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add bitfield methods to embed/extract smaller values from a larger value

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Gered 2013-09-14 13:44:08 -04:00
parent 823d940f55
commit 14e58aad5e
2 changed files with 93 additions and 0 deletions
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61
src/com/blarg/gdx/Bitfield.java
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@ -1,8 +1,13 @@
package com.blarg.gdx;
import com.blarg.gdx.math.MathHelpers;
// this class exists because i am stupid and can never remember the operators used for setting/clearing/toggling bits
public final class Bitfield {
// checking for individual bits
public static boolean isSet(long bit, long bitfield) {
return (bitfield & bit) != 0;
}
@ -19,6 +24,8 @@ public final class Bitfield {
return (bitfield & bit) != 0;
}
// setting individual bits
public static long set(long bit, long bitfield) {
bitfield |= bit;
return (bitfield | bit);
@ -39,6 +46,8 @@ public final class Bitfield {
return bitfield;
}
// clearing individual bits
public static long clear(long bit, long bitfield) {
bitfield &= ~bit;
return bitfield;
@ -59,6 +68,8 @@ public final class Bitfield {
return bitfield;
}
// toggling individual bits on/off
public static long toggle(long bit, long bitfield) {
bitfield ^= bit;
return bitfield;
@ -78,4 +89,54 @@ public final class Bitfield {
bitfield ^= bit;
return bitfield;
}
// extracting smaller int-type values from a subset of bits out of a larger value (bitfield)
public static long extract(long mask, int shift, long bitfield) {
return (bitfield & mask) >> shift;
}
public static int extract(int mask, int shift, int bitfield) {
return (bitfield & mask) >> shift;
}
public static short extract(short mask, int shift, short bitfield) {
return (short)((bitfield & mask) >> shift);
}
public static byte extract(byte mask, int shift, byte bitfield) {
return (byte)((bitfield & mask) >> shift);
}
// setting smaller int-type values in a subset of bits in a larger value (bitfield)
public static long embed(long value, long bitmask, int shift, int valueMaxBitLength, long bitfield) {
long maxValue = MathHelpers.pow(2, valueMaxBitLength) - 1;
long actualValue = (value > maxValue ? maxValue : value) << shift;
return (clear(bitmask, bitfield) | actualValue);
}
public static int embed(int value, int bitmask, int shift, int valueMaxBitLength, int bitfield) {
int maxValue = MathHelpers.pow(2, valueMaxBitLength) - 1;
int actualValue = (value > maxValue ? maxValue : value) << shift;
return (clear(bitmask, bitfield) | actualValue);
}
public static short embed(short value, short bitmask, int shift, int valueMaxBitLength, short bitfield) {
short maxValue = (short)(MathHelpers.pow(2, valueMaxBitLength) - 1);
short actualValue = (short)((value > maxValue ? maxValue : value) << shift);
return (short)(clear(bitmask, bitfield) | actualValue);
}
public static byte embed(byte value, byte bitmask, int shift, int valueMaxBitLength, byte bitfield) {
byte maxValue = (byte)(MathHelpers.pow(2, valueMaxBitLength) - 1);
byte actualValue = (byte)((value > maxValue ? maxValue : value) << shift);
return (byte)(clear(bitmask, bitfield) | actualValue);
}
public static int getMaskFor(int startBit, int numBits) {
int temp = MathHelpers.pow(2, startBit);
return (temp * (MathHelpers.pow(2, numBits))) - temp;
}
}

32
src/com/blarg/gdx/math/MathHelpers.java
View file

@ -90,6 +90,38 @@ public final class MathHelpers {
return (diff <= largest * epsilon);
}
public static float fastInverseSqrt(float x) {
float xhalf = 0.5f * x;
int i = Float.floatToIntBits(x);
i = 0x5f3759df - (i >> 1);
x = Float.intBitsToFloat(i);
x = x * (1.5f - xhalf * x * x);
return x;
}
public static double fastInverseSqrt(double x) {
double xhalf = 0.5d * x;
long i = Double.doubleToLongBits(x);
i = 0x5fe6ec85e7de30daL - (i >> 1);
x = Double.longBitsToDouble(i);
x = x * (1.5d - xhalf * x * x);
return x;
}
public static int pow(int number, int power) {
int result = 1;
for (int i = 0; i < power; ++i)
result *= number;
return result;
}
public static long pow(long number, int power) {
long result = 1;
for (int i = 0; i < power; ++i)
result *= number;
return result;
}
public static int sign(int value) {
if (value < 0)
return -1;