1 files changed, 103 insertions, 0 deletions
diff --git a/netlib/strutils.py b/netlib/strutils.py
new file mode 100644
index 00000000..7a62185b
--- /dev/null
+++ b/netlib/strutils.py
@@ -0,0 +1,103 @@
+import re
+import unicodedata
+import codecs
+
+import six
+
+
+def always_bytes(unicode_or_bytes, *encode_args):
+    if isinstance(unicode_or_bytes, six.text_type):
+        return unicode_or_bytes.encode(*encode_args)
+    return unicode_or_bytes
+
+
+def native(s, *encoding_opts):
+    """
+    Convert :py:class:`bytes` or :py:class:`unicode` to the native
+    :py:class:`str` type, using latin1 encoding if conversion is necessary.
+
+    https://www.python.org/dev/peps/pep-3333/#a-note-on-string-types
+    """
+    if not isinstance(s, (six.binary_type, six.text_type)):
+        raise TypeError("%r is neither bytes nor unicode" % s)
+    if six.PY3:
+        if isinstance(s, six.binary_type):
+            return s.decode(*encoding_opts)
+    else:
+        if isinstance(s, six.text_type):
+            return s.encode(*encoding_opts)
+    return s
+
+
+def clean_bin(s, keep_spacing=True):
+    """
+        Cleans binary data to make it safe to display.
+
+        Args:
+            keep_spacing: If False, tabs and newlines will also be replaced.
+    """
+    if isinstance(s, six.text_type):
+        if keep_spacing:
+            keep = u" \n\r\t"
+        else:
+            keep = u" "
+        return u"".join(
+            ch if (unicodedata.category(ch)[0] not in "CZ" or ch in keep) else u"."
+            for ch in s
+        )
+    else:
+        if keep_spacing:
+            keep = (9, 10, 13)  # \t, \n, \r,
+        else:
+            keep = ()
+        return b"".join(
+            six.int2byte(ch) if (31 < ch < 127 or ch in keep) else b"."
+            for ch in six.iterbytes(s)
+        )
+
+
+def safe_subn(pattern, repl, target, *args, **kwargs):
+    """
+        There are Unicode conversion problems with re.subn. We try to smooth
+        that over by casting the pattern and replacement to strings. We really
+        need a better solution that is aware of the actual content ecoding.
+    """
+    return re.subn(str(pattern), str(repl), target, *args, **kwargs)
+
+
+def bytes_to_escaped_str(data):
+    """
+    Take bytes and return a safe string that can be displayed to the user.
+
+    Single quotes are always escaped, double quotes are never escaped:
+        "'" + bytes_to_escaped_str(...) + "'"
+    gives a valid Python string.
+    """
+    # TODO: We may want to support multi-byte characters without escaping them.
+    # One way to do would be calling .decode("utf8", "backslashreplace") first
+    # and then escaping UTF8 control chars (see clean_bin).
+
+    if not isinstance(data, bytes):
+        raise ValueError("data must be bytes, but is {}".format(data.__class__.__name__))
+    # We always insert a double-quote here so that we get a single-quoted string back
+    # https://stackoverflow.com/questions/29019340/why-does-python-use-different-quotes-for-representing-strings-depending-on-their
+    return repr(b'"' + data).lstrip("b")[2:-1]
+
+
+def escaped_str_to_bytes(data):
+    """
+    Take an escaped string and return the unescaped bytes equivalent.
+    """
+    if not isinstance(data, six.string_types):
+        if six.PY2:
+            raise ValueError("data must be str or unicode, but is {}".format(data.__class__.__name__))
+        raise ValueError("data must be str, but is {}".format(data.__class__.__name__))
+
+    if six.PY2:
+        if isinstance(data, unicode):
+            data = data.encode("utf8")
+        return data.decode("string-escape")
+
+    # This one is difficult - we use an undocumented Python API here
+    # as per http://stackoverflow.com/a/23151714/934719
+    return codecs.escape_decode(data)[0]