[Support] Add a function to MD5 a file's contents.
ClosedPublic

Authored by zturner on Fri, Mar 17, 2:18 PM.

Details

Summary
In doing so, clean up the MD5 interface a little.  Most
existing users only care about the lower 8 bytes of an MD5,
but for some users that care about the upper and lower,
there wasn't a good interface.  Furthermore, consumers
of the MD5 checksum were required to handle endianness
details on their own, so it seems reasonable to abstract
this into a nicer interface that just gives you the right
value.

Diff Detail

Repository
rL LLVM
zturner created this revision.Fri, Mar 17, 2:18 PM

How does it compare to the SHA1 API? Are these in sync? (If not any good reason they're not?)

How does it compare to the SHA1 API? Are these in sync? (If not any good reason they're not?)

It's pretty similar. The main difference is that SHA1 only gives you a sequence of bytes, and there is no option to return the result any other way without manual effort on the part of the user. I don't know if there is any good reason for this. It seems to be fairly common practice for consumers of MD5 checksums to truncate the hash and only use the first 8 bytes or the last 8 bytes. This seems much less common with SHA1 (as in, I don't know of any clients that do this, and I don't know if this affects the security of the hash in any way either).

If we can decide on a reasonable interface that allows both to be consistent, I'm happy to try to implement it (but hopefully orthogonally to this patch), keeping in mind that I'm not a hash expert, so I would not be the person to make any functional changes, but API changes are OK.

mehdi_amini accepted this revision.Mon, Mar 20, 4:11 PM

LGTM. See one comment inline.

(After reading more: this is not really the MD5 interface but the "result" object only.)

llvm/unittests/Support/MD5Test.cpp
70 ↗(On Diff #92206)

I feel we should have a test for with low() and high() here.

This revision is now accepted and ready to land.Mon, Mar 20, 4:11 PM
This revision was automatically updated to reflect the committed changes.