enmi-conf.org: comparison wp/wp-includes/class-wp-token-map.php

equal deleted inserted replaced

-:7b1b88e27a20
+:48c4eec2b7e6
+<?php
+/**
+* Class for efficiently looking up and mapping string keys to string values, with limits.
+*
+* @package    WordPress
+* @since      6.6.0
+*/
+/**
+* WP_Token_Map class.
+*
+* Use this class in specific circumstances with a static set of lookup keys which map to
+* a static set of transformed values. For example, this class is used to map HTML named
+* character references to their equivalent UTF-8 values.
+*
+* This class works differently than code calling `in_array()` and other methods. It
+* internalizes lookup logic and provides helper interfaces to optimize lookup and
+* transformation. It provides a method for precomputing the lookup tables and storing
+* them as PHP source code.
+*
+* All tokens and substitutions must be shorter than 256 bytes.
+*
+* Example:
+*
+*     $smilies = WP_Token_Map::from_array( array(
+*         '8O' => '😯',
+*         ':(' => '🙁',
+*         ':)' => '🙂',
+*         ':?' => '😕',
+*      ) );
+*
+*      true  === $smilies->contains( ':)' );
+*      false === $smilies->contains( 'simile' );
+*
+*      '😕' === $smilies->read_token( 'Not sure :?.', 9, $length_of_smily_syntax );
+*      2    === $length_of_smily_syntax;
+*
+* ## Precomputing the Token Map.
+*
+* Creating the class involves some work sorting and organizing the tokens and their
+* replacement values. In order to skip this, it's possible for the class to export
+* its state and be used as actual PHP source code.
+*
+* Example:
+*
+*      // Export with four spaces as the indent, only for the sake of this docblock.
+*      // The default indent is a tab character.
+*      $indent = '    ';
+*      echo $smilies->precomputed_php_source_table( $indent );
+*
+*      // Output, to be pasted into a PHP source file:
+*      WP_Token_Map::from_precomputed_table(
+*          array(
+*              "storage_version" => "6.6.0",
+*              "key_length" => 2,
+*              "groups" => "",
+*              "long_words" => array(),
+*              "small_words" => "8O\x00:)\x00:(\x00:?\x00",
+*              "small_mappings" => array( "😯", "🙂", "🙁", "😕" )
+*          )
+*      );
+*
+* ## Large vs. small words.
+*
+* This class uses a short prefix called the "key" to optimize lookup of its tokens.
+* This means that some tokens may be shorter than or equal in length to that key.
+* Those words that are longer than the key are called "large" while those shorter
+* than or equal to the key length are called "small."
+*
+* This separation of large and small words is incidental to the way this class
+* optimizes lookup, and should be considered an internal implementation detail
+* of the class. It may still be important to be aware of it, however.
+*
+* ## Determining Key Length.
+*
+* The choice of the size of the key length should be based on the data being stored in
+* the token map. It should divide the data as evenly as possible, but should not create
+* so many groups that a large fraction of the groups only contain a single token.
+*
+* For the HTML5 named character references, a key length of 2 was found to provide a
+* sufficient spread and should be a good default for relatively large sets of tokens.
+*
+* However, for some data sets this might be too long. For example, a list of smilies
+* may be too small for a key length of 2. Perhaps 1 would be more appropriate. It's
+* best to experiment and determine empirically which values are appropriate.
+*
+* ## Generate Pre-Computed Source Code.
+*
+* Since the `WP_Token_Map` is designed for relatively static lookups, it can be
+* advantageous to precompute the values and instantiate a table that has already
+* sorted and grouped the tokens and built the lookup strings.
+*
+* This can be done with `WP_Token_Map::precomputed_php_source_table()`.
+*
+* Note that if there is a leading character that all tokens need, such as `&` for
+* HTML named character references, it can be beneficial to exclude this from the
+* token map. Instead, find occurrences of the leading character and then use the
+* token map to see if the following characters complete the token.
+*
+* Example:
+*
+*     $map = WP_Token_Map::from_array( array( 'simple_smile:' => '🙂', 'sob:' => '😭', 'soba:' => '🍜' ) );
+*     echo $map->precomputed_php_source_table();
+*     // Output
+*     WP_Token_Map::from_precomputed_table(
+*         array(
+*             "storage_version" => "6.6.0",
+*             "key_length" => 2,
+*             "groups" => "si\x00so\x00",
+*             "long_words" => array(
+*                 // simple_smile:[🙂].
