Charset: Create compat-utf8.php module with fallback code.

This is the second in a series of patches to modernize and standardize UTF-8 handling.

When the fallback UTF-8 validation code was added it was placed inside formatting.php; however, that validation logic can be reused for a number of related UTF-8 functions. To faciliate this it should move into a new location and be loaded early. This patch is the first half of doing that, whereby the original fallback function is moved unchanged to the `compat-utf8.php` module. The follow-up patch will abstract the UTF-8 scanning logic for reuse. Splitting this into a move and a separate change involves an extra step, but faciliates tracking the heritage of the code through the changes.

Developed in https://github.com/WordPress/wordpress-develop/pull/9825
Discussed in https://core.trac.wordpress.org/ticket/63863

Follow-up to: [60630].

See #63863.

Built from https://develop.svn.wordpress.org/trunk@60743


git-svn-id: http://core.svn.wordpress.org/trunk@60079 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This commit is contained in:
dmsnell
2025-09-15 19:09:25 +00:00
parent 3d3b98d039
commit 25597755ac
4 changed files with 129 additions and 127 deletions

127
wp-includes/compat-utf8.php Normal file
View File

@@ -0,0 +1,127 @@
<?php
/**
* Fallback mechanism for safely validating UTF-8 bytes.
*
* By implementing a raw method here the code will behave in the same way on
* all installed systems, regardless of what extensions are installed.
*
* @see wp_is_valid_utf8
*
* @since 6.9.0
* @access private
*
* @param string $bytes String which might contain text encoded as UTF-8.
* @return bool Whether the provided bytes can decode as valid UTF-8.
*/
function _wp_is_valid_utf8_fallback( string $bytes ): bool {
$end = strlen( $bytes );
for ( $i = 0; $i < $end; $i++ ) {
/*
* Quickly skip past US-ASCII bytes, all of which are valid UTF-8.
*
* This optimization step improves the speed from 10x to 100x
* depending on whether the JIT has optimized the function.
*/
$i += strspn(
$bytes,
"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" .
"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" .
" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f",
$i
);
if ( $i >= $end ) {
break;
}
/**
* The above fast-track handled all single-byte UTF-8 characters. What
* follows MUST be a multibyte sequence otherwise theres invalid UTF-8.
*
* Therefore everything past here is checking those multibyte sequences.
* Because its possible that there are truncated characters, the use of
* the null-coalescing operator with "\xC0" is a convenience for skipping
