<?php

/**

 * HTTP API: WP_Http_Encoding class

 *

 * @package WordPress

 * @subpackage HTTP

 * @since 4.4.0

 */

/**

 * Core class used to implement deflate and gzip transfer encoding support for HTTP requests.

 *

 * Includes RFC 1950, RFC 1951, and RFC 1952.

 *

 * @since 2.8.0

 */

class WP_Http_Encoding {

	/**

	 * Compress raw string using the deflate format.

	 *

	 * Supports the RFC 1951 standard.

	 *

	 * @since 2.8.0

	 *

	 * @param string $raw      String to compress.

	 * @param int    $level    Optional. Compression level, 9 is highest. Default 9.

	 * @param string $supports Optional, not used. When implemented it will choose

	 *                         the right compression based on what the server supports.

	 */

	public static function compress( $raw, $level = 9, $supports = null ) {

		return gzdeflate( $raw, $level );

	}

	/**

	 * Decompression of deflated string.

	 *

	 * Will attempt to decompress using the RFC 1950 standard, and if that fails

	 * then the RFC 1951 standard deflate will be attempted. Finally, the RFC

	 * 1952 standard gzip decode will be attempted. If all fail, then the

	 * original compressed string will be returned.

	 *

	 * @since 2.8.0

	 *

	 * @param string $compressed String to decompress.

	 * @param int    $length     The optional length of the compressed data.

	 */

	public static function decompress( $compressed, $length = null ) {

		if ( empty( $compressed ) ) {

			return $compressed;

		}

		$decompressed = @gzinflate( $compressed );

		if ( false !== $decompressed ) {

			return $decompressed;

		}

		$decompressed = self::compatible_gzinflate( $compressed );

		if ( false !== $decompressed ) {

			return $decompressed;

		}

		$decompressed = @gzuncompress( $compressed );

		if ( false !== $decompressed ) {

			return $decompressed;

		}

		if ( function_exists( 'gzdecode' ) ) {

			$decompressed = @gzdecode( $compressed );

			if ( false !== $decompressed ) {

				return $decompressed;

			}

		}

		return $compressed;

	}

	/**

	 * Decompression of deflated string while staying compatible with the majority of servers.

	 *

	 * Certain Servers will return deflated data with headers which PHP's gzinflate()

	 * function cannot handle out of the box. The following function has been created from

	 * various snippets on the gzinflate() PHP documentation.

	 *

	 * Warning: Magic numbers within. Due to the potential different formats that the compressed

	 * data may be returned in, some "magic offsets" are needed to ensure proper decompression

	 * takes place. For a simple progmatic way to determine the magic offset in use, see:

	 * https://core.trac.wordpress.org/ticket/18273

	 *

	 * @since 2.8.1

	 *

	 * @link https://core.trac.wordpress.org/ticket/18273

	 * @link https://www.php.net/manual/en/function.gzinflate.php#70875

	 * @link https://www.php.net/manual/en/function.gzinflate.php#77336

	 *

	 * @param string $gzData String to decompress.

	 */

	public static function compatible_gzinflate( $gzData ) {

		// Compressed data might contain a full header, if so strip it for gzinflate().

		if ( "\x1f\x8b\x08" === substr( $gzData, 0, 3 ) ) {

			$i   = 10;

			$flg = ord( substr( $gzData, 3, 1 ) );

			if ( $flg > 0 ) {

				if ( $flg & 4 ) {

					list($xlen) = unpack( 'v', substr( $gzData, $i, 2 ) );

					$i          = $i + 2 + $xlen;

				}

				if ( $flg & 8 ) {

					$i = strpos( $gzData, "\0", $i ) + 1;

				}

				if ( $flg & 16 ) {

					$i = strpos( $gzData, "\0", $i ) + 1;

				}

				if ( $flg & 2 ) {

					$i = $i + 2;

				}

			}

			$decompressed = @gzinflate( substr( $gzData, $i, -8 ) );

			if ( false !== $decompressed ) {

				return $decompressed;

			}

		}

		// Compressed data from java.util.zip.Deflater amongst others.

		$decompressed = @gzinflate( substr( $gzData, 2 ) );

		if ( false !== $decompressed ) {

			return $decompressed;

		}

		return false;

	}

	/**

	 * What encoding types to accept and their priority values.

	 *

	 * @since 2.8.0

	 *

	 * @param string $url

	 * @param array  $args

	 * @return string Types of encoding to accept.

	 */

	public static function accept_encoding( $url, $args ) {

		$type                = array();

		$compression_enabled = self::is_available();

		if ( ! $args['decompress'] ) { // Decompression specifically disabled.

			$compression_enabled = false;

		} elseif ( $args['stream'] ) { // Disable when streaming to file.

			$compression_enabled = false;

		} elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.

			$compression_enabled = false;

		}

		if ( $compression_enabled ) {

			if ( function_exists( 'gzinflate' ) ) {

				$type[] = 'deflate;q=1.0';

			}

			if ( function_exists( 'gzuncompress' ) ) {

				$type[] = 'compress;q=0.5';

			}

			if ( function_exists( 'gzdecode' ) ) {

				$type[] = 'gzip;q=0.5';

			}

		}

		/**

		 * Filters the allowed encoding types.

		 *

		 * @since 3.6.0

		 *

		 * @param string[] $type Array of what encoding types to accept and their priority values.

		 * @param string   $url  URL of the HTTP request.

		 * @param array    $args HTTP request arguments.

		 */

		$type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );

		return implode( ', ', $type );

	}

	/**

	 * What encoding the content used when it was compressed to send in the headers.

	 *

	 * @since 2.8.0

	 *

	 * @return string Content-Encoding string to send in the header.

	 */

	public static function content_encoding() {

		return 'deflate';

	}

	/**

	 * Whether the content be decoded based on the headers.

	 *

	 * @since 2.8.0

	 *

	 * @param array|string $headers All of the available headers.

	 * @return bool

	 */

	public static function should_decode( $headers ) {

		if ( is_array( $headers ) ) {

			if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {

				return true;

			}

		} elseif ( is_string( $headers ) ) {

			return ( stripos( $headers, 'content-encoding:' ) !== false );

		}

		return false;

	}

	/**

	 * Whether decompression and compression are supported by the PHP version.

	 *

	 * Each function is tested instead of checking for the zlib extension, to

	 * ensure that the functions all exist in the PHP version and aren't

	 * disabled.

	 *

	 * @since 2.8.0

	 *

	 * @return bool

	 */

	public static function is_available() {

		return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );

	}

}