[Python-Dev] an idea for improving struct.unpack api (original) (raw)

Gustavo J. A. M. Carneiro gjc at inescporto.pt
Thu Jan 6 16:21:36 CET 2005

On Thu, 2005-01-06 at 13:17 +0000, Michael Hudson wrote:

Ilya Sandler <ilya at bluefir.net> writes:

> A problem: > > The current struct.unpack api works well for unpacking C-structures where > everything is usually unpacked at once, but it > becomes inconvenient when unpacking binary files where things > often have to be unpacked field by field. Then one has to keep track > of offsets, slice the strings,call struct.calcsize(), etc... IMO (and E), struct.unpack is the primitive atop which something more sensible is built. I've certainly tried to build that more sensible thing at least once, but haven't ever got the point of believing what I had would be applicable to the general case... maybe it's time to write such a thing for the standard library.

I've been using this simple wrapper:

def stream_unpack(stream, format): return struct.unpack(format, stream.read(struct.calcsize(format)))

It works with file-like objects, such as file, StringIO, socket.makefile(), etc. Working with streams is useful because sometimes you don't know how much you need to read to decode a message in advance.

Regards.

Cheers, mwh

Gustavo J. A. M. Carneiro <gjc at inescporto.pt> <gustavo at users.sourceforge.net> The universe is always one step beyond logic. -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 3086 bytes Desc: not available Url : http://mail.python.org/pipermail/python-dev/attachments/20050106/349cb526/smime.bin

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