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Full Discussion: to convert int to hex
Top Forums Programming to convert int to hex Post 302152328 by DreamWarrior on Wednesday 19th of December 2007 03:35:19 PM
Old 12-19-2007
Quote:
Originally Posted by WebKruncher
#include <string>
#include <sstream>
using namespace std;

//This spends some extra cycles, offers simplicity, elegance and safety.
string IntToHexString(int i)
{
stringstream ss;
ss<<"0x"<<hex<<i;
string retval; retval=ss.str().c_str();
return retval;
}


//usage
cout<<"Hex for 32 is "<<IntToHexString(32)<<endl;
// as always handle your seh exceptions with a try / catch.
Correct me if I am wrong, but it also either 1) leaks memory, 2) reads a wild pointer, or 3) is thread unsafe:

Logically:

The .c_str call must return a "string".

Given:

A string is a pointer to a "NULL terminated string."

A "NULL terminated string" is a sequence of characters terminated by a '\0' character; we shall call this a "buffer".

A buffer resides somewhere in memory.

Therefore:

The .c_str call must return a pointer a buffer containing its contents.

In order not to leak, the above buffer must be freed at some point. To be freed the buffer must still referenced. Since the caller of IntToHexString does not take a reference then to not leak, either a) someone else must free it or b) someone else has a reference to it.

If (a) then the "somewhere" else may be the destructor of stringstream class. I presume this destructor is called when the stack for your function is cleaned up. This means that the string returned by IntToHexString becomes "wild" as soon as it returns.

If (b) then the buffer can be overwritten at some point by the class still holding a reference to it and therefore can not be thread safe.

If neither a nor b occurs then the code leaks. The only way this is untrue is if the compiler takes care of destroying the string returned by IntToHexString.
 

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LEARN ABOUT SUSE

gnutls_hex2bin

gnutls_hex2bin(3)						      gnutls							 gnutls_hex2bin(3)

NAME

       gnutls_hex2bin - convert hex string into binary buffer.

SYNOPSIS

       #include <gnutls/gnutls.h>

       int gnutls_hex2bin(const char * hex_data, size_t hex_size, char * bin_data, size_t * bin_size);

ARGUMENTS

       const char * hex_data
		   string with data in hex format

       size_t hex_size
		   size of hex data

       char * bin_data
		   output array with binary data

       size_t * bin_size
		   when calling *bin_size should hold size of bin_data, on return will hold actual size of bin_data.

DESCRIPTION

       Convert a buffer with hex data to binary data.

RETURNS

       GNUTLS_E_SUCCESS on success, otherwise an error.

SINCE

       2.4.0

REPORTING BUGS

       Report	bugs   to   <bug-gnutls@gnu.org>.   GnuTLS  home  page:  http://www.gnu.org/software/gnutls/  General  help  using  GNU  software:
       http://www.gnu.org/gethelp/

COPYRIGHT

       Copyright (C) 2008 Free Software Foundation.
       Copying and distribution of this file, with or without modification, are permitted in any medium without  royalty  provided  the  copyright
       notice and this notice are preserved.

SEE ALSO

       The  full documentation for gnutls is maintained as a Texinfo manual.  If the info and gnutls programs are properly installed at your site,
       the command

	      info gnutls

       should give you access to the complete manual.

gnutls								       2.8.6							 gnutls_hex2bin(3)
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