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If you want simple hack, then
std::string s = "/work1/data/xxxx/yyy/file_name.txt";
std::string::size_type lastSep = s.find_last_of('/');
if (lastSep != std::string::npos)
s.erase(lastSep);
If you want a nice cross-platform for manipulating file paths, I'll recommend Boost.FileSystem[^], where you can do this:
boost::filesystem::path justThePath("/work1/data/xxxx/yyy/file_name.txt");
justThePath.remove_filename();
Oh - and it'll happily deal with Windows vs Unix path conventions.
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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ksaw123 wrote: how to extract "only" the path name without the file name in C++
Have you tried PathRemoveFileSpec()?
"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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Hi!
I've been experimenting with custom flow control techniques for bulk transfers over UDP when I discovered something very weird. Please take a look at the following code: it just sends UDP datagrams of size 1400 bytes in an endless loop to some IP address.
SOCKET sock = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
sockaddr_in targetAddr;
targetAddr.sin_addr.s_addr = inet_addr( "...some IP..." );
targetAddr.sin_family = AF_INET;
targetAddr.sin_port = htons( 1337 );
char arr[1400];
long long sent = 0;
while( !kbhit() )
{
for( int i=0; i<1000; ++i )
{
long res;
if( (res=sendto( sock, arr, 1400, 0, (sockaddr*)&targetAddr, sizeof( targetAddr ) )) == SOCKET_ERROR )
{
printf("Error: %d\n", WSAGetLastError() );
return -1;
}
sent += res;
}
printf("\r%d MBs sent", (long)(sent >> 20) );
}
When I run the program, every sendto() call succeeds and reports having sent 1400 bytes of data. The interesting thing is that I get a transfer rate of just about 50 MB/s but 100% CPU usage on one core (mostly kernel-mode). Now:
-- my computer is connected to an Ethernet 100BaseTX network, which obviously does not support the transfer rate above, so datagrams get already lost before even reaching the network. Why does sendto() then reports having sent the data, what is more, why does it not block when I/O buffers fills up? (The documentation says that it should.)
-- how on Earth can someone utilize the full potential of a - say - Gigabit Ethernet network if just sending data even at half of its capacity already causes maximum CPU load?
So, what am I doing wrong, why on Earth does sendto() takes so long?
Any suggestion is very welcome, thanks,
clayman
P.S.: I've run a test with 140 bytes of data each time, and the transfer rate basically dropped to 5 MB/s -- so the _number_ of sendto() calls seems to be the bottle-neck.
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Yes, I do, but I sent the program to some fearless friends without firewall, and they experienced similar results on Windows XP. Meanwhile, I tested the code on other OS-es as well.
So the measurements are for 1400 byte UDP daragrams:
- Windows XP SP 3 (w/ fw): 66 MB/s, 100% CPU-usage/core (mostly kernel)
- Windows 7 RC1 (no firewall): 11.5 MB/s, but only 20% CPU-usage/core, seems to take interface capacity into account (which is, after all, what I would expect in the first place)
- Ubuntu 8.10 on VMware with Tools: 120 MB/s, 100% CPU-usage/core (mostly kernel)
In contrast, I've been able to push data through a loopback TCP connection at 330 MB/s on WindowsXP/CLR, and nearly 500MB/s on Ubuntu.
modified on Tuesday, July 7, 2009 11:13 PM
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1. For Gigabyte transfer, firstly CPU speed is a big factor, so may i know, whats the speed of the CPU.
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Thank you for your question. Test machine was a Intel P35 chipset-based system, Core 2 Duo E6400 2133 MHz CPU, 2GB of RAM, Gigabyte P35-DS3 motherboard.
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CPU is not the problem here,
here the high speed bus to interface to your NIC is the problem.
Check the speed of the bus, it has lot of do. If the bus cannot support more than 100-200 MB/s then we cannot do anything. 
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It is on a PCI-E 1.0 lane, which is 250 MB/s, it should be, and it is enough on Ubuntu 8.10 (at least for 1 gigabit). The question is, what causes the 100% CPU load on Windows XP even at 60MB/s, and on Ubuntu at 130 MB/s.
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http://www.wireshark.org/[^]
for all your network debuggin needs. this is honestly the best thing since sliced bread for networking tools
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I took your advice, and did some testing in Wireshark. Based on "Identification" field in the IP header, which seems to be assigned continuously, everything looks fine down to bottom of the IP layer, but then Wireshark only registers every fifth or so packets as Ethernet frames, which correlaltes well with the fact that a ~60 MB/s datastreams goes down the pipe with a capacity of a 12.5 MB/s (100mbit).