+*                 "\x0bmple_smile:\x04🙂",
+*                 // soba:[🍜] sob:[😭].
+*                 "\x03ba:\x04🍜\x02b:\x04😭",
+*             ),
+*             "short_words" => "",
+*             "short_mappings" => array()
+*         }
+*     );
+*
+* This precomputed value can be stored directly in source code and will skip the
+* startup cost of generating the lookup strings. See `$html5_named_character_entities`.
+*
+* Note that any updates to the precomputed format should update the storage version
+* constant. It would also be best to provide an update function to take older known
+* versions and upgrade them in place when loading into `from_precomputed_table()`.
+*
+* ## Future Direction.
+*
+* It may be viable to dynamically increase the length limits such that there's no need to impose them.
+* The limit appears because of the packing structure, which indicates how many bytes each segment of
+* text in the lookup tables spans. If, however, care were taken to track the longest word length, then
+* the packing structure could change its representation to allow for that. Each additional byte storing
+* length, however, increases the memory overhead and lookup runtime.
+*
+* An alternative approach could be to borrow the UTF-8 variable-length encoding and store lengths of less
+* than 127 as a single byte with the high bit unset, storing longer lengths as the combination of
+* continuation bytes.
+*
+* Since it has not been shown during the development of this class that longer strings are required, this
+* update is deferred until such a need is clear.
+*
+* @since 6.6.0
+*/
+class WP_Token_Map {
+	/**
+	 * Denotes the version of the code which produces pre-computed source tables.
+	 *
+	 * This version will be used not only to verify pre-computed data, but also
+	 * to upgrade pre-computed data from older versions. Choosing a name that
+	 * corresponds to the WordPress release will help people identify where an
+	 * old copy of data came from.
+	 */
+	const STORAGE_VERSION = '6.6.0-trunk';
+	/**
+	 * Maximum length for each key and each transformed value in the table (in bytes).
+	 *
+	 * @since 6.6.0
+	 */
+	const MAX_LENGTH = 256;
+	/**
+	 * How many bytes of each key are used to form a group key for lookup.
+	 * This also determines whether a word is considered short or long.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var int
+	 */
+	private $key_length = 2;
+	/**
+	 * Stores an optimized form of the word set, where words are grouped
+	 * by a prefix of the `$key_length` and then collapsed into a string.
+	 *
+	 * In each group, the keys and lookups form a packed data structure.
+	 * The keys in the string are stripped of their "group key," which is
+	 * the prefix of length `$this->key_length` shared by all of the items
+	 * in the group. Each word in the string is prefixed by a single byte
+	 * whose raw unsigned integer value represents how many bytes follow.
+	 *
+	 *     ┌────────────────┬───────────────┬─────────────────┬────────┐
+	 *     │ Length of rest │ Rest of key   │ Length of value │ Value  │
+	 *     │ of key (bytes) │               │ (bytes)         │        │
+	 *     ├────────────────┼───────────────┼─────────────────┼────────┤
+	 *     │ 0x08           │ nterDot;      │ 0x02            │ ·      │
+	 *     └────────────────┴───────────────┴─────────────────┴────────┘
+	 *
+	 * In this example, the key `CenterDot;` has a group key `Ce`, leaving
+	 * eight bytes for the rest of the key, `nterDot;`, and two bytes for
+	 * the transformed value `·` (or U+B7 or "\xC2\xB7").
+	 *
+	 * Example:
+	 *
+	 *    // Stores array( 'CenterDot;' => '·', 'Cedilla;' => '¸' ).
+	 *    $groups      = "Ce\x00";
+	 *    $large_words = array( "\x08nterDot;\x02·\x06dilla;\x02¸" )
+	 *
+	 * The prefixes appear in the `$groups` string, each followed by a null
+	 * byte. This makes for quick lookup of where in the group string the key
+	 * is found, and then a simple division converts that offset into the index
+	 * in the `$large_words` array where the group string is to be found.
+	 *
+	 * This lookup data structure is designed to optimize cache locality and
+	 * minimize indirect memory reads when matching strings in the set.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var array
+	 */
+	private $large_words = array();
+	/**
+	 * Stores the group keys for sequential string lookup.
