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Router
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|-- 192.168.0.2 <----> 192.168.0.1 (Client1 on LAN1)
|-- 172.16.0.2 <----> 172.16.0.1 (Client1 on LAN2)
|-- 10.10.0.2 <----> 10.10.0.1 (Client1 on LAN3)
Machines Specifications
Router
Windows XP Professional with Service Pack 1
Windows 2000 Server (Dual Boot)
Microsoft Visual Studio 6.0
AMD K6-II 500 MHZ, 256MB RAM
3Com Etherlink III ISAPNP Ethernet Adapter 10Mbps
HP Ethernet with LAN remote power Adapter 10/100 Mbps (PCI)
Intel 21143-Based PCI Fast Ethernet Adapter 10/100 Mbps
Client 1 on LAN 1
Windows 2000 Professional with SP3
Microsoft Visual Studio 6.0
Pentium II 450 MHZ, 256 MB RAM
Realtek RTL8029(AS) PCI Ethernet Adapter 10Mbps
Client 1 on LAN 2
Windows 2000 Professional with SP3
Microsoft Visual Studio 6.0
Pentium III 600 MHz, 128 MB Ram
3Com EtherLink XL 10/100 PCI For Complete PC Management NIC (3C905C-TX)
Client 1 on LAN 3
Windows 2000 Professional with SP3
Microsoft Visual Studio 6.0
Pentium II 266 MHz, 128 MB Ram
Linksys LNE 100 TX Fast Ethernet Adapter (PCI)
This is my network topology. A machine acting as a router is connected to three other machines acting as three different LANs. The problem is with the behaviour of Microsoft’s API Function GetAdaptersInfo(). This function gives complete information about any NIC in a PC such as MAC Address, IP Address, Subnet Mask, Default Gateway etc.
This function works fine when all the PCs are up and network is running. But fails when any one PC from any network is off. GetAdaptersInfo() gives 0.0.0.0 as IP Address, subnet mask etc. of the NIC whose associated network is down. There is nothing documented about this behaviour in MSDN.
One more strange thing is that this function has different behaviour on above four PCs. It works fine regardless of network is up or down on Client1 on LAN1 and on Client1 on LAN2 but fails (means give 0.0.0.0) on Router machine and Client3 on LAN3.
I am unable to understand who is causing this problem.
Whether it is operating system?
Whether it is NIC driver?
or simply it is a bug of GetAdaptersInfo()?
Anybody help please!!!!!!!!!!!1
Thanks
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Hi All,
I am using VC++ 6.0 on a client running Win98.
I need to access a datasource on a webserver running NT 4.0.
The remote database is Access97.
The remote datasource is already set up as a System DSN via ODBC.
The remote datasource is not accessible via a LAN - it must be accessed by domain name or IP address.
I have searced the CDAO documentation but can't determine how to connect to a remote datasource via tcp/ip
Can anyone help with this?
My goal is to populate a combo box with a query from this remote datasource.
I tried ActiveX controls, but the intricacies of creating wrapper classes is beyond me at this time.
It would be faster for me to rewrite the entire project in Visual Basic just so I can use an ActiveX control but I really want to do this in C++.
Does anyone know of perhaps a pre-built class I can drop into my project?
My workaround at this time involves calling a Cold Fusion page on the server and parsing the returned text into the combobox. Very ugly.
Thanks!!!
EDIT
====
Thanks anyways! I cut the Gordian knot and just ported the Access DB over to a MySQL DB and I can connect with a standard ODBC string 
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I am trying t create a switch statment that sitches on names in an array
but I can only come up with a the loop below.
Is there a function that will return the numeric value of a char?
char Names[50]<br />
<br />
for(int i=0; i<50; i++){<br />
int temp = (int)Names[i];<br />
if(temp = the number value of 'pla')<br />
then do some stuff<br />
<br />
if(temp = the number value of 'oct'0)<br />
then do some more stuff<br />
}<br />
Steven
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johnstonsk wrote:
the number value of 'pla'
You can not turn a string into a single int and then compair the ints...
[EDIT]
Well if your string is exactly 4 characters you can use a cast like you did in your code sample but this is the only case that it would reliably work...
[/EDIT]
John
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some of the valuse in the char array vary
pla
oct
frozen
stopped
etc.....
steven
any ideas on how to do this?
steven
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If there are more than 4 characters it won't work with just a cast because an int is 4 characters of data. Since there are only 26 letters and less than 4 billion possible english words ( I assume all are spelled correctly and there are no proper names...) you could come up with an algorithm to convert the words to 4 byte numbers.
John
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you can do it on a char level, but you described a string...
'pla' is impossible
What are you trying to do, to comapre strings ?
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What I am trying to do is I have read in a file and put specific name into an array.
For eash name in the array I want to do something different.
I would like to do a switch statemnt on each name in the name array, but a switch has to be an int.
So, I was going to try to spin through the array and for each element in the char array I was going to get its numeric value and compare it to the numeric value of the char I was looking for.
If the numeric values were the same then the chars must be the same and then we have a match.
