Int32ArrayBitfield.java

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/**
 * Author: Sven Gothel <sgothel@jausoft.com>
 * Copyright (c) 2020 Gothel Software e.K.
 * Copyright (c) 2015 Gothel Software e.K.
 * Copyright (c) 2015 JogAmp Community.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package jau.util;
 
import org.jau.util.BitMath;
import org.jau.util.Bitfield;
 
/**
 * Simple bitfield interface for efficient storage access in O(1).
 * <p>
 * Implementation uses a 32bit integer array for storage.
 * </p>
 */
public class Int32ArrayBitfield implements Bitfield {
    private static final int UNIT_SHIFT = 5;
    private final int[] storage;
    private final int bitSize;
 
    /**
     * @param storageBitSize
     */
    public Int32ArrayBitfield(final int storageBitSize) {
        final int units = Math.max(1, ( storageBitSize + 31 ) >>> UNIT_SHIFT);
        this.storage = new int[units]; // initialized w/ default '0'
        this.bitSize = units << UNIT_SHIFT;
    }
 
    @Override
    public int size() {
        return bitSize;
    }
 
    @Override
    public final void clearField(final boolean bit) {
        final int v;
        if( bit ) {
            v = BitMath.UNSIGNED_INT_MAX_VALUE;
        } else {
            v = 0;
        }
        for(int i=storage.length-1; i>=0; i--) {
            storage[i] = v;
        }
    }
 
    private static final void check(final int size, final int bitnum) throws IndexOutOfBoundsException {
        if( 0 > bitnum || bitnum >= size ) {
            throw new IndexOutOfBoundsException("Bitnum should be within [0.."+(size-1)+"], but is "+bitnum);
        }
    }
 
    @Override
    public final int get32(final int lowBitnum, final int length) throws IndexOutOfBoundsException {
        if( 0 > length || length > 32 ) {
            throw new IndexOutOfBoundsException("length should be within [0..32], but is "+length);
        }
        check(bitSize-length+1, lowBitnum);
        final int u = lowBitnum >>> UNIT_SHIFT;
        final int left = 32 - ( lowBitnum - ( u << UNIT_SHIFT ) ); // remaining bits of first chunk storage
        if( 32 == left ) {
            // fast path
            final int m = BitMath.getBitMask(length);// mask of chunk
            return m & storage[u];
        } else {
            // slow path
            final int l = Math.min(length, left);    // length of first chunk < 32
            final int m = ( 1 << l ) - 1;            // mask of first chunk
            final int d = m & ( storage[u] >>> lowBitnum );
            final int l2 = length - l;               // length of last chunk < 32
            if( l2 > 0 ) {
                final int m2 = ( 1 << l2 ) - 1;      // mask of last chunk
                return d | ( ( m2 & storage[u+1] ) << l );
            } else {
                return d;
            }
        }
    }
    @Override
    public final void put32(final int lowBitnum, final int length, final int data) throws IndexOutOfBoundsException {
        if( 0 > length || length > 32 ) {
            throw new IndexOutOfBoundsException("length should be within [0..32], but is "+length);
        }
        check(bitSize-length+1, lowBitnum);
        final int u = lowBitnum >>> UNIT_SHIFT;
        final int left = 32 - ( lowBitnum - ( u << UNIT_SHIFT ) ); // remaining bits of first chunk storage
        if( 32 == left ) {
            // fast path
            final int m = BitMath.getBitMask(length);// mask of chunk
            storage[u] = ( ( ~m ) & storage[u] )     // keep non-written storage bits
                         | ( m & data );             // overwrite storage w/ used data bits
        } else {
            // slow path
            final int l = Math.min(length, left);    // length of first chunk < 32
            final int m = ( 1 << l ) - 1;            // mask of first chunk
            storage[u] = ( ( ~( m << lowBitnum ) ) & storage[u] ) // keep non-written storage bits
                         | ( ( m & data ) << lowBitnum );         // overwrite storage w/ used data bits
            final int l2 = length - l;               // length of last chunk < 32
            if( l2 > 0 ) {
                final int m2 = ( 1 << l2 ) - 1;      // mask of last chunk
                storage[u+1] = ( ( ~m2 ) & storage[u+1] ) // keep non-written storage bits
                               | ( m2 & ( data >>> l ) ); // overwrite storage w/ used data bits
            }
        }
    }
    @Override
    public final int copy32(final int srcBitnum, final int dstBitnum, final int length) throws IndexOutOfBoundsException {
        final int data = get32(srcBitnum, length);
        put32(dstBitnum, length, data);
        return data;
    }
 
    @Override
    public final boolean get(final int bitnum) throws IndexOutOfBoundsException {
        check(bitSize, bitnum);
        final int u = bitnum >>> UNIT_SHIFT;
        final int b = bitnum - ( u << UNIT_SHIFT );
        return 0 != ( storage[u] & ( 1 << b ) ) ;
    }
 
    @Override
    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;
        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 {
        check(bitSize, bitnum);
        final int u = bitnum >>> UNIT_SHIFT;
        final int b = bitnum - ( u << UNIT_SHIFT );
        final int m = 1 << b;
        storage[u] |=  m;
    }
    @Override
    public final void clear(final int bitnum) throws IndexOutOfBoundsException {
        check(bitSize, bitnum);
        final int u = bitnum >>> UNIT_SHIFT;
        final int b = bitnum - ( u << UNIT_SHIFT );
        final int m = 1 << b;
        storage[u] &= ~m;
    }
    @Override
    public final boolean copy(final int srcBitnum, final int dstBitnum) throws IndexOutOfBoundsException {
        check(bitSize, srcBitnum);
        check(bitSize, dstBitnum);
        final boolean bit;
        // get
        {
            final int u = srcBitnum >>> UNIT_SHIFT;
            final int b = srcBitnum - ( u << UNIT_SHIFT );
            bit = 0 != ( storage[u] & ( 1 << b ) ) ;
        }
        // put
        final int u = dstBitnum >>> UNIT_SHIFT;
        final int b = dstBitnum - ( u << UNIT_SHIFT );
        final int m = 1 << b;
        if( bit ) {
            storage[u] |=  m;
        } else {
            storage[u] &= ~m;
        }
        return bit;
    }
 
    @Override
    public int bitCount() {
        int c = 0;
        for(int i = storage.length-1; i>=0; i--) {
            c += BitMath.bitCount(storage[i]);
        }
        return c;
    }
}