python2 reduction: Merge remaining compat code into common

The remaining compat code (get_string, get_bytes,
cmp) are useful helper routines which we should
simply merge into common (especially since there
is some duplication here).

Signed-off-by: David Mulder <dmulder@suse.com>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>

Autobuild-User(master): David Mulder <dmulder@samba.org>
Autobuild-Date(master): Fri Oct  2 14:49:36 UTC 2020 on sn-devel-184

python/samba/common.py

@@ -1,6 +1,7 @@
 # Samba common functions
 #
 # Copyright (C) Matthieu Patou <mat@matws.net>
+# Copyright (C) Lumir Balhar <lbalhar@redhat.com> 2017
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,15 +17,17 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
-from samba.compat import PY3
 
+def cmp(x, y):
+    """
+    Replacement for built-in function cmp that was removed in Python 3
 
-if PY3:
-    # cmp() exists only in Python 2
-    def cmp(a, b):
-        return (a > b) - (a < b)
+    Compare the two objects x and y and return an integer according to
+    the outcome. The return value is negative if x < y, zero if x == y
+    and strictly positive if x > y.
+    """
 
-    raw_input = input
+    return (x > y) - (x < y)
 
 
 def confirm(msg, forced=False, allow_all=False):
@@ -53,7 +56,7 @@ def confirm(msg, forced=False, allow_all=False):
         prompt = '[y/N/all/none]'
 
     while True:
-        v = raw_input(msg + ' %s ' % prompt)
+        v = input(msg + ' %s ' % prompt)
         v = v.upper()
         if v in mapping:
             return mapping[v]
@@ -67,3 +70,38 @@ def normalise_int32(ivalue):
     return str(ivalue)
 
 
+# Sometimes in PY3 we have variables whose content can be 'bytes' or
+# 'str' and we can't be sure which. Generally this is because the
+# code variable can be initialised (or reassigned) a value from different
+# api(s) or functions depending on complex conditions or logic. Or another
+# common case is in PY2 the variable is 'type <str>' and in PY3 it is
+# 'class <str>' and the function to use e.g. b64encode requires 'bytes'
+# in PY3. In such cases it would be nice to avoid excessive testing in
+# the client code. Calling such a helper function should be avoided
+# if possible but sometimes this just isn't possible.
+# If a 'str' object is passed in it is encoded using 'utf8' or if 'bytes'
+# is passed in it is returned unchanged.
+# Using this function is PY2/PY3 code should ensure in most cases
+# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
+# encodes the variable (see PY2 implementation of this function below)
+def get_bytes(bytesorstring):
+    tmp = bytesorstring
+    if isinstance(bytesorstring, str):
+        tmp = bytesorstring.encode('utf8')
+    elif not isinstance(bytesorstring, bytes):
+        raise ValueError('Expected byte or string for %s:%s' % (type(bytesorstring), bytesorstring))
+    return tmp
+
+# helper function to get a string from a variable that maybe 'str' or
+# 'bytes' if 'bytes' then it is decoded using 'utf8'. If 'str' is passed
+# it is returned unchanged
+# Using this function is PY2/PY3 code should ensure in most cases
+# the PY2 code runs unchanged in PY2 whereas the code in PY3 possibly
+# decodes the variable (see PY2 implementation of this function below)
+def get_string(bytesorstring):
+    tmp = bytesorstring
+    if isinstance(bytesorstring, bytes):
+        tmp = bytesorstring.decode('utf8')
+    elif not isinstance(bytesorstring, str):
+        raise ValueError('Expected byte of string for %s:%s' % (type(bytesorstring), bytesorstring))
+    return tmp