Add encode_hex and decode_hex

Resolves davidaurelio#12

hashids.py

@@ -258,3 +258,28 @@ def decode(self, hashid):
             return numbers if hashid == self.encode(*numbers) else ()
         except ValueError:
             return ()
+
+    def encode_hex(self, hex_str):
+        """Converts a hexadecimal string (e.g. a MongoDB id) to a hashid.
+
+        :param hex_str The hexadecimal string to encodes
+
+        >>> Hashids.encode_hex('507f1f77bcf86cd799439011')
+        'y42LW46J9luq3Xq9XMly'
+        """
+        numbers = (int('1' + hex_str[i:i+12], 16)
+                   for i in range(0, len(hex_str), 12))
+        try:
+            return self.encode(*numbers)
+        except ValueError:
+            return ''
+
+    def decode_hex(self, hashid):
+        """Restores a hexadecimal string (e.g. a MongoDB id) from a hashid.
+
+        :param hashid The hashid to decode
+
+        >>> Hashids.decode_hex('y42LW46J9luq3Xq9XMly')
+        '507f1f77bcf86cd799439011'
+        """
+        return ''.join(('%x' % x)[1:] for x in self.decode(hashid))

test/test_hashids.py

@@ -76,6 +76,16 @@ def test_negative_call(self):
     def test_float_call(self):
         assert Hashids().encode(1, 2.5, 3) == ''
 
+    def test_encode_hex(self):
+        assert Hashids().encode_hex('507f1f77bcf86cd799439011') == 'y42LW46J9luq3Xq9XMly'
+        assert len(Hashids(min_length=1000).encode_hex('507f1f77bcf86cd799439011')) >= 1000
+        assert Hashids().encode_hex('f000000000000000000000000000000000000000000000000000000000000000000000000000000000000f') == \
+               'WxMLpERDrmh25Lp4L3xEfM6WovWYO3IjkRMKR2ogCMVzn4zQlqt1WK8jKq7OsEpy2qyw1Vi2p'
+
+    def test_illegal_hex(self):
+        assert Hashids().encode_hex('') == ''
+        assert Hashids().encode_hex('1234SGT8') == ''
+
 class TestDecoding(object):
     def test_empty_string(self):
         assert Hashids().decode('') == ()
@@ -152,3 +162,15 @@ def test_alphabet_with_two_standard_separators(self):
     def test_only_one_valid(self):
         h = Hashids(min_length=6)
         assert h.decode(h.encode(1)[:-1] + '0') == ()
+
+    def test_decode_hex(self):
+        hex_str = '507f1f77bcf86cd799439011'
+        assert Hashids().decode_hex('y42LW46J9luq3Xq9XMly') == hex_str
+        h = Hashids(min_length=1000)
+        assert h.decode_hex(h.encode_hex(hex_str)) == hex_str
+        assert Hashids().decode_hex('WxMLpERDrmh25Lp4L3xEfM6WovWYO3IjkRMKR2ogCMVzn4zQlqt1WK8jKq7OsEpy2qyw1Vi2p') == \
+               'f000000000000000000000000000000000000000000000000000000000000000000000000000000000000f'
+
+    def test_illegal_decode_hex(self):
+        assert Hashids().decode_hex('') == ''
+        assert Hashids().decode_hex('WxMLpERDrmh25Lp4L3xEfM6WovWYO3IjkRMKR2ogCMVlqt1WK8jKq7OsEp1Vi2p') == ''