zlib,gzip和deflate格式分析之php相互转换

LZ77: 是一种基于字典的无损数据压缩算法(还有 LZ78, LZW 等)

deflate: 也是一种数据压缩算法,实际上就是先用 LZ77 压缩,然后用霍夫曼编码压缩

gzip: 是一种文件结构,也可以算一种压缩格式,通过 defalte 算法压缩数据,然后加上文件头和adler32校验

zlib: 是一个提供了 deflate, zlib, gzip 压缩方法的函数库;也是一种压缩格式(用 deflate 压缩数据,然后加上 zlib 头和 CRC 校验)

 

 1 <?php
 2 
 3 $string = "11aa@#@23123szadler32adler32adler32f..adler32adler32";
 4 $level = 9;
 5 
 6 echo "字符串长度:";
 7 echo strlen($string);
 8 
 9 echo "\r\n-------------------------------\r\ngzcompress压缩后长度:";
10 $zlib = gzcompress($string, $level);
11 echo strlen($zlib);
12 file_put_contents('zlib.txt', $zlib);
13 
14 $src_zlib = substr($zlib, 2, -4);
15 echo "\r\nzlib还原: " . gzinflate($src_zlib);
16 
17 $zlib_header = pack("H*", '78DA');
18 /*
19 0,1   01
20 2,3,4 5e
21 -1,6  9c
22 7+    da
23  */
24 echo "\r\nzlib-header(2位): " . bin2hex($zlib_header);
25 echo "\r\nADLER32校验傎: ";
26 $adler32 = hash('adler32', $string);
27 $zlib_adler32 = pack("H*", $adler32);
28 echo $adler32;
29 
30 echo "\r\n-------------------------------\r\ngzencode压缩后长度:";
31 $gzip = gzencode($string, $level);
32 echo strlen($gzip);
33 file_put_contents('gzip.txt', $gzip);
34 
35 $src_gzip = substr($gzip, 10, -8);
36 echo "\r\ngzip还原: " . gzinflate($src_gzip);
37 $gzip_header = pack("H*", '1F8B0800000000000003');
38 echo "\r\ngzip-header(20位): " . bin2hex($gzip_header);
39 
40 function revx_split($str){
41     return implode('', array_reverse(str_split(sprintf("%08X", $str), 2)));
42 }
43 
44 $crc32 = revx_split(crc32($string));
45 $gzip_crc32 = pack("H*", $crc32);
46 $length = revx_split(strlen($string));
47 $gzip_length = pack("H*", $length);
48 echo "\r\ngzip-crc32: {$crc32}";
49 echo "\r\ngzip-Length: {$length}";
50 
51 echo "\r\n-------------------------------\r\ngzdeflate压缩后长度:";
52 $deflate = gzdeflate($string, $level);
53 echo strlen($deflate);
54 file_put_contents('deflate.txt', $deflate);
55 
56 echo "\r\n-------------------------------\r\n用gzdecode解压gzdeflate:";
57 echo file_put_contents('gzdecode.gz', $gzip_header . $deflate . $gzip_crc32 . $gzip_length);
58 
59 echo "\r\n-------------------------------\r\n用gzuncompress解压gzdeflate:";
60 echo gzuncompress($zlib_header . $deflate . $zlib_adler32);

 

posted @ 2013-03-09 16:15  无嗔  阅读(3154)  评论(2编辑  收藏