In a comment to the previous article on a case insensitive hash code, Stefan Glienke pointed to an approach used in Spring4D’s comparers, which is a delightful hack.
Rather than converting the string to a “proper lower case”, it converts the string to an “approximate lower case” using an “or $20”, which happens to be good enough for a hash on string identifiers.
To figure the trick, one needs to check the ASCII Table. (more…)
A lot of the advice on password hashing says that client-side password hashing is not necessary, provided you are using HTTPS or another secure protocol, for instance in
A new kernel for SHA-3 (Keccak) cryptographic hashing has been committed to the DWScript repository.
It is almost 3 times faster than the Pascal version, makes use of MMX asm, and involved an “ad hoc compiler”.
(more…)
Hash, IndexOf, Lookup, Performance, Search, Sorted, String
As a followup to the previous String Lookup: Hash, Sorted or Unsorted here is a look at what happens for longer strings.
When the string you’re searching have more than a dozen characters, and you only have a few hundreds of them, a clear winner emerges.
When looking up a string, what is the fastest strategy?
A hash map, a sorted list or an unsorted list?
Of course it depends on how many strings you have, but where are the cutoff points?
Here is a quick test, and an interesting tidbit is uncovered…
(more…)
A trivial way to turn a case-sensitive String hash function into a case-insensitive one is to to pass a lower-case (or upper-case) version of the String.
However, in our days of Unicode strings, this is not innocuous…
Following a recent post by A. Bouchez about an optimized CRC32 hash, I took it as an opportunity to re-run a small String Hashing Shootout on the worst hash function collision torture test I know: ZIP codes in UTF-16 (Delphi’s default String format).