Re: [Boost-users] Why is asio clobbering my file before it can be sent?

18 Aug 2011

      Sorry to bother boost-users with a really dumb problem.

It turns out I was running the server and client from the same directory, so one was trying to read from the file while the other was trying to write to it.  

Thanks to those who replied~

--- On Thu, 8/18/11, Andrew Yancy  wrote:
...
From: Andrew Yancy 
Subject: Re: [Boost-users] Why is asio clobbering my file before it can be sent?
To: boost-users@lists.boost.org
Date: Thursday, August 18, 2011, 7:27 AM
Yes, tellg() was just saying that I
had reset the file location pointer, sorry about that. 
However, when I pause using a scanf statement, I can see
that the file's contents have disappeared by just looking in
the windows file browser (see the updated code below). 
Anyone know why that would happen?  Thanks again~
...
I've used the same boilerplate
boost::asio code for years to send a plain text file
"foo.txt" from a server back to a client and it has
always
worked fine.  Suddenly for no apparent reason, the
same
code I've always used with no problems now deletes
the
contents of foo.txt before it can actually be sent to
the
client.  I'm creating foo.txt with a different
program
now, but I don't see how that could make any
difference on
Win32.
Below is the relevant part of the code just before I
use
boost::asio::write to send the contents of foo.txt
back to
the client.  The
contents of the file are somehow lost when the file
name and
size are sent to the client.  Anyone know what's
going
on?  Is there any other information I can provide to
shed light on the problem?  Thanks very much for any
help~
int bar;
std::ifstream source_file("foo.txt", std::ios_base::binary
| std::ios_base::ate);
if (!source_file)
   return __LINE__;
size_t file_size = source_file.tellg();
source_file.seekg(0);
scanf("%d", &bar); //foo.txt is OK here
boost::asio::streambuf request;
std::ostream request_stream(&request);
request_stream << return_fn << "\n" <<
file_size << "\n\n";
boost::asio::write(socket, request);
scanf("%d", &bar); //foo.txt exists but has size 0 now
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