build_library/cgpt.py

#!/usr/bin/python
# Copyright (c) 2012 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.

import copy
import json
import optparse
import os
import re
import sys

# First sector we can use.
START_SECTOR = 64

class ConfigNotFound(Exception):
  pass
class PartitionNotFound(Exception):
  pass
class InvalidLayout(Exception):
  pass
class InvalidAdjustment(Exception):
  pass


BASE_LAYOUT = 'base'
_INHERITED_LAYOUT_KEYS = set(('type', 'label', 'features', 'format',
                              'fs_format',))


def ParseHumanNumber(operand):
  """Parse a human friendly number

  This handles things like 4GiB and 4MB and such.  See the usage string for
  full details on all the formats supported.

  Args:
    operand: The number to parse (may be an int or string)
  Returns:
    An integer
  """
  operand = str(operand)
  negative = -1 if operand.startswith('-') else 1
  if negative == -1:
    operand = operand[1:]
  operand_digits = re.sub(r'\D', r'', operand)

  size_factor = block_factor = 1
  suffix = operand[len(operand_digits):].strip()
  if suffix:
    size_factors = { 'B': 0, 'K': 1, 'M': 2, 'G': 3, 'T': 4, }
    try:
      size_factor = size_factors[suffix[0].upper()]
    except KeyError:
      raise InvalidAdjustment('Unknown size type %s' % suffix)
    if size_factor == 0 and len(suffix) > 1:
      raise InvalidAdjustment('Unknown size type %s' % suffix)
    block_factors = { '': 1024, 'B': 1000, 'IB': 1024, }
    try:
      block_factor = block_factors[suffix[1:].upper()]
    except KeyError:
      raise InvalidAdjustment('Unknown size type %s' % suffix)

  return int(operand_digits) * pow(block_factor, size_factor) * negative


def ParseRelativeNumber(max_number, number):
  """Return the number that is relative to |max_number| by |number|

  We support three forms:
   90% - |number| is a percentage of |max_number|
   100 - |number| is the answer already (and |max_number| is ignored)
   -90 - |number| is subtracted from |max_number|

  Args:
    max_number: The limit to use when |number| is negative or a percent
    number: The (possibly relative) number to parse (may be an int or string)
  """
  max_number = int(max_number)
  number = str(number)
  if number.endswith('%'):
    percent = float(number[:-1]) / 100
    return int(max_number * percent)
  else:
    number = ParseHumanNumber(number)
    if number < 0:
      return max_number + number
    else:
      return number


def _LoadStackedPartitionConfig(filename):
  """Loads a partition table and its possible parent tables.

  This does very little validation.  It's just enough to walk all of the parent
  files and merge them with the current config.  Overall validation is left to
  the caller.

  Args:
    filename: Filename to load into object
  Returns:
    Object containing disk layout configuration
  """
  if not os.path.exists(filename):
    raise ConfigNotFound('Partition config %s was not found!' % filename)
  with open(filename) as f:
    config = json.load(f)

  dirname = os.path.dirname(filename)
  for parent in config.get('parent', '').split():
    parent_filename = os.path.join(dirname, parent)
    parent_config = _LoadStackedPartitionConfig(parent_filename)

    # Now hand merge the current config over the parent config.  Each field
    # has its own stacking rules, so we have to do this.
    parent_config.setdefault('metadata', {})
    parent_config['metadata'].update(config.get('metadata', {}))

    parent_config.setdefault('layouts', config.get('layouts', {}))
    for layout_name, layout in config['layouts'].iteritems():
      for part in layout:
        if 'num' not in part:
          continue
        num = part['num']
        for parent_part in parent_config['layouts'].get(layout_name, []):
          if parent_part.get('num') == num:
            for k, v in part.iteritems():
              if k not in _INHERITED_LAYOUT_KEYS and k in part:
                parent_part[k] = v
            break

    config = parent_config

  config.pop('parent', None)
  return config


def LoadPartitionConfig(filename):
  """Loads a partition tables configuration file into a Python object.

