Question

I am trying to increment a variable in Objective-C. This would seem to be an easy:

dataPos++

but when I do this, the value increases very strangely:

dataPos: 1,
dataPos: 2,
dataPos: 3,
dataPos: 4,
dataPos: 12,
dataPos: 185273100`

This is my code:

int dataPos = 0;
uint8_t temparray[1];
for (int x=0; x < mapX; x++) {
    for (int y=0; y < mapY; y++) {
        for (int z=0; z < mapZ; z++) {
            [mapdata getBytes:&temparray range:NSMakeRange(dataPos, dataPos+1)];
            dataPos++;
            NSLog(@"dataPos: %d", dataPos);
            map[x][y][z] = temparray[0];
        }   
    }  
}

mapData is an NSMutableData, with about 4194308 bytes in it, and map[][][] is a uint8_t array.

I have tried cleaning the build folder, building on both the simulator (Value never increases, stays at 1), and the device.

Any help is much appreciated.

Answer 1

NSMakeRange takes a position and length, not a start and end position. You’re likely reading too much data into temparray and overwriting dataPos in the process. See the Foundation Functions Reference for more info, and rewrite your code to read:

// snip
[mapdata getBytes:&temparray range:NSMakeRange(dataPos, 1)];
// snip