Add python script to read/write u-boot environment

src/platform/uboot-env/uboot-env.py

+#!/usr/bin/python
+#
+# Copyright (c) 2010 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.
+
+from optparse import OptionParser
+import binascii
+import struct
+import sys
+
+# This script allows listing, reading and writing environment variables for
+# u-boot, that usually live in an area of a block device (NVRAM, e.g. NAND or
+# NOR flash).
+# The u-boot environment variable area is a crc (4 bytes) followed by all
+# environment variables as "key=value" strings (\0-terminated) with \0\0
+# (empty string) to indicate the end.
+
+
+class SizeError(Exception):
+  pass
+
+
+def ReadEnviron(file, size=0, offset=0):
+  """Reads the u-boot environment variables from a file into a dict."""
+  f = open(file, "rb")
+  f.seek(offset)
+  if size:
+    data = f.read(size)
+  else:
+    data = f.read()
+  f.close()
+
+  (crc,) = struct.unpack("I", data[0:4])
+  real_data = data[4:]
+  real_crc = binascii.crc32(real_data) & 0xffffffff
+  environ = {}
+  for s in real_data.split('\0'):
+    if not s:
+      break
+    key, value = s.split('=', 1)
+    environ[key] = value
+
+  return (environ, len(data), crc == real_crc)
+
+def WriteEnviron(file, environ, size, offset=0):
+  """Writes the u-boot environment variables from a dict into a file."""
+  strings = ['%s=%s' % (k, environ[k]) for k in environ]
+  data = '\0'.join(strings + [''])
+
+  # pad with \0
+  if len(data) <= size-4:
+    data = data + '\0'*(size-len(data)-4)
+  else:
+    raise SizeError
+
+  crc = binascii.crc32(data) & 0xffffffff
+
+  f = open(file, "r+b")
+  f.seek(offset)
+  f.write(struct.pack("I", crc)[0:4])
+  f.write(data)
+  f.close()
+
+
+def main(argv):
+  parser = OptionParser()
+  parser.add_option('-f', '--file', type='string', dest='filename')
+  parser.add_option('-o', '--offset', type='int', dest='offset', default=0)
+  parser.add_option('-s', '--size', type='int', dest='size', default=0)
+  parser.add_option('--out', type='string', dest='out_filename')
+  parser.add_option('--out-offset', type='string', dest='out_offset')
+  parser.add_option('--out-size', type='string', dest='out_size')
+  parser.add_option('--list', action='store_true', dest='list')
+  parser.add_option('--force', action='store_true', dest='force')
+  parser.add_option('--get', type='string', action='append', dest='get',
+                    default=[])
+  parser.add_option('--set', type='string', action='append', dest='set',
+                    default=[])
+  (options, args) = parser.parse_args()
+  (environ, size, crc) = ReadEnviron(options.filename, options.size,
+                                     options.offset)
+  if not crc:
+    sys.stderr.write('Bad CRC\n')
+    if not options.force:
+      sys.exit(1)
+
+  if options.list:
+    for key in environ:
+      print "%s=%s" % (key, environ[key])
+
+  for key in options.get:
+    try:
+      print environ[key]
+    except KeyError:
+      print ''
+
+  do_write = False
+  for key_value in options.set:
+    key, value = key_value.split('=', 1)
+    environ[key] = value
+    do_write = True
+
+  if do_write:
+    out_filename = options.out_filename
+    out_offset = options.out_offset
+    out_size = options.out_size
+    if not out_filename:
+      out_filename = options.filename
+      out_offset = options.offset
+      out_size = size
+    WriteEnviron(out_filename, environ, out_size, out_offset)
+
+
+if __name__ == '__main__':
+  main(sys.argv)