[gentoo-dev] proposed md5sum change

[Brian Harring]

Hola all,
Straight to the point, I propose instead of md5summing the compressed
distfile, we md5sum the actual data, the tarball.  There are a couple of
reasons/benefits of this-

1) users are currently tied to a specific compression on the tarball-
for those who would want to convert their distfiles to bzip2 rather then
gzip (for space reasons), they're a bit out of luck- yes, they can
attempt to update md5sum digests or force it to ignore the incorrect
sums, but that gets old *real* quick.

2) Say for whatever reason, the tarball gets inflated- if the original
tarball was compressed w/ say bzip2 0.90, and the user has bzip2 1.x,
even if they recompress it they're out of luck- the bzip2 algorithm was
tweaked for better compression after .90, resulting in a different
md5sum then the original. Yet the distfile is still data-correct- it's
just compressed slightly differently.

3) For anyone making a serious attempt at distfile diffs, the
reconstruction process is seriously borked by the possibility that it's
data-correct, but the compression has changed/been improved resulting in
a different md5sum.  I do know JJW's deltup attempt ran smack dab into
this problem w/ the openoffice tarballs.  I've also ran into the
problem, and I'd prefer not to use the deltup method of having both old
bzip2 and current bzip2 installed.

In terms of performance of the md5summing, it would still likely be i/o
limited- decompression would be done in memory after all.
That said and done, I'm not after bludgeoning someone into implementing
this- assuming people don't have any major criticism's against it and it
has more then a snowball's chance in hell of being used I'm more then
willing to code it myself.
Comments/Flames/Death Threats?
~Brian


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