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StringUtils.php
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StringUtils.php
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<?php
namespace Wikimedia\StringUtils;
use ArrayIterator;
use InvalidArgumentException;
use MediaWiki\Libs\UnpackFailedException;
use Wikimedia\Assert\Assert;
use Wikimedia\AtEase\AtEase;
/**
* Methods to play with strings.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
/**
* A collection of static methods to play with strings.
*/
class StringUtils {
/**
* Test whether a string is valid UTF-8.
*
* The function check for invalid byte sequences, overlong encoding but
* not for different normalisations.
*
* @note In MediaWiki 1.21, this function did not provide proper UTF-8 validation.
* In particular, the pure PHP code path did not in fact check for overlong forms.
* Beware of this when backporting code to that version of MediaWiki.
*
* @since 1.21
* @param string $value String to check
* @return bool Whether the given $value is a valid UTF-8 encoded string
*/
public static function isUtf8( $value ) {
return mb_check_encoding( (string)$value, 'UTF-8' );
}
/**
* Explode a string, but ignore any instances of the separator inside
* the given start and end delimiters, which may optionally nest.
* The delimiters are literal strings, not regular expressions.
* @param string $startDelim Start delimiter
* @param string $endDelim End delimiter
* @param string $separator Separator string for the explode.
* @param string $subject Subject string to explode.
* @param bool $nested True iff the delimiters are allowed to nest.
* @return ArrayIterator
*/
public static function delimiterExplode( $startDelim, $endDelim, $separator,
$subject, $nested = false ) {
$inputPos = 0;
$lastPos = 0;
$depth = 0;
$encStart = preg_quote( $startDelim, '!' );
$encEnd = preg_quote( $endDelim, '!' );
$encSep = preg_quote( $separator, '!' );
$len = strlen( $subject );
$m = [];
$exploded = [];
while (
$inputPos < $len &&
preg_match(
"!$encStart|$encEnd|$encSep!S", $subject, $m,
PREG_OFFSET_CAPTURE, $inputPos
)
) {
$match = $m[0][0];
$matchPos = $m[0][1];
$inputPos = $matchPos + strlen( $match );
if ( $match === $separator ) {
if ( $depth === 0 ) {
$exploded[] = substr(
$subject, $lastPos, $matchPos - $lastPos
);
$lastPos = $inputPos;
}
} elseif ( $match === $startDelim ) {
if ( $depth === 0 || $nested ) {
$depth++;
}
} else {
$depth--;
}
}
$exploded[] = substr( $subject, $lastPos );
// This method could be rewritten in the future to avoid creating an
// intermediate array, since the return type is just an iterator.
return new ArrayIterator( $exploded );
}
/**
* Perform an operation equivalent to `preg_replace()`
*
* Matches this code:
*
* preg_replace( "!$startDelim(.*?)$endDelim!", $replace, $subject );
*
* ..except that it's worst-case O(N) instead of O(N^2). Compared to delimiterReplace(), this
* implementation is fast but memory-hungry and inflexible. The memory requirements are such
* that I don't recommend using it on anything but guaranteed small chunks of text.
*
* @param string $startDelim
* @param string $endDelim
* @param string $replace
* @param string $subject
* @return string
*/
public static function hungryDelimiterReplace( $startDelim, $endDelim, $replace, $subject ) {
$segments = explode( $startDelim, $subject );
$output = array_shift( $segments );
foreach ( $segments as $s ) {
$endDelimPos = strpos( $s, $endDelim );
if ( $endDelimPos === false ) {
$output .= $startDelim . $s;
} else {
$output .= $replace . substr( $s, $endDelimPos + strlen( $endDelim ) );
}
}
return $output;
}
/**
* Perform an operation equivalent to `preg_replace_callback()`
*
* Matches this code:
*
* preg_replace_callback( "!$startDelim(.*)$endDelim!s$flags", $callback, $subject );
*
* If the start delimiter ends with an initial substring of the end delimiter,
* e.g. in the case of C-style comments, the behavior differs from the model
* regex. In this implementation, the end must share no characters with the
* start, so e.g. `/*\/` is not considered to be both the start and end of a
* comment. `/*\/xy/*\/` is considered to be a single comment with contents `/xy/`.
*
* The implementation of delimiterReplaceCallback() is slower than hungryDelimiterReplace()
* but uses far less memory. The delimiters are literal strings, not regular expressions.
