This bug was introduced in e837a8800b. In that commit, I increased the
performance of CP949 text conversion, but accidentally broke the case
where 0xC9 (illegal byte to start a character) is followed by a valid
character with a first byte less than 0xA1. The 'broken' behavior is
that both the 0xC9 byte and the following valid character would be
converted to error markers.
When combining all the CJK encoding conversion code in a single file,
I combined some redundant mblen tables. This check will help to ensure
that all the mblen tables are correct.
These (static) tables were defined in a header file, which was included
in two different .c files. That will result in two copies of the tables
being included in the PHP binary.
But the tables were only used in one of the two .c files. Move it where
it is used to avoid needlessly bloating the binary. (I checked in a
hex editor and confirmed that while the previous binary contained two
copies of these tables, it now only contains one.)
Conversion of SJIS-2004 text to UTF-8 using `mb_convert_encoding` is
now about 60% faster than before. (Many other mbstring functions will
also be faster now on SJIS-2004 text.)
This will make it easier to combine duplicated code between all the
CJK text encodings (a significant amount is already combined in this
commit, such as the repeated definitions of SJIS_DECODE and
SJIS_ENCODE), but I hope to remove even more redundancy in the future.
The table used to implement mb_strlen for CP932 has been changed to
the same table as "SJIS-win".
In 6fc8d014df, pakutoma added specialized validity checking functions
for some legacy text encodings like ISO-2022-JP and UTF-7. These
check functions perform a more strict validity check than the encoding
conversion functions for the same text encodings. For example, the
check function for ISO-2022-JP verifies that the string ends in the
correct state required by the specification for ISO-2022-JP.
These check functions are already being used to make detection of text
encoding more accurate when 'strict' detection mode is enabled.
However, since the default is 'non-strict' detection (a bad API design
but we're stuck with it now), most users will not benefit from
pakutoma's work. I was previously reluctant to enable this new logic
for non-strict detection mode. My intention was to reduce the scope of
behavior changes, since almost *any* behavior change may affect *some*
user in a way we don't expect.
However, we definitely have users whose (production) code was broken
by the changes I made in 28b346bc06, and enabling pakutoma's check
functions for non-strict detection mode would un-break it. (See
GH-10192 as an example.) The added checks do also make sense.
In non-strict detection mode, we will not immediately reject candidate
encodings whose validity check function returns false; but they will
be much less likely to be selected. However, failure of the validity
check function is weighted less heavily than an encoding error detected
by the encoding conversion function.
The documentation for mb_detect_encoding says that this function
"Detects the most likely character encoding for string `string` from an
ordered list of candidates".
Prior to 28b346bc06, mb_detect_encoding did not really attempt to
determine the "most likely" text encoding for the input string. It
would just return the first candidate encoding for which the string was
valid. In 28b346bc06, I amended this function so that it uses heuristics
to try to guess which candidate encoding is "most likely".
However, the caller did not have any way to indicate which candidate
text encoding(s) they consider to be more likely, in case the
heuristics applied are inconclusive. In the language of Bayesian
probability, there was no way for the caller to indicate their 'prior'
assignment of probabilities.
Further, the documentation for mb_detect_encoding also says that the
second parameter `encodings` is "a list of character encodings to try,
in order". The documentation clearly implies that the order of
the `encodings` argument should be significant.
Therefore, amend mb_detect_encoding so that while it still uses
heuristics to guess the most likely text encoding for the input string,
it favors those which are earlier in the list of candidate encodings.
One complication is that many callers of mb_detect_encoding use it
in this way:
mb_detect_encoding($string, mb_list_encodings());
In a majority of cases, this is bad code; mb_detect_encoding will both
be much slower and the results will be less reliable than if a smaller
list of candidates is used. However, since such code already exists and
people are using it in production, we should not unnecessarily break it.
The order of candidate encodings obviously does not express any prior
belief of which candidates are more likely in this case, and treating
it as if it did will degrade the accuracy of the result.
Since mb_list_encodings now returns a single, immutable array on each
call, we can avoid that problem by turning off the new behavior when
we receive the array of encodings returned by mb_list_encodings.
This implementation means that if the user does this:
$a = mb_list_encodings();
mb_detect_encoding($string, $a);
...then the order of candidate encodings will not be considered.
However, if the user explicitly initializes their own array of all
supported legacy text encodings, then the order *will* be considered.
The other functions which also follow this new behavior are:
• mb_convert_variables
• mb_convert_encoding (when multiple candidate input encodings are
listed)
Other places where "detection" (or really "guessing") of text encoding
may be performed include:
• mb_send_mail
• Zend engine, when determining the encoding of a PHP script
• mbstring processing of HTTP request contents, when http_input INI
parameter is set to a list
In these cases, the new logic based on order of candidate encodings
is *not* enabled. It *might* be logical to consider the order of
candidate encodings in some or all of these cases, but I'm not sure if
that is true, so it seems wiser to avoid more behavior changes than is
necessary. Further, ever since the new encoding detection heuristics
were implemented in 28b346bc06, we have not received any complaints of
user code being broken in these areas. So I am reluctant to "fix what
isn't broken".
Well, some might say that applying the new detection heuristics
to mb_send_mail, etc. in 28b346bc06 was "fixing what wasn't broken",
but (cough cough) I don't have any comment on that...
This will allow us to easily check in other mbstring functions if the
list of all supported encodings, returned by mb_list_encodings, is
passed in as input to another function.
Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>
We're setting the encoding from PHP_FUNCTION(mb_strpos), but mbfl_strpos would
discard it, setting it to mbfl_encoding_pass, making zend_memnrstr fail due to a
null-pointer exception.
Fixes GH-11217
Closes GH-11220
Compiling in release mode with UBSAN gives me the following compiler warning:
```
In function ‘mb_wchar_to_sjismac’:
mbfilter_sjis.c:1419:89: warning: ‘i’ may be used uninitialized [-Wmaybe-uninitialized]
1419 | buf->state = (i << 24) | (index << 16) | (w & 0xFFFF);
| ^~
mbfilter_sjis.c:1398:42: note: ‘i’ was declared here
1398 | for (int i = 0; i < code_tbl_m_len; i++) {
| ^
```
Since the if condition will always be taken after the goto, we can get
rid of the warning by moving the label inside the if.
Signed-off-by: Alex Dowad <alexinbeijing@gmail.com>
For mb_parse_str, when mbstring.http_input (INI parameter) is a list of
multiple possible text encodings (which is not the case by default),
this new implementation is about 25% faster.
When mbstring.http_input is a single value, then nothing is changed.
(No automatic encoding detection is done in that case.)
The documentation for mb_strcut states:
mb_strcut(
string $string,
int $start,
?int $length = null,
?string $encoding = null
): string
mb_strcut() extracts a substring from a string similarly to mb_substr(),
but operates on bytes instead of characters. If the cut position happens
to be between two bytes of a multi-byte character, the cut is performed
starting from the first byte of that character.
My understanding of the $length parameter for mb_strcut is that it
specified the range of bytes to extract from $string, and that all
characters encoded by those bytes should be included in the returned
string, even if that means the returned string would be longer than
$length bytes. This can happen either if 1) there is more than one way
to encode the same character in $encoding, and one way requires more
bytes than the other, or 2) $encoding uses escape sequences.
However, discussion with users of mb_strcut indicates that many of them
interpret $length as the maximum length of the *returned* string.
This is also the historical behavior of the function.
Hence, there is no need to modify the behavior of mb_strcut and then
remove XFAIL from these test cases afterwards. We can keep the current
behavior.
This (rare) situation was already handled correctly for the 1st and 2nd
of every 3 codepoints in a Base64-encoded section of a UTF-7 string.
