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   1  <?php
   2  /**
   3   * HTTP API: WP_Http_Encoding class
   4   *
   5   * @package WordPress
   6   * @subpackage HTTP
   7   * @since 4.4.0
   8   */
   9  
  10  /**
  11   * Core class used to implement deflate and gzip transfer encoding support for HTTP requests.
  12   *
  13   * Includes RFC 1950, RFC 1951, and RFC 1952.
  14   *
  15   * @since 2.8.0
  16   */
  17  class WP_Http_Encoding {
  18  
  19      /**
  20       * Compress raw string using the deflate format.
  21       *
  22       * Supports the RFC 1951 standard.
  23       *
  24       * @since 2.8.0
  25       *
  26       * @param string $raw      String to compress.
  27       * @param int    $level    Optional. Compression level, 9 is highest. Default 9.
  28       * @param string $supports Optional, not used. When implemented it will choose
  29       *                         the right compression based on what the server supports.
  30       * @return string|false Compressed string on success, false on failure.
  31       */
  32  	public static function compress( $raw, $level = 9, $supports = null ) {
  33          return gzdeflate( $raw, $level );
  34      }
  35  
  36      /**
  37       * Decompression of deflated string.
  38       *
  39       * Will attempt to decompress using the RFC 1950 standard, and if that fails
  40       * then the RFC 1951 standard deflate will be attempted. Finally, the RFC
  41       * 1952 standard gzip decode will be attempted. If all fail, then the
  42       * original compressed string will be returned.
  43       *
  44       * @since 2.8.0
  45       *
  46       * @param string $compressed String to decompress.
  47       * @param int    $length     The optional length of the compressed data.
  48       * @return string|false Decompressed string on success, false on failure.
  49       */
  50  	public static function decompress( $compressed, $length = null ) {
  51  
  52          if ( empty( $compressed ) ) {
  53              return $compressed;
  54          }
  55  
  56          $decompressed = @gzinflate( $compressed );
  57          if ( false !== $decompressed ) {
  58              return $decompressed;
  59          }
  60  
  61          $decompressed = self::compatible_gzinflate( $compressed );
  62          if ( false !== $decompressed ) {
  63              return $decompressed;
  64          }
  65  
  66          $decompressed = @gzuncompress( $compressed );
  67          if ( false !== $decompressed ) {
  68              return $decompressed;
  69          }
  70  
  71          if ( function_exists( 'gzdecode' ) ) {
  72              $decompressed = @gzdecode( $compressed );
  73  
  74              if ( false !== $decompressed ) {
  75                  return $decompressed;
  76              }
  77          }
  78  
  79          return $compressed;
  80      }
  81  
  82      /**
  83       * Decompression of deflated string while staying compatible with the majority of servers.
  84       *
  85       * Certain Servers will return deflated data with headers which PHP's gzinflate()
  86       * function cannot handle out of the box. The following function has been created from
  87       * various snippets on the gzinflate() PHP documentation.
  88       *
  89       * Warning: Magic numbers within. Due to the potential different formats that the compressed
  90       * data may be returned in, some "magic offsets" are needed to ensure proper decompression
  91       * takes place. For a simple pragmatic way to determine the magic offset in use, see:
  92       * https://core.trac.wordpress.org/ticket/18273
  93       *
  94       * @since 2.8.1
  95       *
  96       * @link https://core.trac.wordpress.org/ticket/18273
  97       * @link https://www.php.net/manual/en/function.gzinflate.php#70875
  98       * @link https://www.php.net/manual/en/function.gzinflate.php#77336
  99       *
 100       * @param string $gz_data String to decompress.
 101       * @return string|false Decompressed string on success, false on failure.
 102       */
 103  	public static function compatible_gzinflate( $gz_data ) {
 104  
 105          // Compressed data might contain a full header, if so strip it for gzinflate().
