# * Too few public methods - R0903
# pylint: disable=R0902,R0903
-import os
import hashlib
-from fcntl import ioctl
-import struct
-from itertools import groupby
-from bmaptools.BmapHelpers import human_size, get_block_size
-import array
+from bmaptools.BmapHelpers import human_size
+from bmaptools import Fiemap
# The bmap format version we generate
SUPPORTED_BMAP_VERSION = "1.2"
self._bmap_path = bmap
self._open_bmap_file()
- self.image_size = os.fstat(self._f_image.fileno()).st_size
+ self.fiemap = Fiemap.Fiemap(self._f_image)
+
+ self.image_size = self.fiemap.image_size
self.image_size_human = human_size(self.image_size)
if self.image_size == 0:
raise Error("cannot generate bmap for zero-sized image file '%s'" \
% self._image_path)
- try:
- self.block_size = get_block_size(self._f_image)
- except IOError as err:
- raise Error("cannot get block size for '%s': %s" \
- % (self._image_path, err))
-
- self.blocks_cnt = self.image_size + self.block_size - 1
- self.blocks_cnt /= self.block_size
-
- # Check if the FIEMAP ioctl is supported
- self._is_mapped(0)
+ self.block_size = self.fiemap.block_size
+ self.blocks_cnt = self.fiemap.blocks_cnt
def _bmap_file_start(self):
""" A helper function which generates the starting contents of the
self._f_bmap.write(xml)
- def _is_mapped(self, block):
- """ A helper function which returns 'True' if block number 'block' of
- the image file is mapped and 'False' otherwise.
-
- This function uses the FIEMAP ioctl to detect whether 'block' is mapped
- to the disk. However, we do not use all the power of this ioctl: we
- call it for each and every block, while there is a possibility to call
- it once for a range of blocks, which is a lot faster when dealing with
- huge files. """
-
- # I know that the below cruft is not readable. To understand that, you
- # need to know the FIEMAP interface, which is documented in the
- # Documentation/filesystems/fiemap.txt file in the Linux kernel
- # sources. The ioctl is quite complex and python is not the best tool
- # for dealing with ioctls...
-
- # Prepare a 'struct fiemap' buffer which contains a single
- # 'struct fiemap_extent' element.
- struct_fiemap_format = "=QQLLLL"
- struct_size = struct.calcsize(struct_fiemap_format)
- buf = struct.pack(struct_fiemap_format,
- block * self.block_size,
- self.block_size, 0, 0, 1, 0)
- # sizeof(struct fiemap_extent) == 56
- buf += "\0"*56
- # Python strings are "immutable", meaning that python will pass a copy
- # of the string to the ioctl, unless we turn it into an array.
- buf = array.array('B', buf)
-
- try:
- ioctl(self._f_image, 0xC020660B, buf, 1)
- except IOError as err:
- error_msg = "the FIBMAP ioctl failed for '%s': %s" \
- % (self._image_path, err)
- if err.errno == os.errno.EPERM or err.errno == os.errno.EACCES:
- # The FIEMAP ioctl was added in kernel version 2.6.28 in 2008
- error_msg += " (looks like your kernel does not support FIEMAP)"
-
- raise Error(error_msg)
-
- res = struct.unpack(struct_fiemap_format, buf[:struct_size])
- # res[3] is the 'fm_mapped_extents' field of 'struct fiemap'. If it
- # contains zero, the block is not mapped, otherwise it is mapped.
- return bool(res[3])
-
- def _get_ranges(self):
- """ A helper function which generates ranges of mapped image file
- blocks. """
-
- iterator = xrange(self.blocks_cnt)
- for key, group in groupby(iterator, self._is_mapped):
- if key:
- # Find the first and the last elements of the group
- first = group.next()
- last = first
- for last in group:
- pass
- yield first, last
-
def _bmap_file_end(self):
""" A helper function which generates the final parts of the block map
file: the ending tags and the information about the amount of mapped
self._bmap_file_start()
- # Synchronize the image file before starting to generate its block map
- try:
- self._f_image.flush()
- except IOError as err:
- raise Error("cannot flush image file '%s': %s" \
- % (self._image_path, err))
- try:
- os.fsync(self._f_image.fileno()),
- except OSError as err:
- raise Error("cannot synchronize image file '%s': %s " \
- % (self._image_path, err.strerror))
-
# Generate the block map and write it to the XML block map
# file as we go.
self.mapped_cnt = 0
- for first, last in self._get_ranges():
+ for first, last in self.fiemap.get_mapped_ranges():
self.mapped_cnt += last - first + 1
if include_checksums:
sha1 = self._calculate_sha1(first, last)
--- /dev/null
+""" This module implements python API for the FIEMAP ioctl. The FIEMAP ioctl
+allows to find holes and mapped areas in a file. """
+
+# Note, a lot of code in this module is not very readable, because it deals
+# with the rather complex FIEMAP ioctl. To understand the code, you need to
+# know the FIEMAP interface, which is documented in the
+# Documentation/filesystems/fiemap.txt file in the Linux kernel sources.
