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).
* Han Ideagraphs go up to U+9FEA.
* CJK Compatibility Ideographs are no longer specified as a special
range in remotely recent versions of Unicode.
* Surrogate properties should be assigned to U+D800-U+DFFF, not to
U+10000-U+1FFFF.
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.
ucgendat.c was assuming that a title-case character is a character
that has both lower and upper-case variants. However, there are
title-case characters that only have a lower-case variant. Use the
Lt general character proprety to determine where in the case map
the character should be placed instead.
Updated with UnicodeData-6.0.0d7.txt and included the
source of the generator program with the distribution.
#The replaced tables, generated circa 2002, seem to reflect
#Unicode 3.2. I was unable to generate the same property
#offsets with Unicode 3.2 data, but all the tests I made
#indicate php_unicode_is_prop() is returning the correct
#values. The replaced file merely says it used a "modified
#version" of ucgendat, which is not very helpful. The results
#I got were not significantly different, only slightly higher
#offsets at two properties, which were carried over to the
#subsequent properties.
#I was, however, able to replicate precisely the casing table.
#The extent of the "modifications" besides omitting most of
#the tables, a slightly different layout and the casing table
#offsets having been multiplied by 3 is unclear.
#The test suite showed no regressions; however, it's very poor
#in testing the modified portion of the extension.
