regex - Perl 正则表达式捕获

Question

我有以下文字:

GET /mac/_base_v1/images/chrome/background_repeat.jpg HTTP/1.1  
Host: www.microsoft.com  
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20100101 Firefox/13.0  
Accept: image/png,image/*;q=0.8,*/*;q=0.5  
Accept-Language: en-us,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://www.microsoft.com/mac/base-css  
DNT: 1  
Connection: keep-alive  
HTTP/1.1 200 OK  
Cache-Control: max-age=900  
Content-Type: image/jpegGET /mac/_base_v1/modules/button/images  /buttonlarge_yellownormal.png HTTP/1.1  
Host: www.microsoft.com  
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20100101 Firefox/13.0   
Accept: image/png,image/*;q=0.8,*/*;q=0.5  
Accept-Language: en-us,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://www.microsoft.com/mac/css  
DNT: 1  

和下面的 Perl 正则表达式

while ($1 =~m/((GET|PUT|POST|CONNECT)\s+\S+)(?:(?!GET|PUT|POST|CONNECT\s+\S+).)*?Host:\s([^\n]+).*?User-Agent:\s([^\n]+).*?Referer:\s([^\n]+).*?Connection:/msg) {
    # do something
}

它匹配这个很好

GET /mac/_base_v1/modules/button/images/buttonlarge_yellownormal.png  
www.microsoft.com  
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20100101 Firefox/13.0  
http://www.microsoft.com/mac/css  

但是，我还需要它来检查以下文本:

GET /vi/k_dbVP4r4V4/hqdefault.jpg HTTP/1.1  
Host: i.ytimg.com  
User-Agent: Apple iPad v4.3.5 YouTube v1.0.0.8L1  
Accept-Language: en-us, *;q=0.5  
Gdata-Version: 2  
X-Gdata-Client: ytapi-apple-ipad  
Accept: */*  
Accept-Encoding: gzip, deflate  
Connection: keep-alive  
Q2J}  

并匹配以下内容:

GET /vi/k_dbVP4r4V4/hqdefault.jpg HTTP/1.1  
i.ytimg.com  
Apple iPad v4.3.5 YouTube v1.0.0.8L1  

同时仍然能够匹配成功呈现的先前文本。

Answer 1

HTTP 请求和响应 header 并不像预期的那样容易解析。例如，以下都是等价的:

Accept-Encoding: gzip, deflate

Accept-Encoding: gzip,
    deflate

Accept-Encoding: gzip
Accept-Encoding: deflate

因此，我建议您使用现有的解析器

use strict;
use warnings;
use feature qw( say );
use HTTP::Request qw( );

my $s = <<'__EOI__';
GET /mac/_base_v1/images/chrome/background_repeat.jpg HTTP/1.1  
Host: www.microsoft.com  
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20100101 Firefox/13.0  
Accept: image/png,image/*;q=0.8,*/*;q=0.5  
Accept-Language: en-us,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://www.microsoft.com/mac/base-css  
DNT: 1  
Connection: keep-alive  
HTTP/1.1 200 OK  
Cache-Control: max-age=900  
Content-Type: image/jpegGET /mac/_base_v1/modules/button/images  /buttonlarge_yellownormal.png HTTP/1.1  
Host: www.microsoft.com  
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:13.0) Gecko/20100101 Firefox/13.0   
Accept: image/png,image/*;q=0.8,*/*;q=0.5  
Accept-Language: en-us,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://www.microsoft.com/mac/css  
DNT: 1  
__EOI__

my ($raw_req, $raw_resp) = split qr{(?=^HTTP/)}m, $s;
my $req = HTTP::Request->parse($raw_req);
say $req->method;
say $req->url;
say $req->user_agent;
say $req->header('User-Agent');  # Same as previous