Add fast mb_strcut implementation for UTF-16

Similar to the fast, specialized mb_strcut implementation for UTF-8
in 1f0cf133db, this new implementation of mb_strcut for UTF-16 strings

Add fast mb_strcut implementation for UTF-16

Similar to the fast, specialized mb_strcut implementation for UTF-8
in 1f0cf133db, this new implementation of mb_strcut for UTF-16 strings
just examines a few bytes before each cut point.

Even for short strings, the new implementation is around 2x faster.
For strings around 10,000 bytes in length, it comes out about 100-500x
faster in my microbenchmarks.

The new implementation behaves identically to the old one on valid
UTF-16 strings; a fuzzer was used to help verify this.

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Add fast mb_strcut implementation for UTF-8

The old implementation runs through the entire string to pick out the
part which should be returned by mb_strcut. This creates significant

Add fast mb_strcut implementation for UTF-8

The old implementation runs through the entire string to pick out the
part which should be returned by mb_strcut. This creates significant
performance overhead. The new specialized implementation of mb_strcut
for UTF-8 usually only examines a few bytes around the starting and
ending cut points, meaning it generally runs in constant time.

For UTF-8 strings just a few bytes long, the new implementation is
around 10% faster (according to microbenchmarks which I ran locally).
For strings around 10,000 bytes in length, it is 50-300x faster.
(Yes, that is 300x and not 300%.)

The new implementation behaves identically to the old one on VALID
UTF-8 strings; a fuzzer was used to help ensure this is the case.
On invalid UTF-8 strings, there is a difference: in some cases, the
old implementation will pass invalid byte sequences through unchanged,
while in others it will remove them. The new implementation has
behavior which is perhaps slightly more predictable: it simply backs
up the starting and ending cut points to the preceding "starter
byte" (one which is not a UTF-8 continuation byte).

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PHP_HAVE_BUILTIN_USUB_OVERFLOW macro is defined even if __builtin_usub_overflow not available

...So conditionally including code which uses __builtin_usub_overflow
(for performance) if t

PHP_HAVE_BUILTIN_USUB_OVERFLOW macro is defined even if __builtin_usub_overflow not available

...So conditionally including code which uses __builtin_usub_overflow
(for performance) if the macro is defined is not correct. We also need
to check if the macro is defined as a non-zero value.

Apparently this broke the build for a user whose C compiler is GCC
4.9.4. Sorry, user! That was my fault!

Thanks to Jakub Zelenka for reporting the issue.

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[skip ci] Fix various typos and grammar issues (#11143)

Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are ca

Fix phpGH-10648: add check function pointer into mbfl_encoding

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.)

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Fix phpGH-10648: add check function pointer into mbfl_encoding

Previously, mbstring used the same logic for encoding validation as for
encoding conversion.

However, there are ca

Fix phpGH-10648: add check function pointer into mbfl_encoding

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.

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Add AVX2-accelerated UTF-16 decoding/encoding routines

As with other SIMD-accelerated functions in php-src, the new UTF-16
encoding and decoding routines can be compiled either with AVX2

Add AVX2-accelerated UTF-16 decoding/encoding routines

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.)

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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 shoul

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.

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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 shoul

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.

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Fix legacy text conversion filter for UTF-16

Make necessary changes to filter state before using CK macro.

New internal interface for fast text conversion in mbstring

When converting text to/from wchars, mbstring makes one function call
for each and every byte or wchar to be converted. Typica

New internal interface for fast text conversion in mbstring

When converting text to/from wchars, mbstring makes one function call
for each and every byte or wchar to be converted. Typically, each of
these conversion functions contains a state machine, and its state has
to be restored and then saved for every single one of these calls.
It doesn't take much to see that this is grossly inefficient.

Instead of converting one byte or wchar on each call, the new
conversion functions will either fill up or drain a whole buffer of
wchars on each call. In benchmarks, this is about 3-10× faster.

Adding the new, faster conversion functions for all supported legacy
text encodings still needs some work. Also, all the code which uses
the old-style conversion functions needs to be converted to use the
new ones. After that, the old code can be dropped. (The mailparse
extension will also have to be fixed up so it will still compile.)

