Removed the new LONG2 opcode: it's extravagant. If LONG1 isn't enough,
then the embedded argument consumes at least 256 bytes. The difference between a 3-byte prefix (LONG2 + 2 bytes) and a 5-byte prefix (LONG4 + 4 bytes) is at worst less than 1%. Note that binary strings and binary Unicode strings also have only "size is 1 byte, or size is 4 bytes?" flavors, and I expect for the same reason. The only place a 2-byte thingie was used was in BININT2, where the 2 bytes make up the *entire* embedded argument (and now EXT2 also does this); that's a large savings over 4 bytes, because the total opcode+argument size is so small in the BININT2/EXT2 case. Removed the TAKEN_FROM_ARGUMENT "number of bytes" code, and bifurcated it into TAKEN_FROM_ARGUMENT1 and TAKEN_FROM_ARGUMENT4. Now there's enough info in ArgumentDescriptor objects to deduce the # of bytes consumed by each opcode. Rearranged the order in which proto2 opcodes are listed in pickle.py.
This commit is contained in:
Tim Peters
parent
bdbe74183c
commit
fdb8cfab08
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@ -135,19 +135,18 @@ FALSE = 'I00\n' # not an opcode; see INT docs in pickletools.py
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# Protocol 2 (not yet implemented) (XXX comments will be added later)
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NEWOBJ = '\x81'
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PROTO = '\x80'
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EXT2 = '\x83'
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NEWOBJ = '\x81'
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EXT1 = '\x82'
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TUPLE1 = '\x85'
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EXT2 = '\x83'
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EXT4 = '\x84'
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TUPLE3 = '\x87'
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TUPLE1 = '\x85'
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TUPLE2 = '\x86'
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NEWFALSE = '\x89'
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TUPLE3 = '\x87'
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NEWTRUE = '\x88'
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LONG2 = '\x8b'
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NEWFALSE = '\x89'
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LONG1 = '\x8a'
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LONG4 = '\x8c'
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LONG4 = '\x8b'
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__all__.extend([x for x in dir() if re.match("[A-Z][A-Z0-9_]+$",x)])
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@ -125,7 +125,8 @@ UP_TO_NEWLINE = -1
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# Represents the number of bytes consumed by a two-argument opcode where
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# the first argument gives the number of bytes in the second argument.
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TAKEN_FROM_ARGUMENT = -2
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TAKEN_FROM_ARGUMENT1 = -2 # num bytes is 1-byte unsigned int
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TAKEN_FROM_ARGUMENT4 = -3 # num bytes is 4-byte signed little-endian int
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class ArgumentDescriptor(object):
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__slots__ = (
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@ -133,7 +134,8 @@ class ArgumentDescriptor(object):
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'name',
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# length of argument, in bytes; an int; UP_TO_NEWLINE and
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# TAKEN_FROM_ARGUMENT are negative values for variable-length cases
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# TAKEN_FROM_ARGUMENT{1,4} are negative values for variable-length
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# cases
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'n',
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# a function taking a file-like object, reading this kind of argument
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@ -150,8 +152,9 @@ class ArgumentDescriptor(object):
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self.name = name
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assert isinstance(n, int) and (n >= 0 or
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n is UP_TO_NEWLINE or
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n is TAKEN_FROM_ARGUMENT)
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n in (UP_TO_NEWLINE,
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TAKEN_FROM_ARGUMENT1,
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TAKEN_FROM_ARGUMENT4))
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self.n = n
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self.reader = reader
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@ -341,7 +344,7 @@ def read_string4(f):
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string4 = ArgumentDescriptor(
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name="string4",
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n=TAKEN_FROM_ARGUMENT,
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n=TAKEN_FROM_ARGUMENT4,
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reader=read_string4,
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doc="""A counted string.
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@ -370,7 +373,7 @@ def read_string1(f):
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string1 = ArgumentDescriptor(
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name="string1",
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n=TAKEN_FROM_ARGUMENT,
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n=TAKEN_FROM_ARGUMENT1,
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reader=read_string1,
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doc="""A counted string.
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@ -434,7 +437,7 @@ def read_unicodestring4(f):
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unicodestring4 = ArgumentDescriptor(
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name="unicodestring4",
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n=TAKEN_FROM_ARGUMENT,
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n=TAKEN_FROM_ARGUMENT4,
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reader=read_unicodestring4,
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doc="""A counted Unicode string.
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@ -626,7 +629,7 @@ def read_long1(f):
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long1 = ArgumentDescriptor(
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name="long1",
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n=TAKEN_FROM_ARGUMENT,
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n=TAKEN_FROM_ARGUMENT1,
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reader=read_long1,
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doc="""A binary long, little-endian, using 1-byte size.
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@ -634,36 +637,6 @@ long1 = ArgumentDescriptor(
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many bytes and interprets them as a little-endian 2's-complement long.
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""")
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def read_long2(f):
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r"""
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>>> import StringIO
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>>> read_long2(StringIO.StringIO("\x02\x00\xff\x00"))
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255L
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>>> read_long2(StringIO.StringIO("\x02\x00\xff\x7f"))
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32767L
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>>> read_long2(StringIO.StringIO("\x02\x00\x00\xff"))
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-256L
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>>> read_long2(StringIO.StringIO("\x02\x00\x00\x80"))
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-32768L
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>>>
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"""
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n = read_uint2(f)
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data = f.read(n)
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if len(data) != n:
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raise ValueError("not enough data in stream to read long2")
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return decode_long(data)
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long2 = ArgumentDescriptor(
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name="long2",
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n=TAKEN_FROM_ARGUMENT,
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reader=read_long2,
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doc="""A binary long, little-endian, using 2-byte size.
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This first reads two byte as an unsigned size, then reads that
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many bytes and interprets them as a little-endian 2's-complement long.
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""")
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def read_long4(f):
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r"""
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>>> import StringIO
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@ -688,7 +661,7 @@ def read_long4(f):
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long4 = ArgumentDescriptor(
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name="long4",
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n=TAKEN_FROM_ARGUMENT,
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n=TAKEN_FROM_ARGUMENT4,
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reader=read_long4,
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doc="""A binary representation of a long, little-endian.
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@ -1705,19 +1678,8 @@ opcodes = [
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A more efficient encoding of a Python long; the long1 encoding
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says it all."""),
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I(name="LONG2",
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code='\x8b',
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arg=long2,
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stack_before=[],
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stack_after=[pylong],
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proto=2,
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doc="""Long integer using two-byte length.
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A more efficient encoding of a Python long; the long2 encoding
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says it all."""),
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I(name="LONG4",
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code='\x8c',
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code='\x8b',
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arg=long4,
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stack_before=[],
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stack_after=[pylong],
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