php解压有时会失败-php教程-PHP中文网

采集一个网站的数据时，返回的是以chunked编码，gzip压缩的文档，该网站的服务器显示是iis，。。。

解码chunked没问题，但是解压gzip压缩文档时，偶尔会失败，这样就影响我提取下一组请求连接了。。。

解压10组左右，就会出现解压失败的情况。。

这是解压前的数据：

解压后的数据：

显然在最后一组，解压失败了。。

这是尝试用过的三组方法：

 private function _decompressdata()   {       if($this->is_gzip) {          $this->response_body =  gzinflate(substr($this->response_body,10));           //           //           if($temp = gzdecode($this->response_body)) {//               $this->response_body = $temp;//           } else {//              $this->response_body =  $this->mygzdecode($this->response_body);//           }                     //$this->response_body =  $this->mygzdecode($this->response_body);             //         $this->response_body = gzdecode($this->response_body);       }   }

登录后复制

mygzdecode函数是这一个

 /**    * @desc 自定义解压函数    */   function mygzdecode($data, &$filename = '', &$error = '', $maxlength = null)    {        $len = strlen($data);        if ($len < 18 || strcmp(substr($data, 0, 2), "\x1f\x8b")) {            $error = "not in gzip format.";            return null;  // not gzip format (see rfc 1952)        }        $method = ord(substr($data, 2, 1));  // compression method        $flags = ord(substr($data, 3, 1));  // flags        if ($flags & 31 != $flags) {            $error = "reserved bits not allowed.";            return null;        }        // note: $mtime may be negative (php integer limitations)        $mtime = unpack("v", substr($data, 4, 4));        $mtime = $mtime[1];        $xfl = substr($data, 8, 1);        $os = substr($data, 8, 1);        $headerlen = 10;        $extralen = 0;        $extra = "";        if ($flags & 4) {            // 2-byte length prefixed extra data in header            if ($len - $headerlen - 2 < 8) {                return false;  // invalid            }            $extralen = unpack("v", substr($data, 8, 2));            $extralen = $extralen[1];            if ($len - $headerlen - 2 - $extralen < 8) {                return false;  // invalid            }            $extra = substr($data, 10, $extralen);            $headerlen += 2 + $extralen;        }        $filenamelen = 0;        $filename = "";        if ($flags & 8) {            // c-style string            if ($len - $headerlen - 1 < 8) {                return false; // invalid            }            $filenamelen = strpos(substr($data, $headerlen), chr(0));            if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {                return false; // invalid            }            $filename = substr($data, $headerlen, $filenamelen);            $headerlen += $filenamelen + 1;        }        $commentlen = 0;        $comment = "";        if ($flags & 16) {            // c-style string comment data in header            if ($len - $headerlen - 1 < 8) {                return false;    // invalid            }            $commentlen = strpos(substr($data, $headerlen), chr(0));            if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {                return false;    // invalid header format            }            $comment = substr($data, $headerlen, $commentlen);            $headerlen += $commentlen + 1;        }        $headercrc = "";        if ($flags & 2) {            // 2-bytes (lowest order) of crc32 on header present            if ($len - $headerlen - 2 < 8) {                return false;    // invalid            }            $calccrc = crc32(substr($data, 0, $headerlen)) & 0xffff;            $headercrc = unpack("v", substr($data, $headerlen, 2));            $headercrc = $headercrc[1];            if ($headercrc != $calccrc) {                $error = "header checksum failed.";                return false;    // bad header crc            }            $headerlen += 2;        }        // gzip footer        $datacrc = unpack("v", substr($data, -8, 4));        $datacrc = sprintf('%u', $datacrc[1] & 0xffffffff);        $isize = unpack("v", substr($data, -4));        $isize = $isize[1];        // decompression:        $bodylen = $len - $headerlen - 8;        if ($bodylen < 1) {            // implementation bug!            return null;        }        $body = substr($data, $headerlen, $bodylen);        $data = "";        if ($bodylen > 0) {            switch ($method) {                case 8:                    // currently the only supported compression method:                    $data = gzinflate($body, $maxlength);                    break;                default:                    $error = "unknown compression method.";                    return false;            }        }  // zero-byte body content is allowed        // verifiy crc32        $crc = sprintf("%u", crc32($data));        $crcok = $crc == $datacrc;        $lenok = $isize == strlen($data);        if (!$lenok || !$crcok) {            $error = ( $lenok ? '' : 'length check failed. ') . ( $crcok ? '' : 'checksum failed.');            return false;        }        return $data;    }

