Replace the mapping tables used to convert between UTF-8 and other
character encodings with new radix tree-based maps. Looking up an entry in
a radix tree is much faster than a binary search in the old maps. As a
bonus, the radix tree representation is also more compact, making the
binaries slightly smaller.
The "combined" maps work the same as before, with binary search. They are
much smaller than the main tables, so it doesn't matter so much. However,
the "combined" maps are now stored in the same .map files as the main
tables. This seems more clear, since they're always used together, and
generated from the same source files.
Patch by Kyotaro Horiguchi, with lot of hacking by me at various stages.
Reviewed by Michael Paquier and Daniel Gustafsson.
Discussion: https://www.postgresql.org/message-id/20170306.171609.204324917.horiguchi.kyotaro%40lab.ntt.co.jp
Generate EUC_CN mappings from gb-18030-2000.xml, because GB2312.TXT is no
longer available.
Get UHC from windows-949-2000.xml, it's more up-to-date.
Plus tons more small changes. With these changes, the perl scripts
faithfully produce the *.map files we have in the repository, from the
external source files.
In the passing, fix the Makefile to also download CP932.TXT and CP950.TXT.
Based on patches by Kyotaro Horiguchi, reviewed by Daniel Gustafsson.
Discussion: https://postgr.es/m/08e7892a-d55c-eefe-76e6-7910bc8dd1f3@iki.fi
Heikki Linnakangas
Bruce Momjian