However, it was not handled correctly if it happened on the 3rd,
6th, 9th, etc. codepoint of such a Base64-encoded section.
Previously, mbstring used the same logic for encoding validation as for
encoding conversion.
However, there are cases where we want to use different logic for validation
and conversion. For example, if a string ends up with missing input
required by the encoding, or if a character is input that is invalid
as an encoding but can be converted, the conversion should succeed and
the validation should fail.
To achieve this, a function pointer mb_check_fn has been added to
struct mbfl_encoding to implement the logic used for validation.
Also, added implementation of validation logic for UTF-7, UTF7-IMAP,
ISO-2022-JP and JIS.
(The same change has already been made to PHP 8.2 and 8.3; see
6fc8d014df. This commit is backporting the change to PHP 8.1.)
In 6fc8d014df, pakutoma added some additional validation logic to
mb_detect_encoding. Since the implementation of mb_detect_encoding
has changed significantly between PHP 8.2 and 8.3, when merging this
change down from PHP-8.2 into master, I had to port his code over to
the new implementation in master.
However, I did this in a wrong way. In merge commit 0779950768,
the ported code modifies a function argument (to mb_guess_encoding)
which is marked 'const'. In the Windows CI job, MS VC++ rightly
flags this as a compile error.
Adjust the code to accomplish the same thing, but without destructively
modifying 'const' arguments.
When I built and tested 0779950768 locally, the build was successful
and all tests passed. However, in CI, some CI jobs are failing due to
compile errors. Fix those.
Previously, mbstring used the same logic for encoding validation as for
encoding conversion.
However, there are cases where we want to use different logic for validation
and conversion. For example, if a string ends up with missing input
required by the encoding, or if a character is input that is invalid
as an encoding but can be converted, the conversion should succeed and
the validation should fail.
To achieve this, a function pointer mb_check_fn has been added to
struct mbfl_encoding to implement the logic used for validation.
Also, added implementation of validation logic for UTF-7, UTF7-IMAP,
ISO-2022-JP and JIS.
The behavior of the new mb_encode_mimeheader implementation closely
follows the old implementation, except for three points:
• The old implementation was missing a call to the mbfl_convert_filter
flush function. So it would sometimes truncate the input string just
before its end.
• The old implementation would drop zero bytes when QPrint-encoding.
So for example, if you tried to QPrint-encode the UTF-32BE string
"\x00\x00\x12\x34", its QPrint-encoding would be "=12=34", which
does not decode to a valid UTF-32BE string. This is now fixed.
• In some rare corner cases, the new implementation will choose to
Base64-encode or QPrint-encode the input string, where the old
implementation would have just added newlines to it. Specifically,
this can happen when there is a non-space ASCII character, followed
by a large number of ASCII spaces, followed by a non-ASCII character.
The new implementation is around 2.5-8x faster than the old one,
depending on the text encoding and transfer encoding used. Performance
gains are greater with Base64 transfer encoding than with QPrint
transfer encoding; this is not because QPrint-encoding bytes is slow,
but because QPrint-encoded output is much bigger than Base64-encoded
output and takes more lines, so we have to go through the process of
finding the right place to break a line many more times.
Thanks to Ilija Tovilo for noticing and reporting this problem. Thanks
also to Michael Voříšek for finding the StackOverflow post which
explained the reason for the failure.
* PHP-8.2:
Propagate error checks for mbfl_filt_conv_illegal_output()
Use CK() macro to check the output function in mbfilter_unicode2sjis_emoji_sb()
Make error checks on encoding methods for docomo, kddi, sb consistent
* PHP-8.1:
Propagate error checks for mbfl_filt_conv_illegal_output()
Use CK() macro to check the output function in mbfilter_unicode2sjis_emoji_sb()
Make error checks on encoding methods for docomo, kddi, sb consistent
Some places use an if check, which implicitly checks for a non-zero
value, and some places use > 0. The > 0 is the correct one because at
least some of those functions already use the CK() macro to return -1 on
error. Because -1 != 0 this is wrongly interpreted as a success instead
of a failure.
Multiple tests had to be changed to escape the arguments in shell
commands. Some tests are skipped because they behave differently with
spaces in the path versus without. One notable example of this is the
hashbang test which does not work because spaces in hashbangs paths are
not supported in Linux.
Co-authored-by: Michael Voříšek <mvorisek@mvorisek.cz>
The new implementation is 2.5x-3x faster.
If an invalid charset name was used, the old implementation would get
'stuck' trying to parse the charset name and would not interpret any
other MIME encoded words up to the end of the input string. The new
implementation fixes this bug.
If an (invalid) encoded word ends abruptly and a new (valid) encoded
word starts, the old implementation would not decode the valid encoded
word. The new implementation also fixes this.
Otherwise, the behavior of the new implementation has been designed to
closely match that of the old implementation.
In ed0c0df351, Niels Dossche fixed a bug in mbstring whereby
mb_convert_encoding could dereference a NULL pointer and crash if
it was called on an array, with multiple candidate encodings, and at
least one of the strings inside the array was invalid in all the
candidate encodings.
He kindly included a test case, but after being merged into master,
the test case was not actually testing what it was intended to test.
That is now fixed.
Fixes GH-10627
The php_mb_convert_encoding() function can return NULL on error, but
this case was not handled, which led to a NULL pointer dereference and
hence a crash.
Closes GH-10628
Signed-off-by: George Peter Banyard <girgias@php.net>
Commit 8bbd0952e5 added a check rejecting empty strings; in the
merge commiot 379d9a1cfc however it was changed to a NULL check,
one that did not make sense because ZSTR_VAL() is guaranteed to never
be NULL; the length check was accidently removed by that merge commit.
This bug was found by GCC's -Waddress warning:
ext/mbstring/mbstring.c:748:27: warning: the comparison will always evaluate as ‘true’ for the address of ‘val’ will never be NULL [-Waddress]
748 | if (!new_value || !ZSTR_VAL(new_value)) {
| ^
Closes GH-10532
Signed-off-by: George Peter Banyard <girgias@php.net>
As with other SIMD-accelerated functions in php-src, the new UTF-16
encoding and decoding routines can be compiled either with AVX2
acceleration "always on", "always off", or else with runtime detection
of AVX2 support.
With the new UTF-16 decoder/encoder, conversion of extremely short
strings (as in several bytes) has the same performance as before,
and conversion of medium-length (~100 character) strings is about 65%
faster, but conversion of long (~10,000 character) strings is around
6 times faster.
Many other mbstring functions will also be faster now when handling
UTF-16; for example, mb_strlen is almost 3 times faster on medium
strings, and almost 9 times faster on long strings. (Why does mb_strlen
benefit more from AVX2 acceleration than mb_convert_encoding? It's
because mb_strlen only needs to decode, but not re-encode, the input
string, and the UTF-16 decoder benefits much more from SIMD
acceleration than the UTF-16 encoder.)
In a GitHub thread, Michael Voříšek and Kamil Tekiela mentioned that
the PCRE2 function `pcre_match` can be used to validate UTF-8, and that
historically it was more efficient than mbstring's `mb_check_encoding`.
`mb_check_encoding` is now much faster on hosts with SSE2, and much
faster again on hosts with AVX2. However, while all x86-64 CPUs support
at least SSE2, not all PHP users run their code on x86-64 hardware.
For example, some use recent Macs with ARM CPUs.
Therefore, borrow PCRE2's UTF-8 validation function as a fallback for
hosts with no SSE2/AVX2 support. On long UTF-8 strings, this code is
50% faster than mbstring's existing fallback code.