  Args:
    filename: Filename to load into object
  Returns:
    Object containing disk layout configuration
  """

  valid_keys = set(('_comment', 'hybrid_mbr', 'metadata', 'layouts', 'parent'))
  valid_layout_keys = _INHERITED_LAYOUT_KEYS | set((
      '_comment', 'num', 'blocks', 'block_size', 'fs_blocks', 'fs_block_size',
      'uuid'))

  config = _LoadStackedPartitionConfig(filename)

  try:
    metadata = config['metadata']
    for key in ('block_size', 'fs_block_size'):
      metadata[key] = ParseHumanNumber(metadata[key])

    unknown_keys = set(config.keys()) - valid_keys
    if unknown_keys:
      raise InvalidLayout('Unknown items: %r' % unknown_keys)

    if len(config['layouts']) <= 0:
      raise InvalidLayout('Missing "layouts" entries')

    if not BASE_LAYOUT in config['layouts'].keys():
      raise InvalidLayout('Missing "base" config in "layouts"')

    for layout_name, layout in config['layouts'].iteritems():
      for part in layout:
        unknown_keys = set(part.keys()) - valid_layout_keys
        if unknown_keys:
          raise InvalidLayout('Unknown items in layout %s: %r' %
                              (layout_name, unknown_keys))

        if layout_name != BASE_LAYOUT:
          # Inherit from the base config by num.
          for base_part in config['layouts'][BASE_LAYOUT]:
            if ('num' in base_part and 'num' in part and
                base_part['num'] == part['num']):
              for k, v in base_part.iteritems():
                if k in _INHERITED_LAYOUT_KEYS and k not in part:
                  part[k] = v
              break

        if part['type'] != 'blank':
          for s in ('num', 'label'):
            if not s in part:
              raise InvalidLayout('Layout "%s" missing "%s"' % (layout_name, s))

        part['blocks'] = ParseHumanNumber(part['blocks'])
        part['bytes'] = part['blocks'] * metadata['block_size']

        if 'fs_blocks' in part:
          max_fs_blocks = part['bytes'] / metadata['fs_block_size']
          part['fs_blocks'] = ParseRelativeNumber(max_fs_blocks,
                                                  part['fs_blocks'])
          part['fs_bytes'] = part['fs_blocks'] * metadata['fs_block_size']

          if part['fs_bytes'] > part['bytes']:
            raise InvalidLayout(
                'Filesystem may not be larger than partition: %s %s: %d > %d' %
                (layout_name, part['label'], part['fs_bytes'], part['bytes']))
  except KeyError as e:
    raise InvalidLayout('Layout is missing required entries: %s' % e)

  return config


def GetTableTotals(config, partitions):
  """Calculates total sizes/counts for a partition table.

  Args:
    config: Partition configuration file object
    partitions: List of partitions to process
  Returns:
    Dict containing totals data
  """

  ret = {
    'expand_count': 0,
    'expand_min': 0,
    'block_count': START_SECTOR * config['metadata']['block_size']
  }

  # Total up the size of all non-expanding partitions to get the minimum
  # required disk size.
  for partition in partitions:
    if 'features' in partition and 'expand' in partition['features']:
      ret['expand_count'] += 1
      ret['expand_min'] += partition['blocks']
    else:
      ret['block_count'] += partition['blocks']

  # At present, only one expanding partition is permitted.
  # Whilst it'd be possible to have two, we don't need this yet
  # and it complicates things, so it's been left out for now.
  if ret['expand_count'] > 1:
    raise InvalidLayout('1 expand partition allowed, %d requested'
                        % ret['expand_count'])

  ret['min_disk_size'] = ret['block_count'] + ret['expand_min']

  return ret


def GetPartitionTable(options, config, image_type):
  """Generates requested image_type layout from a layout configuration.
  This loads the base table and then overlays the requested layout over
  the base layout.

