unsigned char .. atol ?

hi .. i was just wonder if there is a function similar to atol, however if will convert a unsigned char to a long ?

Something like

long boom;
unsigned char woot=5;

boom=woot;

???

well ... im just tring to convert a unsigned char into a long int after some bit manip ...


void Test::testFunction(ifstream &inFile)
{
long data;

unsigned char buffer[4];

inFile.seekg(6240, ios::beg);
inFile.read(reinterpret_cast<char *>(&buffer[0]), 4);

(buffer[0]<<8)|buffer[3];
(buffer[1]<<8)|buffer[2];
(buffer[2]<<8)|buffer[1];
(buffer[3]<<8)|buffer[0];

data = atol(buffer); // problem here
}

thanks for any help guys :)

Well you can achieve this by bitwise operators... or a by a strict copying. Remember that a char is 8bits and a long int a 32-bits...

If you change data to this:
long *data;

Then you can do this:
data = (reinterpret_cast<long *> (buffer)); // problem here

Of course, to refer to the value of data, you'll have to dereference it:
cout << *data << endl;

Or create another variable:

Code:

---

long *pdata;
long data;
.
.
pdata = (reinterpret_cast<long *> (buffer)); // problem here
data = *pdata;

---

hey guys, thanks for the input :)

Anways, i tried what you said above swoopy
"data = (reinterpret_cast<long *> (buffer));"
however that did not work. The problem is i need to be able to put the whole contents of "buffer" into one variable of long type.
When shifting bits of an array is there a way to shift everything into one variable ?

ie.

void Test::testFunction(ifstream &inFile)
{
long data;

unsigned char buffer[4];

inFile.seekg(6240, ios::beg);
inFile.read(reinterpret_cast<char *>(&buffer), 4);

data = (buffer[0]<<8)|buffer[3],
(buffer[1]<<8)|buffer[2],
(buffer[2]<<8)|buffer[1],
(buffer[3]<<8)|buffer[0];


}

I try this but only get the first index of the array ? Any help would be appreciated :)

It should store all four bytes into a long. Run this and see what you get. It should output all f's: ffffffff.

Code:

---

long data;
long *pdata;

unsigned char buffer[4] = {0xff,0xff,0xff,0xff};

pdata = (reinterpret_cast<long *> (buffer));
data = *pdata;
cout << "data:" << data << endl;
cout << "data:" << hex << data << endl;

---

Also, be sure you open your file in binary mode.

ifstream inFile(filename,ios::binary);