diff options
| -rw-r--r-- | src/java/com/jogamp/common/util/IntBitfield.java | 34 |
1 files changed, 27 insertions, 7 deletions
diff --git a/src/java/com/jogamp/common/util/IntBitfield.java b/src/java/com/jogamp/common/util/IntBitfield.java index 5220063..e6a2c49 100644 --- a/src/java/com/jogamp/common/util/IntBitfield.java +++ b/src/java/com/jogamp/common/util/IntBitfield.java @@ -27,12 +27,21 @@ */ package com.jogamp.common.util; +/** + * Simple bitfield holder class using an int[] storage. + * <p> + * IntBitfield allows convenient access of a wide field of transient bits using efficient storage in O(1). + * </p> + * <p> + * It can be used e.g. to map key-codes to pressed-state etc. + * </p> + */ public class IntBitfield { /** Unit size in bits, here 32 bits for one int unit. */ public static final int UNIT_SIZE = 32; - final int[] storage; - final long bits; + private final int[] storage; + private final long bits; /** * @param bits @@ -49,8 +58,10 @@ public class IntBitfield { } } + /** Return the capacity of this bit field, i.e. the number of bits stored int this field. */ public final long capacity() { return bits; } + /** Return <code>true</code> if the bit at position <code>bitnum</code> is set, otherwise <code>false</code>. */ public final boolean get(long bitnum) { check(bitnum); final int u = (int) ( bitnum / UNIT_SIZE ); @@ -58,14 +69,23 @@ public class IntBitfield { return 0 != ( storage[u] & ( 1 << b ) ) ; } - public final void put(long bitnum, boolean bit) { + /** + * Set or clear the bit at position <code>bitnum</code> according to <code>bit</code> + * and return the previous value. + */ + public final boolean put(long bitnum, boolean bit) { check(bitnum); final int u = (int) ( bitnum / UNIT_SIZE ); final int b = (int) ( bitnum - ( u * UNIT_SIZE ) ); - if(bit) { - storage[u] |= 1 << b; - } else { - storage[u] &= ~( 1 << b ); + final int m = 1 << b; + final boolean prev = 0 != ( storage[u] & m ) ; + if( prev != bit ) { + if( bit ) { + storage[u] |= m; + } else { + storage[u] &= ~m; + } } + return prev; } } |