  Args:
    options: Flags passed to the script
    config: Partition configuration file object
    image_type: Type of image eg base/test/dev/factory_install
  Returns:
    Object representing a selected partition table
  """

  # We make a deep copy so that changes to the dictionaries in this list do not
  # persist across calls.
  partitions = copy.deepcopy(config['layouts'][BASE_LAYOUT])
  metadata = config['metadata']

  if image_type != BASE_LAYOUT:
    for partition_t in config['layouts'][image_type]:
      for partition in partitions:
        if 'num' in partition_t and 'num' in partition:
          if partition_t['num'] == partition['num']:
            for k, v in partition_t.items():
              partition[k] = v

  for adjustment_str in options.adjust_part.split():
    adjustment = adjustment_str.split(':')
    if len(adjustment) < 2:
      raise InvalidAdjustment('Adjustment "%s" is incomplete' % adjustment_str)

    label = adjustment[0]
    operator = adjustment[1][0]
    operand = adjustment[1][1:]
    ApplyPartitionAdjustment(partitions, metadata, label, operator, operand)

  return partitions


def ApplyPartitionAdjustment(partitions, metadata, label, operator, operand):
  """Applies an adjustment to a partition specified by label

  Args:
    partitions: Partition table to modify
    metadata: Partition table metadata
    label: The label of the partition to adjust
    operator: Type of adjustment (+/-/=)
    operand: How much to adjust by
  """

  partition = GetPartitionByLabel(partitions, label)

  operand_bytes = ParseHumanNumber(operand)
  if operand_bytes % metadata['block_size'] == 0:
    operand_blocks = operand_bytes / metadata['block_size']
  else:
    raise InvalidAdjustment('Adjustment size %s not divisible by block size %s'
                            % (operand_bytes, metadata['block_size']))

  if operator == '+':
    partition['blocks'] += operand_blocks
    partition['bytes'] += operand_bytes
  elif operator == '-':
    partition['blocks'] -= operand_blocks
    partition['bytes'] -= operand_bytes
  elif operator == '=':
    partition['blocks'] = operand_blocks
    partition['bytes'] = operand_bytes
  else:
    raise ValueError('unknown operator %s' % operator)

  if partition['type'] == 'rootfs':
    # If we're adjusting a rootFS partition, we assume the full partition size
    # specified is being used for the filesytem, minus the space reserved for
    # the hashpad.
    partition['fs_bytes'] = partition['bytes']
    partition['fs_blocks'] = partition['fs_bytes'] / metadata['fs_block_size']
    partition['blocks'] = int(partition['blocks'] * 1.15)
    partition['bytes'] = partition['blocks'] * metadata['block_size']


def GetPartitionTableFromConfig(options, layout_filename, image_type):
  """Loads a partition table and returns a given partition table type

  Args:
    options: Flags passed to the script
    layout_filename: The filename to load tables from
    image_type: The type of partition table to return
  """

  config = LoadPartitionConfig(layout_filename)
  partitions = GetPartitionTable(options, config, image_type)

  return partitions


def GetScriptShell():
  """Loads and returns the skeleton script for our output script.

  Returns:
    A string containing the skeleton script
  """

  script_shell_path = os.path.join(os.path.dirname(__file__), 'cgpt_shell.sh')
  with open(script_shell_path, 'r') as f:
    script_shell = ''.join(f.readlines())

  # Before we return, insert the path to this tool so somebody reading the
  # script later can tell where it was generated.
  script_shell = script_shell.replace('@SCRIPT_GENERATOR@', script_shell_path)

  return script_shell


def WriteLayoutFunction(options, sfile, func_name, image_type, config):
  """Writes a shell script function to write out a given partition table.

