Bitfield: Refine API method names, add clearField(boolean), fix put32(..) and bitCount(), add unit test (passed)

2 files changed, 62 insertions, 24 deletions

diff --git a/src/java/com/jogamp/common/util/Bitfield.java b/src/java/com/jogamp/common/util/Bitfield.java
index f7eaeb0..d7ada5a 100644
--- a/src/java/com/jogamp/common/util/Bitfield.java
+++ b/src/java/com/jogamp/common/util/Bitfield.java
@@ -34,26 +34,58 @@ import jogamp.common.util.SyncedBitfield;
  * @since 2.3.2
  */
 public interface Bitfield {
+    /** Maximum 32 bit Unsigned Integer Value: {@code 0xffffffff} == {@value}. */
+    public static final int UNSIGNED_INT_MAX_VALUE = 0xffffffff;
+
     /**
      * Bit operation utilities (static).
      */
     public static class Util {
         /**
+         * Returns the 32 bit mask of n-bits, i.e. n low order 1’s.
+         * <p>
+         * Implementation handles n == 32.
+         * </p>
+         * @throws IndexOutOfBoundsException if {@code b} is out of bounds, i.e. &gt; 32
+         */
+        public static int getBitMask(final int n) {
+            if( 32 > n ) {
+                return ( 1 << n ) - 1;
+            } else if ( 32 == n ) {
+                return UNSIGNED_INT_MAX_VALUE;
+            } else {
+                throw new IndexOutOfBoundsException("n <= 32 expected, is "+n);
+            }
+        }
+
+        /**
          * Returns the number of set bits within given 32bit integer in O(1)
-         * using <i>HAKEM Bit Count</i>:
+         * using a <i>HAKEM 169 Bit Count</i> inspired implementation:
          * <pre>
          *   http://www.inwap.com/pdp10/hbaker/hakmem/hakmem.html
          *   http://home.pipeline.com/~hbaker1/hakmem/hacks.html#item169
          *   http://tekpool.wordpress.com/category/bit-count/
+         *   http://www.hackersdelight.org/
          * </pre>
          */
-        public static final int getBitCount(final int n) {
+        public static final int bitCount(int n) {
             // Note: Original used 'unsigned int',
             // hence we use the unsigned right-shift '>>>'
-            int c = n;
-            c -= (n >>> 1) & 033333333333;
-            c -= (n >>> 2) & 011111111111;
-            return ( (c + ( c >>> 3 ) ) & 030707070707 ) % 63;
+            /**
+             * Original does not work due to lack of 'unsigned' right-shift and modulo,
+             * we need 2-complementary solution, i.e. 'signed'.
+                int c = n;
+                c -= (n >>> 1) & 033333333333;
+                c -= (n >>> 2) & 011111111111;
+                return ( (c + ( c >>> 3 ) ) & 030707070707 ) & 0x3f; // % 63
+            */
+            // Hackers Delight, Figure 5-2, pop1 of pop.c.txt
+            n = n - ((n >>> 1) & 0x55555555);
+            n = (n & 0x33333333) + ((n >>> 2) & 0x33333333);
+            n = (n + (n >>> 4)) & 0x0f0f0f0f;
+            n = n + (n >>> 8);
+            n = n + (n >>> 16);
+            return n & 0x3f;
         }
     }
     /**
@@ -84,12 +116,18 @@ public interface Bitfield {
     /**
      * Returns the storage size in bit units, e.g. 32 bit for implementations using one {@code int} field.
      */
-    int getStorageBitSize();
+    int size();
+
+
+    /**
+     * Set all bits of this bitfield to the given value {@code bit}.
+     */
+    void clearField(final boolean bit);
 
