Legacy conversion code for '7bit' to '8bit' inserts error markers

The use of a special 'vtbl' for converting between '7bit' and
'8bit' text meant that '7bit' text would not be converted

Legacy conversion code for '7bit' to '8bit' inserts error markers

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.

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Imitate legacy behavior when converting non-encodings using mbstring

Fuzzing revealed that something was missed here when making the new
encoding conversion code match the behavior of th

Imitate legacy behavior when converting non-encodings using mbstring

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.

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Use fast text conversion filters to implement php_mb_convert_encoding_ex

Add assertions to help catch buffer overflows in mbstring text conversion code

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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Fix #81693: mb_check_encoding(7bit) segfaults

`php_mb_check_encoding()` now uses conversion to `mbfl_encoding_wchar`.
Since `mbfl_encoding_7bit` has no `input_filter`, no filter can be

Fix #81693: mb_check_encoding(7bit) segfaults

`php_mb_check_encoding()` now uses conversion to `mbfl_encoding_wchar`.
Since `mbfl_encoding_7bit` has no `input_filter`, no filter can be
found. Since we don't actually need to convert to wchar, we encode to
8bit.

Closes GH-7712.

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Use bool in mbfl_filt_conv_output_hex (rather than int)

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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Output illegal character marker for 4-byte illegal characters > 0x7FFFFFFF

Some text encodings supported by mbstring (such as UCS-4) accept 4-byte
characters. When mbstring encounters an

Output illegal character marker for 4-byte illegal characters > 0x7FFFFFFF

Some text encodings supported by mbstring (such as UCS-4) accept 4-byte
characters. When mbstring encounters an illegal byte sequence for the
encoding it is using, it should emit an 'illegal character' marker,
which can either be a single character like '?', an HTML hexadecimal
entity, or a marker string like 'BAD+XXXX'.

Because of the use of signed integers to hold 4-byte characters,
illegal 4-byte sequences with a 'negative' value (one with the high
bit set) were not handled correctly when emitting the illegal char
marker. The result is that such illegal sequences were just skipped
over (and the marker was not emitted to the output). Fix that.

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Remove duplicate implementation of CP932 from mbstring

Sigh. Double sigh. After fruitlessly searching the Internet for information on
this mysterious text encoding called "SJIS-open", I

Remove duplicate implementation of CP932 from mbstring

Sigh. Double sigh. After fruitlessly searching the Internet for information on
this mysterious text encoding called "SJIS-open", I wrote a script to try
converting every Unicode codepoint from 0-0xFFFF and compare the results from
different variants of Shift-JIS, to see which one "SJIS-open" would be most
similar to.

The result? It's just CP932. There is no difference at all. So why do we have
two implementations of CP932 in mbstring?

In case somebody, somewhere is using "SJIS-open" (or its aliases "SJIS-win" or
"SJIS-ms"), add these as aliases to CP932 so existing code will continue to
work.

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Remove unneeded 'filter_ctor' member from mbfl_convert_filter struct

This function pointer is only called when initializing the struct. After that
nothing is done with it. Therefore, the

Remove unneeded 'filter_ctor' member from mbfl_convert_filter struct

This function pointer is only called when initializing the struct. After that
nothing is done with it. Therefore, there is no need to keep it in the struct.

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Consolidate all single-byte encodings in one source file

We can squeeze out a lot of duplicated code in this way.

Don't redundantly flush mbstring filters multiple times

Each flush function in a chain of mbstring conversion filters always
calls the next flush function in the chain. So it is not nece

Don't redundantly flush mbstring filters multiple times

Each flush function in a chain of mbstring conversion filters always
calls the next flush function in the chain. So it is not necessary to
explicitly flush the second filter in a chain. (Due to this bug, in many
cases, flush functions were actually being called three times.)

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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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Remove useless byte{2,4}{be,le} encodings from mbstring

There is no meaningful difference between these and UCS-{2,4}. They are
just a little bit more lax about passing errors silently.

Remove useless byte{2,4}{be,le} encodings from mbstring

There is no meaningful difference between these and UCS-{2,4}. They are
just a little bit more lax about passing errors silently. They also have
no known use.

Alias to UCS-{2,4} in case someone, somewhere is using them.

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Remove dead code from mbfilter_iso8859_{2,4,5,9,10,13,14,15,16}.c

...Plus some dead code related to ISO-8859-1.

Avoid compiler warnings related to mbstring flush functions

fix mbfl function prototypes
re-add mbfl_convert_filter_feed API
re-add pointer cast

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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Refactor mbfl_convert.c

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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Remove unused functions from mbstring

- mbfl_buffer_converter_reset
- mbfl_buffer_converter_strncat
- mbfl_buffer_converter_getbuffer
- mbfl_oddlen
- mbfl_filter_output_pipe_

Remove unused functions from mbstring

- mbfl_buffer_converter_reset
- mbfl_buffer_converter_strncat
- mbfl_buffer_converter_getbuffer
- mbfl_oddlen
- mbfl_filter_output_pipe_flush
- mbfl_memory_device_output2
- mbfl_memory_device_output4
- mbfl_is_support_encoding
- mbfl_buffer_converter_feed2
- _php_mb_regex_globals_dtor
- mime_header_encoder_feed
- mime_header_decoder_feed
- mbfl_convert_filter_feed

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Inline unneeded indirection for mbstring memory management

All memory allocation and deallocation for mbstring bounces through a table of
function pointers before going to emalloc/efree/

Inline unneeded indirection for mbstring memory management

All memory allocation and deallocation for mbstring bounces through a table of
function pointers before going to emalloc/efree/etc. But this is unnecessary.
The allocators are never swapped out. Better to just call them directly.

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Spec mbfl allocators as infallible

And remove all NULL checks.

Don't short-circuit MBFL_OUTPUTFILTER_ILLEGAL_MODE_NONE

Make sure we always go through mbfl_filt_conv_illegal_output(), so
that the number of illegal characters gets counted.