* length checks on every continuation bytes. This works because 0xC0 is
* always invalid in a UTF-8 string, meaning that if the string has been
* truncated, it will find 0xC0 and reject as invalid UTF-8.
*
* > [The following table] lists all of the byte sequences that are well-formed
* > in UTF-8. A range of byte values such as A0..BF indicates that any byte
* > from A0 to BF (inclusive) is well-formed in that position. Any byte value
* > outside of the ranges listed is ill-formed.
*
* > Table 3-7. Well-Formed UTF-8 Byte Sequences
* ╭─────────────────────┬────────────┬──────────────┬─────────────┬──────────────╮
* │ Code Points │ First Byte │ Second Byte │ Third Byte │ Fourth Byte │
* ├─────────────────────┼────────────┼──────────────┼─────────────┼──────────────┤
* │ U+0000..U+007F │ 00..7F │ │ │ │
* │ U+0080..U+07FF │ C2..DF │ 80..BF │ │ │
* │ U+0800..U+0FFF │ E0 │ A0..BF │ 80..BF │ │
* │ U+1000..U+CFFF │ E1..EC │ 80..BF │ 80..BF │ │
* │ U+D000..U+D7FF │ ED │ 80..9F │ 80..BF │ │
* │ U+E000..U+FFFF │ EE..EF │ 80..BF │ 80..BF │ │
* │ U+10000..U+3FFFF │ F0 │ 90..BF │ 80..BF │ 80..BF │
* │ U+40000..U+FFFFF │ F1..F3 │ 80..BF │ 80..BF │ 80..BF │
* │ U+100000..U+10FFFF │ F4 │ 80..8F │ 80..BF │ 80..BF │
* ╰─────────────────────┴────────────┴──────────────┴─────────────┴──────────────╯
*
* Notice that all valid third and forth bytes are in the range 80..BF. This
* validator takes advantage of that to only check the range of those bytes once.
*
* @see https://lemire.me/blog/2018/05/09/how-quickly-can-you-check-that-a-string-is-valid-unicode-utf-8/
* @see https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G27506
*/
$b1 = ord( $bytes[ $i ] );
$b2 = ord( $bytes[ $i + 1 ] ?? "\xC0" );
// Valid two-byte code points.
if ( $b1 >= 0xC2 && $b1 <= 0xDF && $b2 >= 0x80 && $b2 <= 0xBF ) {
$i++;
continue;
}
$b3 = ord( $bytes[ $i + 2 ] ?? "\xC0" );
// Valid three-byte code points.
if ( $b3 < 0x80 || $b3 > 0xBF ) {
return false;
}
if (
( 0xE0 === $b1 && $b2 >= 0xA0 && $b2 <= 0xBF ) ||
( $b1 >= 0xE1 && $b1 <= 0xEC && $b2 >= 0x80 && $b2 <= 0xBF ) ||
( 0xED === $b1 && $b2 >= 0x80 && $b2 <= 0x9F ) ||
( $b1 >= 0xEE && $b1 <= 0xEF && $b2 >= 0x80 && $b2 <= 0xBF )
) {
$i += 2;
continue;
}
$b4 = ord( $bytes[ $i + 3 ] ?? "\xC0" );
// Valid four-byte code points.
if ( $b4 < 0x80 || $b4 > 0xBF ) {
return false;
}
if (
( 0xF0 === $b1 && $b2 >= 0x90 && $b2 <= 0xBF ) ||
( $b1 >= 0xF1 && $b1 <= 0xF3 && $b2 >= 0x80 && $b2 <= 0xBF ) ||
( 0xF4 === $b1 && $b2 >= 0x80 && $b2 <= 0x8F )
) {
$i += 3;
continue;
}
// Any other sequence is invalid.
return false;
}
// Reaching the end implies validating every byte.
return true;
}

