int/long types, and use the new PyLong_FromUnsignedLong() and
PyLong_AsUnsignedLong() interfaces instead.
Semantic change: the 'I' format will now always return a long int.
- Conform to standard Python C coding styles.
- All static symbols were renamed and shorted.
- Eyeballed all return values and memory references.
- Fixed a bug in signal.pause() so that exceptions raised in signal
handlers are now properly caught after pause() returns.
- Removed SIGCPU and SIGFSZ. We surmise that these were typos for the
previously missing SIGXCPU and SIGXFSZ.
data formats. The _xdr module is no longer used, since struct
supports the required IEEE floats and doubles.
(I have one doubt about not using _xdr. The struct module doesn't
handle Inf, NaN and gradual underflow correctly. If the _xdr module
does these things better, it may still have a (small) competitive
advantage. On the other hand, since not all platforms support IEEE
floating point, it's not clear that it would be a good idea to ever
transfer Inf or NaNs. Gradual underflow can be fixed in the struct
module.
module. (Small problem: struct.pack() won't deal with the Python long
ints returned by struct.unpack() for the 'L' format. Worked around
that for now.)
-- The whole implementation is now more table-driven.
-- Unsigned integers. Format characters 'B', 'H', 'I' and 'L'
mean unsigned byte, short, int and long. For 'I' and 'L', the return
value is a Python long integer if a Python plain integer can't
represent the required range (note: this is dependent on the size of
the relevant C types only, not of the sign of the actual value).
-- A new format character 's' packs/unpacks a string. When given a
count prefix, this is the size of the string, not a repeat count like
for the other format characters; e.g. '10s' means a single 10-byte
string, while '10c' means 10 characters. For packing, the string is
truncated or padded with null bytes as appropriate to make it fit.
For unpacking, the resulting string always has exactly the specified
number of bytes. As a special case, '0s' means a single, empty
string (while '0c' means 0 characters).
-- Various byte order options. The first character of the format
string determines the byte order, size and alignment, as follows:
First character Byte order size and alignment
'@' native native
'=' native standard
'<' little-endian standard
'>' big-endian standard
'!' network (= big-endian) standard
If the first character is not one of these, '@' is assumed.
Native byte order is big-endian or little-endian, depending on the
host system (e.g. Motorola and Sun are big-endian; Intel and DEC are
little-endian).
Native size and alignment are determined using the C compiler's sizeof
expression. This is always combined with native byte order.
Standard size and alignment are as follows: no alignment is required
for any type (so you have to use pad bytes); short is 2 bytes; int and
long are 4 bytes. In this mode, there is no support for float and
double.
Note the difference between '@' and '=': both use native byte order,
but the size and alignment of the latter is standardized.
The form '!' is available for those poor souls who can't remember
whether network byte order is big-endian or little-endian.
There is no way to indicate non-native byte order (i.e. force
byte-swapping); use the appropriate choice of '<' or '>'.
Guido van Rossum
Barry Warsaw
Roger E. Masse
Fred Drake