tuple iterators.
+
+  Args:
+    items: the sequence of objects to iterate on
+    base_name: the base name for all objects
+    reverse: whether iteration should be in reverse order
+    name_format_func: a function to apply to the name string
+  Yields:
+    An iterator whose i-th invocation returns (items[i], name), where name ==
+    base_name + '[i]' (with a formatting function optionally applied to it).
+
+  """
+  idx, inc = (len(items), -1) if reverse else (1, 1)
+  for item in items:
+    item_name = '%s[%d]' % (base_name, idx)
+    if name_format_func:
+      item_name = name_format_func(item, item_name)
+    yield (item, item_name)
+    idx += inc
+
+
+def _OperationNameFormatter(op, op_name):
+  return '%s(%s)' % (op_name, OpType.NAMES.get(op.type, '?'))
+
+
+def OperationIter(operations, base_name, reverse=False):
+  """An (item, name) iterator for update operations."""
+  return _ObjNameIter(operations, base_name, reverse=reverse,
+                      name_format_func=_OperationNameFormatter)
+
+
+def ExtentIter(extents, base_name, reverse=False):
+  """An (item, name) iterator for operation extents."""
+  return _ObjNameIter(extents, base_name, reverse=reverse)
+
+
+def SignatureIter(sigs, base_name, reverse=False):
+  """An (item, name) iterator for signatures."""
+  return _ObjNameIter(sigs, base_name, reverse=reverse)