Parsing char array in C++

Question

I'm coding a httpserver and I'm stuck at parsing GET requests. How would I parse a char buffer with something like

GET /images/logo.png HTTP/1.1

So that I only get the path and file extension but ignore the other parts?

How would I use substr to get that certain portion? I can set a start value but the end part is never certain. — Kraffs
– Kraffs, Commented Aug 13, 2011 at 0:19
Have you read the specs? You can find them here: w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1 and you'll see what are the parts of the request line and how they're delimited... — Eugen Constantin Dinca
– Eugen Constantin Dinca, Commented Aug 13, 2011 at 0:23
the HTTP1.1 protocol requires the browser to include a hostname and the hostname wont always be the same sadly. — Kraffs
– Kraffs, Commented Aug 13, 2011 at 0:25
Without having set out to be nasty, if you can't parse this string perhaps an HTTP server is not the best project for you at this stage! — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Aug 13, 2011 at 0:31

ildjarn · Accepted Answer · 2011-08-13 00:26:16Z

2

You don't say specifically say what sort of storage this string is in - simple char* or some string class.

So, in general, you could either do it the rather simple and dirty way, by splitting the string on the space character, and taking the second or middle section. Or, a better approach would be to get familiar with Regular Expressions. C++ has several regex libraries - Boost is well regarded.

edited Aug 13, 2011 at 0:26

ildjarn

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answered Aug 13, 2011 at 0:21

iandotkelly

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9 Comments

Kraffs Over a year ago

It is stored in a char array with the size of 2042 bytes. Is there any simple way to do this without using a library?

iandotkelly Over a year ago

Yes, you could iterate through the char array, and only pull out characters between the first and second space into a second array. I would recommend using regex's however - it would then just become a call to match the input string against a pattern - and the library does all the hard work.

iandotkelly Over a year ago

You need to be careful with URL encoding too - how are spaces encoded in this string, '%20' or similar?

ildjarn Over a year ago

@Kraffs : VC++ 2010 comes with an implementation of C++0x's regex library, built-in -- see here for docs. Alternatively, you could use Boost.Xpressive, which is header-only (no building/linking required) unlike Boost.Regex.

john Over a year ago

strtok is the devil's function.

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