Qt-interest Archive, March 2007
Re: File read problem
Message 1 in thread
I even tried that It doesn't work.I dont know what's the problem.
Duane Hebert wrote:
>> The file* is the basic . It doesn't even work with that.
>>
>
> How about the fstream sample that I posted? What is the format of your
> text? Is it not ascii?
>
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Message 2 in thread
"Srikanth Bemineni" <sbemineni@xxxxxxxxxxxx> wrote in message
news:45E6180B.5080807@xxxxxxxxxxxxxxx
>I even tried that It doesn't work.I dont know what's the problem.
> Duane Hebert wrote:
>>> The file* is the basic . It doesn't even work with that.
>>>
>>
>> How about the fstream sample that I posted? What is the format of your
>> text? Is it not ascii?
Well that's pretty simple code. What's your debugger tell you?
At each line, you should be able to inspect
what getline() is returning. Are you sure this is a straight
text file? Are you trying this by itself or in the context of
some other code that may be trashing memory?
It's hard to offer more assistance without more information.
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Message 3 in thread
"Srikanth Bemineni" <sbemineni@xxxxxxxxxxxx> wrote in message
news:45E6180B.5080807@xxxxxxxxxxxxxxx
>I even tried that It doesn't work.I dont know what's the problem.
OK, I fixed a couple of typoes and this actually compiles and
runs. Copy your file to c:/test.txt (if your using windows
of change the filename if you're not)
I used it to open a 115000 line text file with
no problem. If it doesn't display all of your lines,
put a break point on the push_back and find the
last line that it reads and start debugging it.
#include <string>
#include <vector>
#include <fstream>
#include <iostream>
using namespace std;
int main() {
ifstream infile("c:/test.txt");
if(!infile.is_open()) return 1;
string buffer;
vector<string> vec;
while(getline(infile,buffer)) {
vec.push_back(buffer);
}
int x = vec.size();
for(std::vector<string>::iterator it = vec.begin(); it != vec.end(); ++it)
cout << *it << "\n";
system("pause");
return 0;
}
--
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Message 4 in thread
Thank you very much.I found out the problem.The problem is in QString
the databuffer which i was in using. what is the maximum size a QString
can hold.
Duane Hebert wrote:
> "Srikanth Bemineni" <sbemineni@xxxxxxxxxxxx> wrote in message
> news:45E6180B.5080807@xxxxxxxxxxxxxxx
>
>> I even tried that It doesn't work.I dont know what's the problem.
>>
>
> OK, I fixed a couple of typoes and this actually compiles and
> runs. Copy your file to c:/test.txt (if your using windows
> of change the filename if you're not)
>
> I used it to open a 115000 line text file with
> no problem. If it doesn't display all of your lines,
> put a break point on the push_back and find the
> last line that it reads and start debugging it.
>
> #include <string>
> #include <vector>
> #include <fstream>
> #include <iostream>
> using namespace std;
> int main() {
> ifstream infile("c:/test.txt");
> if(!infile.is_open()) return 1;
> string buffer;
> vector<string> vec;
> while(getline(infile,buffer)) {
> vec.push_back(buffer);
> }
> int x = vec.size();
> for(std::vector<string>::iterator it = vec.begin(); it != vec.end(); ++it)
> cout << *it << "\n";
> system("pause");
>
> return 0;
> }
>
>
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Message 5 in thread
"Srikanth Bemineni" <sbemineni@xxxxxxxxxxxx> wrote in message
news:45E63297.1050805@xxxxxxxxxxxxxxx
> Thank you very much.I found out the problem.The problem is in QString
> the databuffer which i was in using. what is the maximum size a QString
> can hold.
Not sure. I thought you originally said
that you were loading around 1000 lines of text.
Even if the lines are long <g> it doesn't sound like
you'd be exceeding the size of a QString.
--
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Message 6 in thread
After you sending the technique of storing the buffer in a vector i was
able to get back the whole accumulated buffer from the vector. In the
process I also accumulated the QString buffer I had, now when i retrieve
the QString buffer I got less number of values compared to the vector
buffer.So it is obvious that the QString after some limit avoids to
append any characters.
