lib/wic/filemap.py

4 # SPDX-License-Identifier: GPL-2.0-only
9 are supported - the FIEMAP ioctl and the 'SEEK_HOLE / SEEK_DATA' features of
10 the file seek syscall. The former is implemented by the 'FilemapFiemap' class,
11 the latter is implemented by the 'FilemapSeek' class. Both classes provide the
12 same API. The 'filemap' function automatically selects which class can be used
13 and returns an instance of the class.
33     # Get the block size of the host file-system for the image file by calling
51 class ErrorNotSupp(Exception):
54     is not supported either by the kernel or the file-system.
58 class Error(Exception):
59     """A class for all the other exceptions raised by this module."""
63 class _FilemapBase(object):
65     This is a base class for a couple of other classes in this module. This
66     class simply performs the common parts of the initialization process: opens
73         Initialize a class instance. The 'image' argument is full path to the
102         self.blocks_cnt = self.image_size + self.block_size - 1
118         self._log.debug("block size %d, blocks count %d, image size %d"
122         """The class destructor which just closes the image file."""
168     returns '-1'.  Otherwise the data or hole position is returned."""
176             return -1
178             raise ErrorNotSupp("the kernel or file-system does not support "
183 class FilemapSeek(_FilemapBase):
185     This class uses the 'SEEK_HOLE' and 'SEEK_DATA' to find file block mapping.
191         """Refer the '_FilemapBase' class for the documentation."""
193         # Call the base class constructor first
231             self._log.debug("lseek(0, SEEK_HOLE) returned %d" % offs)
232             raise ErrorNotSupp("the file-system does not support "
239         """Refer the '_FilemapBase' class for the documentation."""
241         if offs == -1:
246         self._log.debug("FilemapSeek: block_is_mapped(%d) returns %s"
262             if start == -1 or start >= limit or start == self.image_size:
266             if end == -1 or end == self.image_size:
272             end_blk = end // self.block_size - 1
273             self._log.debug("FilemapSeek: yielding range (%d, %d)"
278         """Refer the '_FilemapBase' class for the documentation."""
279         self._log.debug("FilemapSeek: get_mapped_ranges(%d,  %d(%d))"
280                         % (start, count, start + count - 1))
307 class FilemapFiemap(_FilemapBase):
309     This class provides API to the FIEMAP ioctl. Namely, it allows to iterate
312     This class synchronizes the image file every time it invokes the FIEMAP
313     ioctl in order to work-around early FIEMAP implementation kernel bugs.
318         Initialize a class instance. The 'image' argument is full the file
322         # Call the base class constructor first
329         self._buf_size -= _FIEMAP_SIZE
352             raise Error("bad block number %d, should be within [0, %d]"
359         # synchronizing the file is a necessary work-around.
371                          "by the file-system"
385         """Refer the '_FilemapBase' class for the documentation."""
392         self._log.debug("FilemapFiemap: block_is_mapped(%d) returns %s"
437                 # Extent length and offset have to be block-aligned
441                 if extent_block > start + count - 1:
445                 last = min(extent_block + extent_count, start + count) - 1
453         """Refer the '_FilemapBase' class for the documentation."""
454         self._log.debug("FilemapFiemap: get_mapped_ranges(%d,  %d(%d))"
455                         % (start, count, start + count - 1))
460             if last_prev == first - 1:
463                 self._log.debug("FilemapFiemap: yielding range (%d, %d)"
468         self._log.debug("FilemapFiemap: yielding range (%d, %d)"
472 class FilemapNobmap(_FilemapBase):
474     This class is used when both the 'SEEK_DATA/HOLE' and FIEMAP are not
479         """Refer the '_FilemapBase' class for the documentation."""
481         # Call the base class constructor first
486         """Refer the '_FilemapBase' class for the documentation."""
490         """Refer the '_FilemapBase' class for the documentation."""
491         self._log.debug("FilemapNobmap: get_mapped_ranges(%d,  %d(%d))"
492                         % (start, count, start + count - 1))
493         yield (start, start + count -1)
497     Create and return an instance of a Filemap class - 'FilemapFiemap' or
499     FIEMAP ioctl is supported, an instance of the 'FilemapFiemap' class is
501     'FilemapSeek' class is returned. If none of these are supported, the
535             dst_size = os.path.getsize(src_fname) + seek - skip
551         written += start - skip - written
557         dst_file.seek(seek + start - skip, os.SEEK_SET)
560         to_read = end - start
565                 chunk_size = to_read - read
568                 size = length - written