+	 *
+	 * The offset into this string where the group key appears corresponds with the index
+	 * into the group array where the rest of the group string appears. This is an optimization
+	 * to improve cache locality while searching and minimize indirect memory accesses.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var string
+	 */
+	private $groups = '';
+	/**
+	 * Stores an optimized row of small words, where every entry is
+	 * `$this->key_size + 1` bytes long and zero-extended.
+	 *
+	 * This packing allows for direct lookup of a short word followed
+	 * by the null byte, if extended to `$this->key_size + 1`.
+	 *
+	 * Example:
+	 *
+	 *     // Stores array( 'GT', 'LT', 'gt', 'lt' ).
+	 *     "GT\x00LT\x00gt\x00lt\x00"
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var string
+	 */
+	private $small_words = '';
+	/**
+	 * Replacements for the small words, in the same order they appear.
+	 *
+	 * With the position of a small word it's possible to index the translation
+	 * directly, as its position in the `$small_words` string corresponds to
+	 * the index of the replacement in the `$small_mapping` array.
+	 *
+	 * Example:
+	 *
+	 *     array( '>', '<', '>', '<' )
+	 *
+	 * @since 6.6.0
+	 *
+	 * @var string[]
+	 */
+	private $small_mappings = array();
+	/**
+	 * Create a token map using an associative array of key/value pairs as the input.
+	 *
+	 * Example:
+	 *
+	 *     $smilies = WP_Token_Map::from_array( array(
+	 *          '8O' => '😯',
+	 *          ':(' => '🙁',
+	 *          ':)' => '🙂',
+	 *          ':?' => '😕',
+	 *       ) );
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param array $mappings   The keys transform into the values, both are strings.
+	 * @param int   $key_length Determines the group key length. Leave at the default value
+	 *                          of 2 unless there's an empirical reason to change it.
+	 *
+	 * @return WP_Token_Map|null Token map, unless unable to create it.
+	 */
+	public static function from_array( $mappings, $key_length = 2 ) {
+		$map             = new WP_Token_Map();
+		$map->key_length = $key_length;
+		// Start by grouping words.
+		$groups = array();
+		$shorts = array();
+		foreach ( $mappings as $word => $mapping ) {
+			if (
+				self::MAX_LENGTH <= strlen( $word ) ||
+				self::MAX_LENGTH <= strlen( $mapping )
+			) {
+				_doing_it_wrong(
+					__METHOD__,
+					sprintf(
+						/* translators: 1: maximum byte length (a count) */
+						__( 'Token Map tokens and substitutions must all be shorter than %1$d bytes.' ),
+						self::MAX_LENGTH
+					),
+					'6.6.0'
+				);
+				return null;
+			}
+			$length = strlen( $word );
+			if ( $key_length >= $length ) {
+				$shorts[] = $word;
+			} else {
+				$group = substr( $word, 0, $key_length );
+				if ( ! isset( $groups[ $group ] ) ) {
+					$groups[ $group ] = array();
+				}
+				$groups[ $group ][] = array( substr( $word, $key_length ), $mapping );
+			}
+		}
+		/*
+		 * Sort the words to ensure that no smaller substring of a match masks the full match.
+		 * For example, `Cap` should not match before `CapitalDifferentialD`.
+		 */
+		usort( $shorts, 'WP_Token_Map::longest_first_then_alphabetical' );
+		foreach ( $groups as $group_key => $group ) {
+			usort(
+				$groups[ $group_key ],
+				static function ( $a, $b ) {
+					return self::longest_first_then_alphabetical( $a[0], $b[0] );
+				}
+			);
+		}
+		// Finally construct the optimized lookups.
+		foreach ( $shorts as $word ) {
+			$map->small_words     .= str_pad( $word, $key_length + 1, "\x00", STR_PAD_RIGHT );
+			$map->small_mappings[] = $mappings[ $word ];
+		}
+		$group_keys = array_keys( $groups );
+		sort( $group_keys );
+		foreach ( $group_keys as $group ) {
+			$map->groups .= "{$group}\x00";
+			$group_string = '';
+			foreach ( $groups[ $group ] as $group_word ) {
+				list( $word, $mapping ) = $group_word;
+				$word_length    = pack( 'C', strlen( $word ) );
+				$mapping_length = pack( 'C', strlen( $mapping ) );
+				$group_string  .= "{$word_length}{$word}{$mapping_length}{$mapping}";
+			}
+			$map->large_words[] = $group_string;
+		}
+		return $map;
+	}
+	/**
+	 * Creates a token map from a pre-computed table.