From some local benchmarks which I ran, the AVX2-based version is about
2.8x faster than the SSE2-based version on long (~10,000 byte) strings,
1.6x faster on medium (~100 byte) strings, and just about the same
on very short strings.
I followed the example of the code in the 'standard' module, using
preprocessor directives so that the code can be compiled in any of
4 ways:
1) With no AVX2 support at all (for example, when PHP is compiled for
CPU architectures other than AMD64)
2) For CPUs with AVX2 only (for example, when PHP is built with
CCFLAGS='-march=native' on a host which implements AVX2)
3) With runtime detection of AVX2 performed by the dynamic linker;
this requires a dynamic linker which supports the STT_GNU_IFUNC
symbol type extension to the ELF binary standard. This is true of
glibc's dynamic linker, as of late 2009.
4) With runtime detection of AVX2 performed by the module init function.
The detection is done by checking the output of CPUID and then a
function pointer is set accordingly. In this case, all calls to the
UTF-8 validation routine are indirect calls through that
function pointer.
This code is a few percent faster for short UTF-8 strings. For long
(~10,000 byte) strings, it is also consistently faster on my local
microbenchmarks, but by less than 1%.
This moves them from ``.data`` to ``.rodata`` and allows more compiler optimizations.
* ext/opcache/zend_accelerator_hash: make prime_numbers const
* Zend/zend_signal: make zend_sigs const
* ext/dba: make dba_handler pointers const
* ext/exif: make php_tiff_bytes_per_format and other globals const
* ext/intl/grapheme: make grapheme_extract_iters const
* ext/mstring: make rare_codepoint_bitvec const
* ext/snmp: make objid_mib const
* ext/opcache: make all zend_shared_memory_handlers const
When this INI option is enabled, it reverts the line separator for
headers and message to LF which was a non conformant behavior in PHP 7.
It is done because some non conformant MTAs fail to parse CRLF line
separator for headers and body.
This is used for mail and mb_send_mail functions.
Thanks to the GitHub user 'titanz35' for pointing out that the new
implementation of mb_detect_encoding had poor detection accuracy on
UTF-8 and UTF-16 strings with a byte-order mark.
The new SSE2-based implementation of mb_check_encoding for UTF-8 is
about 10% faster for 0-5 byte strings, more than 3 times faster for
~100-byte strings, and just under 4 times faster for ~10,000-byte
strings.
I believe it may be possible to make this function much faster again.
Some possible directions for further performance optimization include:
• If other ISA extensions like AVX or AVX-512 are available, use a
similar algorithm, but process text in blocks of 32 or 64 bytes
(instead of 16 bytes).
• If other SIMD ISA extensions are available, use the greater variety
of available instructions to make some of the checks tighter.
• Even if only SSE/SSE2 are available, find clever ways to squeeze
instructions out of the hot path. This would probably require a lot
of perusing instruction mauals and thinking hard about which SIMD
instructions could be used to perform the same checks with fewer
instructions.
• Find a better algorithm, possibly one where more checks could be
combined (just as the current algorithm combines the checks for
certain overlong code units and reserved codepoints).
Instead of checking the 'encoding number' to see if we are converting
case for ISO-8859-9 text, compare pointers instead.
This should free up 1 register in php_unicode_convert_case.
The capital Greek letter sigma (Σ) should be lowercased as σ except
when it appears at the end of a word; in that case, it should be
lowercased as the special form ς.
This rule is included in the Unicode data file SpecialCasing.txt.
The condition for applying the rule is called "Final_Sigma" and is
defined in Unicode technical report 21. The rule is:
• For the special casing form to apply, the capital letter sigma must
be preceded by 0 or more "case-ignorable" characters, preceded by
at least 1 "cased" character.
• Further, capital sigma must NOT be followed by 0 or more
case-ignorable characters and then at least 1 cased character.
"Case-ignorable" characters include certain punctuation marks, like
the apostrophe, as well as various accent marks. There are actually
close to 500 different case-ignorable characters, including accent marks
from Cyrillic, Hebrew, Armenian, Arabic, Syriac, Bengali, Gujarati,
Telugu, Tibetan, and many other alphabets. This category also includes
zero-width spaces, codepoints which indicate RTL/LTR text direction,
certain musical symbols, etc.
Since the rule involves scanning over "0 or more" of such
case-ignorable characters, it may be necessary to scan arbitrarily far
to the left and right of capital sigma to determine whether the special
lowercase form should be used or not. However, since we are trying to
be both memory-efficient and CPU-efficient, this implementation limits
how far to the left we will scan. Generally, we scan up to 63 characters
to the left looking for a "cased" character, but not more.
When scanning to the right, we go up to the end of the string if
necessary, even if it means scanning over thousands of characters.
Anyways, it is almost impossible to imagine that natural text will
include "words" with more than 63 successive apostrophes (for example)
followed by a capital sigma.
Closes GH-8096.
We now have a couple of mbstring functions which have fast paths for
strings marked as 'valid UTF-8'. Later, we may likely have more. So
that these fast paths can be used more frequently, mark UTF-8 strings
emitted by mbstring as 'valid UTF-8'. This is always a correct thing
to do, because mbstring never returns invalid UTF-8 as the result of
a conversion (or similar) operation.
Internally, we do have a conversion mode which deliberately emits
invalid UTF-8 in some cases. (This is done to prevent unwanted matches
when we are converting strings to UTF-8 before performing matching
operations on them.) For such strings, don't set the 'valid UTF-8' flag.
It probably wouldn't hurt anything to set it, because strings generated
using that special conversion mode should *never* be returned to
userland, and I don't think we do anything with them which cares about
the IS_STR_VALID_UTF8 flag... but still, it would likely cause
confusion for developers.
One small piece of this was obtained from Stack Overflow. According to
Stack Overflow's Terms of Service, all user-contributed code on SO is
provided under a Creative Commons license. I believe this license is
compatible with the code being included in PHP.
Benchmarking results (UTF-8 only, for strings which have already been
checked using mb_check_encoding):
For very short (0-5 byte) strings, mb_strlen is 12% faster.
The speedup gets greater and greater on longer input strings; for
strings around 100KB, mb_strlen is 23 times faster.
Currently the 'fast' code is gated behind a GC flag check which ensures
it is only used on strings which have already been checked for UTF-8
validity. This is because the accelerated code will return different
results on some invalid UTF-8 strings.
I like the asm which gcc -O3 generates on this modified code...
and guess what: my CPU likes it too!
(The asm is noticeably tighter, without any extra operations in the
path which dispatches to the code for decoding a 1-byte, 2-byte,
3-byte, or 4-byte character. It's just CMP, conditional jump, CMP,
conditional jump, CMP, conditional jump.
...Though I was admittedly impressed to see gcc could implement the
boolean expression `c >= 0xC2 && c <= 0xDF` with just 3 instructions:
add, CMP, then conditional jump. Pretty slick stuff there, guys.)
Benchmark results:
UTF-8, short - to UTF-16LE faster by 7.36% (0.0001 vs 0.0002)
UTF-8, short - to UTF-16BE faster by 6.24% (0.0001 vs 0.0002)
UTF-8, medium - to UTF-16BE faster by 4.56% (0.0003 vs 0.0003)
UTF-8, medium - to UTF-16LE faster by 4.00% (0.0003 vs 0.0003)
UTF-8, long - to UTF-16BE faster by 1.02% (0.0215 vs 0.0217)
UTF-8, long - to UTF-16LE faster by 1.01% (0.0209 vs 0.0211)
MacJapanese has a somewhat unusual feature that when mapped to
Unicode, many characters map to sequences of several codepoints.
Add test cases demonstrating how mb_str_split and mb_substr behave in
this situation.