See the code below .
ifstream infile(fileName.ascii());
if(!infile.is_open()) return 1;
string buffer;
vector<string> buffervec;
while(getline(infile,buffer)) {
buffervec.push_back(buffer);
}
for(std::vector<string>::iterator it = buffervec.begin(); it !=
buffervec.end(); ++it)
{
qDebug("%s", ((string)(*it)).c_str());
dataBuffer.append(*it);
}
qDebug("------------------------------------------------------------------");
qDebug("%s", dataBuffer.ascii());
qDebug("------------------------------------------------------------------");
qDebug("databuffer count = %d", dataBuffer.length());
Duane Hebert wrote:
> "Srikanth Bemineni" <sbemineni@xxxxxxxxxxxx> wrote in message
> news:45E63297.1050805@xxxxxxxxxxxxxxx
>
>> Thank you very much.I found out the problem.The problem is in QString
>> the databuffer which i was in using. what is the maximum size a QString
>> can hold.
>>
>
> Not sure. I thought you originally said
> that you were loading around 1000 lines of text.
> Even if the lines are long <g> it doesn't sound like
> you'd be exceeding the size of a QString.
>
>
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>
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Message 7 in thread
On 01.03.07 10:57:03, Srikanth Bemineni wrote:
> After you sending the technique of storing the buffer in a vector i was able
> to get back the whole accumulated buffer from the vector. In the process I also
> accumulated the QString buffer I had, now when i retrieve the QString buffer I
> got less number of values compared to the vector buffer.So it is obvious that
> the QString after some limit avoids to append any characters.
No, QString does not do this. The only limiting factor can be your
memory, see qstring.cpp:operator+=. It grows the QString memory and
copies the characters from the appended string. Nothing more.
Also as I said in the other thread I read in a 16MB text file into a
qstring, no problem. How large is your file?
Andreas
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Message 8 in thread
Hi,
> After you sending the technique of storing the buffer in a vector i was
> able to get back the whole accumulated buffer from the vector. In the
> process I also accumulated the QString buffer I had, now when i retrieve
> the QString buffer I got less number of values compared to the vector
> buffer.So it is obvious that the QString after some limit avoids to
> append any characters.
OK, then this has nothing to do with reading files, we should be able to
reproduce without even reading a file.
I'm unable to reproduce anything using the following example, a modified
version of yours which doesn't read a file:
#include <qstring.h>
#include <vector>
#include <string>
using namespace std;
int main() {
const char data[] = "abcdefghijklmnopqrstuvwxyz0123456789";
const int SIZE = 100;
vector<string> buffervec;
for (int i = 0; i < SIZE; ++i)
buffervec.push_back(data);
QString dataBuffer;
for(vector<string>::iterator it = buffervec.begin(); it !=
buffervec.end(); ++it)
{
qDebug("%s", it->c_str());
dataBuffer.append(QString(*it));
}
qDebug("------------------------------------------------------------------");
qDebug("%s", dataBuffer.ascii());
qDebug("------------------------------------------------------------------");
qDebug("databuffer count = %d", dataBuffer.length());
}
Can you try this example? What do you see? What do you expect? If it
works for you, could you modify it so that it doesn't work?
Also what sort of file are you reading? What is its encoding? How big is it?
--
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Message 9 in thread
"Dimitri" <dimitri@xxxxxxxxxxxxx> wrote in message
news:es6va8$i4m$1@xxxxxxxxxxxxxxxxxxxxx
> for(vector<string>::iterator it = buffervec.begin(); it !=
> buffervec.end(); ++it)
> {
> qDebug("%s", it->c_str());
> dataBuffer.append(QString(*it));
> }
>
But he's doing:
qDebug("%s", ((string)(*it)).c_str());
dataBuffer.append(*it);
i.e. using a c style cast to cast *it to a string.
This is not necessary.
qDebug("%s",*it.c_str()); should work no?
But more probably the problem, is the next
line where he's appending a std::string to a QString.
Does that actually work?
Maybe changing that to:
databuffer.append(*it.c_str()); would be better.
Or will this cause problems with nulls?
Well he said it was a text file but...
--
[ signature omitted ]
Message 10 in thread
Hi,
> But he's doing:
>
> qDebug("%s", ((string)(*it)).c_str());
> dataBuffer.append(*it);
>
>
> i.e. using a c style cast to cast *it to a string.
> This is not necessary.
Indeed, "*it" is already a string. The cast is a no-op, which is why I
removed it. That shouldn't be an issue.
> qDebug("%s",*it.c_str()); should work no?
