php gzdecode,gzip解码函数gzdecode()

朱雀 2022-11-18 13:39 72阅读 0赞

最近采集土豆，发现土豆的页面貌似用了gzip，当使用file\_get\_contents()获取得到的是一些乱码，当时试着将页面的编码改来改去，但还是不行，想到了以前碰到类似的情况，好吧，果然。

分析：

大概有2种情况，1是自身的页面编码，和获取的页面编码不一致。

另外的一种情况就是，目标页面用了gzip技术。

用以下的函数可解决这个问题：

function gzdecode($data) \{

$len = strlen ( $data );

if ($len < 18 || strcmp ( substr ( $data, 0, 2 ), "\\x1f\\x8b" )) \{

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) \{

// Reserved bits are set -- NOT ALLOWED by RFC 1952

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 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;

php gzdecode,gzip解码函数gzdecode()

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