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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Fix mangled kana output for JIS encoding

For JIS encoding, hiragana and katakana can be input in multiple forms.
One form uses JISX 0201 escape sequences. Another is called 'GR-invoked'

Fix mangled kana output for JIS encoding

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.

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Adjust number of error markers emitted for truncated ISO-2022-JP escape sequence

Fuzzing revealed a small difference between the number of error
markers which the legacy ISO-2022-JP and

Adjust number of error markers emitted for truncated ISO-2022-JP escape sequence

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.

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Add more tests for mbstring encoding conversion

When testing the preceding commits, I used a script to generate a large
number of random strings and try to find strings which would yield

Add more tests for mbstring encoding conversion

When testing the preceding commits, I used a script to generate a large
number of random strings and try to find strings which would yield
different outputs from the new and old encoding conversion code.
Some were found. In most cases, analysis revealed that the new code
was correct and the old code was not.

In all cases where the new code was incorrect, regression tests were
added. However, there may be some value in adding regression tests
for cases where the old code was incorrect as well. That is done here.

This does not cover every case where the new and old code yielded
different results. Some of them were very obscure, and it is proving
difficult even to reproduce them (since I did not keep a record of
all the input strings which triggered the differing output).

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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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Add more tests for ISO-2022-JP and JIS7/8 text conversion

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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Add more tests for ISO-2022-JP/JIS7/JIS8 text conversion

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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Migrate more SKIPIF -> EXTENSIONS (#7139)

This is a mix of more automated and manual migration. It should remove all applicable extension_loaded() checks outside of skipif.inc files.

JIS7/JIS8 encoding: treat truncated multibyte characters as error

JIS7/JIS8 encoding: handle invalid 2nd byte for Kanji correctly

Previously, in ISO-2022-JP/JIS7/JIS8, if an escape sequence (starting with 0x1B)
appeared where the 2nd byte of a multibyt

JIS7/JIS8 encoding: handle invalid 2nd byte for Kanji correctly

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.)

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