View File

@@ -969,132 +969,6 @@ function wp_is_valid_utf8( string $bytes ): bool {
: _wp_is_valid_utf8_fallback( $bytes );
}
/**
* Fallback mechanism for safely validating UTF-8 bytes.
*
* By implementing a raw method here the code will behave in the same way on
* all installed systems, regardless of what extensions are installed.
*
* @see wp_is_valid_utf8
*
* @since 6.9.0
* @access private
*
* @param string $bytes String which might contain text encoded as UTF-8.
* @return bool Whether the provided bytes can decode as valid UTF-8.
*/
function _wp_is_valid_utf8_fallback( string $bytes ): bool {
$end = strlen( $bytes );
for ( $i = 0; $i < $end; $i++ ) {
/*
* Quickly skip past US-ASCII bytes, all of which are valid UTF-8.
*
* This optimization step improves the speed from 10x to 100x
* depending on whether the JIT has optimized the function.
*/
$i += strspn(
$bytes,
"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f" .
"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" .
" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f",
$i
);
if ( $i >= $end ) {
break;
}
/**
* The above fast-track handled all single-byte UTF-8 characters. What
* follows MUST be a multibyte sequence otherwise theres invalid UTF-8.
*
* Therefore everything past here is checking those multibyte sequences.
* Because its possible that there are truncated characters, the use of
* the null-coalescing operator with "\xC0" is a convenience for skipping
* length checks on every continuation bytes. This works because 0xC0 is
* always invalid in a UTF-8 string, meaning that if the string has been
* truncated, it will find 0xC0 and reject as invalid UTF-8.
*
* > [The following table] lists all of the byte sequences that are well-formed
* > in UTF-8. A range of byte values such as A0..BF indicates that any byte
* > from A0 to BF (inclusive) is well-formed in that position. Any byte value
* > outside of the ranges listed is ill-formed.
*
* > Table 3-7. Well-Formed UTF-8 Byte Sequences
* ╭─────────────────────┬────────────┬──────────────┬─────────────┬──────────────╮
* │ Code Points │ First Byte │ Second Byte │ Third Byte │ Fourth Byte │
* ├─────────────────────┼────────────┼──────────────┼─────────────┼──────────────┤
* │ U+0000..U+007F │ 00..7F │ │ │ │
* │ U+0080..U+07FF │ C2..DF │ 80..BF │ │ │
* │ U+0800..U+0FFF │ E0 │ A0..BF │ 80..BF │ │
* │ U+1000..U+CFFF │ E1..EC │ 80..BF │ 80..BF │ │
* │ U+D000..U+D7FF │ ED │ 80..9F │ 80..BF │ │
* │ U+E000..U+FFFF │ EE..EF │ 80..BF │ 80..BF │ │
* │ U+10000..U+3FFFF │ F0 │ 90..BF │ 80..BF │ 80..BF │
* │ U+40000..U+FFFFF │ F1..F3 │ 80..BF │ 80..BF │ 80..BF │
* │ U+100000..U+10FFFF │ F4 │ 80..8F │ 80..BF │ 80..BF │
* ╰─────────────────────┴────────────┴──────────────┴─────────────┴──────────────╯
*
* Notice that all valid third and forth bytes are in the range 80..BF. This
* validator takes advantage of that to only check the range of those bytes once.
*
* @see https://lemire.me/blog/2018/05/09/how-quickly-can-you-check-that-a-string-is-valid-unicode-utf-8/
* @see https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter-3/#G27506
*/
$b1 = ord( $bytes[ $i ] );
$b2 = ord( $bytes[ $i + 1 ] ?? "\xC0" );
// Valid two-byte code points.
if ( $b1 >= 0xC2 && $b1 <= 0xDF && $b2 >= 0x80 && $b2 <= 0xBF ) {
$i++;
continue;
}
$b3 = ord( $bytes[ $i + 2 ] ?? "\xC0" );
// Valid three-byte code points.
if ( $b3 < 0x80 || $b3 > 0xBF ) {
return false;
}
if (
( 0xE0 === $b1 && $b2 >= 0xA0 && $b2 <= 0xBF ) ||
( $b1 >= 0xE1 && $b1 <= 0xEC && $b2 >= 0x80 && $b2 <= 0xBF ) ||
( 0xED === $b1 && $b2 >= 0x80 && $b2 <= 0x9F ) ||
( $b1 >= 0xEE && $b1 <= 0xEF && $b2 >= 0x80 && $b2 <= 0xBF )
) {
$i += 2;
continue;
}
$b4 = ord( $bytes[ $i + 3 ] ?? "\xC0" );
// Valid four-byte code points.
if ( $b4 < 0x80 || $b4 > 0xBF ) {
return false;
}
if (
( 0xF0 === $b1 && $b2 >= 0x90 && $b2 <= 0xBF ) ||
( $b1 >= 0xF1 && $b1 <= 0xF3 && $b2 >= 0x80 && $b2 <= 0xBF ) ||
( 0xF4 === $b1 && $b2 >= 0x80 && $b2 <= 0x8F )
) {
$i += 3;
continue;
}
// Any other sequence is invalid.
return false;
}
// Reaching the end implies validating every byte.
return true;
}
/**
* Converts a number of special characters into their HTML entities.
*

View File

@@ -16,7 +16,7 @@
*
* @global string $wp_version
*/
$wp_version = '6.9-alpha-60742';
$wp_version = '6.9-alpha-60743';
/**
* Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

View File

@@ -32,6 +32,7 @@ define( 'WPINC', 'wp-includes' );
*/
global $wp_version, $wp_db_version, $tinymce_version, $required_php_version, $required_php_extensions, $required_mysql_version, $wp_local_package;
require ABSPATH . WPINC . '/version.php';
require ABSPATH . WPINC . '/compat-utf8.php';
require ABSPATH . WPINC . '/compat.php';
require ABSPATH . WPINC . '/load.php';