     /**
      * Returns {@code length} bits from this storage,
      * starting with the lowest bit from the storage position {@code lowBitnum}.
-     * @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #getStorageBitSize()}-{@code length}].
+     * @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #size()}-{@code length}].
      * @param length number of bits to read, constrained to [0..32].
      * @throws IndexOutOfBoundsException if {@code rightBitnum} is out of bounds
      * @see #put32(int, int, int)
@@ -99,8 +137,8 @@ public interface Bitfield {
     /**
      * Puts {@code length} bits of given {@code data} into this storage,
      * starting w/ the lowest bit to the storage position {@code lowBitnum}.
-     * @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #getStorageBitSize()}-{@code length}].
-     * @param length number of bits to read, constrained to [0..32].
+     * @param lowBitnum storage bit position of the lowest bit, restricted to [0..{@link #size()}-{@code length}].
+     * @param length number of bits to write, constrained to [0..32].
      * @param data the actual bits to be put into this storage
      * @throws IndexOutOfBoundsException if {@code rightBitnum} is out of bounds
      * @see #get32(int, int)
@@ -114,8 +152,8 @@ public interface Bitfield {
      * Implementation shall operate as if invoking {@link #get32(int, int)}
      * and then {@link #put32(int, int, int)} sequentially.
      * </p>
-     * @param srcLowBitnum source bit number, restricted to [0..{@link #getStorageBitSize()}-1].
-     * @param dstLowBitnum destination bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @param srcLowBitnum source bit number, restricted to [0..{@link #size()}-1].
+     * @param dstLowBitnum destination bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      * @see #get32(int, int)
      * @see #put32(int, int, int)
@@ -124,7 +162,7 @@ public interface Bitfield {
 
     /**
      * Return <code>true</code> if the bit at position <code>bitnum</code> is set, otherwise <code>false</code>.
-     * @param bitnum bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @param bitnum bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      */
     boolean get(final int bitnum) throws IndexOutOfBoundsException;
@@ -132,21 +170,21 @@ public interface Bitfield {
     /**
      * Set or clear the bit at position <code>bitnum</code> according to <code>bit</code>
      * and return the previous value.
-     * @param bitnum bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @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;
 
     /**
      * Set the bit at position <code>bitnum</code> according to <code>bit</code>.
-     * @param bitnum bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @param bitnum bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      */
     void set(final int bitnum) throws IndexOutOfBoundsException;
 
     /**
      * Clear the bit at position <code>bitnum</code> according to <code>bit</code>.
-     * @param bitnum bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @param bitnum bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      */
     void clear(final int bitnum) throws IndexOutOfBoundsException;
@@ -154,17 +192,17 @@ public interface Bitfield {
     /**
      * Copies the bit at position {@code srcBitnum} to position {@code dstBitnum}
      * and returning <code>true</code> if the bit is set, otherwise <code>false</code>.
-     * @param srcBitnum source bit number, restricted to [0..{@link #getStorageBitSize()}-1].
-     * @param dstBitnum destination bit number, restricted to [0..{@link #getStorageBitSize()}-1].
+     * @param srcBitnum source bit number, restricted to [0..{@link #size()}-1].
+     * @param dstBitnum destination bit number, restricted to [0..{@link #size()}-1].
      * @throws IndexOutOfBoundsException if {@code bitnum} is out of bounds
      */
     boolean copy(final int srcBitnum, final int dstBitnum) throws IndexOutOfBoundsException;
 
     /**
-     * Returns the number of set bits within this bitfield.
+     * Returns the number of one bits within this bitfield.
      * <p>
-     * Utilizes {#link {@link Bitfield.Util#getBitCount(int)}}.
+     * Utilizes {#link {@link Bitfield.Util#bitCount(int)}}.
      * </p>
      */
-    int getBitCount();
+    int bitCount();
 }
diff --git a/src/java/com/jogamp/common/util/IntBitfield.java b/src/java/com/jogamp/common/util/IntBitfield.java
index 3ef5bb7..e7a9d70 100644
--- a/src/java/com/jogamp/common/util/IntBitfield.java
+++ b/src/java/com/jogamp/common/util/IntBitfield.java
@@ -140,10 +140,10 @@ public class IntBitfield {
         return prev;
     }
     /**
-     * @deprecated Use {@link Bitfield.Util#getBitCount(int)}.
+     * @deprecated Use {@link Bitfield.Util#bitCount(int)}.
      */
     public static final int getBitCount(final int n) {
-        return Bitfield.Util.getBitCount(n);
+        return Bitfield.Util.bitCount(n);
     }
 
     /**
@@ -155,7 +155,7 @@ public class IntBitfield {
     public long getBitCount() {
         long c = 0;
         for(int i = storage.length-1; i>=0; i--) {
-            c += Bitfield.Util.getBitCount(storage[i]);
+            c += Bitfield.Util.bitCount(storage[i]);
         }
         return c;
     }