+	 * This skips the initialization cost of generating the table.
+	 *
+	 * This function should only be used to load data created with
+	 * WP_Token_Map::precomputed_php_source_tag().
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param array $state {
+	 *     Stores pre-computed state for directly loading into a Token Map.
+	 *
+	 *     @type string $storage_version Which version of the code produced this state.
+	 *     @type int    $key_length      Group key length.
+	 *     @type string $groups          Group lookup index.
+	 *     @type array  $large_words     Large word groups and packed strings.
+	 *     @type string $small_words     Small words packed string.
+	 *     @type array  $small_mappings  Small word mappings.
+	 * }
+	 *
+	 * @return WP_Token_Map Map with precomputed data loaded.
+	 */
+	public static function from_precomputed_table( $state ) {
+		$has_necessary_state = isset(
+			$state['storage_version'],
+			$state['key_length'],
+			$state['groups'],
+			$state['large_words'],
+			$state['small_words'],
+			$state['small_mappings']
+		);
+		if ( ! $has_necessary_state ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Missing required inputs to pre-computed WP_Token_Map.' ),
+				'6.6.0'
+			);
+			return null;
+		}
+		if ( self::STORAGE_VERSION !== $state['storage_version'] ) {
+			_doing_it_wrong(
+				__METHOD__,
+				/* translators: 1: version string, 2: version string. */
+				sprintf( __( 'Loaded version \'%1$s\' incompatible with expected version \'%2$s\'.' ), $state['storage_version'], self::STORAGE_VERSION ),
+				'6.6.0'
+			);
+			return null;
+		}
+		$map = new WP_Token_Map();
+		$map->key_length     = $state['key_length'];
+		$map->groups         = $state['groups'];
+		$map->large_words    = $state['large_words'];
+		$map->small_words    = $state['small_words'];
+		$map->small_mappings = $state['small_mappings'];
+		return $map;
+	}
+	/**
+	 * Indicates if a given word is a lookup key in the map.
+	 *
+	 * Example:
+	 *
+	 *     true  === $smilies->contains( ':)' );
+	 *     false === $smilies->contains( 'simile' );
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $word             Determine if this word is a lookup key in the map.
+	 * @param string $case_sensitivity Optional. Pass 'ascii-case-insensitive' to ignore ASCII case when matching. Default 'case-sensitive'.
+	 * @return bool Whether there's an entry for the given word in the map.
+	 */
+	public function contains( $word, $case_sensitivity = 'case-sensitive' ) {
+		$ignore_case = 'ascii-case-insensitive' === $case_sensitivity;
+		if ( $this->key_length >= strlen( $word ) ) {
+			if ( 0 === strlen( $this->small_words ) ) {
+				return false;
+			}
+			$term    = str_pad( $word, $this->key_length + 1, "\x00", STR_PAD_RIGHT );
+			$word_at = $ignore_case ? stripos( $this->small_words, $term ) : strpos( $this->small_words, $term );
+			if ( false === $word_at ) {
+				return false;
+			}
+			return true;
+		}
+		$group_key = substr( $word, 0, $this->key_length );
+		$group_at  = $ignore_case ? stripos( $this->groups, $group_key ) : strpos( $this->groups, $group_key );
+		if ( false === $group_at ) {
+			return false;
+		}
+		$group        = $this->large_words[ $group_at / ( $this->key_length + 1 ) ];
+		$group_length = strlen( $group );
+		$slug         = substr( $word, $this->key_length );
+		$length       = strlen( $slug );
+		$at           = 0;
+		while ( $at < $group_length ) {
+			$token_length   = unpack( 'C', $group[ $at++ ] )[1];
+			$token_at       = $at;
+			$at            += $token_length;
+			$mapping_length = unpack( 'C', $group[ $at++ ] )[1];
+			$mapping_at     = $at;
+			if ( $token_length === $length && 0 === substr_compare( $group, $slug, $token_at, $token_length, $ignore_case ) ) {
+				return true;
+			}
+			$at = $mapping_at + $mapping_length;
+		}
+		return false;
+	}
+	/**
+	 * If the text starting at a given offset is a lookup key in the map,
+	 * return the corresponding transformation from the map, else `false`.
