Hi,

We can speeds up sed by caching result of result mbrtowc() for single
byte characters.  It is effective especially in non-UTF8 multibyte
locales which is expensive calculatation.

$ yes $(printf %040d 0) | head -1000000 >k

Before:

$ time -p env LC_ALL=ja_JP.eucjp sed/sed -ne /a.b/p k
real 1.93
user 1.61
sys 0.27

After patching

$ time -p env LC_ALL=ja_JP.eucjp sed/sed -ne /a.b/p k
real 0.46
user 0.42
sys 0.03

Thanks,
Norihiro