When adding these tests, I found the behavior of mb_substr was wrong
due to an inconsistency between the string "length" as measured by
mb_strlen and the number of native MacJapanese characters which
mb_substr would count when iterating over the string using the
mblen_table. This has been fixed.
I believe that mb_strstr will also return wrong results in some cases
for MacJapanese. I still need to come up with unit tests which
demonstrate the problem and figure out how to fix it.
Various mbstring legacy text encodings have what is called an 'mblen_table';
a table which gives the length of a multi-byte character using a lookup on
the first byte value. Several mbstring functions have a 'fast path' which uses
this table when it is available.
However, it turns out that iterating through a string using the mblen_table
is surprisingly slow. I found that by deleting this 'fast path' from mb_strlen,
while mb_strlen becomes a few percent slower on very small strings (0-5 bytes),
very large performance gains can be achieved on medium to long input strings.
Part of the reason for this is because our text decoding filters are so much
faster now.
Here are some benchmarks:
EUC-KR, short (0-5 chars) - master faster by 11.90% (0.0000 vs 0.0000)
EUC-JP, short (0-5 chars) - master faster by 10.88% (0.0000 vs 0.0000)
BIG-5, short (0-5 chars) - master faster by 10.66% (0.0000 vs 0.0000)
UTF-8, short (0-5 chars) - master faster by 8.91% (0.0000 vs 0.0000)
CP936, short (0-5 chars) - master faster by 6.27% (0.0000 vs 0.0000)
UHC, short (0-5 chars) - master faster by 5.38% (0.0000 vs 0.0000)
SJIS, short (0-5 chars) - master faster by 5.20% (0.0000 vs 0.0000)
UTF-8, medium (~100 chars) - new faster by 127.51% (0.0004 vs 0.0002)
UTF-8, long (~10000 chars) - new faster by 87.94% (0.0319 vs 0.0170)
UTF-8, very long (~100000 chars) - new faster by 88.25% (0.3199 vs 0.1699)
SJIS, medium (~100 chars) - new faster by 208.89% (0.0004 vs 0.0001)
SJIS, long (~10000 chars) - new faster by 253.57% (0.0319 vs 0.0090)
CP936, medium (~100 chars) - new faster by 126.08% (0.0004 vs 0.0002)
CP936, long (~10000 chars) - new faster by 200.48% (0.0319 vs 0.0106)
EUC-KR, medium (~100 chars) - new faster by 146.71% (0.0004 vs 0.0002)
EUC-KR, long (~10000 chars) - new faster by 212.05% (0.0319 vs 0.0102)
EUC-JP, medium (~100 chars) - new faster by 186.68% (0.0004 vs 0.0001)
EUC-JP, long (~10000 chars) - new faster by 295.37% (0.0320 vs 0.0081)
BIG-5, medium (~100 chars) - new faster by 173.07% (0.0004 vs 0.0001)
BIG-5, long (~10000 chars) - new faster by 269.19% (0.0319 vs 0.0086)
UHC, medium (~100 chars) - new faster by 196.99% (0.0004 vs 0.0001)
UHC, long (~10000 chars) - new faster by 256.39% (0.0323 vs 0.0091)
This does raise the question: is using the 'mblen_table' worthwhile for
other mbstring functions, such as mb_str_split? The answer is yes, it
is worthwhile; you see, while mb_strlen only needs to decode the input
string but not re-encode it, when mb_str_split is implemented using
the conversion filters, it needs to both decode the string and then
re-encode it. This means that there is more potential to gain
performance by using the 'mblen_table'. Benchmarking shows that in a
few cases, mb_str_split becomes faster when the 'mblen_table fast path'
is deleted, but in the majority of cases, it becomes slower.
As a performance optimization, mbstring implements some functions using
tables which give the (byte) length of a multi-byte character using a
lookup based on the value of the first byte. These tables are called
`mblen_table`.
For many years, the mblen_table for SJIS has had '2' in position 0x80.
That is wrong; it should have been '1'. Reasons:
For SJIS, SJIS-2004, and mobile variants of SJIS, 0x80 has never been
treated as the first byte of a 2-byte character. It has always been
treated as a single erroneous byte. On the other hand, 0x80 is a valid
character in MacJapanese... but a 1-byte character, not a 2-byte one.
The same applies to bytes 0xFD-FF; these are 1-byte characters in
MacJapanese, and in other SJIS variants, they are not valid (as the
first byte of a character).
Thanks to the GitHub user 'youkidearitai' for finding this problem.
This boosts the speed of BIG5 encoding conversion by just 1-2%.
I tried various other tweaks to the BIG5 decoding routine to see if
I could make it faster at the cost of using a larger conversion table,
but at least on the machine I am using for benchmarking, these other
changes just made things slower.
This gives a 25% speed boost for conversion operations on long strings
(~10,000 codepoints). For shorter strings, the speed boost is less
(as the input gets smaller, it is progressively swamped more and more
by the overhead of entering and exiting the conversion function).
When benchmarking string conversion speed, we are measuring not only
the speed of the decoder, but also the time which it takes to re-encode
the string in another encoding like UTF-8 or UTF-16. So the performance
increase for functions which only need to decode but not re-encode the
input string will be much more than 25%.
As with CP936, iterating over the PUA table and looking for matches in
it was a significant bottleneck for GB18030 decoding (though not as
severe a bottleneck as for CP936, since more is involved in GB18030
decoding than CP936 decoding).
Here are some benchmark results after optimizing out that bottleneck:
GB18030, medium - to UTF-16BE - faster by 60.71% (0.0007 vs 0.0017)
GB18030, medium - to UTF-8 - faster by 59.88% (0.0007 vs 0.0017)
GB18030, long - to UTF-8 - faster by 44.91% (0.0669 vs 0.1214)
GB18030, long - to UTF-16BE - faster by 43.05% (0.0672 vs 0.1181)
GB18030, short - to UTF-8 - faster by 27.22% (0.0003 vs 0.0004)
GB18030, short - to UTF-16BE - faster by 26.98% (0.0003 vs 0.0004)
(The 'short' test strings had 0-5 codepoints each, 'medium' ~100
codepoints, and 'long' ~10,000 codepoints. For each benchmark, the
test harness cycled through all the test strings 40,000 times.)
In the previous commit, the branch in mb_strlen which implements the
function using the mblen_table (when one is available) was removed.
This made mb_strlen faster for just about every legacy text encoding
which had an mblen_table... except for CP936, which became much slower.
This indicated that our decoding filter for CP936 was slow. I checked
and found iterating over the PUA table was a major bottleneck. After
optimizing that bottleneck out, benchmarks for text encoding conversion
speed were as follows:
CP936, short - to UTF-8 - faster by 10.44% (0.0003 vs 0.0003)
CP936, short - to UTF-16BE - faster by 11.45% (0.0003 vs 0.0003)
CP936, medium - to UTF-8 - faster by 139.09% (0.0012 vs 0.0005)
CP936, medium - to UTF-16BE - faster by 140.34% (0.0013 vs 0.0005)
CP936, long - to UTF-16BE - faster by 215.88% (0.0538 vs 0.0170)
CP936, long - to UTF-8 - faster by 232.41% (0.0528 vs 0.0159)
This does not fully express how much faster the CP936 decoder is now,
since these conversion benchmarks are not only measuring the speed of
decoding CP936, but then also re-encoding the codepoints as UTF-8 or
UTF-16.
For functions like mb_strlen, which just need to decode but not
re-encode the text, the gain in performance is much larger.
For CP950 conversion, the bounds check is needed before doing a lookup
in big5_ucs_table, since the first byte of a CP950 multibyte
character can be up to 0xFE. For BIG5, we only accept 1st bytes up
to 0xF9, and it is not possible for the lookup to go out of bounds.
