Charset: Introduce WP_Encoding for standardized handling.

src/wp-includes/class-wp-encoding.php

@@ -0,0 +1,96 @@
+<?php
+
+/**
+ * Core class for interacting with text encodings.
+ *
+ * @see https://encoding.spec.whatwg.org/
+ *
+ * @since 7.0.0
+ */
+class WP_Encoding {
+	/**
+	 * Decodes a character-encoding label into a supported encoding name.
+	 *
+	 * > The table below lists all encodings and their labels user agents must
+	 * > support. User agents must not support any other encodings or labels.
+	 *
+	 * @see https://encoding.spec.whatwg.org/#names-and-labels
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $label
+	 * @return string|null
+	 */
+	public static function name_from_label( string $label ): ?string {
+		/*
+		 * > To get an encoding from a string label, run these steps:
+		 * > 1. Remove any leading and trailing ASCII whitespace from label.
+		 * > 2. If label is an ASCII case-insensitive match for any of the labels listed in the table below,
+		 * > then return the corresponding encoding; otherwise return failure.
+		 */
+		$label = trim( $label, " \t\f\r\n" );
+		$label = strtolower( $label );
+		$label = " {$label} ";
+
+		/**
+		 * Mapping of encoding name and space-separated set of labels mapping to it.
+		 *
+		 * Every label should be surrounded on each side by spaces, as space is not a possible
+		 * character in a label, making string lookup efficient.
+		 *
+		 * @todo Add generator script for JSON source.
+		 *
+		 * @see https://encoding.spec.whatwg.org/encodings.json
+		 */
+		$table = array(
+			'UTF-8'          => ' unicode-1-1-utf-8 unicode11utf8 unicode20utf8 utf-8 utf8 x-unicode20utf8 ',
+			'IBM866'         => ' 866 cp866 csibm866 ibm866 ',
+			'ISO-8859-2'     => ' csisolatin2 iso-8859-2 iso-ir-101 iso8859-2 iso88592 iso_8859-2 iso_8859-2:1987 l2 latin2 ',
+			'ISO-8859-3'     => ' csisolatin3 iso-8859-3 iso-ir-109 iso8859-3 iso88593 iso_8859-3 iso_8859-3:1988 l3 latin3 ',
+			'ISO-8859-4'     => ' csisolatin4 iso-8859-4 iso-ir-110 iso8859-4 iso88594 iso_8859-4 iso_8859-4:1988 l4 latin4 ',
+			'ISO-8859-5'     => ' csisolatincyrillic cyrillic iso-8859-5 iso-ir-144 iso8859-5 iso88595 iso_8859-5 iso_8859-5:1988 ',
+			'ISO-8859-6'     => ' arabic asmo-708 csiso88596e csiso88596i csisolatinarabic ecma-114 iso-8859-6 iso-8859-6-e iso-8859-6-i iso-ir-127 iso8859-6 iso88596 iso_8859-6 iso_8859-6:1987 ',
+			'ISO-8859-7'     => ' csisolatingreek ecma-118 elot_928 greek greek8 iso-8859-7 iso-ir-126 iso8859-7 iso88597 iso_8859-7 iso_8859-7:1987 sun_eu_greek ',
+			'ISO-8859-8'     => ' csiso88598e csisolatinhebrew hebrew iso-8859-8 iso-8859-8-e iso-ir-138 iso8859-8 iso88598 iso_8859-8 iso_8859-8:1988 visual ',
+			'ISO-8859-8-I'   => ' csiso88598i iso-8859-8-i logical ',
+			'ISO-8859-10'    => ' csisolatin6 iso-8859-10 iso-ir-157 iso8859-10 iso885910 l6 latin6 ',