+	 *
+	 * This function returns the translated string, but accepts an optional
+	 * parameter `$matched_token_byte_length`, which communicates how many
+	 * bytes long the lookup key was, if it found one. This can be used to
+	 * advance a cursor in calling code if a lookup key was found.
+	 *
+	 * Example:
+	 *
+	 *     false === $smilies->read_token( 'Not sure :?.', 0, $token_byte_length );
+	 *     '😕'  === $smilies->read_token( 'Not sure :?.', 9, $token_byte_length );
+	 *     2     === $token_byte_length;
+	 *
+	 * Example:
+	 *
+	 *     while ( $at < strlen( $input ) ) {
+	 *         $next_at = strpos( $input, ':', $at );
+	 *         if ( false === $next_at ) {
+	 *             break;
+	 *         }
+	 *
+	 *         $smily = $smilies->read_token( $input, $next_at, $token_byte_length );
+	 *         if ( false === $next_at ) {
+	 *             ++$at;
+	 *             continue;
+	 *         }
+	 *
+	 *         $prefix  = substr( $input, $at, $next_at - $at );
+	 *         $at     += $token_byte_length;
+	 *         $output .= "{$prefix}{$smily}";
+	 *     }
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string  $text                       String in which to search for a lookup key.
+	 * @param int     $offset                     Optional. How many bytes into the string where the lookup key ought to start. Default 0.
+	 * @param ?int    &$matched_token_byte_length Optional. Holds byte-length of found token matched, otherwise not set. Default null.
+	 * @param string  $case_sensitivity           Optional. Pass 'ascii-case-insensitive' to ignore ASCII case when matching. Default 'case-sensitive'.
+	 * @return string|null Mapped value of lookup key if found, otherwise `null`.
+	 */
+	public function read_token( $text, $offset = 0, &$matched_token_byte_length = null, $case_sensitivity = 'case-sensitive' ) {
+		$ignore_case = 'ascii-case-insensitive' === $case_sensitivity;
+		$text_length = strlen( $text );
+		// Search for a long word first, if the text is long enough, and if that fails, a short one.
+		if ( $text_length > $this->key_length ) {
+			$group_key = substr( $text, $offset, $this->key_length );
+			$group_at = $ignore_case ? stripos( $this->groups, $group_key ) : strpos( $this->groups, $group_key );
+			if ( false === $group_at ) {
+				// Perhaps a short word then.
+				return strlen( $this->small_words ) > 0
+					? $this->read_small_token( $text, $offset, $matched_token_byte_length, $case_sensitivity )
+					: null;
+			}
+			$group        = $this->large_words[ $group_at / ( $this->key_length + 1 ) ];
+			$group_length = strlen( $group );
+			$at           = 0;
+			while ( $at < $group_length ) {
+				$token_length   = unpack( 'C', $group[ $at++ ] )[1];
+				$token          = substr( $group, $at, $token_length );
+				$at            += $token_length;
+				$mapping_length = unpack( 'C', $group[ $at++ ] )[1];
+				$mapping_at     = $at;
+				if ( 0 === substr_compare( $text, $token, $offset + $this->key_length, $token_length, $ignore_case ) ) {
+					$matched_token_byte_length = $this->key_length + $token_length;
+					return substr( $group, $mapping_at, $mapping_length );
+				}
+				$at = $mapping_at + $mapping_length;
+			}
+		}
+		// Perhaps a short word then.
+		return strlen( $this->small_words ) > 0
+			? $this->read_small_token( $text, $offset, $matched_token_byte_length, $case_sensitivity )
+			: null;
+	}
+	/**
+	 * Finds a match for a short word at the index.
+	 *
+	 * @since 6.6.0.
+	 *
+	 * @param string $text                       String in which to search for a lookup key.
+	 * @param int    $offset                     Optional. How many bytes into the string where the lookup key ought to start. Default 0.
+	 * @param ?int   &$matched_token_byte_length Optional. Holds byte-length of found lookup key if matched, otherwise not set. Default null.
+	 * @param string $case_sensitivity           Optional. Pass 'ascii-case-insensitive' to ignore ASCII case when matching. Default 'case-sensitive'.