As I've learned, this layer is usually implemented in the network card driver. A poorly written driver software of interface specification may be the cause of this "no block" problem.
As for the transfer rate, I'm still puzzled.
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clayman87 wrote: Why does sendto() then reports having sent the data...
One of the fundamental differences between UDP and TCP is that UDP is an unreliable transport service because it does not guarantee data packet delivery and no notification is sent if a packet is not delivered.
"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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Let me rephrase my question.
MSDN states: "If no buffer space is available within the transport system to hold the data to be transmitted, sendto will block unless the socket has been placed in a nonblocking mode".
In the protocol stack, at which layer is this buffer space located?
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Alternatively consider TCP for bulk data transfer. With UDP you would also need to do more housekeeping, like throwing away duplicate packages and resending missing ones.
With TCP it could be good to use a large send buffer (64KB or more per sending socket). This can improve the throughput because the kernel will have data available as soon as it can send more, without waiting or notifying user space application.
Hope it helps.
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As far as I know, there's no way to establish a TCP connection between two passive (behind NAT) clients, which is partly what I want to accomplish.
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clayman87 wrote: As far as I know, there's no way to establish a TCP connection between two passive (behind NAT) clients, which is partly what I want to accomplish.
Peer to peer... no, but maybe with a peer in the middle (one needs to be able to accept incoming connections).
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Yes, a third party is inherently needed to establish a connection (STUN server), but relaying all the traffic through it is just not an option. As I know of no way to do this separately (handshake vs. traffic) with TCP, I was forced to switch to UDP.
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Exploring the alternatives... since the routers between LAN and internet are the problem, how about Zeroconf/UPnP (or another application level protocol) that would allow incoming TCP data streams. I am not sure if it is an option in reality.
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Well, I didn't want to go that way, but I'm going to be out of options very soon, it seems. Thanks for the replies.
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Is it possible that your Ethernet hardware does not have a controller? Should not PHY only adapters use CPU to move data?
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I am having a VC++ MFC Dialog based application,where I have a module in which
some Convertion function takes place.Here it has to convert some 10 groups.Each group i.e 10 groups are split into 10 functions..for example:
function1()
{
//code
}
function2()
{
//code
}...and so on..till
function10()
{
//code
}
Here these codes are written for "convertion form".I have provided a button from the main form."Convert",if I click on that it will process all the 10 functions, converts and the converted 10 values are displayed in 10 edit boxes in the convertion form once the convertion is over.In between,when the convertion is taking place I have also placed a dialog box which says it is in progress.
Now I want to add a progress bar in this dialog box so that along with the message,the progress bar can show how much is completed..Can anyone please suggest me how to achieve this solution..
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kokilag wrote: Now I want to add a progress bar in this dialog box so that along with the message,the progress bar can show how much is completed..Can anyone please suggest me how to achieve this solution..
Just add a progress bar control to the dialog's template (i.e., the .rc file). Associate a CProgressCtrl member variable with that control. Call its SetRange() method.
"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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As David said use CProgressCtrl::SetRange with the values 1 and 100.
Call CProgressCtrl::SetStep with a value of 10.
After each function completes call CProgressCtrl::StepIt to advance the progress control.
«_Superman_»
I love work. It gives me something to do between weekends.
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OK..but where should I include the progressbar..Is it in that dialog?and these statements,ie..
CProgressCtrl::SetRange
CProgressCtrl::SetStep
CProgressCtrl::StepIt
Should I include these statements in Create function of the progressbar i.e,
void fun()::CreateProgressBar()
{
}
or in
void fun()::OnOutofmemoryProgress1(NMHDR* pNMHDR, LRESULT* pResult)
{
}
coz once I drag the progressbar from the toolbox into the form and double click on that,then the above function,i.e void fun()::OnOutofmemoryProgress1(NMHDR* pNMHDR, LRESULT* pResult)
{
}
will be taken by default.So what should I go?
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Drag the progress bar onto the dialog.
Right click on the progress and select Add Variable.
Add a variable of type CProgressCtrl, let's say prg
In the OnInitDialog function of the dialog class do prg.SetRange(0, 100); and prg.SetStep(10);
In the place where you're calling your functions you call prg.StepIt().
function1();
prg.StepIt();
function2();
prg.StepIt();
function3();
prg.StepIt();
.
.
.
«_Superman_»
I love work. It gives me something to do between weekends.
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