Converts a string into a collation key that can be compared with other collation keys produced by the same function using strcmp().
In order to sort filenames correctly, this function treats the dot ‘.’ as a special case. Most dictionary orderings seem to consider it insignificant, thus producing the ordering “event.c” “eventgenerator.c” “event.h” instead of “event.c” “event.h” “eventgenerator.c”. Also, we would like to treat numbers intelligently so that “file1” “file10” “file5” is sorted as “file1” “file5” “file10”.
Note that this function depends on the [current locale][setlocale].
Available since: 2.8
A UTF-8 encoded string.
The data is owned by the caller of the function. The value is a NUL terminated UTF-8 string.
str, in bytes, or -1 if