I hope that all made sense.
thanks, steven
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Well if your string is exactly 4 characters you can use a cast like you did in your code sample but this is the only case that it would reliably work...
John
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Do you have any other ways that I can spin through an array and for each element in it do something different depending on the name??
steven
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Why can't you use a string compare function and put the actual strings in if statements instead of a big switch statement.
John
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This "char Names[50];" is an array of characters not strings/names. If if was a list of known names then you could use "if else" as follows:
if( !strcmp(Names[i],"some name" )
else if( !strcmp(Names[i],"some other name" )
This is 'C' code; in both 'C' and 'C++' there are more complicated, to start with, yet easier to maintain methods of accomplishing your goal.
INTP
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I know I am asking why you are doing something rather than just answering your question so I apologize.
First, there is a way to get the numeric value of a char. Just cast the char as an int and there you go.
Second, there is no numeric value of a string so you can't do what you are asking.
In your sample code, you show:
char Names[50]
for(int i=0; i<50; i++)
{
int temp = (int)Names[i]; // reinitialization error?
if(temp = the number value of 'pla')
then do some stuff;
if(temp = the number value of 'oct'0)
then do some more stuff;
}
Where is your switch statement?
Are you simulating the switch with the if statements?
In the sample shown, you have a single name which can be up to 50 chars long. You are merely comparing 1 letter from that same name at a time. If you need 50 names, you'll need to define a 2 dimensional array like char Names[50][30];
If you absolutely have to use a switch statement (like a school project) you can create a struct which contains a key value and when you populate the struct you can increment the key.
struct NameStruct
{
char Names[50][30];
int key;
};
Then you can use the NameStruct.key value in your switch statement and access the names with NameStruct.Names[key]
If your end goal is to be able to loop through an array of strings and take a different action for each string you could try:
char Names[50][MAX_NAME_LENGTH];
int x;
for (x = 0; x < MAX_NAME_LENGTH; x++)
{
if(!strcmp(Names[x], "Text to compare"))
DoSomething();
if(!strcmp(Names[x], "Other text to compare"))
DoSomethingElse();
........
if(!strcmp(Names[x], "Last text to compare"))
DoSomethingEtirelyDifferent();
}
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for (x = 0; x < MAX_NAME_LENGTH; x++)
Should be
for (x = 0; x < 50; x++)
and you should use the 'if else' construct to avoid unneeded calls to strcmp().
INTP
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John R. Shaw wrote:
for (x = 0; x < MAX_NAME_LENGTH; x++)
Should be
for (x = 0; x < 50; x++)
and you should use the 'if else' construct to avoid unneeded calls to strcmp().
 You are correct of course. Thank you!
I'm going to live forever or die trying!
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Believe me I don't have to do this for a school project.
I have created a tool that display flight simulator data in real time.
Long story short:
(this is just another feature of the program)
The flight simulator writes to a file and I use the getline() function to get the names of signals that the sim wrote and put them in TSimHeader_arr[0].Name[i] which is an array in a struct.
anyways I think the function (char)strdup(name.c_str())isn't putting them in the char array correctly.
Because when I read them bach out they are strange characters.
I don't know how to do this.
Does anyone???
steven
void setInitialValues(){<br />
sSignal.SimWriteFlag=1; <br />
sSignal.DisplayReadFlag=0; <br />
sHeader.SimStatus=setSimStatus();<br />
<br />
string name,unit,min,max,value;<br />
<br />
for(int i=0; i<sizeof(sHeader.Name); i++){<br />
getline(fin, name, ',');<br />
<br />
if(name == "STOP")<br />
break;<br />
getline(fin, unit, ',');<br />
getline(fin, min, ',');<br />
getline(fin, max, ',');<br />
getline(fin, value);<br />
<br />
TSimHeader_arr[0].Name[i] = (char)strdup(name.c_str()); <br />
TSimHeader_arr[0].Unit[i] = (char)strdup(unit.c_str()); <br />
TSimHeader_arr[0].Min[i] = atof(min.c_str());<br />
TSimHeader_arr[0].Max[i] = atof(max.c_str());<br />
TSimSignal_arr[0].Value[i] = atof(value.c_str());<br />
<br />
<br />
<br />
sig_count ++;<br />
<br />
}<br />
<br />
TSimHeader_arr[0].SignalCount = sig_count;<br />
<br />
writeRfmData();<br />
createRandNum();<br />
}
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Prototype: char *_strdup( const char *strSource );
Bad: (char)strdup(name.c_str()); // this is incorrect usage
Good: strdup(name.c_str()); // normal usage
Ok: (char*)strdup(name.c_str()); // this is redundant
INTP
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If it's a simple piece of work you want to do for each item, just use a chain of if statements using strcmp() to compare.
If it's harder (which I assume it is since you've got 50 entries in your table), define a function pointer type:
typedef int (PFNTASK*)(
const char* szName,
);
int DoPla( const char* szName, );
int DoOct( const char* szName, );Then define a structure:
typedef struct
{
const char* szName;
PFNTASK pfnTask;
} TaskEntry;Now define your array:
TaskEntry namesAndTasks[] =
{
{ "pla", DoPla },
{ "oct", DoOct }
};Finally, search for the operation to perform:
for( int iTask = 0; iTask < 50; ++i )
{
if ( strcmp(
temp,
namesAndTasks[iTask].szName
) == 0 )
{
namesAndTasks.pfnTask( temp, );
break;
}
}Usually quite effective. I prefer it to a long switch statement, even when I have sequential integer codes to switch on.