登录后复制

也就是说，连续解压时，会出现解压失败的情况

回复讨论(解决方案)

php 已经提供了 gzdecode 函数
如果你的 php 版本实在很低，没有 gzdecode 函数
那么 php 代码级的 gzdecode 函数是

function gzdecode($data) {   $len = strlen($data);   if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {     return $data;  // Not GZIP format (See RFC 1952)   }   $method = ord(substr($data,2,1));  // Compression method   $flags  = ord(substr($data,3,1));  // Flags   if ($flags & 31 != $flags) {     // Reserved bits are set -- NOT ALLOWED by RFC 1952     return data;   }   // NOTE: $mtime may be negative (PHP integer limitations)   $mtime = unpack("V", substr($data,4,4));   $mtime = $mtime[1];   $xfl   = substr($data,8,1);   $os    = substr($data,8,1);   $headerlen = 10;   $extralen  = 0;   $extra     = "";   if ($flags & 4) {     // 2-byte length prefixed EXTRA data in header     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $extralen = unpack("v",substr($data,8,2));     $extralen = $extralen[1];     if ($len - $headerlen - 2 - $extralen < 8) {       return false;    // Invalid format     }     $extra = substr($data,10,$extralen);     $headerlen += 2 + $extralen;   }   $filenamelen = 0;   $filename = "";   if ($flags & 8) {     // C-style string file NAME data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $filenamelen = strpos(substr($data,8+$extralen),chr(0));     if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {       return false;    // Invalid format     }     $filename = substr($data,$headerlen,$filenamelen);     $headerlen += $filenamelen + 1;   }   $commentlen = 0;   $comment = "";   if ($flags & 16) {     // C-style string COMMENT data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));     if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {       return false;    // Invalid header format     }     $comment = substr($data,$headerlen,$commentlen);     $headerlen += $commentlen + 1;   }   $headercrc = "";   if ($flags & 1) {     // 2-bytes (lowest order) of CRC32 on header present     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;     $headercrc = unpack("v", substr($data,$headerlen,2));     $headercrc = $headercrc[1];     if ($headercrc != $calccrc) {       return false;    // Bad header CRC     }     $headerlen += 2;   }   // GZIP FOOTER - These be negative due to PHP's limitations   $datacrc = unpack("V",substr($data,-8,4));   $datacrc = $datacrc[1];   $isize = unpack("V",substr($data,-4));   $isize = $isize[1];   // Perform the decompression:   $bodylen = $len-$headerlen-8;   if ($bodylen < 1) {     // This should never happen - IMPLEMENTATION BUG!     return null;   }   $body = substr($data,$headerlen,$bodylen);   $data = "";   if ($bodylen > 0) {     switch ($method) {       case 8:         // Currently the only supported compression method:         $data = gzinflate($body);         break;       default:         // Unknown compression method         return false;     }   } else {     // I'm not sure if zero-byte body content is allowed.     // Allow it for now...  Do nothing...   }   // Verifiy decompressed size and CRC32:   // NOTE: This may fail with large data sizes depending on how   //       PHP's integer limitations affect strlen() since $isize   //       may be negative for large sizes.   if ($isize != strlen($data) || crc32($data) != $datacrc) {     // Bad format!  Length or CRC doesn't match!     return false;   }   return $data; }