  Args:
    options: Flags passed to the script
    sfile: File handle we're writing to
    func_name: Function name to write out for specified layout
    image_type: Type of image eg base/test/dev/factory_install
    config: Partition configuration file object
  """

  partitions = GetPartitionTable(options, config, image_type)
  partition_totals = GetTableTotals(config, partitions)

  lines = [
    '%s() {' % func_name,
    'create_image $1 %d %s' % (
        partition_totals['min_disk_size'],
        config['metadata']['block_size']),
    'local curr=%d' % START_SECTOR,
    '${GPT} create $1',
  ]

  # Pass 1: Set up the expanding partition size.
  for partition in partitions:
    partition['var'] = partition['blocks']

    if partition['type'] != 'blank':
      if partition['num'] == 1:
        if 'features' in partition and 'expand' in partition['features']:
          lines += [
            'local stateful_size=%s' % partition['blocks'],
            'if [ -b $1 ]; then',
            '  stateful_size=$(( $(numsectors $1) - %d))' %
                partition_totals['block_count'],
            'fi',
          ]
          partition['var'] = '${stateful_size}'

  lines += [
    ': $(( stateful_size -= (stateful_size %% %d) ))' % (
        config['metadata']['fs_block_size'],),
  ]

  # Pass 2: Write out all the cgpt add commands.
  for partition in partitions:
    if partition['type'] != 'blank':
      lines += [
        '${GPT} add -i %d -b ${curr} -s %s -t %s -l "%s" $1 && ' % (
            partition['num'], str(partition['var']), partition['type'],
            partition['label']),
      ]

    # Increment the curr counter ready for the next partition.
    if partition['var'] != 0:
      lines += [
        ': $(( curr += %s ))' % partition['var'],
      ]

  # Set default priorities on kernel partitions.
  prio = 15
  for n in (2, 4, 6):
    partition = GetPartitionByNumber(partitions, n)
    if partition['type'] != 'blank':
      lines += [
        '${GPT} add -i %s -S 0 -T 15 -P %i $1' % (n, prio)
      ]
      prio = 0

  lines += ['${GPT} boot -p -b $2 -i 12 $1']
  if config.get('hybrid_mbr'):
    lines += ['install_hybrid_mbr $1']
  lines += ['${GPT} show $1']

  sfile.write('%s\n}\n' % '\n  '.join(lines))


def WritePartitionSizesFunction(options, sfile, func_name, image_type, config):
  """Writes out the partition size variable that can be extracted by a caller.

  Args:
    options: Flags passed to the script
    sfile: File handle we're writing to
    func_name: Function name to write out for specified layout
    image_type: Type of image eg base/test/dev/factory_install
    config: Partition configuration file object
  """
  lines = [
    '%s() {' % func_name,
    'DEFAULT_ROOTDEV=%s' % config['metadata'].get('rootdev', ''),
  ]

  partitions = GetPartitionTable(options, config, image_type)
  for partition in partitions:
    for key in ('label', 'num'):
      if key in partition:
        shell_label = str(partition[key]).replace('-', '_').upper()
        part_bytes = partition['bytes']
        fs_bytes = partition.get('fs_bytes', part_bytes)
        part_format = partition.get('format', '')
        fs_format = partition.get('fs_format', '')
        lines += [
            'PARTITION_SIZE_%s=%s' % (shell_label, part_bytes),
            '     DATA_SIZE_%s=%s' % (shell_label, fs_bytes),
            '        FORMAT_%s=%s' % (shell_label, part_format),
            '     FS_FORMAT_%s=%s' % (shell_label, fs_format),
        ]

  sfile.write('%s\n}\n' % '\n  '.join(lines))


def GetPartitionByNumber(partitions, num):
  """Given a partition table and number returns the partition object.

  Args:
    partitions: List of partitions to search in
    num: Number of partition to find
  Returns:
    An object for the selected partition
  """
  for partition in partitions:
    if partition.get('num', None) == int(num):
      return partition

  raise PartitionNotFound('Partition %s not found' % num)


def GetPartitionByLabel(partitions, label):
  """Given a partition table and label returns the partition object.

