slog(): Add only_printable keyword argument

Add only_printable keyword argument to slog(). It defaults to False.
If it's true, non-printable characters are not logged but replaced
with a printable character.

Signed-off-by: Jan Lindemann <jan@janware.com>

tools/python/jwutils/log.py

@@ -2,6 +2,7 @@ from __future__ import print_function
 import syslog
 import sys
 import inspect
+import re
 from os.path import basename
 from datetime import datetime
 from typing import List, Tuple
@@ -13,6 +14,18 @@ try:
 except NameError:
     basestring = str
 
+_special_chars = {
+    '\a' : '\\a',
+    '\b' : '\\b',
+    '\t' : '\\t',
+    '\n' : '\\n',
+    '\v' : '\\v',
+    '\f' : '\\f',
+    '\r' : '\\r',
+}
+
+_special_char_regex = re.compile("(%s)" % "|".join(map(re.escape, _special_chars.keys())))
+
 EMERG                = syslog.LOG_EMERG
 ALERT                = syslog.LOG_ALERT
 CRIT                 = syslog.LOG_CRIT
@@ -101,7 +114,7 @@ def slog_m(prio: int, *args, **kwargs) -> None: # export
     for line in margs[1:].split('\n'):
         slog(prio, line, **kwargs, caller=caller)
 
-def slog(prio: int, *args, **kwargs) -> None: # export
+def slog(prio: int, *args, only_printable=False, **kwargs) -> None: # export
 
     if prio > _level:
         return
@@ -132,6 +145,9 @@ def slog(prio: int, *args, **kwargs) -> None: # export
         margs = ''
         for a in args:
             margs += ' ' + str(a)
+        if only_printable:
+            margs = _special_char_regex.sub(lambda mo: _special_chars[mo.string[mo.start():mo.end()]], margs)
+            margs = re.sub('[\x01-\x1f]', '.', margs)
         msg += color_on + margs + color_off
 
     if not len(msg):