*
* @param string $startDelim Start delimiter
* @param string $endDelim End delimiter
* @param callable $callback Function to call on each match
* @param string $subject
* @param string $flags Regular expression flags
* @return string
*/
private static function delimiterReplaceCallback( $startDelim, $endDelim, $callback,
$subject, $flags = ''
) {
$inputPos = 0;
$outputPos = 0;
$contentPos = 0;
$output = '';
$foundStart = false;
$encStart = preg_quote( $startDelim, '!' );
$encEnd = preg_quote( $endDelim, '!' );
$strcmp = strpos( $flags, 'i' ) === false ? 'strcmp' : 'strcasecmp';
$endLength = strlen( $endDelim );
$m = [];
while ( $inputPos < strlen( $subject ) &&
preg_match( "!($encStart)|($encEnd)!S$flags", $subject, $m, PREG_OFFSET_CAPTURE, $inputPos )
) {
$tokenOffset = $m[0][1];
if ( $m[1][0] != '' ) {
if ( $foundStart &&
$strcmp( $endDelim, substr( $subject, $tokenOffset, $endLength ) ) == 0
) {
# An end match is present at the same location
$tokenType = 'end';
$tokenLength = $endLength;
} else {
$tokenType = 'start';
$tokenLength = strlen( $m[0][0] );
}
} elseif ( $m[2][0] != '' ) {
$tokenType = 'end';
$tokenLength = strlen( $m[0][0] );
} else {
throw new InvalidArgumentException( 'Invalid delimiter given to ' . __METHOD__ );
}
if ( $tokenType == 'start' ) {
# Only move the start position if we haven't already found a start
# This means that START START END matches outer pair
if ( !$foundStart ) {
# Found start
$inputPos = $tokenOffset + $tokenLength;
# Write out the non-matching section
$output .= substr( $subject, $outputPos, $tokenOffset - $outputPos );
$outputPos = $tokenOffset;
$contentPos = $inputPos;
$foundStart = true;
} else {
# Move the input position past the *first character* of START,
# to protect against missing END when it overlaps with START
$inputPos = $tokenOffset + 1;
}
} elseif ( $tokenType == 'end' ) {
if ( $foundStart ) {
# Found match
$output .= $callback( [
substr( $subject, $outputPos, $tokenOffset + $tokenLength - $outputPos ),
substr( $subject, $contentPos, $tokenOffset - $contentPos )
] );
$foundStart = false;
} else {
# Non-matching end, write it out
$output .= substr( $subject, $inputPos, $tokenOffset + $tokenLength - $outputPos );
}
$inputPos = $outputPos = $tokenOffset + $tokenLength;
} else {
throw new InvalidArgumentException( 'Invalid delimiter given to ' . __METHOD__ );
}
}
if ( $outputPos < strlen( $subject ) ) {
$output .= substr( $subject, $outputPos );
}
return $output;
}
/**
* Perform an operation equivalent to `preg_replace()` with flags.
*
* Matches this code:
*
* preg_replace( "!$startDelim(.*)$endDelim!$flags", $replace, $subject );
*
* @param string $startDelim Start delimiter regular expression
* @param string $endDelim End delimiter regular expression
* @param string $replace Replacement string. May contain $1, which will be
* replaced by the text between the delimiters
* @param string $subject String to search
* @param string $flags Regular expression flags
* @return string The string with the matches replaced
*/
public static function delimiterReplace(
$startDelim, $endDelim, $replace, $subject, $flags = ''
) {
return self::delimiterReplaceCallback(
$startDelim, $endDelim,
static function ( array $matches ) use ( $replace ) {
return strtr( $replace, [ '$0' => $matches[0], '$1' => $matches[1] ] );
},
$subject, $flags
);
}
/**
* More or less "markup-safe" str_replace()
* Ignores any instances of the separator inside `<...>`
* @param string $search
* @param string $replace
* @param string $text
* @return string
*/
public static function replaceMarkup( $search, $replace, $text ) {
$placeholder = "\x00";
// Remove placeholder instances
$text = str_replace( $placeholder, '', $text );
// Replace instances of the separator inside HTML-like tags with the placeholder
$cleaned = self::delimiterReplaceCallback(
'<', '>',
static function ( array $matches ) use ( $search, $placeholder ) {
return str_replace( $search, $placeholder, $matches[0] );
},
$text
);
// Explode, then put the replaced separators back in
$cleaned = str_replace( $search, $replace, $cleaned );
$text = str_replace( $placeholder, $search, $cleaned );
return $text;
}
/**
* Utility function to check if the given string is a valid PCRE regex. Avoids
* manually calling suppressWarnings and restoreWarnings, and provides a
* one-line solution without the need to use @.
*
* @since 1.34
* @param string $string The string you want to check being a valid regex
* @return bool
*/
public static function isValidPCRERegex( $string ) {
AtEase::suppressWarnings();
// @phan-suppress-next-line PhanParamSuspiciousOrder False positive
$isValid = preg_match( $string, '' );
AtEase::restoreWarnings();
return $isValid !== false;
}
/**
* Escape a string to make it suitable for inclusion in a preg_replace()
* replacement parameter.
*
* @param string $string
* @return string
*/
public static function escapeRegexReplacement( $string ) {
$string = str_replace( '\\', '\\\\', $string );
return str_replace( '$', '\\$', $string );
}
/**
* Workalike for explode() with limited memory usage.
*
* @param string $separator
* @param string $subject
* @return ArrayIterator|ExplodeIterator
*/
public static function explode( $separator, $subject ) {
if ( substr_count( $subject, $separator ) > 1000 ) {
return new ExplodeIterator( $separator, $subject );
} else {
return new ArrayIterator( explode( $separator, $subject ) );
}
}
/**
* Wrapper around php's unpack.
*
* @param string $format The format string (See php's docs)
* @param string $data A binary string of binary data
* @param int|false $length The minimum length of $data or false. This is to
* prevent reading beyond the end of $data. false to disable the check.
*
* Also be careful when using this function to read unsigned 32 bit integer
* because php might make it negative.
*
* @throws UnpackFailedException If $data not long enough, or if unpack fails
* @return array Associative array of the extracted data
* @since 1.42
*/
public static function unpack( string $format, string $data, $length = false ): array {
Assert::parameterType( [ 'integer', 'false' ], $length, '$length' );
if ( $length !== false ) {
$realLen = strlen( $data );
if ( $realLen < $length ) {
throw new UnpackFailedException( "Tried to unpack a "
. "string of length $realLen, but needed one "
. "of at least length $length."
);
}
}
AtEase::suppressWarnings();
$result = unpack( $format, $data );
AtEase::restoreWarnings();
if ( $result === false ) {
// If it cannot extract the packed data.
throw new UnpackFailedException( "unpack could not unpack binary data" );
}
return $result;
}
}
/** @deprecated class alias since 1.44 */
class_alias( StringUtils::class, 'StringUtils' );

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