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Thread: Can somebody show how to read bytes?

  1. #1
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    Default Can somebody show how to read bytes?

    Hey people,I've been searching for hours now about how to read bytes from a file.
    What I want to do,is open an .exe file,take the bytes and output them as binary(100101)/hex(FFA2)...

    I have searched this in plain c++ and Qt as well..but none good answer.
    All I get are some strange chars,or a string "MZP" in console....

    I have tried QFile,QIODevice,QByteArray..but no result.

    Can anyone please explain me how to do this?

    Thanks.

  2. #2
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    Default Re: Can somebody show how to read bytes?

    I have tried QFile,QIODevice,QByteArray..but no result.
    Show what you have tried.
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    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.

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    Default Re: Can somebody show how to read bytes?

    Quote Originally Posted by "BumbleBee" View Post
    Hey people,I've been searching for hours now about how to read bytes from a file.
    QIODevice::read()

    All I get are some strange chars,or a string "MZP" in console....
    And what did you expect to receive? A happy smiling face?
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    Default Re: Can somebody show how to read bytes?

    Well,I have tried many different combination with different syntax...I cannot post a certain code,as there were many things I tried..

    Can you please post a working piece?

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    Default Re: Can somebody show how to read bytes?

    Post the the code you thought was the best of the things you tried, and we can pick it up from there.
    ==========================signature=============== ==================
    S.O.L.I.D principles (use them!):
    https://en.wikipedia.org/wiki/SOLID_...iented_design)

    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.

  6. #6
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    Default Re: Can somebody show how to read bytes?

    Sure.
    Well I made this:
    Qt Code:
    1. #include <QtCore/QCoreApplication>
    2. #include <QFile>
    3. #include <QDebug>
    4.  
    5. int main(int argc, char *argv[])
    6. {
    7. QCoreApplication a(argc, argv);
    8.  
    9. QFile f("C:\\Program Files (x86)\\TeamViewer\\Version6\\TeamViewer.exe");
    10. if( !f.exists() )
    11.  
    12. {
    13. // It does not exist
    14. qDebug() << "The file does not exist.\n";
    15. }
    16.  
    17. // It exists, open it
    18. if(!f.open(QIODevice::ReadOnly))
    19. {
    20. // It could not open
    21. qDebug() << "Failed to open.";
    22.  
    23. return 0;
    24. }
    25.  
    26. // It opened, now we need to close it
    27. qDebug() << "Success";
    28.  
    29. int size = f.size();
    30. qDebug() << "size: " << size;
    31.  
    32. QDataStream data(&f);
    33. char * buffer;
    34. uint u = sizeof(f);
    35. data.readBytes(buffer,u);
    36.  
    37.  
    38. f.close();
    39. return a.exec();
    40. }
    To copy to clipboard, switch view to plain text mode 

    Then I thought that I may need to make a loop,in order to read a byte after byte..but still nothing.

  7. #7
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    Default Re: Can somebody show how to read bytes?

    The code doesn't make much sense really. Why don't you just use QIODevice::read() on your QFile object?
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  8. #8
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    Default Re: Can somebody show how to read bytes?

    Sorry,

    Qt Code:
    1. int main(int argc, char *argv[])
    2. {
    3. QCoreApplication a(argc, argv);
    4.  
    5. QFile f("C:\\Program Files (x86)\\TeamViewer\\Version6\\TeamViewer.exe");
    6.  
    7. ....
    8. int size = f.size();
    9. qDebug() << "size: " << size;
    10.  
    11. QDataStream data(&f);
    12. char * buffer;
    13. uint u = sizeof(f);
    14. data.readBytes(buffer,u);
    15.  
    16.  
    17. f.close();
    18. return a.exec();
    19. }
    To copy to clipboard, switch view to plain text mode 

    what you're doing??

    1. You're using a pointer "buffer" as array of bytes (WRONG)
    2. You're using sizeof of an object as amount of data to read (WRONG)


    for 1. it's strange that your program doesn't crash

    I suggest you

    Qt Code:
    1. int size = f.size();
    2. qDebug() << "size: " << size;
    3.  
    4. QByteArray buffer = f.read (size);
    To copy to clipboard, switch view to plain text mode 

    and use directly "buffer"
    Last edited by mcosta; 19th April 2011 at 17:07. Reason: updated contents
    A camel can go 14 days without drink,
    I can't!!!

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    Default Re: Can somebody show how to read bytes?

    Quote Originally Posted by "BumbleBee" View Post
    All I get are some strange chars,or a string "MZP" in console....
    Which is the ascii representation of the file [All EXE files start with the letters 'MZ'], so you have already managed to read the file. All you need to do is convert your ascii into hex or binary. See the docs on how to do that or write your own conversion function.

  10. #10
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    Default Re: Can somebody show how to read bytes?

    You do not need or want to use QDataStream for this task. As Wysota points out a simple call to QIODevice::read() or readAll() will suffice. As mcosta points out you are flirting with crashing by using a char* pointer that is not initialised to point at allocated memory: Qt provides structures to handle this for you.

    Your problem comes down to:
    1. Open file and report error if file not opened: See QFile and QIODevice open() and errorString().
    2. Read file content into memory. See QByteArray and QIODevice::read() or readAll().
    3. Close file. See QFile::close()
    4. Do something with content. See QByteArray::toHex()

    That description is about the same length as a basic implementation.

  11. #11
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    Default Re: Can somebody show how to read bytes?

