Converting NSData to int

Question

I\'ve an NSData object, the length is 4 bytes .These four bytes i\'m extracting from another NSData object using ,

fourByteData=[completeData subdataWithRang         


        

Answer 1

Assuming _vertexData is NSData here and you know what data (types) to expect in your buffer you can iterate thru this block with NSData's .length property. In this Example each data block was 32 Bytes (storing 8 x float values) and i was interested in logging starting at the 5th float value

float a,b,c,d; //prepare some values, no need to initialize

// loop thru assuming 8 floats are stored after each other
for (NSUInteger v = 0; v < _vertexData.length; v += sizeof(float)*8 ) {

    // set a starting point for the range, here the 5th float
    NSUInteger shift = v + (sizeof(float)*4);

    // store result in a..
    [_vertexData getBytes:&a range:NSMakeRange(shift,sizeof(a))];

    // increase the starting point by the size of data before
    shift += sizeof(a);

    [_vertexData getBytes:&b range:NSMakeRange(shift,sizeof(b))];

    shift += sizeof(b);
    [_vertexData getBytes:&c range:NSMakeRange(shift,sizeof(c))];

    shift += sizeof(c);
    [_vertexData getBytes:&d range:NSMakeRange(shift,sizeof(d))];

    fprintf(stderr, "r%f, g%f, b%f, a%f \n", a,b,c,d );
}

this could have been written much shorter, but for the sake of clarity and with less use of miss leading castings

maybe this helps someone