im tring to make vhd file and im having problems

[william427]

hi im having trouble with this part>>>>per.name = williamc;
i cant figure out how to get it to take >>>>per.name = "williamc";
i just started c++ been reading alot ,i was using vb6 ,
what it does or what im tring to get it to is take williamc as char name
but im stuck.
thanks

#include <fstream> // for ifstream, ofstream, ios_base
#include <iostream>// for cin, cout, endl
// you can just say `using namespace std;` here instead of all these 'using's
using std::ios_base;
using std::cout;
using std::cin;
using std::endl;

// just creating a constant for the name of the database
static const char *DATABASE_FILE = "pr1.bin";

// the data that will go into the database
struct Person {

   char name[8];
   int Features;
   int FFVersion;  
   int DataOffset;
   int TimeStamp;
   int CreatorApplication;
   int CreatorVersion;  
   int CreatorHostOS;
   int OriginalSize;
   int CurrentSize;
   int DiskGeometry;
   int DiskType;
   int Checksum;  
   int UniqueId;
   int SavedState;
   //int Reserved;

};


// this function takes a pointer to a Person struct
// that will be filled with the data in the file
bool LoadDB(Person *per) {
  // first parameter is the name of the file
  // second is the open flags. 
  //    `in` says you will read from the file
  //    `binary` says you will read binary data instead of simple text
  std::ifstream fin(DATABASE_FILE, ios_base::in | ios_base::binary);
  
  // if we couldn't open the file (it may not exist); fail
  if (!fin.is_open())
    return false;
  
  // the file is open; tell the read function to look at `per` as a
  // char pointer instead of a Person pointer so that `fin` can place
  // one byte at a time into the struct
  // the second parameter tells read() how many bytes to read
  // Note: do not use the ">>" operator to read from a binary file 
  fin.read((char*)per, sizeof(Person));
  fin.close();// close the file - not necessary, but we should be neat

  // success  
  return true;
}

// this function takes a pointer to a Person struct
// that will be written into the file
bool SaveDB(Person *per) {
  // these flags say:
  //    `out` - we will be writing data into the file
  //    `binary` - we will be writing binary data and not simple text
  //    `trunc` - if the file already exists, truncate (wipe out) the existing data
  std::ofstream fout(DATABASE_FILE, ios_base::out | ios_base::binary | ios_base::trunc);
  // couldn't open it (disk error?); fail
  if (!fout.is_open())
    return false;

  // notice this time we cast the Person pointer to a const char* because we aren't
  // altering the structure this time; rather we're just looking at it's contents.  
  fout.write((const char*)per, sizeof(Person));
  fout.close();// close the file - not necessary, but we should be neat

  // success  
  return true;
}

int main() {
  // create an empty person struct
  Person per;
  
  // load the data in the db file
  if (LoadDB(&per)) {
    // print what we loaded into our Person struct
    cout << "Loaded Database...\n";
    cout << "name = " << per.name << endl;
    cout << "Features = " << per.Features << endl;
    cout << "FFVersion = " << per.FFVersion << endl;
    cout << "DataOffset = " << per.DataOffset << endl;
    cout << "TimeStamp = " << per.TimeStamp << endl;
    cout << "CreatorApplication = " << per.CreatorApplication << endl;
    cout << "CreatorVersion = " << per.CreatorVersion << endl;
    cout << "CreatorHostOS = " << per.CreatorHostOS << endl;
    cout << "OriginalSize = " << per.OriginalSize << endl;
    cout << "CurrentSize = " << per.CurrentSize << endl;
    cout << "DiskGeometry = " << per.DiskGeometry << endl;
    cout << "DiskType = " << per.DiskType << endl;
    cout << "Checksum = " << per.Checksum << endl;
    cout << "UniqueId = " << per.UniqueId << endl;
    cout << "SavedState = " << per.SavedState << endl;
    cout << endl;
  }

    
    per.name = williamc;
    per.Features = 0x00000;
    per.FFVersion = 0x00010000;  
    per.DataOffset = 0xFFFFFFFF;
    per.TimeStamp = 101000;
    per.CreatorApplication = 87776732;
    per.CreatorVersion = 0x0100;  
    per.CreatorHostOS = 0x5769326B;
    per.OriginalSize = 5243392;
    per.CurrentSize = 5243392;
    per.DiskGeometry = 00065535;
    per.DiskType = 2;
    per.Checksum = 31;  
    per.UniqueId = 427112341;
    per.SavedState = 1;








  //(cin >> per.salary).get();// note .getline() clears its own newline character

  // save the new user-entered data  
  if (SaveDB(&per))
    cout << "\nDatabase saved!\n";
  else
    cout << "\nUnable to save database!\n";

    system("pause");
 
  // return 0 on success (main() should never be void!)
  return 0;
}

[Peter87]

c strings are null terminated so "williamc" is actually 9 characters. If you increase the length of name you can use strcpy to write the "williamc" to per.name.
std::strcpy(per.name, "williamc");

If you don't want per.name to be null terminated you can do
std::memcpy(per.name, "williamc", 8);
but don't do this unless you know what you are doing.

[william427]

so thats why.
it must ony be 8 characters long .
if i had to write to 85 bytes ,like asm does ,im doing it the wrong way i think.
thanks all

[william427]

the first program didnt work to make a vhd file even though i followed Virtual Hard Disk Image Format Specification from ms.theres still more work i have to do to figure out how to addjust the file size.this will make a 200 megabyte file.if you see anything i can do better please tell me.



what i was woundering is can i load an array with numbers and other arrays in the array?

int main()
{
  BYTE  cur_char;

  ofstream out("test.vhd",ios::out | ios::binary); 
  if (!out.is_open())
    return false;
     for (int n=0; n<3072; n++) {
    cur_char = 0; { out << cur_char;  }
  } 
  out.seekp(0,ofstream::beg); 
  BYTE holdarray[] = {99,111,110,101,99,116,105,120,0,0,0,2,0,1,0,0,0,0,0,0,0,0,2,0,23,69,64,121,118,112,99,32,0,5,0,3,87,105,50,107,0,0,0,0,12,128,0,0,0,0,0,0,12,128,0,0,3,57,16,31,0,0,0,3,255,255,238,229,44,180,124,213,158,221,17,225,130,42,201,29,129,166,153,95};
   //write to outfile
  out.write((char *) &holdarray,sizeof holdarray); 
  out.seekp (512);
  BYTE holdarray2[] = {99,120,115,112,97,114,115,101,255,255,255,255,255,255,255,255,0,0,0,0,0,0,6,0,0,1,0,0,0,0,0,100,0,32,0,0,255,255,244,19};
  out.write ((char*)&holdarray2, sizeof holdarray2);
  out.seekp (1536);
     for (int n=1536; n<1936; n++) {
    cur_char = 255; { out << cur_char;  }
  } 
  out.seekp (2560);
  out.write ((char*)&holdarray, sizeof holdarray);

  out.close();
   return 0;
}

[Peter87]

william427 wrote:

the first program didnt work to make a vhd file even though i followed Virtual Hard Disk Image Format Specification from ms.

Make sure that you use the correct size in bytes for the different fields.

[william427]

virtual pc will run mine but no other program will mount it.
do yall know what im doing wrong ,id like to do it in c++.

because following the specifications does not explain certian details as the second program i have up shows.
thanks all

[william427]

hey all if i followed Virtual Hard Disk Image Format Specification from ms.
and im running win xp how do i go about mounting my file using c++,is it possible and what topic do i search to find more on the subject?
thanks