Previously, mbstring would accept a lot of things which were not valid
UHC text. No more.
- Don't allow single-byte control characters to appear where the 2nd
byte of a multi-byte character should be.
- Validate that the 2nd byte of a multi-byte character is in the
expected range.
- Treat it as an error if a multi-byte character is truncated.
Also add a test suite to confirm that UHC conversion (both to and from
Unicode) works according to spec.
Sigh. Double sigh. After fruitlessly searching the Internet for information on
this mysterious text encoding called "SJIS-open", I wrote a script to try
converting every Unicode codepoint from 0-0xFFFF and compare the results from
different variants of Shift-JIS, to see which one "SJIS-open" would be most
similar to.
The result? It's just CP932. There is no difference at all. So why do we have
two implementations of CP932 in mbstring?
In case somebody, somewhere is using "SJIS-open" (or its aliases "SJIS-win" or
"SJIS-ms"), add these as aliases to CP932 so existing code will continue to
work.
Also fix a couple small problems with UTF-32 and UTF-8 support:
- UTF-32 would pass very large codepoints (>= 0x80000000), which are
not valid.
- UTF-8 would sometimes emit two error marker characters for a single
bad input byte.
1. Update: http://www.php.net/license/3_01.txt to https, as there is anyway server header "Location:" to https.
2. Update few license 3.0 to 3.01 as 3.0 states "php 5.1.1, 4.1.1, and earlier".
3. In some license comments is "at through the world-wide-web" while most is without "at", so deleted.
4. fixed indentation in some files before |
- Treat it as error if multi-byte string or escape sequence is truncated
- Don't allow 'control' characters or escape sequences to appear in the middle
of a multi-byte char
As with ISO-2022-JP-KDDI, the main reference used to develop the tests was
the behavior of the existing code. It would have been better to have some
independent reference which we could cross-check our code against, but I
couldn't find one.
- Treat it as an error if a multi-byte character or escape sequence is truncated
- When converting other encodings to ISO-2022-JP-KDDI, don't swallow trailing
hash characters or digits
- Don't allow 'control' characters to appear in the middle of a multi-byte char
Note: I was not able to find any kind of official or even semi-official
specification for this legacy encoding. Therefore, the test suite for
ISO-2022-JP-KDDI is based largely on the behavior of the existing code.
Verifying the correctness of program code in this way is very questionable.
In a sense, all you are proving is that the code "does what it does". However,
the test suite will still expose any unintended _changes_ to behavior.
To detect errors in conversion from Unicode to another text encoding, each
mbstring conversion filter object maintains a count of 'bad' characters. After
a conversion operation finishes, this count is checked to see if there was any
error.
The problem with CP50220 was that mbstring used a chain of two conversion filter
objects. The 'bad character count' would be incremented on the second object in
the chain, but this didn't do anything, as only the count on the first such
object is ever checked.
Fix this by implementing the conversion using a single conversion filter object,
rather than a chain of two. This is possible because of the recent refactoring,
which pulled out the needed logic for CP50220 conversion into a helper function.
There's no need to dynamically allocate a struct to hold the 'mode' parameter;
just store it directly in `filt->opaque`. Some other things were also being done
in an unnecessarily roundabout way.
Also, the 'copy' function for CP50220 conversion filters was *both* broken
and unnecessary. Broken, because it malloc'd memory which was never freed by
anything. Unnecessary, because the point of the copy is so that various
algorithms can try running bytes through a conversion filter and see how many
output bytes or characters result, and then back out by restoring the filters
to their previous state. But here's the thing; CP50220 conversion filters don't
hold cached bytes, which is the main thing which would need to be restored to a
previous state.
This function pointer is only called when initializing the struct. After that
nothing is done with it. Therefore, there is no need to keep it in the struct.
This constructor function doesn't do anything different than the generic one.
There's no need to invoke it, either, when initializing a CP50220 conversion
filter.
Instead of manually maintaining the data in eaw_table.h, it is now automatically
generated by ucgendat/ucgendat.php, using the EastAsianWidth.txt file from
the Unicode Consortium.
