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.. _recover:
.. module:: ezdxf.recover
Recover
=======
This module provides functions to "recover" ASCII DXF documents with structural
flaws, which prevents the regular :func:`ezdxf.read` and :func:`ezdxf.readfile`
functions to load the document.
The :func:`read` and :func:`readfile` functions will repair as much
flaws as possible and run the required audit process automatically
afterwards and return the result of this audit process:
.. code-block:: Python
import sys
import ezdxf
from ezdxf import recover
try:
doc, auditor = recover.readfile("messy.dxf")
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file.')
sys.exit(2)
# DXF file can still have unrecoverable errors, but this is maybe just
# a problem when saving the recovered DXF file.
if auditor.has_errors:
auditor.print_error_report()
The loading functions also decode DXF-Unicode encoding automatically
e.g. "\\U+00FC" -> "ΓΌ".
All these efforts cost some time, loading the DXF document with
:func:`ezdxf.read` or :func:`ezdxf.readfile` is faster.
.. warning::
This module will load DXF files which have decoding errors, most likely binary
data stored in XRECORD entities, these errors are logged as unrecoverable
``AuditError.DECODE_ERRORS`` in the :attr:`Auditor.errors` attribute, but no
:class:`DXFStructureError` exception will be raised, because for many use
cases this errors can be ignored.
Writing such files back with `ezdxf` may create **invalid** DXF files, or
at least some **information will be lost** - handle with care!
To avoid this problem use :code:`recover.readfile(filename, errors='strict')`
which raises an :class:`UnicodeDecodeError` exception for such binary data.
Catch the exception and handle this DXF files as unrecoverable.
Loading Scenarios
-----------------
1. It will work
~~~~~~~~~~~~~~~
Mostly DXF files from AutoCAD or BricsCAD (e.g. for In-house solutions):
.. code-block:: Python
try:
doc = ezdxf.readfile(name)
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
2. DXF file with minor flaws
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DXF files have only minor flaws, like undefined resources:
.. code-block:: Python
try:
doc = ezdxf.readfile(name)
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
auditor = doc.audit()
if auditor.has_errors:
auditor.print_error_report()
3. Try Hard
~~~~~~~~~~~
From trusted and untrusted sources but with good hopes, the worst case works
like a cache miss, you pay for the first try and pay the extra fee for the
recover mode:
.. code-block:: Python
try: # Fast path:
doc = ezdxf.readfile(name)
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
# Catch all DXF errors:
except ezdxf.DXFError:
try: # Slow path including fixing low level structures:
doc, auditor = recover.readfile(name)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
# DXF file can still have unrecoverable errors, but this is maybe
# just a problem when saving the recovered DXF file.
if auditor.has_errors:
print(f'Found unrecoverable errors in DXF file: {name}.')
auditor.print_error_report()
4. Just use the slow recover module
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Untrusted sources and expecting many invalid or corrupted DXF files, you
always pay an extra fee for the recover mode:
.. code-block:: Python
try: # Slow path including fixing low level structures:
doc, auditor = recover.readfile(name)
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
# DXF file can still have unrecoverable errors, but this is maybe
# just a problem when saving the recovered DXF file.
if auditor.has_errors:
print(f'Found unrecoverable errors in DXF file: {name}.')
auditor.print_error_report()
5. Unrecoverable Decoding Errors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If files contain binary data which can not be decoded by the document encoding,
it is maybe the best to ignore these files, this works in normal and recover
mode:
.. code-block:: Python
try:
doc, auditor = recover.readfile(name, errors='strict')
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
except UnicodeDecodeError:
print(f'Decoding error in DXF file: {name}.')
sys.exit(3)
6. Ignore/Locate Decoding Errors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sometimes ignoring decoding errors can recover DXF files or at least
you can detect where the decoding errors occur:
.. code-block:: Python
try:
doc, auditor = recover.readfile(name, errors='ignore')
except IOError:
print(f'Not a DXF file or a generic I/O error.')
sys.exit(1)
except ezdxf.DXFStructureError:
print(f'Invalid or corrupted DXF file: {name}.')
sys.exit(2)
if auditor.has_errors:
auditor.print_report()
The error messages with code :attr:`AuditError.DECODING_ERROR` shows the
approximate line number of the decoding error:
"Fixed unicode decoding error near line: xxx."
.. hint::
This functions can handle only ASCII DXF files!
.. autofunction:: readfile
.. autofunction:: read
.. autofunction:: explore
|
