Document low-level utilities

This commit documents lowl-level utilities and miscellanious
classes.

Part of #9

Author: DirectXMan12

gssapi/raw/cython_converters.pyx

@@ -5,6 +5,7 @@ from gssapi.raw.types import MechType, NameType
 
 
 cdef OID c_make_oid(gss_OID oid):
+    """Create an OID from a C OID struct pointer"""
     cdef OID res = OID()
     res.raw_oid = oid[0]
     return res

gssapi/raw/exceptions.pyx

@@ -2,6 +2,8 @@ from gssapi.raw.cython_types cimport OM_uint32
 
 from gssapi.raw.misc import GSSError
 
+"""Specific exceptions for GSSAPI errors"""
+
 
 cdef extern from "gssapi.h":
     # calling errors

gssapi/raw/mech_krb5.pyx

@@ -5,6 +5,13 @@ from gssapi.raw.cython_converters cimport c_make_oid
 
 from gssapi.raw import types as gsstypes
 
+"""Kerberos-specific constants
+
+Upon import, this module will populate
+Kerberos-specific constants into NameType
+and MechType.
+"""
+
 
 cdef extern from "gssapi/gssapi_krb5.h":
     gss_OID gss_mech_krb5

gssapi/raw/types.pyx

@@ -108,6 +108,17 @@ class MechType(object):
 
 
 class GenericFlagSet(collections.MutableSet):
+    """A set backed by a 32-bit integer
+
+    This is a set backed by a 32 bit integer.
+    the members are integers where only one
+    bit is set.
+
+    The class supports normal set operations,
+    as well as traditional "flag set" operations,
+    such as bitwise AND, OR, and XOR.
+    """
+
     __slots__ = '_val'
     MAX_VAL = 1 << 31
 
@@ -201,6 +212,15 @@ class GenericFlagSet(collections.MutableSet):
 
 
 class IntEnumFlagSet(GenericFlagSet):
+    """A set backed by a 32-bit integer with enum members
+
+    This class is a :class:`GenericFlagSet` where the returned
+    members are values in an :class:`IntEnum`.
+
+    It functions exactly like a `GenericFlagSet`, except that
+    it also supports bitwise operations with the enum values.
+    """
+
     __slots__ = ('_val', '_enum')
 
     def __init__(self, enum, flags=None):