Something must be said about the deleted test case. Back in 2004, someone
noticed that `mb_strwidth` didn't comply with Unicode 4.0. A test case was
added to expose the problem. Well, time keeps moving on, and with the changing
years, new Unicodes are born and old Unicodes die. Some characters which were
counted as double-width in Unicode 4.0 are no longer such in Unicode 13.0,
which renders the test case obsolete.
At the same time, make a couple of spelling/grammar fixes in ucgendat.php.
This flag indicated that an encoding was 'multi-byte'; it can use a variable
number of bytes to encode each character. As it turns out, we don't actually
need to check this flag anywhere, so it's better to remove it.
MicroSoft invented three encodings very similar to ISO-2022-JP/JIS7/JIS8, called
CP50220, CP50221, and CP50222. All three are supported by mbstring.
Since these encodings are very similar, some code can be shared. Actually,
conversion of CP50220/1/2 to Unicode is exactly the same operation; it's when
converting from Unicode to CP50220/1/2 that some small differences arise in how
certain katakana are handled.
The most important common code was a function called `mbfl_filt_wchar_jis_ms`.
The `jis_ms` part doubtless refers to the fact that these encodings are modified
versions of 'JIS' invented by 'MS'. mbstring also went a step further and exported
'JIS-ms' to userland as a separate encoding from CP50220/1/2. If users requested
'JIS-ms' conversion, they got something like CP50220/1/2, minus their special
ways of handling half-width katakana when converting from Unicode.
But... that 'encoding' is not something which actually exists in the world outside
of mbstring. CP50220/1/2 do exist in MicroSoft software, but not 'JIS-ms'.
For a text encoding conversion library, inventing new variant encodings and
implementing them is not very productive. Our interest is in handling text
encodings which real people actually use for... you know, storing actual text
and things like that.
CP50220 is a variant of ISO-2022-JP invented by MicroSoft, which handles some
Unicode characters which are not representable in ISO-2022-JP by converting
them to similar characters which are representable.
What, then, is CP50220-raw? An Internet search turns up absolutely nothing.
Reference works which I consulted don't say anything about it. Other text
conversion libraries don't support it.
From looking at the code: It's just the same as CP50220, but it accepts
unmapped JIS X 0208 characters passed through from other Japanese encodings
and silently encodes them using the usual ISO-2022-JP escape sequence and
representation for JIS X 0208 characters.
It's hard to see how this could be useful. OK, let me come out and say it:
it's _not_ useful. We can confidently jettison this (mis)feature.
Unicode has a range of 'private' codepoints which individual applications can
use for their own purposes. When they were inventing CP932, MicroSoft mapped
these 'private' or 'user' codepoints to ten new rows added to the JIS X 0208
character table. (JIS X 0208 is based on a 94x94 table; MS used rows 95-114
for private characters.)
`mbfl_filt_conv_wchar_jis_ms` converted these private codepoints to rows 85-94
rather than 95-114. The code included a link to a document on the OpenGroup
web site, dating back to 1996 [1], which proposed mapping private codepoints to
these rows. However, that is not consistent with what mbstring does when
converting CP5022x to Unicode.
There seems to be a dearth of information on CP5022x on the web. However, I
did find one (Japanese-language) page on CP50221, which states that it maps
kuten codes 0x7F21-0x927E to the 'private' Unicode codepoints [2].
As a side note, using rows higher than 95 does seem to defeat one purpose of
using an ISO-2022-JP variant: ISO-2022-JP was specifically designed to be
"7-bit clean", but once you go beyond row 95, the ku codes are 0x80 and up,
so 8 bits are needed.
[1] https://web.archive.org/web/20000229180004/http://www.opengroup.or.jp/jvc/cde/ucs-conv.html
[2] https://www.wdic.org/w/WDIC/Microsoft%20Windows%20Codepage%20%3A%2050221
Essentially, CP5022{0,1,2} are to CP932 as ISO-2022-JP is to Shift-JIS.