Because the code size is smaller, this can sometimes run faster than a huge switch statement too.
--
Mike Dimmick
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Mike Dimmick wrote:
Usually quite effective. I prefer it to a long switch statement, even when I have sequential integer codes to switch on.
Because the code size is smaller, this can sometimes run faster than a huge switch statement too.
Actually, most modern compilers (and this includes VC) translate switch statements on large numbers of integer variables to jump tables.
On C#, switches on strings are allowed, and above a certain threshold the compiler generates a Hashtable with jump locations and the strings as a key.
ORACLE One Real A$#h%le Called Lary Ellison
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I'm sure they do. I meant from a code maintenance point of view: it's a lot easier to maintain (I think) a set of moderately simple functions than it is to maintain a 500-line function with a huge switch statement in it.
Of course, you can still code the dispatching mechanism like:
switch ( iValue )
{
case 0:
HandleCase0();
break;
case 1:
HandleCase1();
break;
default:
assert( !"Error in case statement!" );
break;
}but that gets very boring, very quickly. Unless there was some clear profiling indication that the table version was too slow for a given code path, I'd stick to that.
As for how common libraries implement it: in Win32 programming, you typically write a big switch statement. MFC's message maps are table-based (complicated somewhat by supporting ranges). ATL's BEGIN_MSG_MAP family of macros mask a honking great if/else if chain.
The hash table implementation is probably nicer if you have a fixed set and can calculate it all in advance, and either know that you can't get false-positives or check that there's a match before you jump. For general, intelligible coding, I use the array. The threshold is obviously because the hash table has an overhead in the hash function and the extra check in any case.
MFC has, IIRC, a small hash table for each class with a message map which contains the most recently used message map entries, so it doesn't have to search the whole table (and potentially the base class's table, and its base class, and so on down) every time a common message arrives.
My solution does require that all your operations will take the same parameters. This ain't necessarily so. One of my implementations was for a varargs function where you had command identifiers, and each command could take 0, 1 or 2 parameters. So I had to have a parameter count field as part of my jump table structure which indicated what you needed to cast the function pointer to. Again, MFC does something similar for its message maps.
--
Mike Dimmick
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Mike Dimmick wrote:
but that gets very boring, very quickly. Unless there was some clear profiling indication that the table version was too slow for a given code path, I'd stick to that.
I agree. Actually, everytime I see a huge switch statement (as I'm an OOP die-hard) I start to ask what's wrong with the design, since this should be solved by a virtual method call. Not all switches should be virtual calls, but normally they indicate some design flaw in an OOP world.
ORACLE One Real A$#h%le Called Lary Ellison
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Generally I'd agree, but in the case where you'd basically need an object for each 'arm' of the switch statement which you wouldn't use anywhere else, it's wasteful of programming time. The virtual method case is generally more maintainable, sure.
Of course you may well need some kind of factory method or object to create the objects, so you're either back to the switch statement again, or some other kind of creation table.
Languages with reflection can of course use the name of the class in order to create one; the advantage that MFC's Run-time Class Information has over the C++ language's standard RTTI is that you can (if your class uses DECLARE_DYNCREATE or DECLARE_SERIAL) perform dynamic creation through the RUNTIME_CLASS macro.
--
Mike Dimmick
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/* ATOF.C: This program shows how numbers stored
* as strings can be converted to numeric values
* using the atof, atoi, and atol functions.
*/
#include <stdlib.h>
#include <stdio.h>
void main( void )
{
char *s; double x; int i; long l;
s = " -2309.12E-15"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = "7.8912654773d210"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = " -9885 pigs"; /* Test of atoi */
i = atoi( s );
printf( "atoi test: ASCII string: %s\t\tinteger: %d\n", s, i );
s = "98854 dollars"; /* Test of atol */
l = atol( s );
printf( "atol test: ASCII string: %s\t\tlong: %ld\n", s, l );
}
Output
atof test: ASCII string: -2309.12E-15 float: -2.309120e-012
atof test: ASCII string: 7.8912654773d210 float: 7.891265e+210
atoi test: ASCII string: -9885 pigs integer: -9885
atol test: ASCII string: 98854 dollars long: 98854
Dr Abudawood
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Hi,
I want to add a window to my application that will show a list of items.
For that I create a CFrameWand with a ClistCtrl view inside.
the problem is that the cunstructor of CFrameWnd is protected by default.
How can I pop up the window ?
Is there a method to do it without touching the specific constructor ?
Shay
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I assume you are talking about a CFrameWnd derrived class of your own created by the class wizzard. You can either use dynamic creation (IMPLEMENT_DYANMIC ...) or make the constructor public yourself. I do the second all the time but in the past I have done some work with creating class instances using the GetRuntimeClass() stuff..
John
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