WP_Translation_File_MO::parse_file()

	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;
	}