Currently, siphash is used for strings up to 36 bytes. hmac-md5 is used
for longer strings.
This switch-over is a remnant of the previous hash-function that was
used, which apparently was slower with longer input strings.
This change serves no purpose anymore. I performed a few performance tests
on strings of varying sizes:
For a 40 byte string with 10 million iterations:
siphash: 0.31 seconds
hmac-md5: 3.8 seconds
For a 1080 byte string with 10 million iterations:
siphash: 4.2 seconds
hmac-md5: 17 seconds
For a 18360 byte string with 10 million iterations:
siphash: 69 seconds
hmac-md5: 240 seconds
Hence, this commit removes the use of hmac-md5.
This change causes reordering of lines in a few logs.
This commit also changes the datastructure for the seed in probabilistic/Hasher
to get rid of a type-punning warning.
There were cases where coercing a record value with an uninitialized
field could cause a null pointer dereference even though the field
can validly be unset since it has &optional.