As Shift-JIS and ISO-2022-JP both encode characters from the JIS X 0208 charset,
CP932 and CP5022x both encode characters from JIS X 0208 _plus_ extra characters
added as MicroSoft vendor extensions.
Among the added characters are a number of symbols which MS put in the 13th row
of the 94x94 character table. (In JIS X 0208, that row is empty.)
mbfilter_cp50220x.c had an `if` clause which was intended to handle the
conversion of characters in that 13th row, but it was dead code, as the previous
clause was always true in those cases. The solution is to reverse the order of
those two clauses (just as they already appeared in mbfilter_cp932.c).
Don't allow escape sequences to start in the middle of a multibyte character.
Also, don't silently pass through illegal bytes which appear where the 2nd
byte of a multibyte character should be.
Previously, in ISO-2022-JP/JIS7/JIS8, if an escape sequence (starting with 0x1B)
appeared where the 2nd byte of a multibyte character should have been, mbstring
would forget all about the truncated multibyte character and happily accept the
escape sequence. However, such sequences are not legal and should be flagged as
errors.
Also, any other illegal bytes appearing where the 2nd byte of a multibyte
character was expected were just passed through quietly to the output. Fix that.
Also add a test suite for both ISO-2022-JP and JIS7/JIS8. (These are extremely
similar encodings; JIS7 and JIS8 are variants of ISO-2022-JP. mbstring's 'JIS'
is actually a combination of JIS7 _and_ JIS8, since the extensions which each
one adds to ISO-2022-JP are disjoint.)
In other legacy Japanese encodings like Shift-JIS, we are now using a specific
JISX 0208 character for the Unicode overline (U+203E). Previously, the single
byte 0x7E was used, but an ASCII 0x7E does not represent an overline, so this
was changed.
However, JIS7/JIS8 can represent characters in the JISX 0201 character set as
well. That character set also includes an overline character, which takes less
bytes to encode than the corresponding JISX 0208 character, so we'll use it.
This is what mbstring had been doing for a long time; but it changed as a
side effect of the recent changes to how U+203E is encoded in Shift-JIS, etc.
So change it back.
These encodings have multiple modes which can be selected via escape sequences.
The default starting mode is ASCII. If a string _ends_ in a different mode, we
emit a 'redundant' escape sequence to switch back to ASCII.
If the resulting string is never concatenated with other strings, that extra
escape sequence serves no purpose. But if the resulting string is concatenated
with other strings of the same encoding, it ensures that the resulting string
will be valid.
This issue dates back to some commits I merged recently, which made encodings
like Shift-JIS-2004 use appropriate JIS X 0208 characters to represent
backslashes and tildes, rather than single-byte characters which are used in
those encodings with a different meaning (for example, in these encodings,
0x5C is used for a halfwidth Yen sign, rather than a backslash).
There was an unintended side effect: ISO-2022-JP-2004 was also made to
represent backslashes and tildes using JIS X 0208 characters. However,
ISO-2022-JP explicitly includes ASCII as one of its selectable character sets,
and ISO-2022-JP-2004 is just an extension of ISO-2022-JP. So when converting
text to ISO-2022-JP-2004, we can convert Unicode backslashes and tildes to ASCII
rather than using the corresponding JIS X 0208 characters.
Except for vanilla Shift-JIS, where 0x7E is a halfwidth overline/macron.
As for Shift-JIS-2004, it has an added character (byte sequence 0x854A)
which was defined as a halfwidth macron in JIS X 0213:2000, so we use that.
By entering this character in the JIS X 0208 conversion table, we can
remove a bunch of explicit `if` clauses in different conversion filters.
It also means that U+FF5E can be converted into SJIS-mac now; I don't
know why this one SJIS variant rejected U+FF5E before, since 0x8160
means the same thing in SJIS-mac as the others.
Converting U+203E to 0x7E was especially wrong for CP932, where 0x7E
represents a tilde.
