Re: cin.get hang with CGI and IIS

From:
Ulrich Eckhardt <eckhardt@satorlaser.com>
Newsgroups:
microsoft.public.vc.language
Date:
Tue, 18 Dec 2007 11:19:23 +0100
Message-ID:
<dejk35-d3u.ln1@satorlaser.homedns.org>
Chris wrote:

On Dec 17, 8:11 am, Ulrich Eckhardt <eckha...@satorlaser.com> wrote:

Chris wrote:

Hi, I'm using CGI with MS IIS and Visual Studio 2003.


CGIs simply call programs and communicate with them via stdin/stdout. Can
you reproduce the problem outside IIS?

My problem is when I'm trying to read post data, I use
cin.get(buffer, size), where buffer is a new char[size + 1] and size
is the atoi of getenv("CONTENT_LENGTH").


atoi() has its dangers, so I wouldn't use it. 'new' also has its dangers,
so a 'vector<char> buffer(size+1)' should be better.

My problem is, it cuts off one character at the end. And if I use
cin.get(buffer, size + 1), it just sits there waiting for more data.

Do I have to roll my own solution, or use fread? Is there some way to
use cin.get work for me, without having to call it twice (the second
time calling cin.get(buffer[size-1])?


Chris, I'm only guessing what could cause that, but are you perhaps
bitten by the CR/LF conversion from DOS? I know that HTTP uses '\r\n' as
line terminator and that probably includes the content length. If your
program then reads a line and has the CR/LF converted to a single '\n',
you will obviously be short one character.

Uli

Well,

#1) how do you recommend attempted recreation? set the environment
variables and then pipe a known file in?


Yes. If that doesn't help, obviously IIS is doing something differently.
Note that I don't have IIS nor do I know anything about it (well, it's an
HTTP server) so I can't recreate your problems otherwise.
 

#2) What are the dangers involved in new and atoi?


Creating memory leaks and invoking undefined behaviour. The problem is
mainly concerning error-handling, for resources stored in raw pointers it
should be fairly obvious, for atoi() it's the fact that it doesn't signal
errors.

#3) Finally, I used _setmode to set stdin as binary and noticed that
when doing a post, there's no CR/LF characters.


What if you set it to text? Are there CR/LF pairs then? Maybe IIS actively
filters the CR/LF pairs but doesn't adjust the content length?

Uli

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