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    <h3>Editing: class-wp-translation-file-mo.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?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-&gt;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-&gt;parsed = true;

		$file_contents = file_get_contents( $this-&gt;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 &lt; 24 ) {
			$this-&gt;error = 'Invalid data';
			return false;
		}

		$this-&gt;uint32 = $this-&gt;detect_endian_and_validate_file( substr( $file_contents, 0, 4 ) );

		if ( false === $this-&gt;uint32 ) {
			return false;
		}

		$offsets = substr( $file_contents, 4, 24 );

		if ( false === $offsets ) {
			return false;
		}

		$offsets = unpack( &quot;{$this-&gt;uint32}rev/{$this-&gt;uint32}total/{$this-&gt;uint32}originals_addr/{$this-&gt;uint32}translations_addr/{$this-&gt;uint32}hash_length/{$this-&gt;uint32}hash_addr&quot;, $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'] &gt; 0 ) {
			$this-&gt;error = 'Unsupported revision';
			return false;
		}

		if ( $offsets['translations_addr'] &gt; $file_length || $offsets['originals_addr'] &gt; $file_length ) {
			$this-&gt;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 ) {
			$o = unpack( &quot;{$this-&gt;uint32}length/{$this-&gt;uint32}pos&quot;, $original_data[ $i ] );
			$t = unpack( &quot;{$this-&gt;uint32}length/{$this-&gt;uint32}pos&quot;, $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, &quot;\0&quot; );

			// Metadata about the MO file is stored in the first translation entry.
			if ( '' === $original ) {
				foreach ( explode( &quot;\n&quot;, $translation ) as $meta_line ) {
					if ( '' === $meta_line || ! str_contains( $meta_line, ':' ) ) {
						continue;
					}

					list( $name, $value ) = array_map( 'trim', explode( ':', $meta_line, 2 ) );

					$this-&gt;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( &quot;\0&quot;, (string) $original );

				$this-&gt;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-&gt;headers as $header =&gt; $value ) {
			$headers_string .= &quot;{$header}: $value\n&quot;;
		}
		$entries     = array_merge( array( '' =&gt; $headers_string ), $this-&gt;entries );
		$entry_count = count( $entries );

		if ( false === $this-&gt;uint32 ) {
			$this-&gt;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-&gt;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-&gt;uint32 . '*', strlen( $original ), $entry_offsets );
			$entry_offsets += strlen( $original ) + 1;
			$o_entries     .= $original . &quot;\0&quot;;
		}

		foreach ( $entries as $translations ) {
			$t_addr        .= pack( $this-&gt;uint32 . '*', strlen( $translations ), $entry_offsets );
			$entry_offsets += strlen( $translations ) + 1;
			$t_entries     .= $translations . &quot;\0&quot;;
		}

		return $file_header . $o_addr . $t_addr . $o_entries . $t_entries;
	}
}
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