C / C++ / MFC

Vaclav_ wrote:

Would assigning it outside the function defeat the "scope" of the class?

class Vector3i {
private:
   std::array<int,3> data;
public:
   // example 1: change own member variable
   void fill(const int value) {
      data.fill(value);
   }
   // example 2: change member variable from another instance
   void swap(Vector3i& other) {
      std::swap(data, other.data);
   }
};

1. There is no way to know whether the representation is 1 bit/value or 1 byte/value (this is a quality of implementation issue)
2. There is no way to know whether the underlying type is an array of chars, ints, or some other type
3. There is no way to know whether bit 0 is the MSB or the LSB of the underlying type

struct  op_status {
    unsigned int  status_1:2;
    unsigned int  status_2:2;
    unsigned int  error:6;
};

int devfd = open("/dev/a_device", O_RDWR);

struct op_status i2c_status;

read(devfd, &i2c_status, sizeof(i2c_status));

if(i2c_status.status_1 == 1) {
    /* do something */
} else if ( i2c_status.status_1 == 2 && i2c_status.status_2 = 1) {
    switch(i2c_status.error) {
        case 1:  /* handle error code 1 */
            break;
        case 2:  /* handle error code 2 */
            break;
        ...
        default: /* do something else */
    }
}

k5054 wrote:

looking a <bitset>, I don't see a nice way to group the bits together to treat them as a single unit, like you can using bit-fields.

	// build a common function to set / reset bits
	// shift data into correct bit postion
	cout << " data 0x" << hex << +data << endl;
	data <<= iLSbit;
	cout << " shifted data 0x" << hex << +data << endl;
	int iDataBit;
	for (int iBit = iLSbit; iBit != iMSbit + 1; iBit++) {
#ifdef DEBUG
		cout << "processing  bit " << dec << +iBit << endl;
		// clear bit
		buf[0] &= ~(1UL << iBit); // don't need this
#endif
		// set or reset bit
		// check data bit @ position
		iDataBit = (data >> iBit) & 1U;
#ifdef DEBUG
		cout << " iDataBit " << hex << +iDataBit << endl;
#endif
		if (iDataBit) {
#ifdef DEBUG
			cout << "set bit  @ position " << dec << iBit << endl;
#endif
			buf[0] |= (1UL << iBit);
		} else {
#ifdef DEBUG
			cout << "clear bit @ position " << dec << iBit << endl;
#endif
			// clear bit
			buf[0] &= ~(1UL << iBit);
		}
	}