MDF scramble static method: scramble text blocks and keep original fi…

…le structure (useful for privacy concerns when sending mdf files for debug purpose)

ISSUE_TEMPLATE.md

@@ -32,4 +32,8 @@ except ImportError:
   _please write here the error traceback_
 
 # Description
+
+The fastest way to debug is to have the original file. For data protection you can use the static 
+method _scramble_ to scramble all text blocks, and send the scrambled file by e-mail.
+
 _Please describe the issue here._

asammdf/mdf.py

@@ -34,11 +34,16 @@
     MDF3_VERSIONS,
     MDF4_VERSIONS,
     SUPPORTED_VERSIONS,
+    UINT64,
+    randomized_string,
 )
 from .v2_v3_blocks import Channel as ChannelV3
 from .v2_v3_blocks import HeaderBlock as HeaderV3
+from .v4_blocks import SourceInformation
+from .v4_blocks import ChannelConversion as ChannelConversionV4
 from .v4_blocks import Channel as ChannelV4
 from .v4_blocks import HeaderBlock as HeaderV4
+from .v4_blocks import TextBlock as TextBlockV4
 from .v4_blocks import ChannelArrayBlock, EventBlock
 from . import v4_constants as v4c
 
@@ -2599,6 +2604,143 @@ def whereis(self, channel):
         else:
             return tuple()
 
+    @staticmethod
+    def scramble(name, memory='low'):
+        """ scramble text blocks and keep original file strcuture
+
+        Parameters
+        ----------
+        name : str
+            file name
+        memory : str
+            memory option; default *'low'*
+
+        """
+
+        memory = validate_memory_argument(memory)
+        mdf = MDF(name, memory=memory)
+        texts = {}
+
+        if mdf.version >= '4.00':
+            Channel = ChannelV4
+            ChannelConversion = ChannelConversionV4
+            TextBlock = TextBlockV4
+
+            stream = mdf._file
+
+            if mdf.header['comment_addr']:
+                stream.seek(mdf.header['comment_addr'] + 8)
+                size = UINT64(stream.read(8))[0] - 24
+                texts[mdf.header['comment_addr']] = randomized_string(size)
+
+            for fh in mdf.file_history:
+                addr = fh['comment_addr']
+                if addr and addr not in texts:
+                    stream.seek(addr + 8)
+                    size = UINT64(stream.read(8))[0] - 24
+                    texts[addr] = randomized_string(size)
+
+            for ev in mdf.events:
+                for addr in (ev['comment_addr'], ev['name_addr']):
+                    if addr and addr not in texts:
+                        stream.seek(addr + 8)
+                        size = UINT64(stream.read(8))[0] - 24
+                        texts[addr] = randomized_string(size)
+
+            for gp in mdf.groups:
+
+                addr = gp['data_group']['comment_addr']
+                if addr and addr not in texts:
+                    stream.seek(addr + 8)
+                    size = UINT64(stream.read(8))[0] - 24
+                    texts[addr] = randomized_string(size)
+
+                cg = gp['channel_group']
+                for addr in (
+                        cg['acq_name_addr'],
+                        cg['comment_addr']):
+                    if cg['flags'] & v4c.FLAG_CG_BUS_EVENT:
+                        continue
+
+                    if addr and addr not in texts:
+                        stream.seek(addr + 8)
+                        size = UINT64(stream.read(8))[0] - 24
+                        texts[addr] = randomized_string(size)
+
+                    source = cg['acq_source_addr']
+                    if source:
+                        source = SourceInformation(address=source, stream=stream)
+                        for addr in (
+                                source['name_addr'],
+                                source['path_addr'],
+                                source['comment_addr']):
+                            if addr and addr not in texts:
+                                stream.seek(addr + 8)
+                                size = UINT64(stream.read(8))[0] - 24
+                                texts[addr] = randomized_string(size)
+
+                for ch in gp['channels']:
+                    if mdf.memory == 'minimum':
+                        ch = Channel(address=ch, stream=stream,
+                                     load_metadata=False)
+
+                    for addr in (
+                            ch['name_addr'],
+                            ch['unit_addr'],
+                            ch['comment_addr']):
+                        if addr and addr not in texts:
+                            stream.seek(addr + 8)
+                            size = UINT64(stream.read(8))[0] - 24
+                            texts[addr] = randomized_string(size)
+
+                    source = ch['source_addr']
+                    if source:
+                        source = SourceInformation(address=source, stream=stream)
+                        for addr in (
+                                source['name_addr'],
+                                source['path_addr'],
+                                source['comment_addr']):
+                            if addr and addr not in texts:
+                                stream.seek(addr + 8)
+                                size = UINT64(stream.read(8))[0] - 24
+                                texts[addr] = randomized_string(size)
+
+                    conv = ch['conversion_addr']
+                    if conv:
+                        conv = ChannelConversion(address=conv, stream=stream)
+                        for addr in (
+                                conv['name_addr'],
+                                conv['unit_addr'],
+                                conv['comment_addr']):
+                            if addr and addr not in texts:
+                                stream.seek(addr + 8)
+                                size = UINT64(stream.read(8))[0] - 24
+                                texts[addr] = randomized_string(size)
+                        if conv['conversion_type'] == v4c.CONVERSION_TYPE_ALG:
+                            addr = conv['formula_addr']
+                            if addr and addr not in texts:
+                                stream.seek(addr + 8)
+                                size = UINT64(stream.read(8))[0] - 24
+                                texts[addr] = randomized_string(size)
+
+                        for key, block in conv.referenced_blocks.items():
+                            if block:
+                                if block['id'] == b'##TX':
+                                    addr = block.address
+                                    if addr not in texts:
+                                        stream.seek(addr + 8)
+                                        size = block['block_len'] - 24
+                                        texts[addr] = randomized_string(size)
+            mdf.close()
+
+            with open(name, 'rb+') as mdf:
+                for addr, bts in texts.items():
+                    mdf.seek(addr + 24)
+                    mdf.write(bts)
+
+        else:
+            raise NotImplementedError()
+
 
