Implement full case mapping according to SpecialCasing.txt and
also full case folding according to CaseFolding.txt (F). There
are a number of caveats:
* Only language-agnostic and unconditional full case mapping
is implemented. The only language-agnostic conditional case
mapping rule relates to Greek sigma in final position
(Final_Sigma). Correctly handling this requires both arbitrary
lookahead and lookbehind, which would require some larger
changes to how the case mapping is implemented. This is a
possible future extension.
* The only language-specific handling that is implemented is
for Turkish dotted/undotted Is, if the ISO-8859-9 encoding
is used. This matches the previous behavior and makes sure
that no codepoints not supported by the encoding are
produced. A future extension would be to also handle the
Turkish mappings specified by SpecialCasing.txt based on
the mbfl internal language.
* Full case folding is implemented, but case-insensitive mb_*
operations continue to use simple case folding. The reason is
that full case folding of the haystack string may change the
position at which a match occurred. This would have to be
mapped back into the position in the original string.
* mb_convert_case() exposes both the full and the simple case
mapping / folding, where full is the default. The constants
are:
* MB_CASE_LOWER (used by mb_strtolower)
* MB_CASE_UPPER (used by mb_strtolower)
* MB_CASE_TITLE
* MB_CASE_FOLD
* MB_CASE_LOWER_SIMPLE
* MB_CASE_UPPER_SIMPLE
* MB_CASE_TITLE_SIMPLE
* MB_CASE_FOLD_SIMPLE (used by case-insensitive operations)
Instead of performing a binary search, use a hashtable to store
the case maps. In particular a minimal perfect hash construction
is used, which does not require collision resolution (but does
use an auxiliary table for the hash perturbation).
Previously the case mapping table was segregated by the type of
the character (upper, lower, title) and always stored the other
two variants (key, other1, other2). Now the table is segregated
by the target type (key, other). As only very few characters have
more than one target this only slightly increases the size of the
table.
The advantage of this layout is that we only need to perform a
single table lookup in the case table. Previously, depending on
the case that was hit, either one lookup in the property table,
or two lookups in the property table and one lookup in the case
table were required.
This changes the layout from libunicode in the OpenLDAP project
-- however, the last commit there was over 10 years ago, so I
don't see value in keeping this in sync.
mb_strtoupper() was converting lowercase characters into
titlecase characters, instead of uppercase characters. Luckily
there are only very few characters with a distinct titlecase
representation, so this mostly worked out okay...
In particular strings now store encoding rather than the
no_encoding.
I've also pruned out libmbfl APIs that existed in two forms, one
using no_encoding and the other using encoding. We were not actually
using any of the former.
As a side-effect mb_strtolower() and mb_strtoupper() now correctly
handle a NULL encoding parameter by using the internal encoding.
This is what caused the two test changes.
Do not try to extract the properties from a bitmask. Instead make
the function variadic and pass all properties individually.
Also add a php_unicode_is_prop1() function to check only a single
property.
