I’m skimming through a very popular game’s source code at the moment and I came across these variables inside of this class.
public static final BlockPos ORIGIN = new BlockPos(0, 0, 0);
private static final int NUM_X_BITS = 1 + MathHelper.calculateLogBaseTwo(MathHelper.roundUpToPowerOfTwo(30000000));
private static final int NUM_Z_BITS = NUM_X_BITS;
private static final int NUM_Y_BITS = 64 - NUM_X_BITS - NUM_Z_BITS;
private static final int Y_SHIFT = 0 + NUM_Z_BITS;
private static final int X_SHIFT = Y_SHIFT + NUM_Y_BITS;
private static final long X_MASK = (1L << NUM_X_BITS) - 1L;
private static final long Y_MASK = (1L << NUM_Y_BITS) - 1L;
private static final long Z_MASK = (1L << NUM_Z_BITS) - 1L;
What is the point of initializing these this way instead of just calculating it once and initializing with the answer?
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The point in initializing them this way is that it makes it clear to the reader where the values come from.
I can look at the code and see that it is creating bitmasks for 64 bit values with parts X,Y,Z where the X and Z values must hold at least 30,000,000 and that is using the remaining space for the Y values.
Imagine the code looked like this:
private static final long X_MASK = 335544321
private static final long Y_MASK = 16383
private static final long Z_MASK = 335544321
Would it be as clear what the values meant? Have you memorized what ‘2^25’ is, and even if you have, do you know why ‘2^25’ was chosen?
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