- A new pickle protocol (protocol 3) is added with explicit support

  for bytes.  This is the default protocol.  It intentionally cannot
  be unpickled by Python 2.x.

- When a pickle	written	by Python 2.x contains an (8-bit) str
  instance, this is now decoded to a (Unicode) str instance.  The
  encoding used to do this defaults to ASCII, but can be overridden
  via two new keyword arguments to the Unpickler class.  Previously
  this would create bytes instances, which is usually wrong: str
  instances are often used to pickle attribute names etc., and text is
  more common than binary data anyway.

1 files changed, 86 insertions, 23 deletions

diff --git a/Lib/pickletools.py b/Lib/pickletools.py
index ca09c03..37dad9b 100644
--- a/Lib/pickletools.py
+++ b/Lib/pickletools.py
@@ -746,6 +746,11 @@ pyfloat = StackObject(
               doc="A Python float object.")
 
 pystring = StackObject(
+               name='string',
+               obtype=bytes,
+               doc="A Python (8-bit) string object.")
+
+pybytes = StackObject(
                name='bytes',
                obtype=bytes,
                doc="A Python bytes object.")
@@ -753,7 +758,7 @@ pystring = StackObject(
 pyunicode = StackObject(
                 name='str',
                 obtype=str,
-                doc="A Python string object.")
+                doc="A Python (Unicode) string object.")
 
 pynone = StackObject(
              name="None",
@@ -868,7 +873,7 @@ class OpcodeInfo(object):
             assert isinstance(x, StackObject)
         self.stack_after = stack_after
 
-        assert isinstance(proto, int) and 0 <= proto <= 2
+        assert isinstance(proto, int) and 0 <= proto <= 3
         self.proto = proto
 
         assert isinstance(doc, str)
@@ -995,7 +1000,9 @@ opcodes = [
 
       The argument is a repr-style string, with bracketing quote characters,
       and perhaps embedded escapes.  The argument extends until the next
-      newline character.
+      newline character.  (Actually, they are decoded into a str instance
+      using the encoding given to the Unpickler constructor. or the default,
+      'ASCII'.)
       """),
 
     I(name='BINSTRING',
@@ -1008,7 +1015,9 @@ opcodes = [
 
       There are two arguments:  the first is a 4-byte little-endian signed int
       giving the number of bytes in the string, and the second is that many
-      bytes, which are taken literally as the string content.
+      bytes, which are taken literally as the string content.  (Actually,
+      they are decoded into a str instance using the encoding given to the
+      Unpickler constructor. or the default, 'ASCII'.)
       """),
 
     I(name='SHORT_BINSTRING',
@@ -1021,6 +1030,36 @@ opcodes = [
 
       There are two arguments:  the first is a 1-byte unsigned int giving
       the number of bytes in the string, and the second is that many bytes,
+      which are taken literally as the string content.  (Actually, they
+      are decoded into a str instance using the encoding given to the
+      Unpickler constructor. or the default, 'ASCII'.)
+      """),
+
+    # Bytes (protocol 3 only; older protocols don't support bytes at all)
+
+    I(name='BINBYTES',
+      code='B',
+      arg=string4,
+      stack_before=[],
+      stack_after=[pybytes],
+      proto=3,
+      doc="""Push a Python bytes object.
+
+      There are two arguments:  the first is a 4-byte little-endian signed int
+      giving the number of bytes in the string, and the second is that many
+      bytes, which are taken literally as the bytes content.
+      """),
+
+    I(name='SHORT_BINBYTES',
+      code='C',
+      arg=string1,
+      stack_before=[],
+      stack_after=[pybytes],
+      proto=1,
+      doc="""Push a Python string object.
+
+      There are two arguments:  the first is a 1-byte unsigned int giving
+      the number of bytes in the string, and the second is that many bytes,
       which are taken literally as the string content.
       """),
 
@@ -2006,9 +2045,9 @@ class _Example:
 
 _dis_test = r"""
 >>> import pickle
->>> x = [1, 2, (3, 4), {bytes(b'abc'): "def"}]
->>> pkl = pickle.dumps(x, 0)
->>> dis(pkl)
+>>> x = [1, 2, (3, 4), {b'abc': "def"}]
+>>> pkl0 = pickle.dumps(x, 0)
+>>> dis(pkl0)
     0: (    MARK
     1: l        LIST       (MARK at 0)
     2: p    PUT        0
@@ -2025,19 +2064,32 @@ _dis_test = r"""
    25: (    MARK
    26: d        DICT       (MARK at 25)
    27: p    PUT        2
-   30: S    STRING     'abc'
-   37: p    PUT        3
-   40: V    UNICODE    'def'
-   45: p    PUT        4
-   48: s    SETITEM
-   49: a    APPEND
-   50: .    STOP
+   30: c    GLOBAL     'builtins bytes'
+   46: p    PUT        3
+   49: (    MARK
+   50: (        MARK
+   51: l            LIST       (MARK at 50)
+   52: p        PUT        4
+   55: L        LONG       97
+   59: a        APPEND
+   60: L        LONG       98
+   64: a        APPEND
+   65: L        LONG       99
+   69: a        APPEND
+   70: t        TUPLE      (MARK at 49)
+   71: p    PUT        5
+   74: R    REDUCE
+   75: V    UNICODE    'def'
+   80: p    PUT        6
+   83: s    SETITEM
+   84: a    APPEND
+   85: .    STOP
 highest protocol among opcodes = 0
 
 Try again with a "binary" pickle.
 
->>> pkl = pickle.dumps(x, 1)
->>> dis(pkl)
+>>> pkl1 = pickle.dumps(x, 1)
+>>> dis(pkl1)
     0: ]    EMPTY_LIST
     1: q    BINPUT     0
     3: (    MARK
@@ -2050,13 +2102,24 @@ Try again with a "binary" pickle.
    14: q        BINPUT     1
    16: }        EMPTY_DICT
    17: q        BINPUT     2
-   19: U        SHORT_BINSTRING 'abc'
-   24: q        BINPUT     3
-   26: X        BINUNICODE 'def'
-   34: q        BINPUT     4
-   36: s        SETITEM
-   37: e        APPENDS    (MARK at 3)
-   38: .    STOP
+   19: c        GLOBAL     'builtins bytes'
+   35: q        BINPUT     3
+   37: (        MARK
+   38: ]            EMPTY_LIST
+   39: q            BINPUT     4
+   41: (            MARK
+   42: K                BININT1    97
+   44: K                BININT1    98
+   46: K                BININT1    99
+   48: e                APPENDS    (MARK at 41)
+   49: t            TUPLE      (MARK at 37)
+   50: q        BINPUT     5
+   52: R        REDUCE
+   53: X        BINUNICODE 'def'
+   61: q        BINPUT     6
+   63: s        SETITEM
+   64: e        APPENDS    (MARK at 3)
+   65: .    STOP
 highest protocol among opcodes = 1
 
 Exercise the INST/OBJ/BUILD family.