For many years, the code has contained a TODO comment indicating
that the original author had wanted to do this.
Using smart_str makes the code shorter and cleaner, and it is another
step towards removing a bunch of legacy mbstring code which will soon
be unneeded.
Regarding the optional 3rd `strict` argument to mb_detect_encoding,
the documentation states:
Controls the behaviour when string is not valid in any of the listed encodings.
If strict is set to false, the closest matching encoding will be returned;
if strict is set to true, false will be returned.
(Ref: https://www.php.net/manual/en/function.mb-detect-encoding.php)
Because of bugs in the implementation, mb_detect_encoding did not always
behave according to this description when `strict` was false.
For example:
<?php
echo var_export(mb_detect_encoding("\xc0\x00", "UTF-8", false));
// Before this commit, prints: false
// After this commit, prints: 'UTF-8'
Because `strict` is false in the above example, mb_detect_encoding
should return the 'closest matching encoding', which is UTF-8, since
that is the only candidate encoding. (Incidentally, this example shows
that using mb_detect_encoding with a single candidate encoding in
non-strict mode is useless.)
The new implementation fixes this bug. It also fixes another problem
with the old implementation as regards non-strict detection mode:
The old implementation would stop processing of the input string using
a particular candidate encoding as soon as it saw an error in that
encoding, even in non-strict mode. This means that it could not really
detect the 'closest matching encoding'; rather, what it would return
in non-strict mode was 'the encoding in which the first decoding error
is furthest from the beginning of the input string'.
In non-strict mode, the new implementation continues trying to process
the input string to its end even after seeing an error. This makes it
possible to determine in which candidate encoding the string has the
smallest number of errors, i.e. the 'closest matching encoding'.
Rejecting candidate encodings as soon as it saw an error gave the old
implementation a marked performance advantage in non-strict mode;
however, the new implementation still beats it in most cases. Here are
a few sample microbenchmark results:
UTF-8, ~100 codepoints, strict mode
Old: 0.080s (100,000 calls)
New: 0.026s (" " )
UTF-8, ~100 codepoints, non-strict mode
Old: 0.079s (100,000 calls)
New: 0.033s (" " )
UTF-8, ~10000 codepoints, strict mode
Old: 6.708s (60,000 calls)
New: 1.383s (" " )
UTF-8, ~10000 codepoints, non-strict mode
Old: 6.705s (60,000 calls)
New: 3.044s (" " )
Notice that the old implementation had almost identical performance
between strict and non-strict mode, while the new suffers a significant
performance penalty for non-strict detection. This is the cost of
implementing the behavior specified in the documentation.
A couple more sample results:
SJIS, ~10000 codepoints, strict mode
Old: 4.563s
New: 1.084s
SJIS, ~10000 codepoints, non-strict mode
Old: 4.569s
New: 2.863s
This is the only case I found where the new implementation loses:
UTF-16LE, ~10000 codepoints, non-strict mode
Old: 1.514s
New: 2.813s
The reason is because the test strings happened to be invalid right from
the first few bytes for all the candidate encodings except for UTF-16LE;
so the old implementation would immediately reject all those encodings
and only process the entire string in UTF-16LE.
I believe mb_detect_encoding could be made much faster if we identified
good criteria for when to reject candidate encodings before reaching
the end of the input string.
There is no great difference between the old and new code for text
encodings which either 1) use a fixed number of bytes per codepoint or
2) for which we have an 'mblen' table which enables us to find the
length of a multi-byte character using a table lookup indexed by the
first byte value.
The big difference is for other text encodings, where we have to
actually decode the string to split it. For such text encodings,
such as ISO-2022-JP and UTF-16, I measured a speedup of 50%-120% over
the previous implementation.
Add 4 codepoints commonly used to write Turkish text to our table
of 'commonly used' Unicode codepoints. These are:
• U+011F LATIN SMALL LETTER G WITH BREVE
• U+0130 LATIN CAPITAL LETTER I WITH DOT ABOVE
• U+0131 LATIN SMALL LETTER DOTLESS I
• U+015F LATIN SMALL LETTER S WITH CEDILLA
The 'h' flag makes mb_convert_kana convert zenkaku hiragana to hankaku
katakana; 'k' makes it convert zenkaku katakana to hankaku katakana.
When working on the implementation of mb_convert_kana, I added some
additional checks to catch combinations of flags which do not make
sense; but there is no conflict between 'h' and 'k' (they control
conversions for two disjoint ranges of codepoints) and this combination
should not have been restricted.
Thanks to the GitHub user 'akira345' for reporting this problem.
Closes GH-10174.
I way want to confirm different on mbstring PHP 8.1 or newer and
PHP 8.0 or older, but when I port to PHP 8.0 from PHP 8.1 or newer
phpt files, it stopped die() function when test failed. I want to
make a list, so I don't want to stop it.
If you execute full test, set $testFailedLimit to -1 in
encoding_tests.inc.
In GitHub issue 9613, it was reported that mb_strpos wrongly matches the
character '?' against any invalid string, even when the character '?'
clearly does not appear in the invalid string. This behavior has existed
at least since PHP 5.2.
The reason for the behavior is that mb_strpos internally converts the
haystack and needle to UTF-8 before performing a search. When converting
to UTF-8, regardless of the setting of mb_substitute_character, libmbfl
would use '?' as an error marker for invalid byte sequences. Once those
invalid input sequences were replaced with '?', then naturally, they
would match against occurrences of the actual character '?' (when it
appeared as a 'normal' character, not as an error marker). This would
happen regardless of whether the error was in the haystack and '?' was
used in the needle, or whether the error was in the needle and '?' was
used in the haystack.
Why would libmbfl use '?' rather than the mb_substitute_character set
by the user? Remember that libmbfl was originally a separate library
which was imported into the PHP codebase. mb_substitute_character is an
mbstring API function, not something built into libmbfl. When mbstring
would call into libmbfl, it would provide the error replacement
character to libmbfl as a parameter. However, when libmbfl would perform
conversion operations internally, and not because of a direct call from
mbstring, it would use its own error replacement character.
Example:
<?php
$questionMark = "\x00?";
$badUTF16 = "\xDB\x00"; // half of a surrogate pair
echo mb_strpos($questionMark, $badUTF16, 0, 'UTF-16BE'), "\n";
echo mb_strpos($badUTF16, $questionMark, 0, 'UTF-16BE'), "\n";
Incidentally, this behavior does not occur if the text encoding is
UTF-8, because no conversion is needed in that case.
mb_stripos had a similar issue, but instead of always using '?' as an
error marker internally, it would use the selected
mb_substitute_character. So, for example, if the mb_substitute_character
was '%', then occurrences of '%' in the haystack would match invalid
bytes in the needle, and vice versa.
Example:
<?php
mb_substitute_character(0x25); // '%'
$percent = "\x00%";
$badUTF16 = "\xDB\x00"; // half of a surrogate pair
echo mb_stripos($percent, $badUTF16, 0, 'UTF-16BE'), "\n";
echo mb_stripos($badUTF16, $percent, 0, 'UTF-16BE'), "\n";
This behavior (of mb_stripos) still occurs even if the text encoding is
UTF-8, because case folding is still needed to make the search
case-insensitive.
It is not hard to think of scenarios where these strange and unintuitive
behaviors could cause security vulnerabilities. In the discussion on
GH issue 9613, Christoph Becker suggested that mb_str{i,}pos should
simply refuse to operate on invalid strings. However, this would almost
certainly break existing production code.