  Args:
    partitions: List of partitions to search in
    label: Label of partition to find
  Returns:
    An object for the selected partition
  """
  for partition in partitions:
    if 'label' not in partition:
      continue
    if partition['label'] == label:
      return partition

  raise PartitionNotFound('Partition "%s" not found' % label)


def WritePartitionScript(options, image_type, layout_filename, sfilename):
  """Writes a shell script with functions for the base and requested layouts.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    sfilename: Filename to write the finished script to
  """

  config = LoadPartitionConfig(layout_filename)

  with open(sfilename, 'w') as f:
    script_shell = GetScriptShell()
    f.write(script_shell)

    for func, layout in (('base', BASE_LAYOUT), ('partition', image_type)):
      WriteLayoutFunction(options, f, 'write_%s_table' % func, layout, config)
      WritePartitionSizesFunction(options, f, 'load_%s_vars' % func, layout,
                                  config)

    # TODO: Backwards compat.  Should be killed off once we update
    #       cros_generate_update_payload to use the new code.
    partitions = GetPartitionTable(options, config, BASE_LAYOUT)
    partition = GetPartitionByLabel(partitions, 'ROOT-A')
    f.write('ROOTFS_PARTITION_SIZE=%s\n' % (partition['bytes'],))


def GetBlockSize(_options, layout_filename):
  """Returns the partition table block size.

  Args:
    options: Flags passed to the script
    layout_filename: Path to partition configuration file
  Returns:
    Block size of all partitions in the layout
  """

  config = LoadPartitionConfig(layout_filename)
  return config['metadata']['block_size']


def GetFilesystemBlockSize(_options, layout_filename):
  """Returns the filesystem block size.

  Args:
    options: Flags passed to the script

  This is used for all partitions in the table that have filesystems.

  Args:
    layout_filename: Path to partition configuration file
  Returns:
    Block size of all filesystems in the layout
  """

  config = LoadPartitionConfig(layout_filename)
  return config['metadata']['fs_block_size']


def GetType(options, image_type, layout_filename, num):
  """Returns the type of a given partition for a given layout.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    Type of the specified partition.
  """
  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)
  return partition.get('type')


def GetPartitions(options, image_type, layout_filename):
  """Returns the partition numbers for the image_type.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
  Returns:
    A space delimited string of partition numbers.
  """
  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition_nums = []
  return ' '.join(str(p['num']) for p in partitions if 'num' in p)


def GetUUID(options, image_type, layout_filename, num):
  """Returns the filesystem UUID of a given partition for a given layout type.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    UUID of specified partition. Defaults to random if not set.
  """
  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)
  return partition.get('uuid', 'random')


def GetPartitionSize(options, image_type, layout_filename, num):
  """Returns the partition size of a given partition for a given layout type.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    Size of selected partition in bytes
  """

  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)

  return partition['bytes']


def GetFilesystemFormat(options, image_type, layout_filename, num):
  """Returns the filesystem format of a given partition for a given layout type.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    Format of the selected partition's filesystem
  """

  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)

  return partition.get('fs_format')


def GetFilesystemSize(options, image_type, layout_filename, num):
  """Returns the filesystem size of a given partition for a given layout type.

  If no filesystem size is specified, returns the partition size.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    Size of selected partition filesystem in bytes
  """

  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)

  if 'fs_bytes' in partition:
    return partition['fs_bytes']
  else:
    return partition['bytes']


def GetLabel(options, image_type, layout_filename, num):
  """Returns the label for a given partition.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
    num: Number of the partition you want to read from
  Returns:
    Label of selected partition, or 'UNTITLED' if none specified
  """

  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
  partition = GetPartitionByNumber(partitions, num)

  if 'label' in partition:
    return partition['label']
  else:
    return 'UNTITLED'


def DoDebugOutput(options, image_type, layout_filename):
  """Prints out a human readable disk layout in on-disk order.