+	 * @return string|null Mapped value of lookup key if found, otherwise `null`.
+	 */
+	private function read_small_token( $text, $offset, &$matched_token_byte_length, $case_sensitivity = 'case-sensitive' ) {
+		$ignore_case  = 'ascii-case-insensitive' === $case_sensitivity;
+		$small_length = strlen( $this->small_words );
+		$search_text  = substr( $text, $offset, $this->key_length );
+		if ( $ignore_case ) {
+			$search_text = strtoupper( $search_text );
+		}
+		$starting_char = $search_text[0];
+		$at = 0;
+		while ( $at < $small_length ) {
+			if (
+				$starting_char !== $this->small_words[ $at ] &&
+				( ! $ignore_case || strtoupper( $this->small_words[ $at ] ) !== $starting_char )
+			) {
+				$at += $this->key_length + 1;
+				continue;
+			}
+			for ( $adjust = 1; $adjust < $this->key_length; $adjust++ ) {
+				if ( "\x00" === $this->small_words[ $at + $adjust ] ) {
+					$matched_token_byte_length = $adjust;
+					return $this->small_mappings[ $at / ( $this->key_length + 1 ) ];
+				}
+				if (
+					$search_text[ $adjust ] !== $this->small_words[ $at + $adjust ] &&
+					( ! $ignore_case || strtoupper( $this->small_words[ $at + $adjust ] !== $search_text[ $adjust ] ) )
+				) {
+					$at += $this->key_length + 1;
+					continue 2;
+				}
+			}
+			$matched_token_byte_length = $adjust;
+			return $this->small_mappings[ $at / ( $this->key_length + 1 ) ];
+		}
+		return null;
+	}
+	/**
+	 * Exports the token map into an associate array of key/value pairs.
+	 *
+	 * Example:
+	 *
+	 *     $smilies->to_array() === array(
+	 *         '8O' => '😯',
+	 *         ':(' => '🙁',
+	 *         ':)' => '🙂',
+	 *         ':?' => '😕',
+	 *     );
+	 *
+	 * @return array The lookup key/substitution values as an associate array.
+	 */
+	public function to_array() {
+		$tokens = array();
+		$at            = 0;
+		$small_mapping = 0;
+		$small_length  = strlen( $this->small_words );
+		while ( $at < $small_length ) {
+			$key            = rtrim( substr( $this->small_words, $at, $this->key_length + 1 ), "\x00" );
+			$value          = $this->small_mappings[ $small_mapping++ ];
+			$tokens[ $key ] = $value;
+			$at += $this->key_length + 1;
+		}
+		foreach ( $this->large_words as $index => $group ) {
+			$prefix       = substr( $this->groups, $index * ( $this->key_length + 1 ), 2 );
+			$group_length = strlen( $group );
+			$at           = 0;
+			while ( $at < $group_length ) {
+				$length = unpack( 'C', $group[ $at++ ] )[1];
+				$key    = $prefix . substr( $group, $at, $length );
+				$at    += $length;
+				$length = unpack( 'C', $group[ $at++ ] )[1];
+				$value  = substr( $group, $at, $length );
+				$tokens[ $key ] = $value;
+				$at            += $length;
+			}
+		}
+		return $tokens;
+	}
+	/**
+	 * Export the token map for quick loading in PHP source code.
+	 *
+	 * This function has a specific purpose, to make loading of static token maps fast.
+	 * It's used to ensure that the HTML character reference lookups add a minimal cost
+	 * to initializing the PHP process.
+	 *
+	 * Example:
+	 *
+	 *     echo $smilies->precomputed_php_source_table();
+	 *
+	 *     // Output.
+	 *     WP_Token_Map::from_precomputed_table(
+	 *         array(
+	 *             "storage_version" => "6.6.0",
+	 *             "key_length" => 2,
+	 *             "groups" => "",
+	 *             "long_words" => array(),
+	 *             "small_words" => "8O\x00:)\x00:(\x00:?\x00",
+	 *             "small_mappings" => array( "😯", "🙂", "🙁", "😕" )
+	 *         )
+	 *     );
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $indent Optional. Use this string for indentation, or rely on the default horizontal tab character. Default "\t".
+	 * @return string Value which can be pasted into a PHP source file for quick loading of table.
