A system I’m building needs to convert non-negative Ruby integers into shortest-possible UTF-8 string (should be octet string; see Edit below) values. The only requirement on the strings is that their lexicographic order be identical to the natural order on integers.
What’s the best Ruby way to do this?
We can assume the integers are 32 bits and the sign bit is 0. This is successful:
(i >> 24).chr + ((i >> 16) & 0xff).chr + ((i >> 8) & 0xff).chr + (i & 0xff).chr
But it appears to be 1) garbage-intense and 2) ugly. I’ve also looked at pack solutions, but these don’t seem portable due to byte order.
FWIW, the application is Redis hash field names. Building keys may be a performance bottleneck, but probably not. This question is mostly about the “Ruby way”.
Edit
Abpve I should have said “shortest possible string of octets” rather than UFT-8, since this is what Redis actually
stores for field keys. @Mark Reed’s excellent suggestion to try true UTF-8 packing ssems to work. The redis gem I am using seems to properly convert extended codes to octet sequences for Redis: For example,
REDIS.hset('hash', [0x12345678].pack('U'), 'foo')
works fine. But then
REDIS.hkeys('hash')
returns
"\xFC\x92\x8D\x85\x99\xB8"
I need to verify the lexicographic order of these strings is correct, but it looks good so far.
End edit
If it has to be valid UTF-8, you’re not going to get much of an improvement over just encoding the code-point as a UTF-8 character; one of the features of UTF-8 is that encoded characters sort in the proper numeric order, and it only uses the minimal number of bytes necessary under the rules of the format.
Note that UTF-8 is byte-oriented, so there are no endianness concerns.
If you didn’t actually mean UTF-8, then please clarify what you did mean.