From 1507b376bada782b5064a0151d9b7871d1360b40 Mon Sep 17 00:00:00 2001
From: Sven Gothel <sgothel@jausoft.com>
Date: Sat, 27 Oct 2012 03:41:38 +0200
Subject: IntBitfield: Add API doc; Enhance put() method, return previous value
to be used more versatile and write only if value changed.
---
src/java/com/jogamp/common/util/IntBitfield.java | 34 +++++++++++++++++++-----
1 file changed, 27 insertions(+), 7 deletions(-)
(limited to 'src/java/com/jogamp/common/util/IntBitfield.java')
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;
}
}
--
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