diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/l10n/class-wp-translation-file-mo.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/l10n/class-wp-translation-file-mo.php	Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,239 @@
+<?php
+/**
+ * I18N: WP_Translation_File_MO class.
+ *
+ * @package WordPress
+ * @subpackage I18N
+ * @since 6.5.0
+ */
+
+/**
+ * Class WP_Translation_File_MO.
+ *
+ * @since 6.5.0
+ */
+class WP_Translation_File_MO extends WP_Translation_File {
+	/**
+	 * Endian value.
+	 *
+	 * V for little endian, N for big endian, or false.
+	 *
+	 * Used for unpack().
+	 *
+	 * @since 6.5.0
+	 * @var false|'V'|'N'
+	 */
+	protected $uint32 = false;
+
+	/**
+	 * The magic number of the GNU message catalog format.
+	 *
+	 * @since 6.5.0
+	 * @var int
+	 */
+	const MAGIC_MARKER = 0x950412de;
+
+	/**
+	 * Detects endian and validates file.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $header File contents.
+	 * @return false|'V'|'N' V for little endian, N for big endian, or false on failure.
+	 */
+	protected function detect_endian_and_validate_file( string $header ) {
+		$big = unpack( 'N', $header );
+
+		if ( false === $big ) {
+			return false;
+		}
+
+		$big = reset( $big );
+
+		if ( false === $big ) {
+			return false;
+		}
+
+		$little = unpack( 'V', $header );
+
+		if ( false === $little ) {
+			return false;
+		}
+
+		$little = reset( $little );
+
+		if ( false === $little ) {
+			return false;
+		}
+
+		// Force cast to an integer as it can be a float on x86 systems. See https://core.trac.wordpress.org/ticket/60678.
+		if ( (int) self::MAGIC_MARKER === $big ) {
+			return 'N';
+		}
+
+		// Force cast to an integer as it can be a float on x86 systems. See https://core.trac.wordpress.org/ticket/60678.
+		if ( (int) self::MAGIC_MARKER === $little ) {
+			return 'V';
+		}
+
+		$this->error = 'Magic marker does not exist';
+		return false;
+	}
+
+	/**
+	 * Parses the file.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @return bool True on success, false otherwise.
+	 */
+	protected function parse_file(): bool {
+		$this->parsed = true;
+
+		$file_contents = file_get_contents( $this->file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents
+
+		if ( false === $file_contents ) {
+			return false;
+		}
+
+		$file_length = strlen( $file_contents );
+
+		if ( $file_length < 24 ) {
+			$this->error = 'Invalid data';
+			return false;
+		}
+
+		$this->uint32 = $this->detect_endian_and_validate_file( substr( $file_contents, 0, 4 ) );
+
+		if ( false === $this->uint32 ) {
+			return false;
+		}
+
+		$offsets = substr( $file_contents, 4, 24 );
+
+		if ( false === $offsets ) {
+			return false;
+		}
+
+		$offsets = unpack( "{$this->uint32}rev/{$this->uint32}total/{$this->uint32}originals_addr/{$this->uint32}translations_addr/{$this->uint32}hash_length/{$this->uint32}hash_addr", $offsets );
+
+		if ( false === $offsets ) {
+			return false;
+		}
+
+		$offsets['originals_length']    = $offsets['translations_addr'] - $offsets['originals_addr'];
+		$offsets['translations_length'] = $offsets['hash_addr'] - $offsets['translations_addr'];
+
+		if ( $offsets['rev'] > 0 ) {
+			$this->error = 'Unsupported revision';
+			return false;
+		}
+
+		if ( $offsets['translations_addr'] > $file_length || $offsets['originals_addr'] > $file_length ) {
+			$this->error = 'Invalid data';
+			return false;
+		}
+
+		// Load the Originals.
+		$original_data     = str_split( substr( $file_contents, $offsets['originals_addr'], $offsets['originals_length'] ), 8 );
+		$translations_data = str_split( substr( $file_contents, $offsets['translations_addr'], $offsets['translations_length'] ), 8 );
+
+		foreach ( array_keys( $original_data ) as $i ) {
+			$o = unpack( "{$this->uint32}length/{$this->uint32}pos", $original_data[ $i ] );
+			$t = unpack( "{$this->uint32}length/{$this->uint32}pos", $translations_data[ $i ] );
+
+			if ( false === $o || false === $t ) {
+				continue;
+			}
+
+			$original    = substr( $file_contents, $o['pos'], $o['length'] );
+			$translation = substr( $file_contents, $t['pos'], $t['length'] );
+			// GlotPress bug.
+			$translation = rtrim( $translation, "\0" );
+
+			// Metadata about the MO file is stored in the first translation entry.
+			if ( '' === $original ) {
+				foreach ( explode( "\n", $translation ) as $meta_line ) {
+					if ( '' === $meta_line ) {
+						continue;
+					}
+
+					list( $name, $value ) = array_map( 'trim', explode( ':', $meta_line, 2 ) );
+
+					$this->headers[ strtolower( $name ) ] = $value;
+				}
+			} else {
+				/*
+				 * In MO files, the key normally contains both singular and plural versions.
+				 * However, this just adds the singular string for lookup,
+				 * which caters for cases where both __( 'Product' ) and _n( 'Product', 'Products' )
+				 * are used and the translation is expected to be the same for both.
+				 */
+				$parts = explode( "\0", (string) $original );
+
+				$this->entries[ $parts[0] ] = $translation;
+			}
+		}
+
+		return true;
+	}
+
+	/**
+	 * Exports translation contents as a string.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @return string Translation file contents.
+	 */
+	public function export(): string {
+		// Prefix the headers as the first key.
+		$headers_string = '';
+		foreach ( $this->headers as $header => $value ) {
+			$headers_string .= "{$header}: $value\n";
+		}
+		$entries     = array_merge( array( '' => $headers_string ), $this->entries );
+		$entry_count = count( $entries );
+
+		if ( false === $this->uint32 ) {
+			$this->uint32 = 'V';
+		}
+
+		$bytes_for_entries = $entry_count * 4 * 2;
+		// Pair of 32bit ints per entry.
+		$originals_addr    = 28; /* header */
+		$translations_addr = $originals_addr + $bytes_for_entries;
+		$hash_addr         = $translations_addr + $bytes_for_entries;
+		$entry_offsets     = $hash_addr;
+
+		$file_header = pack(
+			$this->uint32 . '*',
+			// Force cast to an integer as it can be a float on x86 systems. See https://core.trac.wordpress.org/ticket/60678.
+			(int) self::MAGIC_MARKER,
+			0, /* rev */
+			$entry_count,
+			$originals_addr,
+			$translations_addr,
+			0, /* hash_length */
+			$hash_addr
+		);
+
+		$o_entries = '';
+		$t_entries = '';
+		$o_addr    = '';
+		$t_addr    = '';
+
+		foreach ( array_keys( $entries ) as $original ) {
+			$o_addr        .= pack( $this->uint32 . '*', strlen( $original ), $entry_offsets );
+			$entry_offsets += strlen( $original ) + 1;
+			$o_entries     .= $original . "\0";
+		}
+
+		foreach ( $entries as $translations ) {
+			$t_addr        .= pack( $this->uint32 . '*', strlen( $translations ), $entry_offsets );
+			$entry_offsets += strlen( $translations ) + 1;
+			$t_entries     .= $translations . "\0";
+		}
+
+		return $file_header . $o_addr . $t_addr . $o_entries . $t_entries;
+	}
+}