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Remove useless constant MBFL_ENCTYPE_MWC2

mbstring no longer provides 'long' substitutions for erroneous input bytes

Previously, mbstring had a special mode whereby it would convert
erroneous input byte sequences to output like

mbstring no longer provides 'long' substitutions for erroneous input bytes

Previously, mbstring had a special mode whereby it would convert
erroneous input byte sequences to output like "BAD+XXXX", where "XXXX"
would be the erroneous bytes expressed in hexadecimal. This mode could
be enabled by calling `mb_substitute_character("long")`.

However, accurately reproducing input byte sequences from the cached
state of a conversion filter is often tricky, and this significantly
complicates the implementation. Further, the means used for passing
the erroneous bytes through to where the "BAD+XXXX" text is generated
only allows for up to 3 bytes to be passed, meaning that some erroneous
byte sequences are truncated anyways.

More to the point, a search of publically available PHP code indicates
that nobody is really using this feature anyways.

Incidentally, this feature also provided error output like "JIS+XXXX"
if the input 'should have' represented a JISX 0208 codepoint, but it
decodes to a codepoint which does not exist in the JISX 0208 charset.
Similarly, specific error output was provided for non-existent
JISX 0212 codepoints, and likewise for JISX 0213, CP932, and a few
other charsets. All of that is now consigned to the flames.

However, "long" error markers also include a somewhat more useful
"U+XXXX" marker for Unicode codepoints which were successfully
decoded from the input text, but cannot be represented in the output
encoding. Those are still supported.

With this change, there is no need to use a variety of special values
in the high bits of a wchar to represent different types of error
values. We can (and will) just use a single error value. This will be
equal to -1.

One complicating factor: Text conversion functions return an integer to
indicate whether the conversion operation should be immediately
aborted, and the magic 'abort' marker is -1. Also, almost all of these
functions would return the received byte/codepoint to indicate success.
That doesn't work with the new error value; if an input filter detects
an error and passes -1 to the output filter, and the output filter
returns it back, that would be taken to mean 'abort'.

Therefore, amend all these functions to return 0 for success.

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Test behavior of 'long' illegal character markers

After mb_substitute_character("long"), mbstring will respond to
erroneous input by inserting 'long' error markers into the output.
D

Test behavior of 'long' illegal character markers

After mb_substitute_character("long"), mbstring will respond to
erroneous input by inserting 'long' error markers into the output.
Depending on the situation, these error markers will either look like
BAD+XXXX (for general bad input), U+XXXX (when the input is OK, but it
converts to Unicode codepoints which cannot be represented in the
output encoding), or an encoding-specific marker like JISX+XXXX or
W932+XXXX.

We have almost no tests for this feature. Add a bunch of tests to
ensure that all our legacy encoding handlers work in a reasonable
way when 'long' error markers are enabled.

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Combine MBFL_ENCTYPE_MWC2{BE,LE} constants

These constants indicate that a text encoding uses 2+ bytes for each character,
and is either big endian or little endian (respectively). But n

Combine MBFL_ENCTYPE_MWC2{BE,LE} constants

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?)

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Remove mbstring identify filters

mbstring had an 'identify filter' for almost every supported text encoding
which was used when auto-detecting the most likely encoding for a string.

Remove mbstring identify filters

mbstring had an 'identify filter' for almost every supported text encoding
which was used when auto-detecting the most likely encoding for a string.
It would run over the string and set a 'flag' if it saw anything which
did not appear likely to be the encoding in question.

One problem with this scheme was that encodings which merely appeared
less likely to be the correct one were completely rejected, even if there
was no better candidate. Another problem was that the 'identify filters'
had a huge amount of code duplication with the 'conversion filters'.

Eliminate the identify filters. Instead, when auto-detecting text
encoding, use conversion filters to see whether the input string is valid
in candidate encodings or not. At the same type, watch the type of
codepoints which the string decodes to and mark it as less likely if
non-printable characters (ESC, form feed, bell, etc.) or 'private use
area' codepoints are seen.

Interestingly, one old test case in which JIS text was misidentified
as UTF-8 (and this wrong behavior was enshrined in the test) was 'fixed'
and the JIS string is now auto-detected as JIS.

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Improve error handling for UTF-16{,BE,LE}

Catch various errors such as the first part of a surrogate pair not being
followed by a proper second part, the first part of a surrogate pair a

Improve error handling for UTF-16{,BE,LE}

Catch various errors such as the first part of a surrogate pair not being
followed by a proper second part, the first part of a surrogate pair appearing
at the end of a string, the second part of a surrogate pair appearing out
of place, and so on.