    To suplement what was already said - I strongely discourage you from reading the whole file into memory since 1) you don't know how big it is and 2) most likely you don't need to have all the data available at once. Read as much as you need, process it and then read more if you need more.
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  12. #12
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    Default Re: Can somebody show how to read bytes?

    Qt Code:
    1. int size = f.size();
    2.  
    3. QByteArray bytes = f.readAll();
    4.  
    5. qDebug() << bytes; //outputs ""MZP
    6.  
    7. qDebug() << bytes.toHex(); //Same output :(
    To copy to clipboard, switch view to plain text mode 

  13. #13
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    Default Re: Can somebody show how to read bytes?

    What do you expect to read??

    You're reading a binary file!
    A camel can go 14 days without drink,
    I can't!!!

  14. #14
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    Default Re: Can somebody show how to read bytes?

    What do you mean?

    I want to convert that to hex...

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    Default Re: Can somebody show how to read bytes?

    For me this code

    Qt Code:
    1. char data [] = { 0xaa, 0x01, 0x00, 0xFF, 0xBA};
    2. QByteArray ba (data, 5);
    3.  
    4. qDebug() << ba;
    5. qDebug() << ba.toHex();
    To copy to clipboard, switch view to plain text mode 

    print

    Qt Code:
    1. "ª
    2. "aa0100ffba"
    To copy to clipboard, switch view to plain text mode 
    A camel can go 14 days without drink,
    I can't!!!

  16. #16
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    Default Re: Can somebody show how to read bytes?

    How is this related to my source?
    i get MZP when reading Anscii like wysota said.
    But Chris said I have to convert that QBA to hex..which doesn't work...

  17. #17
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    Default Re: Can somebody show how to read bytes?

    Quote Originally Posted by "BumbleBee" View Post
    But Chris said I have to convert that QBA to hex..which doesn't work...
    What doesn't work? What's the point of dumping the whole file to the screen in its hexadecimal form?

    Qt Code:
    1. #include <QFile>
    2. #include <stdio.h>
    3.  
    4. int main(int argc, char **argv) {
    5. QFile f(argv[1]);
    6. f.open(QFile::ReadOnly);
    7. int offset = 0;
    8. while(!f.atEnd()){
    9. QByteArray ba = f.read(16).toHex();
    10. QString offsetStr = QString::number(offset, 16);
    11. while(offsetStr.size()<8) offsetStr.prepend('0');
    12. printf("0x%s\t", qPrintable(offsetStr));
    13. offset+=16;
    14.  
    15. for(int i=ba.size()-2;i>0;i-=2) {
    16. ba.insert(i, ' ');
    17. }
    18.  
    19. printf("%s\n", ba.constData());
    20. }
    21. return 0;
    22. }
    To copy to clipboard, switch view to plain text mode 
    Last edited by wysota; 20th April 2011 at 10:23.
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    Please ask Qt related questions on the forum and not using private messages or visitor messages.


  18. #18
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    Default Re: Can somebody show how to read bytes?

    Why doesn't work?

    This code

    Qt Code:
    1. void Widget::on_openFileButton_clicked()
    2. {
    3. QString fileName = QFileDialog::getOpenFileName (
    4. this,
    5. tr ("Open File"),
    6. ".",
    7. tr ("Executable files (*exe)"));
    8.  
    9. if (!fileName.isEmpty ()) {
    10. QFile f (fileName);
    11.  
    12. const int SIZE = 100;
    13. int readSize;
    14.  
    15. f.open (QIODevice::ReadOnly);
    16. readSize = (f.size () > SIZE)? SIZE: f.size ();
    17.  
    18. QByteArray ba = f.read (readSize);
    19.  
    20. ui->rawDataEdit->setPlainText (ba);
    21. ui->hexDataEdit->setPlainText (ba.toHex ());
    22. }
    23. }
    To copy to clipboard, switch view to plain text mode 

    shows this output when I select a EXE file

    imagine1.JPG
    A camel can go 14 days without drink,
    I can't!!!

  19. #19
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    Default Re: Can somebody show how to read bytes?

    Quote Originally Posted by "BumbleBee" View Post
    Qt Code:
    1. int size = f.size();
    2.  
    3. QByteArray bytes = f.readAll();
    4.  
    5. qDebug() << bytes; //outputs ""MZP
    6.  
    7. qDebug() << bytes.toHex(); //Same output :(
    To copy to clipboard, switch view to plain text mode 
    Unpossible!

  20. #20
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    Default Re: Can somebody show how to read bytes?

    Quote Originally Posted by wysota View Post
    What doesn't work? What's the point of dumping the whole file to the screen in its hexadecimal form?

    Qt Code:
    1. #include <QFile>
    2. #include <stdio.h>
    3.  
    4. int main(int argc, char **argv) {
    5. QFile f(argv[1]);
    6. f.open(QFile::ReadOnly);
    7. int offset = 0;
    8. while(!f.atEnd()){
    9. QByteArray ba = f.read(16).toHex();
    10. QString offsetStr = QString::number(offset, 16);
    11. while(offsetStr.size()<8) offsetStr.prepend('0');
    12. printf("0x%s\t", qPrintable(offsetStr));
    13. offset+=16;
    14.  
    15. for(int i=ba.size()-2;i>0;i-=2) {
    16. ba.insert(i, ' ');
    17. }
    18.  
    19. printf("%s\n", ba.constData());
    20. }
    21. return 0;
    22. }
    To copy to clipboard, switch view to plain text mode 
    I need to take the hex,in order to encrypt it and save it as a new exe...btw,your code makes an infinite loop....

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