Implemented encoding for strings

* Packer by default uses `utf-8` encoding by default
* Unpacker uses `None` by default, so no decoding is done
* Both pack and unpack has `encoding` and `unicode_errors` arguments,
  if `encoding` is `None` no encoding/decoding is done, otherwise
  it is python codec. `unicode_errors` is supplied as `errors`
  parameter to codec

test/test_pack.py

@@ -15,14 +15,63 @@ def testPack():
             0, 1, 127, 128, 255, 256, 65535, 65536,
             -1, -32, -33, -128, -129, -32768, -32769,
             1.0,
-        "", "a", "a"*31, "a"*32,
+        b"", b"a", b"a"*31, b"a"*32,
         None, True, False,
-        (), ((),), ((), None,), 
-        {None: 0}, 
-        (1<<23), 
+        (), ((),), ((), None,),
+        {None: 0},
+        (1<<23),
         ]
     for td in test_data:
         check(td)
 
+def testPackUnicode():
+    test_data = [
+        u"", u"abcd", (u"defgh",), u"Русский текст",
+        ]
+    for td in test_data:
+        re = unpacks(packs(td, encoding='utf-8'), encoding='utf-8')
+        assert_equal(re, td)
+
+def testPackUTF32():
+    test_data = [
+        u"", u"abcd", (u"defgh",), u"Русский текст",
+        ]
+    for td in test_data:
+        print(packs(td, encoding='utf-32'))
+        re = unpacks(packs(td, encoding='utf-32'), encoding='utf-32')
+        assert_equal(re, td)
+
+def testPackBytes():
+    test_data = [
+        b"", b"abcd", (b"defgh",),
+        ]
+    for td in test_data:
+        check(td)
+
+def testIgnoreUnicodeErrors():
+    re = unpacks(packs(b'abc\xeddef'),
+        encoding='utf-8', unicode_errors='ignore')
+    assert_equal(re, "abcdef")
+
+@raises(UnicodeDecodeError)
+def testStrictUnicodeUnpack():
+    unpacks(packs(b'abc\xeddef'), encoding='utf-8')
+
+@raises(UnicodeEncodeError)
+def testStrictUnicodePack():
+    packs(u"abc\xeddef", encoding='ascii', unicode_errors='strict')
+
+def testIgnoreErrorsPack():
+    re = unpacks(packs(u"abcФФФdef", encoding='ascii', unicode_errors='ignore'), encoding='utf-8')
+    assert_equal(re, u"abcdef")
+
+@raises(TypeError)
+def testNoEncoding():
+    packs(u"abc", encoding=None)
+
+def testDecodeBinary():
+    re = unpacks(packs(u"abc"), encoding=None)
+    assert_equal(re, b"abc")
+
 if __name__ == '__main__':
     main()