> But more probably the problem, is the next
> line where he's appending a std::string to a QString.
> Does that actually work?
>
> Maybe changing that to:
> databuffer.append(*it.c_str()); would be better.
> Or will this cause problems with nulls?
> Well he said it was a text file but...
Exactly, this is why I asked for the file or a self-contained example. I
suspect the file contains '\0' characters or that there are encoding
issues involved.
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Message 11 in thread
>After you sending the technique of storing the buffer in a vector i was
able to get back the whole accumulated >buffer from the vector. In the
process I also accumulated the QString buffer I had, now when i retrieve the
>QString buffer I got less number of values compared to the vector buffer.So
it is obvious that the QString after >some limit avoids to append any
characters.
Have you debugged this yet to see where the problem is?
Do you have some nulls in the file that may be causing a problem
when converting from string to qstring?
No one seems to be able to duplicate your problem so you
may need to do some debugging to find the specific error.
Try inspecting each buffer that you're copying.
--
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Message 12 in thread
On 28.02.07 19:55:35, Srikanth Bemineni wrote:
> Thank you very much.I found out the problem.The problem is in QString the
> databuffer which i was in using. what is the maximum size a QString can hold.
There's no limitation documented, so I think the limits are set by your
machine. Now I'm not 100% sure on this, because internally the QString
class uses a d-pointer, which should be allocated on the heap, to store
the text, but it might be worthwhile to create the QString on the heap
and not on the stack...
Anyway, in your original post you talked about a file of about 938
lines. So your lines are something like thousands of characters long?
How large is the whole file?
I just tried the Qt code you posted earlier on a 16 Meg testfile and it
was read perfectly well with a QString created on the stack. Also I
noticed that the code you posted was for Qt4, not Qt3 as you said you
are using...
Andreas
--
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Message 13 in thread
Hi,
I was busy with some other so was not able to go through this problem.
This is the code I am using to read and display the file which I have
already shared with you guys. Lets go through each one of them.Read I am
using the traditional c++ method to read the file. and it is working
absolutely fine. Now lets come to the display. Instead of using the the
normal cout I used the QT qDebug . I really don't know what is the
internal functionality of the qDebug is, but if the string is to large
then qDebug is not able to write the string to the out put buffer.I
tested this with some other string still it is the same case qDebug will
not display the complete buffer if it large. I feel like qDebug was
meant to be like that or it was designed keeping a short string in mind.
Somebody please confirm this.
Srikanth Bemineni wrote:
> The file* is the basic . It doesn't even work with that.
> Duane Hebert wrote:
>> FILE* s give me a headache but in either
>> case, what's databuffer and how is it initialized?
>> Which version of Qt are you using?
>>
>>
>>> QFile read_file(fileName);
>>> if (!read_file.open(QIODevice::ReadOnly))
>>> return;
>>> QString line
>>> QTextStream in(&fileName);
>>> while (!in.atEnd())
>>> {
>>> line = in.readLine();
>>>
>>
>> What if you debug line?
>>
>>
>>> databuffer += line;
>>> }
>>>
>> qDebug("------------------------------------------------------------------")
>> ;
>> qDebug("%s", dataBuffer.ascii());
>> qDebug("------------------------------------------------------------------")
>> ;
>> qDebug("databuffer count = %d", dataBuffer.length());
>> return true;
>>
>> debug's for the referenceonly.In first the count and length are same.
>>
>>
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>> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx with "unsubscribe" in the subject or the body.
>> List archive and information: http://lists.trolltech.com/qt-interest/
>>
>>
>>
>
>
> --
> With Regards
> Srikanth Bemineni
> Geotrace Technologies
> 281-497-8440 extn 228
>
>
>
>
>
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Message 14 in thread
Hi,
> I was busy with some other so was not able to go through this problem.
>
> This is the code I am using to read and display the file which I have
> already shared with you guys.
Are you certain you have shared it with us? I can't find any reference
to this file in your posts.
I'm certain that the problem is that you're attempting to read a file
containing the character '\0' or something like that. If so it should be
considered as a binary file, not a text file.
If you do make the file available on some site, we could check it for you.
> [...]
> not display the complete buffer if it large. I feel like qDebug was
> meant to be like that or it was designed keeping a short string in mind.
>
> Somebody please confirm this.
The documentation should be able to confirm that:
http://doc.trolltech.com/4.2/qtglobal.html#qDebug
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