Pack of (- 2^31-1) is wrong #42

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maxtaco opened this Issue Feb 26, 2013 · 1 comment

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@maxtaco
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maxtaco commented Feb 26, 2013

In Python:

from struct import *
pack('q', -2147483649)

will yield \xff\xff\xff\x7f\xff\xff\xff\xff

Which is what I'd expected too (the Big Endian two's complement of -2147483649 )

Also, the Python msgpack library gets it right:

import msgpack
msgpack.packb(-2147483649)

Yields: \xd3\xff\xff\xff\xff\x7f\xff\xff\xff

Here's how it works with the Node purepack module (which I maintain and use msgpack to test against):

pp = require 'purepack'
pp.pack(-2147483649, 'buffer')
<Buffer d3 ff ff ff ff 7f ff ff ff>

I had to jump through some hoops to get this working in pure JavaScript, I'm not sure if there's a better way with the V8 extension method...

@maxtaco maxtaco added a commit to maxtaco/node-msgpack that referenced this issue Feb 26, 2013
@maxtaco maxtaco This fixes Issue #42 and puts in at least one regression test for 64-bit
integer values, which work in node.js up to about 2^54 and down to
-2^54. May as well make a best effort to get them right.  This issue is
due to a regression introduced in commits  6b4c80c and 0b4f361, which
taken together always encode larger integers as doubles, even when
they shouldn't be.
abe2d18
@godsflaw
Collaborator

Merged the pull request to fix this.

@godsflaw godsflaw closed this Jun 14, 2013
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