+			'ISO-8859-13'    => ' iso-8859-13 iso8859-13 iso885913 ',
+			'ISO-8859-14'    => ' iso-8859-14 iso8859-14 iso885914 ',
+			'ISO-8859-15'    => ' csisolatin9 iso-8859-15 iso8859-15 iso885915 iso_8859-15 l9 ',
+			'ISO-8859-16'    => ' iso-8859-16 ',
+			'KOI8-R'         => ' cskoi8r koi koi8 koi8-r koi8_r ',
+			'KOI8-U'         => ' koi8-ru koi8-u ',
+			'macintosh'      => ' csmacintosh mac macintosh x-mac-roman ',
+			'windows-874'    => ' dos-874 iso-8859-11 iso8859-11 iso885911 tis-620 windows-874 ',
+			'windows-1250'   => ' cp1250 windows-1250 x-cp1250 ',
+			'windows-1251'   => ' cp1251 windows-1251 x-cp1251 ',
+			'windows-1252'   => ' ansi_x3.4-1968 ascii cp1252 cp819 csisolatin1 ibm819 iso-8859-1 iso-ir-100 iso8859-1 iso88591 iso_8859-1 iso_8859-1:1987 l1 latin1 us-ascii windows-1252 x-cp1252 ',
+			'windows-1253'   => ' cp1253 windows-1253 x-cp1253 ',
+			'windows-1254'   => ' cp1254 csisolatin5 iso-8859-9 iso-ir-148 iso8859-9 iso88599 iso_8859-9 iso_8859-9:1989 l5 latin5 windows-1254 x-cp1254 ',
+			'windows-1255'   => ' cp1255 windows-1255 x-cp1255 ',
+			'windows-1256'   => ' cp1256 windows-1256 x-cp1256 ',
+			'windows-1257'   => ' cp1257 windows-1257 x-cp1257 ',
+			'windows-1258'   => ' cp1258 windows-1258 x-cp1258 ',
+			'x-mac-cyrillic' => ' x-mac-cyrillic x-mac-ukrainian ',
+			'GBK'            => ' chinese csgb2312 csiso58gb231280 gb2312 gb_2312 gb_2312-80 gbk iso-ir-58 x-gbk ',
+			'gb18030'        => ' gb18030 ',
+			'Big5'           => ' big5 big5-hkscs cn-big5 csbig5 x-x-big5 ',
+			'EUC-JP'         => ' cseucpkdfmtjapanese euc-jp x-euc-jp ',
+			'ISO-2022-JP'    => ' csiso2022jp iso-2022-jp ',
+			'Shift_JIS'      => ' csshiftjis ms932 ms_kanji shift-jis shift_jis sjis windows-31j x-sjis ',
+			'EUC-KR'         => ' cseuckr csksc56011987 euc-kr iso-ir-149 korean ks_c_5601-1987 ks_c_5601-1989 ksc5601 ksc_5601 windows-949 ',
+			'replacement'    => ' csiso2022kr hz-gb-2312 iso-2022-cn iso-2022-cn-ext iso-2022-kr replacement ',
+			'UTF-16BE'       => ' unicodefffe utf-16be ',
+			'UTF-16LE'       => ' csunicode iso-10646-ucs-2 ucs-2 unicode unicodefeff utf-16 utf-16le ',
+			'x-user-defined' => ' x-user-defined ',
+		);
+
+		foreach ( $table as $name => $labels ) {
+			if ( str_contains( $labels, $label ) ) {
+				return $name;
+			}
+		}
+
+		return null;
+	}
+}

src/wp-settings.php

@@ -256,6 +256,7 @@
 require ABSPATH . WPINC . '/class-wp-oembed-controller.php';
 require ABSPATH . WPINC . '/media.php';
 require ABSPATH . WPINC . '/http.php';
+require ABSPATH . WPINC . '/class-wp-encoding.php';
 require ABSPATH . WPINC . '/html-api/html5-named-character-references.php';
 require ABSPATH . WPINC . '/html-api/class-wp-html-attribute-token.php';
 require ABSPATH . WPINC . '/html-api/class-wp-html-span.php';