For vanilla Shift-JIS and Shift-JIS-2004, converting to 0x7E is acceptable,
since 0x7E does represent an overline/macron in those encodings.
Follow the same principle in CP51932, which is closely related to CP932.
When Microsoft created CP932 (their version of Shift-JIS), they explicitly
used bytes 0-0x7F to represent ASCII characters rather than JIS X 0201
characters.
So when converting Unicode to CP932, it is not correct to convert U+00A5
to CP932 0x5C. Fortunately, CP932 does have a multi-byte FULLWIDTH YEN SIGN
character which we can use instead.
CP51932 uses the same extended character set as CP932; while CP932 is
MicroSoft's extended version of Shift-JIS, CP51932 is their extended version
of EUC-JP. So the same reasoning applies to CP51932.
Shift-JIS-2004 is an extension of Shift-JIS, which uses 0x5C for the Yen
sign. Therefore, it is not correct to convert ASCII 0x5C (backslash) to
Shift-JIS-2004 0x5C (yen sign). JIS X 0208 does have a backslash, so we
can convert ASCII backslash to SJIS-2004 backslash instead.
From time immemorial, there has been confusion around the treatment
of 0x5C bytes on systems using legacy Japanese encodings. JIS X 0201
specified that 0x5C means a yen sign, and thus fonts on Japanese systems,
including early versions of Windows, displayed a 0x5C byte as a yen sign.
This meant that when ASCII text files were displayed on such systems,
what were meant to be backslashes would appear as yen signs. Japanese C
programmers could write character escapes using yen signs, and C compilers
built on the assumption that the input was ASCII would interpret these
escapes as desired. Likewise for shell scripts. Et cetera, et cetera...
Therefore, if the input to `mb_convert_encoding` is (for example) a C
program, and after converting to Shift-JIS-2004, the user wishes to feed
the output into a C compiler, *then* perhaps ASCII 0x5C should be mapped
to SJIS 0x5C. However, this scenario is ridiculous and will never happen.
A more realistic scenario might be: an article written in SJIS-2004 has
embedded Windows file paths (like 'C:\Program Files'), with yen signs used
as a path separator. If we convert SJIS-2004 0x5C to ASCII 0x5C, then the
path separators will be 'fixed' by the conversion.
For general written texts, it is much better to convert backslashes to...
backslashes. And yen signs, to yen signs.
Lots of problems here.
- Don't pass 'control' characters through silently in the middle of a
multi-byte character.
- Treat it as an error if a multi-byte character is truncated.
- For ESC sequences used to encode emoji on earlier Softbank phones, if an
invalid ESC sequence is found, don't pass it through. Rather, handle it as
an error and respect `mb_substitute_character`.
- In ranges used by mobile vendors for emoji, if a certain byte sequence
doesn't map to any emoji, don't emit a mangled value (actually a raw
(ku*94)+ten value, which may not even be a valid Unicode codepoint at all).
- When converting Unicode to SJIS-Mobile, don't mangle codepoints which fall
in the 2nd range of MicroSoft vendor extensions.
Some vendor-specific emoji have been mapped to standard Unicode codepoints
now, rather than 'private use area' codepoints. When the legacy code was
written, these codepoints may not have existed yet in the Unicode standard
which was current at that time.
Also do a major code cleanup -- remove dead code, rearrange what is left,
use some new macros and helper functions to make the code clearer...
These constants indicate that a text encoding uses 2+ bytes for each character,
and is either big endian or little endian (respectively). But nothing in
mbstring cares about the difference between MBFL_ENCTYPE_MWC2BE and
MBFL_ENCTYPE_MWC2LE.
(Actually, nothing cares about whether these flags are set at all...
maybe we should just remove them?)
These flags identify text encodings in mbstring which use a constant number of
bytes per character. While some parts of the code do use these flags, usually
to detect cases which can be optimized due to constant-width encoding, nothing
cares whether the encodings are 'LE' (little-endian) or 'BE' (big-endian).
So we can simplify things by combining constants.
