CODEWITHSUNDEEP
c++winapidynamic
nullPointer2
nullPointer2

Reputation: 87

Writing dynamic data to files in win32

I'm having trouble with win32. I have to write some dynamic data to a file in win32 using c++. I know the basics of how to write strings to the file, but how can we write a data of ints, floats etc to a file.

I have a file which I'm copying the data to another newly created file. I need to write the data of ints, floats etc to this file at top. I know we can add the data by

char buff[] = "hello";

and copy this to file, I don't know how I can do this with different kinds of data types. Any help?

char buf[] = "hello";  //Null terminate
LPVOID lpMsgBuf; 
DWORD byteWritten = 0;
HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
BOOL ReadFileReturn;

HANDLE hFile = CreateFile("MYFILE.blo",    // open MYFILE.blo 
            GENERIC_WRITE | GENERIC_READ,              
            FILE_SHARE_READ,               // share for reading 
            NULL,                          // no security 
            OPEN_EXISTING,                   // existing file only 
            FILE_ATTRIBUTE_NORMAL,         // normal file 
            NULL);                         // no attr
ReadFileReturn = ReadFile(hFile,buf,30,&byteWritten,NULL);    
if(ReadFileReturn)
{
    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
                  NULL,
                  GetLastError(),
                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
                 (LPTSTR) &lpMsgBuf,
                  0,
                  NULL);
    WriteFile(hStdOut,buf,sizeof buf,NULL,NULL);

}
else
{
    WriteFile(hStdOut,"It Failed",sizeof "It Failed",NULL,NULL);

}

Upvotes: 0

Views: 1117

Answers (2)

Ali
Ali

Reputation: 1409

That depends how you are opening your file (in which mode actually). If you have opened them in a text mode, everything regardless of its type will get written in the form of string/text. Otherwise you can choose to open file in binary mode. In that mode int will be written as int, float will be written as float etc.

Here's a link for describing the difference between both types of files http://www.fileinfo.com/help/binary_vs_text_files

You can perhaps try something like:

char str[80] = "";
int a = 1, b = 2;
int n = sprintf(str, "%d", a+b);
DWORD bytesWritten;
WriteFile(fileHandle, str, strlen(str), &bytesWritten, NULL);

Upvotes: 1

dsign
dsign

Reputation: 12700

Check this:

http://www.cplusplus.com/reference/ostream/ostream/write/

So basically you do this:

 .... 
 std::ofstream myfile("filename");
 double my_data = 15;
 myfile.write( static_cast< const char*>(&my_data), sizeof( double ) );
 ...

The previous snippet is a bit crude, you might need to check issues like endiannes and alignment.

Upvotes: 0

Related Questions