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UTF-16 text conversion handles truncated characters as illegal

This broke one old test (Zend/tests/multibyte_encoding_003.phpt), which used
a PHP script encoded as UTF-16. The problem wa

UTF-16 text conversion handles truncated characters as illegal

This broke one old test (Zend/tests/multibyte_encoding_003.phpt), which used
a PHP script encoded as UTF-16. The problem was that to terminate the test
script, we need the text: "\n--EXPECT--". Out of that text, the terminating
newline (0x0A byte) becomes part of the resulting test script; but a bare
0x0A byte with no 0x00 is not valid UTF-16.

Since we now treat truncated UTF-16 characters as erroneous, an extra '?' is
appended to the output as an 'illegal character' marker.

Really, if we are running PHP scripts which are treated as encoded in UTF-16
or some other arbitrary text encoding (not ASCII), and the script is not
actually a valid string in that encoding, inserting '?' characters into the
code which the PHP interpreter runs is a bad thing to do. In such cases, the
script shouldn't be treated as UTF-16 (or whatever) at all.

I wonder if mbstring's encoding detection is being used in 'non-strict' mode?

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Add identify filter for UTF-16, UTF-16LE, UTF-16BE

There was one faulty test in the suite which only passed before because UTF-16 had no
identify filter. After this was fixed, it exposed

Add identify filter for UTF-16, UTF-16LE, UTF-16BE

There was one faulty test in the suite which only passed before because UTF-16 had no
identify filter. After this was fixed, it exposed the problem with the test.

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Refactor mbfl_ident.c, mbfl_encoding.c, mbfl_memory_device.c, mbfl_string.c

- Make everything less gratuitously verbose
- Don't litter the code with lots of unneeded NULL checks (for thi

Refactor mbfl_ident.c, mbfl_encoding.c, mbfl_memory_device.c, mbfl_string.c

- Make everything less gratuitously verbose
- Don't litter the code with lots of unneeded NULL checks (for things which
will never be NULL)
- Don't return success/failure code from functions which can never fail
- For encoding structs, don't use pointers to pointers to pointers for the
list of alias strings. Pointers to pointers (2 levels of indirection)
is what actually makes sense. This gets rid of some extraneous
dereference operations.

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Remove useless validity check when converting UTF-16LE -> wchar

The check ensures that the decoded codepoint is between 0x10000-0x10FFFF,
which is the valid range which can be encoded in

Remove useless validity check when converting UTF-16LE -> wchar

The check ensures that the decoded codepoint is between 0x10000-0x10FFFF,
which is the valid range which can be encoded in a UTF-16 surrogate pair.
However, just looking at the code, it's obvious that this will be true.
First of all, 0x10000 is added to the decoded codepoint on the previous
line, so how could it be less than 0x10000?

Further, even if the 20 data bits already decoded were 0xFFFFF (all ones),
when you add 0x10000, it comes to 0x10FFFF, which is the very top of the
valid range. So how could the decoded codepoint be more than 0x10FFFF?
It can't.

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Refactor UTF-16LE -> wchar conversion code

Remove unneeded function mbfl_filt_conv_common_dtor

This is a default destructor for mbfl_convert_filter structs. The thing is: there
isn't really anything that needs to be done to those

Remove unneeded function mbfl_filt_conv_common_dtor

This is a default destructor for mbfl_convert_filter structs. The thing is: there
isn't really anything that needs to be done to those structs before freeing them.
The default destructor just zeroed out some fields, but there's no reason why
we should actually do that.

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Remove redundant includes from mbstring (and make sure correct config.h is used)

Very interesting... it turns out that when Valgrind support was enabled,
`#include "config.h"` from withi

Remove redundant includes from mbstring (and make sure correct config.h is used)

Very interesting... it turns out that when Valgrind support was enabled,
`#include "config.h"` from within mbstring was actually including the file "config.h"
from Valgrind, and not the one from mbstring!!

This is because -I/usr/include/valgrind was added to the compiler invocation _before_
-Iext/mbstring/libmbfl.

Make sure we actually include the file which was intended.

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Fix [-Wmissing-field-initializers] compiler warning in mbstring

Add missing NULL pointer for mbfl_convert_vtbl struct.