 106          if ( "\x1f\x8b\x08" === substr( $gz_data, 0, 3 ) ) {
 107              $i   = 10;
 108              $flg = ord( substr( $gz_data, 3, 1 ) );
 109              if ( $flg > 0 ) {
 110                  if ( $flg & 4 ) {
 111                      list($xlen) = unpack( 'v', substr( $gz_data, $i, 2 ) );
 112                      $i          = $i + 2 + $xlen;
 113                  }
 114                  if ( $flg & 8 ) {
 115                      $i = strpos( $gz_data, "\0", $i ) + 1;
 116                  }
 117                  if ( $flg & 16 ) {
 118                      $i = strpos( $gz_data, "\0", $i ) + 1;
 119                  }
 120                  if ( $flg & 2 ) {
 121                      $i = $i + 2;
 122                  }
 123              }
 124              $decompressed = @gzinflate( substr( $gz_data, $i, -8 ) );
 125              if ( false !== $decompressed ) {
 126                  return $decompressed;
 127              }
 128          }
 129  
 130          // Compressed data from java.util.zip.Deflater amongst others.
 131          $decompressed = @gzinflate( substr( $gz_data, 2 ) );
 132          if ( false !== $decompressed ) {
 133              return $decompressed;
 134          }
 135  
 136          return false;
 137      }
 138  
 139      /**
 140       * What encoding types to accept and their priority values.
 141       *
 142       * @since 2.8.0
 143       *
 144       * @param string $url
 145       * @param array  $args
 146       * @return string Types of encoding to accept.
 147       */
 148  	public static function accept_encoding( $url, $args ) {
 149          $type                = array();
 150          $compression_enabled = self::is_available();
 151  
 152          if ( ! $args['decompress'] ) { // Decompression specifically disabled.
 153              $compression_enabled = false;
 154          } elseif ( $args['stream'] ) { // Disable when streaming to file.
 155              $compression_enabled = false;
 156          } elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.
 157              $compression_enabled = false;
 158          }
 159  
 160          if ( $compression_enabled ) {
 161              if ( function_exists( 'gzinflate' ) ) {
 162                  $type[] = 'deflate;q=1.0';
 163              }
 164  
 165              if ( function_exists( 'gzuncompress' ) ) {
 166                  $type[] = 'compress;q=0.5';
 167              }
 168  
 169              if ( function_exists( 'gzdecode' ) ) {
 170                  $type[] = 'gzip;q=0.5';
 171              }
 172          }
 173  
 174          /**
 175           * Filters the allowed encoding types.
 176           *
 177           * @since 3.6.0
 178           *
 179           * @param string[] $type Array of what encoding types to accept and their priority values.
 180           * @param string   $url  URL of the HTTP request.
 181           * @param array    $args HTTP request arguments.
 182           */
 183          $type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );
 184  
 185          return implode( ', ', $type );
 186      }
 187  
 188      /**
 189       * What encoding the content used when it was compressed to send in the headers.
 190       *
 191       * @since 2.8.0
 192       *
 193       * @return string Content-Encoding string to send in the header.
 194       */
 195  	public static function content_encoding() {
 196          return 'deflate';
 197      }
 198  
 199      /**
 200       * Whether the content be decoded based on the headers.
 201       *
 202       * @since 2.8.0
 203       *
 204       * @param array|string $headers All of the available headers.
 205       * @return bool
 206       */
 207  	public static function should_decode( $headers ) {
 208          if ( is_array( $headers ) ) {
 209              if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {
 210                  return true;
 211              }
 212          } elseif ( is_string( $headers ) ) {
 213              return ( stripos( $headers, 'content-encoding:' ) !== false );
 214          }
 215  
 216          return false;
 217      }
 218  
 219      /**
 220       * Whether decompression and compression are supported by the PHP version.
 221       *
 222       * Each function is tested instead of checking for the zlib extension, to
 223       * ensure that the functions all exist in the PHP version and aren't
 224       * disabled.
 225       *
 226       * @since 2.8.0
 227       *
 228       * @return bool
 229       */
 230  	public static function is_available() {
 231          return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );
 232      }
 233  }