This commit mitigates the problem in a less intrusive way: it ensures
that while invalid haystacks can match invalid needles (even if the
specific invalid bytes are different), invalid bytes in the haystack
will never match '?' OR occurrences of the mb_substitute_character in
the needle, and vice versa.
This does represent a backwards compatibility break, but a small one.
Since it mitigates a potential security problem, I believe this is
appropriate.
Closes GH-9613.
Instead of case-folding a string and then converting it to UTF-8 as a
separate operation, why not convert it to UTF-8 at the same time as
we fold case?
For non-UTF-8 encodings, this typically makes mb_stripos about 2x
faster.
The performance gain from this change depends on the text encoding and
input string size. For very small strings, other overheads tend to swamp
the performance gains to some extent, such that the speedup is less than
2x. For medium-length strings (~100 bytes or so), the speedup is
typically around 2.5x.
The greatest performance gains are for UTF-8 strings which have already
been marked as valid (using the GC flags on the zend_string object);
for those, the speedup is more than 10x in many cases.
The previous implementation first converted the haystack and needle to
wchars, then searched for matches between the two sequences of wchars.
Because we use -1 as an error marker when converting to wchars, error
markers from invalid byte sequences in the haystack would match error
markers from invalid byte sequences in the needle, even if the specific
invalid byte sequence was different. I am not sure whether this behavior
is really desirable or not, but anyways, this new implementation
follows the same behavior so as not to cause BC breaks.
On longer MacJapanese strings, conversion speed is boosted by 60-80%.
On medium-length strings, conversion speed is boosted around 20-30%.
For very short strings, there is no appreciable difference.
While benchmarking the new implementation of mb_substr, I found it was
slower than the old one only when the selected encoding was SJIS.
Investigation showed that the new text conversion filter for SJIS
was a touch slower than the old one.
With this optimization, the new SJIS decoder is about 20% faster than
the old one.
This boosts the performance of mb_strpos, mb_stripos, mb_strrpos,
mb_strripos, mb_strstr, mb_stristr, mb_strrchr, and mb_strrichr when
used on non-UTF-8 strings. mb_substr is also faster.
With UTF-8 input, there is no appreciable difference in performance for
mb_strpos, mb_stripos, mb_strrpos, etc. This is expected, since the only
real difference here (aside from shorter and simpler code) is that the
new text conversion code is used when converting non-UTF-8 input strings
to UTF-8. (This is done because internally, mb_strpos, etc. work only
on UTF-8 text.)
For ASCII, speed is boosted by 30-65%. For other legacy text encodings,
the degree of performance improvement will depend on how slow the
legacy conversion code was.
One other minor, but notable difference is that strings encoded using
UTF-8 variants from Japanese mobile vendors (SoftBank, KDDI, Docomo)
will not undergo encoding conversion but will be processed "as is". It
is expected that this will result in a large performance boost for
such input strings; but realistically, the number of users who work
with such strings is probably minute.
I was not originally planning to include mb_substr in this commit, but
fuzzing of the reimplemented mb_strstr revealed that mb_substr needed
to be reimplemented, too; using the old mbfl_substr, which was based
on the old text conversion filters, in combination with functions which
use the new text conversion filters caused bugs.
The performance boost for mb_substr varies from 10%-500%, depending
on the encoding and input string used.
In b5ff87ca71, I made a number of adjustments to our conversion code
for CP1252. One of the adjustments was to make the mappings match those
published by the Unicode Consortium in the file CP1252.TXT. These do
not include mappings for the CP1252 bytes 0x81, 0x8D, 0x8F, 0x90, and
0x9D.
Rostyslav Gulka reported that this caused a problem. His application
stores binary JPEG data in an MS-SQL database. When they SELECT the
binary data out of the database, it is treated as CP1252 text and
automatically converted to UTF-8. To recover the original binary
data, they then do a conversion from UTF-8 to CP1252.
Obviously, that does not work if certain CP1252 bytes do not map to
any Unicode codepoint at all.
While this is a very unusual application of text encoding conversion,
and we might choose not to support it if there was no other basis for
including those mappings, it seems that Microsoft does actually include
them in the Win32 API as "best fit" mappings. These are extra mappings
from Unicode to other text encodings, which the Win32 API function
WideCharToMultiByte uses by default unless the WC_NO_BEST_FIT_CHARS
flag was passed.
A list of these "best fit" mappings for CP1252 can be found here:
https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WindowsBestFit/bestfit1252.txt
When decoding a 3-byte UTF-8 code unit, redundant checks for overlong
code unit and for illegal codepoints from U+D800-DFFF were included.
Both of these conditions are caught by the line which reads:
if ((c2 & 0xC0) != 0x80 || (c == 0xF0 && c2 < 0x90) || (c == 0xF4 && c2 >= 0x90)) {
As such, there is no reason to check for the same error conditions again.
Likewise, when decoding a 4-byte UTF-8 code unit, there was a
redundant check for overlong code unit. That was already caught by the
line which reads:
if ((c2 & 0xC0) != 0x80 || (c == 0xF0 && c2 < 0x90) || (c == 0xF4 && c2 >= 0x90)) {
For JIS encoding, hiragana and katakana can be input in multiple forms.
One form uses JISX 0201 escape sequences. Another is called 'GR-invoked'
kana.
In the context of ISO-2022 encoding, bytes with a zero bit in the MSB
are called "GL" (or "graphics left") and those with the MSB set are
called "GR" (or "graphics right"). Regarding the variants of
ISO-2022-JP which are called "JIS7" and "JIS8", Wikipedia states:
"Other, older variants known as JIS7 and JIS8 build directly on the
7-bit and 8-bit encodings defined by JIS X 0201 and allow use of JIS X
0201 kana from G1 without escape sequences, using Shift Out and Shift
In or setting the eighth bit (GR-invoked), respectively."
In harmony with this, we have always accepted bytes from 0xA3-0xDF and
decoded them to the corresponding hiragana/katakana. However, at some
point I accidentally broke output for these kana. You can see the
problem in 3v4l.org by running this program:
<?php
echo bin2hex(mb_convert_encoding("\xA3", 'JIS', 'JIS'));
The results are:
Output for 8.2rc1 - rc3
1b244200231b2842
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.25, 8.1.12
1b2849231b2842
Output for 8.1.0 - 8.1.11
1b284923
You can see that from 8.1.0 - 8.1.11, there was a missing escape
sequence at the end. That was caused because the flush functions were
not being called properly, and has already been fixed. However, this
also shows that the output for 8.2rc1-rc3 is completely invalid.
It is trying to output a JISX 0208 sequence, but with 0x00 as one of
the JISX 0208 bytes, which is illegal.
Add the missing code which will make the new text conversion filters
behave the same as the old ones when outputting hiragana/katakana in
JIS encoding.
This bug was found when I was fuzzing a patch related to mb_strpos.
In some cases, the legacy text conversion code for UTF-7 (and
UTF7-IMAP) would correctly recognize an error for a Base64-encoded
section which was not correctly padded with zero bits, but the new
(and faster) text conversion code would not.
Specifically, if the input string ended abruptly after the 4th or 7th
byte of a Base64-encoded section, the new conversion code would
confirm that the trailing padding bits from the previous byte (3rd or
6th) were zeroes, but would not check whether the 4th or 7th byte
itself encoded any non-zero bits. The legacy conversion code did
perform this check and would treat the input string as invalid.
Actually, even if the 4th or 7th byte does encode only (padding) zero
bits, this is still a problem, because there is no reason to have a
4th (or 7th) byte in that case. The UTF-7 string should have ended
on the previous byte instead.
Apply the same fix for both UTF-7 and UTF7-IMAP.