+	 */
+	public function precomputed_php_source_table( $indent = "\t" ) {
+		$i1 = $indent;
+		$i2 = $i1 . $indent;
+		$i3 = $i2 . $indent;
+		$class_version = self::STORAGE_VERSION;
+		$output  = self::class . "::from_precomputed_table(\n";
+		$output .= "{$i1}array(\n";
+		$output .= "{$i2}\"storage_version\" => \"{$class_version}\",\n";
+		$output .= "{$i2}\"key_length\" => {$this->key_length},\n";
+		$group_line = str_replace( "\x00", "\\x00", $this->groups );
+		$output    .= "{$i2}\"groups\" => \"{$group_line}\",\n";
+		$output .= "{$i2}\"large_words\" => array(\n";
+		$prefixes = explode( "\x00", $this->groups );
+		foreach ( $prefixes as $index => $prefix ) {
+			if ( '' === $prefix ) {
+				break;
+			}
+			$group        = $this->large_words[ $index ];
+			$group_length = strlen( $group );
+			$comment_line = "{$i3}//";
+			$data_line    = "{$i3}\"";
+			$at           = 0;
+			while ( $at < $group_length ) {
+				$token_length   = unpack( 'C', $group[ $at++ ] )[1];
+				$token          = substr( $group, $at, $token_length );
+				$at            += $token_length;
+				$mapping_length = unpack( 'C', $group[ $at++ ] )[1];
+				$mapping        = substr( $group, $at, $mapping_length );
+				$at            += $mapping_length;
+				$token_digits   = str_pad( dechex( $token_length ), 2, '0', STR_PAD_LEFT );
+				$mapping_digits = str_pad( dechex( $mapping_length ), 2, '0', STR_PAD_LEFT );
+				$mapping = preg_replace_callback(
+					"~[\\x00-\\x1f\\x22\\x5c]~",
+					static function ( $match_result ) {
+						switch ( $match_result[0] ) {
+							case '"':
+								return '\\"';
+							case '\\':
+								return '\\\\';
+							default:
+								$hex = dechex( ord( $match_result[0] ) );
+								return "\\x{$hex}";
+						}
+					},
+					$mapping
+				);
+				$comment_line .= " {$prefix}{$token}[{$mapping}]";
+				$data_line    .= "\\x{$token_digits}{$token}\\x{$mapping_digits}{$mapping}";
+			}
+			$comment_line .= ".\n";
+			$data_line    .= "\",\n";
+			$output .= $comment_line;
+			$output .= $data_line;
+		}
+		$output .= "{$i2}),\n";
+		$small_words  = array();
+		$small_length = strlen( $this->small_words );
+		$at           = 0;
+		while ( $at < $small_length ) {
+			$small_words[] = substr( $this->small_words, $at, $this->key_length + 1 );
+			$at           += $this->key_length + 1;
+		}
+		$small_text = str_replace( "\x00", '\x00', implode( '', $small_words ) );
+		$output    .= "{$i2}\"small_words\" => \"{$small_text}\",\n";
+		$output .= "{$i2}\"small_mappings\" => array(\n";
+		foreach ( $this->small_mappings as $mapping ) {
+			$output .= "{$i3}\"{$mapping}\",\n";
+		}
+		$output .= "{$i2})\n";
+		$output .= "{$i1})\n";
+		$output .= ')';
+		return $output;
+	}
+	/**
+	 * Compares two strings, returning the longest, or whichever
+	 * is first alphabetically if they are the same length.
+	 *
+	 * This is an important sort when building the token map because
+	 * it should not form a match on a substring of a longer potential
+	 * match. For example, it should not detect `Cap` when matching
+	 * against the string `CapitalDifferentialD`.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $a First string to compare.
+	 * @param string $b Second string to compare.
+	 * @return int -1 or lower if `$a` is less than `$b`; 1 or greater if `$a` is greater than `$b`, and 0 if they are equal.
+	 */
+	private static function longest_first_then_alphabetical( $a, $b ) {
+		if ( $a === $b ) {
+			return 0;
+		}
+		$length_a = strlen( $a );
+		$length_b = strlen( $b );
+		// Longer strings are less-than for comparison's sake.
+		if ( $length_a !== $length_b ) {
+			return $length_b - $length_a;
+		}
+		return strcmp( $a, $b );
+	}
+}

changeset 21	48c4eec2b7e6
child 22	8c2e4d02f4ef