  This will round values larger than 1MB, it's exists to quickly
  visually verify a layout looks correct.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
  """
  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)

  label_len = max([len(x['label']) for x in partitions if 'label' in x])
  type_len = max([len(x['type']) for x in partitions if 'type' in x])

  msg = 'num:%4s label:%-*s type:%-*s size:%-10s fs_size:%-10s features:%s'
  for partition in partitions:
    if partition['bytes'] < 1024 * 1024:
      size = '%d B' % partition['bytes']
    else:
      size = '%d MiB' % (partition['bytes'] / 1024 / 1024)

    if 'fs_bytes' in partition:
      if partition['fs_bytes'] < 1024 * 1024:
        fs_size = '%d B' % partition['fs_bytes']
      else:
        fs_size = '%d MiB' % (partition['fs_bytes'] / 1024 / 1024)
    else:
      fs_size = 'auto'

    print msg % (
        partition.get('num', 'auto'),
        label_len,
        partition.get('label', ''),
        type_len,
        partition.get('type', ''),
        size,
        fs_size,
        partition.get('features', ''),
    )


def DoParseOnly(options, image_type, layout_filename):
  """Parses a layout file only, used before reading sizes to check for errors.

  Args:
    options: Flags passed to the script
    image_type: Type of image eg base/test/dev/factory_install
    layout_filename: Path to partition configuration file
  """
  _ = GetPartitionTableFromConfig(options, layout_filename, image_type)


def main(argv):
  action_map = {
    'write': {
      'usage': ['<image_type>', '<partition_config_file>', '<script_file>'],
      'func': WritePartitionScript,
    },
    'readblocksize': {
      'usage': ['<partition_config_file>'],
      'func': GetBlockSize,
    },
    'readfsblocksize': {
      'usage': ['<partition_config_file>'],
      'func': GetFilesystemBlockSize,
    },
    'readpartsize': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetPartitionSize,
    },
    'readfsformat': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetFilesystemFormat,
    },
    'readfssize': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetFilesystemSize,
    },
    'readlabel': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetLabel,
    },
    'readtype': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetType,
    },
    'readpartitionnums': {
      'usage': ['<image_type>', '<partition_config_file>'],
      'func': GetPartitions,
    },
    'readuuid': {
      'usage': ['<image_type>', '<partition_config_file>', '<partition_num>'],
      'func': GetUUID,
    },
    'debug': {
      'usage': ['<image_type>', '<partition_config_file>'],
      'func': DoDebugOutput,
    },
    'parseonly': {
      'usage': ['<image_type>', '<partition_config_file>'],
      'func': DoParseOnly,
    }
  }

  usage = """%prog <action> [options]

For information on the JSON format, see:
  http://dev.chromium.org/chromium-os/building-chromium-os/disk-layout-format

The --adjust_part flag takes arguments like:
  <label>:<op><size>
Where:
  <label> is a label name as found in the disk layout file
  <op> is one of the three: + - =
  <size> is a number followed by an optional size qualifier:
         B, KiB, MiB, GiB, TiB: bytes, kibi-, mebi-, gibi-, tebi- (base 1024)
         B,   K,   M,   G,   T: short hand for above
         B,  KB,  MB,  GB,  TB: bytes, kilo-, mega-, giga-, tera- (base 1000)

This will set the ROOT-A partition size to 1 gibibytes (1024 * 1024 * 1024 * 1):
  --adjust_part ROOT-A:=1GiB
This will grow the ROOT-A partition size by 500 mebibytes (1024 * 1024 * 500):
  --adjust_part ROOT-A:+500MiB
This will shrink the ROOT-A partition size by 10 mebibytes (1024 * 1024 * 10):
  --adjust_part ROOT-A:-20MiB

Actions:
""" + '\n'.join(['%20s %s' % (x, ' '.join(action_map[x]['usage']))
                 for x in sorted(action_map)])
  parser = optparse.OptionParser(usage=usage)
  parser.add_option("--adjust_part", dest="adjust_part",
                    help="adjust partition sizes", default="")
  (options, args) = parser.parse_args(args=argv[1:])

  if len(args) < 1 or args[0] not in action_map:
    parser.error('need a valid action to perform')
  else:
    action_name = args[0]
    action = action_map[action_name]
    if len(action['usage']) == len(args) - 1:
      ret = action['func'](options, *args[1:])
      if ret is not None:
        print ret
    else:
      sys.exit('Usage: %s %s %s' % (sys.argv[0], args[0],
               ' '.join(action['usage'])))


if __name__ == '__main__':
  main(sys.argv)