The PCRE extension is already doing this. The flag is set when a string
is determined to be valid UTF-8, and cleared in
zend_string_forget_hash_val.
We might as well make good use of it in mbstring as well.
This should result in a negligible slowdown for non-UTF-8 strings,
bad UTF-8 strings, and good UTF-8 strings which are checked only once.
However, when microbenchmarking this change using a variety of text
encodings and string lengths, I found that in most of these cases,
the 'new' code was a few percent faster. In a couple of cases, the 'old'
code was a few percent faster. This was not a result of sampling error,
since I could reproduce these test results repeatedly, and even when
running a large number of iterations. Both the new and old code
were compiled with -O3 -march=native. My (unproved) hypothesis is that
although the new code appears to only add one more conditional branch,
the compiler may emit slightly different code from before (perhaps
with different register allocation and so on), and this may cause some
cases to run slightly faster and others to run slightly slower. I have
not disassembled the old and new binaries to see if an examination of
the emitted assembly code would support this hypothesis.
For good UTF-8 strings which are checked repeatedly, the speedup is
about 40% even for strings 1-5 bytes in length. For ~100 byte strings,
it is ~700%, and for ~10000 byte strings, it is ~80000%.
I tried fuzzing MBString's php_mb_check_encoding function and
pcre2lib's valid_utf function to see if I could find any cases where
their output would be different. After running the fuzzer for a couple
of minutes, it had tried more than 1 million test cases without finding
any where the output was different. Therefore, it appears that
MBString's UTF-8 validation is compatible with PCRE's.
Some of the legacy text encodings which were used in this regression
test are deprecated in PHP-8.2+. The deprecation warnings break the
expected output. Since using these encodings in mbstring is now
deprecated, I think there is little point in keeping them in this test.
So they are now removed from it.
Further, in 219fff376b, I made a change to avoid a situation where the
legacy UTF7-IMAP conversion code gets stuck in a wrong state when its
attempt to emit a character fails. When a Base64-encoded section of
input ended with -, the previous code would FIRST emit a character if
necessary (using the CK or "check" macro, which causes the function to
return immediately if the downstream filter function returns an error
code), and THEN update its own state to indicate that it is now in
ASCII rather than Base64 mode.
If the downstream filter function returned an error code, the CK macro
would then cause the UTF7-IMAP filter function to return immediately
WITHOUT setting its own state to indicate that the Base64-encoded
section was done.
I fixed this by updating the filter state as needed BEFORE calling CK...
but I missed updating the filter state in the case where the Base64
section ends normally and there is no need to emit anything.
Again, in 6d525a425e, I modified the legacy conversion code for
ISO-2022-KR to try to comply more closely with the RFC for this
text encoding. The RFC states that before any occurrence of 'Shift In'
or 'Shift Out' codes in a ISO-2022-KR string, a special escape
sequence must appear at least ONCE, at the beginning of a line.
The previous code did not comply with this requirement. I made it
comply by always emitting this escape sequence at the beginning of
the first line.
Since mb_strcut (wrongly) determines when it has consumed enough of
the input string by looking at the length of its output in bytes, this
extra escape sequence makes mb_strcut consume 4 bytes less of an
ISO-2022-KR string than would otherwise be the case. When this
strange behavior of mb_strcut is fixed, this test will have to be
adjusted to restore the previous expected outputs for ISO-2022-KR.
The existing implementation of mb_strcut extracts part of a
multi-byte encoded string by pulling out raw bytes and then running
them through a conversion filter to ensure that the output is valid
in the requested encoding.
If the conversion filter emits error markers when doing the final
'flush' operation which ends the conversion of the extracted bytes,
these error markers may (in some cases) be included in the output.
The conversion operation does not respect the value of
mb_substitute_character; rather, it always uses '?' as an error marker.
So this issue manifests itself as unwanted '?' characters being
inserted into the output.
This issue has existed for a long time, but became noticeable in PHP
8.1 because for at least some of the supported text encodings, mbstring
is now more strict about emitting error markers when strings end in an
illegal state.
The simplest fix is to suppress error markers during the final flush
operation.
While working on a fix for this problem, another problem with mb_strcut
was discovered; since it decides when to stop consuming bytes from
the input by looking at the byte length of its OUTPUT, anything which
causes extra bytes to be emitted to the output may cause mb_strcut to
not consume all the bytes in the requested range.
The one case where we DO emit extra output bytes is for encodings
which have a selectable mode, like ISO-2022-JP; if a string in such
an encoding ends in a mode which is not the default, we emit an ending
escape sequence which changes back to the default mode. This is done
so that concatenating strings in such encodings is safe.
However, as mentioned, this can cause the output of mb_strcut to be
shorter than it logically should be. This bug has existed for a long
time, and fixing it now will be a BC break, so we may not fix it right
away.
Therefore, tests for THIS fix which don't pass because of that OTHER
bug have been split out into a separate test file (gh9535b.phpt), and
that file has been marked XFAIL.
* PHP-8.2:
Add regression test for problem with mb_encode_mimeheader reported as GH-9683
In legacy text conversion filters, reset filter state in 'flush' function
* PHP-8.1:
Add regression test for problem with mb_encode_mimeheader reported as GH-9683
In legacy text conversion filters, reset filter state in 'flush' function
Up until now, I believed that mbstring had been designed such
that (legacy) text conversion filter objects should not be
re-used after the 'flush' function is called to complete a
text conversion operation.
However, it turns out that the implementation of
_php_mb_encoding_handler_ex DID re-use filter objects
after flush. That means that functions which were based on
_php_mb_encoding_handler_ex, including mb_parse_str and
php_mb_post_handler, would break in some cases; state left
over from converting one substring (perhaps a variable name)
would affect the results of converting another substring
(perhaps the value of the same variable), and could cause
extraneous characters to get inserted into the output.
All this code should be deleted soon, but fixing it helps me
to avoid spurious failures when fuzzing the new/old code to
look for differences in behavior.
(This bug fix commit was originally applied to PHP-8.2 when fuzzing
the new mbstring text conversion code to check for differences with
the old code. Later, Kentaro Ohkouchi kindly reported a problem with
mb_encode_mimeheader under PHP 8.1 which was caused by the same issue.
Hence, this commit was backported to PHP-8.1.)
Fixes GH-9683.
In 0d0029d729 and 315d48b434, I changed the mappings used for Unicode
to Shift-JIS-2004, in an attempt to follow the JISC specification
more closely. However, feedback from Japanese PHP users indicates
that most users of SJIS-2004 expect 0x5C and 0x7E to be treated as
equivalent to the same ASCII bytes. This is due to a long history of
non-complying implementations which then became a de-facto standard.
Therefore, restore the earlier mappings for U+005C and U+007E.
Thanks to the GitHub user 'youkidearitai' for reporting this issue.
Fixes GH-9528.
In e2459857af, I combined mbstring's "SJIS-win" text encoding
into CP932. This was done after doing some testing which appeared
to show that the mappings for "SJIS-win" were the same as those
for "CP932".
Later, it was found that there was actually a small difference
prior to e2459857af when converting Unicode to CP932. The
mappings for the following two codepoints were different:
CP932 SJIS-win
U+203E 0x7E 0x81 0x50
U+00A5 0x5C 0x81 0x8F
As shown, mbstring's "CP932" mapped Unicode's 'OVERLINE' and
'YEN SIGN' to the ASCII bytes which have conflicting uses in
most legacy Japanese text encodings. "SJIS-win" mapped these
to equivalent JIS X 0208 fullwidth characters.
Since e2459867af was not intended to cause any user-visible
change in behavior, I am rolling back the merge of "CP932"
and "SJIS-win".