+
+import os
+import struct
+import array
+import fcntl
+import itertools
+from bmaptools import BmapHelpers
+
+class Error(Exception):
+ """ A class for exceptions generated by this module. We currently support
+ only one type of exceptions, and we basically throw human-readable problem
+ description in case of errors. """
+ pass
+
+class Fiemap:
+ """ This class provides API to the FIEMAP ioctl. Namely, it allows to
+ iterate over all mapped blocks and over all holes. """
+
+ def _open_image_file(self):
+ """ Open the image file. """
+
+ try:
+ self._f_image = open(self._image_path, 'rb')
+ except IOError as err:
+ raise Error("cannot open image file '%s': %s" \
+ % (self._image_path, err))
+
+ self._f_image_needs_close = True
+
+ def __init__(self, image):
+ """ Initialize a class instance. The 'image' argument is full path to
+ the file to operate on, or a file object to operate on. """
+
+ self._f_image_needs_close = False
+
+ if hasattr(image, "fileno"):
+ self._f_image = image
+ self._image_path = image.name
+ else:
+ self._image_path = image
+ self._open_image_file()
+
+ self.image_size = os.fstat(self._f_image.fileno()).st_size
+
+ try:
+ self.block_size = BmapHelpers.get_block_size(self._f_image)
+ except IOError as err:
+ raise Error("cannot get block size for '%s': %s" \
+ % (self._image_path, err))
+
+ self.blocks_cnt = self.image_size + self.block_size - 1
+ self.blocks_cnt /= self.block_size
+
+ # Synchronize the image file to make sure FIEMAP returns correct values
+ try:
+ self._f_image.flush()
+ except IOError as err:
+ raise Error("cannot flush image file '%s': %s" \
+ % (self._image_path, err))
+ try:
+ os.fsync(self._f_image.fileno()),
+ except OSError as err:
+ raise Error("cannot synchronize image file '%s': %s " \
+ % (self._image_path, err.strerror))
+
+ # Check if the FIEMAP ioctl is supported
+ self.block_is_mapped(0)
+
+ def __del__(self):
+ """ The class destructor which closes the opened files. """
+
+ if self._f_image_needs_close:
+ self._f_image.close()
+
+ def block_is_mapped(self, block):
+ """ This function returns 'True' if block number 'block' of the image
+ file is mapped and 'False' otherwise. """
+
+ # Prepare a 'struct fiemap' buffer which contains a single
+ # 'struct fiemap_extent' element.
+ struct_fiemap_format = "=QQLLLL"
+ struct_size = struct.calcsize(struct_fiemap_format)
+ buf = struct.pack(struct_fiemap_format,
+ block * self.block_size,
+ self.block_size, 0, 0, 1, 0)
+ # sizeof(struct fiemap_extent) == 56
+ buf += "\0"*56
+ # Python strings are "immutable", meaning that python will pass a copy
+ # of the string to the ioctl, unless we turn it into an array.
+ buf = array.array('B', buf)
+
+ try:
+ fcntl.ioctl(self._f_image, 0xC020660B, buf, 1)
+ except IOError as err:
+ error_msg = "the FIBMAP ioctl failed for '%s': %s" \
+ % (self._image_path, err)
+ if err.errno == os.errno.EPERM or err.errno == os.errno.EACCES:
+ # The FIEMAP ioctl was added in kernel version 2.6.28 in 2008
+ error_msg += " (looks like your kernel does not support FIEMAP)"
+
+ raise Error(error_msg)
+
+ res = struct.unpack(struct_fiemap_format, buf[:struct_size])
+ # res[3] is the 'fm_mapped_extents' field of 'struct fiemap'. If it
+ # contains zero, the block is not mapped, otherwise it is mapped.
+ return bool(res[3])
+
+ def block_is_unmapped(self, block):
+ """ This function returns 'True' if block number 'block' of the image
+ file is not mapped (hole) and 'False' otherwise. """
+
+ return not self.block_is_mapped(block)
+
+ def _get_ranges(self, test_func):
+ """ Internal helper generator which produces list of mapped or unmapped
+ blocks. The 'test_func' is a function object which tests whether a
+ block is mapped or unmapped. """
+
+ iterator = xrange(self.blocks_cnt)
+ for key, group in itertools.groupby(iterator, test_func):
+ if key:
+ # Find the first and the last elements of the group
+ first = group.next()
+ last = first
+ for last in group:
+ pass
+ yield first, last
+
+ def get_mapped_ranges(self):
+ """ Generate ranges of mapped blocks in the file. """
+
+ return self._get_ranges(self.block_is_mapped)
+
+ def get_unmapped_ranges(self):
+ """ Generate ranges of unmapped blocks in the file. """
+
+ return self._get_ranges(self.block_is_unmapped)
projects / tools / bmap-tools.git / commitdiff