5 files changed, 27 insertions, 15 deletions
diff --git a/src/java/com/jogamp/common/util/Bitfield.java b/src/java/com/jogamp/common/util/Bitfield.java
index d7ada5a..4b2b9d5 100644
--- a/src/java/com/jogamp/common/util/Bitfield.java
+++ b/src/java/com/jogamp/common/util/Bitfield.java
@@ -173,7 +173,7 @@ public interface Bitfield {
      * @param bitnum bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      */
-    void put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException;
+    boolean put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException;
 
     /**
      * Set the bit at position <code>bitnum</code> according to <code>bit</code>.
diff --git a/src/java/jogamp/common/util/Int32ArrayBitfield.java b/src/java/jogamp/common/util/Int32ArrayBitfield.java
index 3dcb9ae..5bc95eb 100644
--- a/src/java/jogamp/common/util/Int32ArrayBitfield.java
+++ b/src/java/jogamp/common/util/Int32ArrayBitfield.java
@@ -142,16 +142,20 @@ public class Int32ArrayBitfield implements Bitfield {
     }
 
     @Override
-    public final void put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
+    public final boolean put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
         check(bitSize, bitnum);
         final int u = bitnum >>> UNIT_SHIFT;
         final int b = bitnum - ( u << UNIT_SHIFT );
         final int m = 1 << b;
-        if( bit ) {
-            storage[u] |=  m;
-        } else {
-            storage[u] &= ~m;
+        final boolean prev = 0 != ( storage[u] & m ) ;
+        if( prev != bit ) {
+            if( bit ) {
+                storage[u] |=  m;
+            } else {
+                storage[u] &= ~m;
+            }
         }
+        return prev;
     }
     @Override
     public final void set(final int bitnum) throws IndexOutOfBoundsException {
diff --git a/src/java/jogamp/common/util/Int32Bitfield.java b/src/java/jogamp/common/util/Int32Bitfield.java
index 9bf2117..7b55a59 100644
--- a/src/java/jogamp/common/util/Int32Bitfield.java
+++ b/src/java/jogamp/common/util/Int32Bitfield.java
@@ -115,14 +115,18 @@ public class Int32Bitfield implements Bitfield {
         return 0 != ( storage & ( 1 << bitnum ) ) ;
     }
     @Override
-    public final void put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
+    public final boolean put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
         check(UNIT_SIZE, bitnum);
         final int m = 1 << bitnum;
-        if( bit ) {
-            storage |=  m;
-        } else {
-            storage &= ~m;
+        final boolean prev = 0 != ( storage & m ) ;
+        if( prev != bit ) {
+            if( bit ) {
+                storage |=  m;
+            } else {
+                storage &= ~m;
+            }
         }
+        return prev;
     }
     @Override
     public final void set(final int bitnum) throws IndexOutOfBoundsException {
diff --git a/src/java/jogamp/common/util/SyncedBitfield.java b/src/java/jogamp/common/util/SyncedBitfield.java
index c23d7ea..49c27b0 100644
--- a/src/java/jogamp/common/util/SyncedBitfield.java
+++ b/src/java/jogamp/common/util/SyncedBitfield.java
@@ -70,8 +70,8 @@ public class SyncedBitfield implements Bitfield {
     }
 
     @Override
-    public final synchronized void put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
-        impl.put(bitnum, bit);
+    public final synchronized boolean put(final int bitnum, final boolean bit) throws IndexOutOfBoundsException {
+        return impl.put(bitnum, bit);
     }
 
     @Override
diff --git a/src/junit/com/jogamp/common/util/TestBitfield00.java b/src/junit/com/jogamp/common/util/TestBitfield00.java
index a2d5d73..bb8ca37 100644
--- a/src/junit/com/jogamp/common/util/TestBitfield00.java
+++ b/src/junit/com/jogamp/common/util/TestBitfield00.java
@@ -320,12 +320,16 @@ public class TestBitfield00 extends SingletonJunitCase {
             assertEquals(bf, lowBitnum+1, d.val, d.pattern, oneBitCount);
         }
 
+        // test put() return value (previous value)
+        bf.clearField(false);
+        Assert.assertEquals(msg+", bitpos "+0, false, bf.put(lowBitnum+0, true));
+        Assert.assertEquals(msg+", bitpos "+0,  true, bf.put(lowBitnum+0, false));
+
         //
         // via put
         //
-        bf.clearField(false);
         for(int i=0; i<d.bitSize; i++) {
-            bf.put(lowBitnum+i, 0 != ( d.val & ( 1 << i ) ));
+            Assert.assertEquals(msg+", bitpos "+i, false, bf.put(lowBitnum+i, 0 != ( d.val & ( 1 << i ) )));
         }
         Assert.assertEquals(msg, d.val, bf.get32(lowBitnum, d.bitSize));
         for(int i=0; i<d.bitSize; i++) {