It seems doubtful whether these two text encodings should
be kept separate or merged in a future release. An extensive
discussion of the related historical background and
compatibility issues involved can be found in this
GitHub thread:
https://github.com/php/php-src/issues/8308
Because this routine used a signed char buffer to hold the bytes
in a (possible) HTML entity, any bytes with the MSB set would
be sign-extended when converting to int; for example, 0x86 would
become 0xFFFFFF86 (or -121).
Codepoints with huge values, like 0xFFFFFF86, are not valid and
if any were passed to the output filter, it would treat them
as errors and emit error markers.
• The legacy conversion code did not emit an error marker if an
escape sequence was truncated.
• BOTH old and new conversion code would shift from KSC5601
(KS X 1001) mode to ASCII mode on an invalid escape sequence.
This doesn't make any sense.
SJIS-Mobile#SOFTBANK text encoding supports special escape sequences,
which shift the decoder into a mode where each single byte represents
an emoji. To get out of this mode, a 0xF (SHIFT OUT) byte can be
used.
After one of these special escape sequences, the new conversion
code expected to see at least one more byte. However, there doesn't
seem to be any particular reason why it should be treated as an
error condition if a string ends abruptly after one of these
escapes. Well, the escape sequence is useless in that case, but
it is a complete and valid escape sequence.
The legacy conversion code did allow a string to end immediately
after one of these escape sequences. Amend the new code to allow
the same.
The use of a special 'vtbl' for converting between '7bit' and
'8bit' text meant that '7bit' text would not be converted to
wchars before going to '8bit'. This meant that the special
value MBFL_BAD_INPUT, which we use to flag an erroneous byte
sequence in input text (and which is required by functions
like mb_check_encoding), would pass directly to the output,
instead of being converted to the error marker specified
by mb_substitute_character.
This issue dates back to the time when I removed the mbfl
'identify filters' and made encoding validity checking and
encoding detection rely only on the conversion filters.
Up until now, I believed that mbstring had been designed such
that (legacy) text conversion filter objects should not be
re-used after the 'flush' function is called to complete a
text conversion operation.
However, it turns out that the implementation of
_php_mb_encoding_handler_ex DID re-use filter objects
after flush. That means that functions which were based on
_php_mb_encoding_handler_ex, including mb_parse_str and
php_mb_post_handler, would break in some cases; state left
over from converting one substring (perhaps a variable name)
would affect the results of converting another substring
(perhaps the value of the same variable), and could cause
extraneous characters to get inserted into the output.
All this code should be deleted soon, but fixing it helps me
to avoid spurious failures when fuzzing the new/old code to
look for differences in behavior.
EUC-JP-2004 includes special byte sequences starting with 0x8E
for kana. The legacy output routine for EUC-JP-2004 emits
these sequences if the value of the output variable `s` is
between 0x80 and 0xFF.
Since the same routine was also used for SJIS-2004 and
ISO-2022-JP-2004, before 8a915ed26c, the same 0x8E sequences
would be emitted when converting to those text encodings as well.
But that is completely wrong. 0x8E 0x__ does not mean the same
in SJIS-2004 or ISO-2022-JP-2004 as it does in EUC-JP-2004.
Therefore, in 8a915ed26c, I fixed the legacy conversion routine
by checking whether the output encoding is EUC-JP-2004 or not.
If it's not, and `s` is 0x80-0xFF, I made it emit an error.
Well, it turns out that single bytes with values from 0xA1
to 0xDF are meaningful in SJIS-2004. To emit these bytes when
appropriate, I had to amend the legacy conversion routine again.
(For clarity, this does NOT mean reverting to the behavior prior
to 8a915ed26c. We were right not to emit sequences starting with
0x8E in SJIS-2004. But in SJIS-2004, we *do* sometimes need to
emit single bytes from 0xA1-0xDF.)
CP50220 converts some codepoints which represent kana
(hiragana/katakana) to a different form. This is the only difference
between CP50220 and CP50221 (which doesn't perform such conversion).
In some cases, this conversion means collapsing two codepoints to
a single output byte sequence. Since the legacy text conversion
filters only worked a byte at a time, the legacy filter had to
cache a byte, then wait until it was called again with the next
byte to compare the cached byte with the following one.
That was all fine, but it didn't work as intended when there were
errors (invalid byte sequences) in the input. Our code (both old
and new) for emitting error markers recursively calls the same
conversion filter. When the old CP50220 filter was called
recursively, the logic for managing cached bytes did not behave
as intended. As a result, the error markers could be reordered
with other characters in the output.
I used an ugly hack to fix this in 6938e3512; when making a
recursive call to emit an error marker, temporarily swap out
`filter->filter_function` to bypass the byte-caching code,
so the error marker immediately goes through to the output.
This worked, but I overlooked the fact that the very same
problem can occur if an invalid byte sequence is detected
*in the flush function*. Apply the same (ugly) fix.
The legacy Base64 conversion code in mbstring automatically
wrapped the output to 72 columns, and the new code imitates
this behavior. Frankly, I'm not sure if this is a good idea
or not (people could easily manually wrap it if they want to),
but have stuck with this behavior for backwards compatibility.
However, fuzzing revealed one case where we were not wrapping
to 72 columns; if the input string is not a multiple of 3
characters, meaning that the output must be padded, and the
point where we must add the final (padded) output happens to
be just beyond 72 columns.
Fuzzing revealed a small difference between the number of error
markers which the legacy ISO-2022-JP and JIS7/8 conversion code
emitted for truncated escape sequences and those emitted by the
new code. The behavior of the old code seems more reasonable
here, so we will imitate it.
In 04e59c916f, I amended the UTF-8 conversion code, so that when given
invalid input, it would emit a number of errors markers harmonizing
with the WHATWG's specification of the standard UTF-8 decoding
algorithm. (Which, gentle reader of commit logs, you can find online
at https://encoding.spec.whatwg.org/#utf-8-decoder.) However, the code
in 04e59c916f was faulty in the case that a truncated UTF-8 code unit
starts with 0xF1.
Then, in dc1ba61d09, when making a small refactoring to a different
part of the UTF-8 conversion code, I inexplicably broke part of the
working code, causing the same fault which was already present with
truncated UTF-8 code units starting with 0xF1 to also occur with
0xF2 and 0xF3 as well. I don't remember what inane thoughts I was
thinking when I pulled off this feat of utter mental confusion.
None of these cases were covered by unit tests, by the way.
Thankfully, my trusty fuzzer picked up on this when testing the
new implementation of mb_parse_str (since the legacy UTF-8
conversion filter did not suffer from the same problem, and I was
fuzzing to find any differences in behavior between the old and
new implementations).
Fortuitously, the fuzzer also picked up another issue which was
present in 04e59c916f. I was emitting only one error marker for
truncated code units starting with 0xE0 or 0xED, in cases where
the WHATWG standard indicates two should be emitted. Examples
are 0xE0 0x9F <END OF STRING> or 0xED 0xA0 <END OF STRING>.
Code units starting with 0xE0-0xED should have 3 bytes. If the
first byte is 0xE0, the second MUST be 0xA0 or greater. (Otherwise,
the codepoint could have fit in a two-byte code unit.) And if the
first byte is 0xED, the second MUST be 0x9F or less. According to
the WHATWG algorithm, step 4, if the second byte is outside the
legal range, then the decoder should emit an error... AND
reprocess the out-of-range byte. The reprocessing will then
cause another error. That's why the decoder should indicate two
errors and not one.
Fuzzing revealed that something was missed here when making the new
encoding conversion code match the behavior of the old code. In the
next major release of PHP, support for these non-encodings will be
dropped, but in the meantime, it is better to match the legacy
behavior.
