<?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

	 *

	 * @static

	 *

	 * @param string $raw String to compress.

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

	 * @param string $supports Optional, not used. When implemented it will choose the right compression based on what the server supports.

	 * @return string|false False on failure.

	 */

	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

	 *

	 * @static

	 *

	 * @param string $compressed String to decompress.

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

	 * @return string|bool False on failure.

	 */

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

		if ( empty($compressed) )

			return $compressed;

		if ( false !== ( $decompressed = @gzinflate( $compressed ) ) )

			return $decompressed;

		if ( false !== ( $decompressed = self::compatible_gzinflate( $compressed ) ) )

			return $decompressed;

		if ( false !== ( $decompressed = @gzuncompress( $compressed ) ) )

			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://secure.php.net/manual/en/function.gzinflate.php#70875

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

	 *

	 * @static

	 *

	 * @param string $gzData String to decompress.

	 * @return string|bool False on failure.

	 */

	public static function compatible_gzinflate($gzData) {

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

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

			$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

	 *

	 * @static

	 *

	 * @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 array  $type Encoding types allowed. Accepts 'gzinflate',

		 *                     'gzuncompress', 'gzdecode'.

		 * @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

	 *

	 * @static

	 *

	 * @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

	 *

	 * @static

	 *

	 * @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

	 *

	 * @static

	 *

	 * @return bool

	 */

	public static function is_available() {

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

	}

}