 if __name__ == '__main__':
     pass

asammdf/mdf_v4.py

@@ -52,6 +52,7 @@
 from .signal import Signal
 from .conversion_utils import conversion_transfer
 from .utils import (
+    UINT64,
     CHANNEL_COUNT,
     CONVERT_LOW,
     CONVERT_MINIMUM,

asammdf/utils.py

@@ -8,6 +8,7 @@
 import xml.etree.ElementTree as ET
 
 from collections import namedtuple
+from random import randint
 from struct import Struct
 from warnings import warn
 
@@ -122,17 +123,18 @@ class MdfException(Exception):
     pass
 
 
-# pylint: disable=W0622
-def bytes(obj):
-    """ Python 2 compatibility function """
-    try:
-        return obj.__bytes__()
-    except AttributeError:
-        if isinstance(obj, str):
-            return obj
-        else:
-            raise
-# pylint: enable=W0622
+if PYVERSION < 3:
+    # pylint: disable=W0622
+    def bytes(obj):
+        """ Python 2 compatibility function """
+        try:
+            return obj.__bytes__()
+        except AttributeError:
+            if isinstance(obj, str):
+                return obj
+            else:
+                raise
+    # pylint: enable=W0622
 
 
 def extract_cncomment_xml(comment):
@@ -916,3 +918,23 @@ def add(self, channel_name, group_index, channel_index):
                 self[channel_name].append(
                     entry
                 )
+
+
+def randomized_string(size):
+    """ get a \0 terminated string of size length
+
+    Parameters
+    ----------
+    size : int
+        target string length
+
+    Returns
+    -------
+    string : bytes
+        randomized string
+
+    """
+    if PYVERSION >= 3:
+        return bytes(randint(65, 90) for _ in range(size - 1)) + b'\0'
+    else:
+        return ''.join(chr(randint(65, 90)) for _ in range(size - 1)) + '\0'