登录后复制

自己对比一下，看看是否是你抄写错了

既然函数会在传入长度和 crc32 校验失败时返回假，那么你就应该判断一下再进行下一步工作

php 已经提供了 gzdecode 函数
如果你的 php 版本实在很低，没有 gzdecode 函数
那么 php 代码级的 gzdecode 函数是

function gzdecode($data) {   $len = strlen($data);   if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {     return $data;  // Not GZIP format (See RFC 1952)   }   $method = ord(substr($data,2,1));  // Compression method   $flags  = ord(substr($data,3,1));  // Flags   if ($flags & 31 != $flags) {     // Reserved bits are set -- NOT ALLOWED by RFC 1952     return data;   }   // NOTE: $mtime may be negative (PHP integer limitations)   $mtime = unpack("V", substr($data,4,4));   $mtime = $mtime[1];   $xfl   = substr($data,8,1);   $os    = substr($data,8,1);   $headerlen = 10;   $extralen  = 0;   $extra     = "";   if ($flags & 4) {     // 2-byte length prefixed EXTRA data in header     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $extralen = unpack("v",substr($data,8,2));     $extralen = $extralen[1];     if ($len - $headerlen - 2 - $extralen < 8) {       return false;    // Invalid format     }     $extra = substr($data,10,$extralen);     $headerlen += 2 + $extralen;   }   $filenamelen = 0;   $filename = "";   if ($flags & 8) {     // C-style string file NAME data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $filenamelen = strpos(substr($data,8+$extralen),chr(0));     if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {       return false;    // Invalid format     }     $filename = substr($data,$headerlen,$filenamelen);     $headerlen += $filenamelen + 1;   }   $commentlen = 0;   $comment = "";   if ($flags & 16) {     // C-style string COMMENT data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));     if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {       return false;    // Invalid header format     }     $comment = substr($data,$headerlen,$commentlen);     $headerlen += $commentlen + 1;   }   $headercrc = "";   if ($flags & 1) {     // 2-bytes (lowest order) of CRC32 on header present     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;     $headercrc = unpack("v", substr($data,$headerlen,2));     $headercrc = $headercrc[1];     if ($headercrc != $calccrc) {       return false;    // Bad header CRC     }     $headerlen += 2;   }   // GZIP FOOTER - These be negative due to PHP's limitations   $datacrc = unpack("V",substr($data,-8,4));   $datacrc = $datacrc[1];   $isize = unpack("V",substr($data,-4));   $isize = $isize[1];   // Perform the decompression:   $bodylen = $len-$headerlen-8;   if ($bodylen < 1) {     // This should never happen - IMPLEMENTATION BUG!     return null;   }   $body = substr($data,$headerlen,$bodylen);   $data = "";   if ($bodylen > 0) {     switch ($method) {       case 8:         // Currently the only supported compression method:         $data = gzinflate($body);         break;       default:         // Unknown compression method         return false;     }   } else {     // I'm not sure if zero-byte body content is allowed.     // Allow it for now...  Do nothing...   }   // Verifiy decompressed size and CRC32:   // NOTE: This may fail with large data sizes depending on how   //       PHP's integer limitations affect strlen() since $isize   //       may be negative for large sizes.   if ($isize != strlen($data) || crc32($data) != $datacrc) {     // Bad format!  Length or CRC doesn't match!     return false;   }   return $data; }

登录后复制

我的是PHP 5.6 ，
gzinflate(substr($this->response_body,10));

gzdecode($this->response_body)

mygzdecode($this->response_body);

这三种方法都可以用，但都遇到同一个问题，连续解压时，会出现解压失败的问题。

大婶，新年快乐哈

自己对比一下，看看是否是你抄写错了

既然函数会在传入长度和 crc32 校验失败时返回假，那么你就应该判断一下再进行下一步工作

好的。

在网络上传输的数据，出现错误是不可避免的，但概率不高
重读一下，通常就可以了

主要是你要有容错策略

自己对比一下，看看是否是你抄写错了

既然函数会在传入长度和 crc32 校验失败时返回假，那么你就应该判断一下再进行下一步工作

// Verifiy CRC32
        $crc = sprintf("%u", crc32($data));
        $crcOK = $crc == $datacrc;
        $lenOK = $isize == strlen($data);
        if (!$lenOK || !$crcOK) {
            $this->status = ( $lenOK ? '' : 'Length check FAILED. ') . ( $crcOK ? '' : 'Checksum FAILED.');
            return false;
        }
        return $data;
检测出来了，是这里校验失败了。。。

对链接http://www.cnu.cc/works/111706发起请求
Length check FAILED. Checksum FAILED.

在网络上传输的数据，出现错误是不可避免的，但概率不高
重读一下，通常就可以了

主要是你要有容错策略

对。。。这个地方确实需要加强。。。只做了重置连接，没有对收到数据的完整性做校验。。

在网络上传输的数据，出现错误是不可避免的，但概率不高
重读一下，通常就可以了

主要是你要有容错策略

OK了，连续采集10分钟，没出问题。。。THX，，摸摸大

传输过程出问题，导致部分数据没有了，而解压失败。

把需要解压的文件加入解压列表，每隔5秒-10秒判断解压文件是否变化，如无变化，则解压，解压失败做标记，继续下一个解压。

传输过程出问题，导致部分数据没有了，而解压失败。