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Library providing immutable/persistent collection classes for
Java. While collections are immutable they provide methods for
adding and removing values by creating new modified copies of
themselves. Each copy shares almost all of its structure with
other copies to minimize memory consumption.
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// Neither the name of the Burton Computer Corporation nor the names
// of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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package org.javimmutable.collections.array.bit32;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.Indexed;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.cursors.StandardCursor;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
@Immutable
public class StandardBit32Array
extends Bit32Array
{
private final int bitmask;
private final T[] entries;
private StandardBit32Array(int bitmask,
T[] entries)
{
this.bitmask = bitmask;
this.entries = entries;
}
@SuppressWarnings("unchecked")
StandardBit32Array()
{
this(0, (T[])new Object[0]);
}
/**
* Constructor for efficiently creating a Bit32Array with consecutive indexes of up to 32 - startIndex elements
* from an Indexed collection. (limit - offset) must be in the range 0 to (32 - startIndex) inclusive.
*
* @param source
* @param offset
* @param limit
*/
@SuppressWarnings("unchecked")
StandardBit32Array(Indexed source,
int offset,
int limit)
{
final int size = limit - offset;
if ((size < 0) || (size > 32)) {
throw new IllegalArgumentException("invalid size " + size);
} else {
final T[] entries = (T[])new Object[size];
for (int i = 0; i < size; ++i) {
entries[i] = source.get(offset + i);
}
if (size == 32) {
this.bitmask = -1;
} else {
this.bitmask = (1 << size) - 1;
}
this.entries = entries;
}
}
/**
* Constructor for efficiently creating a new instance with exactly two values.
* index1 and index2 must not be equal.
*
* @param index1
* @param value1
* @param index2
* @param value2
*/
@SuppressWarnings("unchecked")
StandardBit32Array(int index1,
T value1,
int index2,
T value2)
{
assert index1 != index2;
bitmask = (1 << index1) | (1 << index2);
entries = (T[])((index1 > index2) ? new Object[]{value2, value1} : new Object[]{value1, value2});
}
@SuppressWarnings({"unchecked", "RedundantCast"})
static StandardBit32Array fullWithout(Object[] entries,
int withoutIndex)
{
assert entries.length == 32;
final T[] newEntries = (T[])new Object[31];
System.arraycopy((T[])entries, 0, newEntries, 0, withoutIndex);
System.arraycopy((T[])entries, withoutIndex + 1, newEntries, withoutIndex, 31 - withoutIndex);
final int newMask = ~(1 << withoutIndex);
return new StandardBit32Array(newMask, newEntries);
}
@Override
@Nullable
public T getValueOr(int index,
@Nullable T defaultValue)
{
checkIndex(index);
final int bit = 1 << index;
final int bitmask = this.bitmask;
if ((bitmask & bit) == 0) {
return defaultValue;
} else {
return entries[realIndex(bitmask, bit)];
}
}
@Nonnull
public Holder find(int index)
{
checkIndex(index);
final int bit = 1 << index;
final int bitmask = this.bitmask;
if ((bitmask & bit) == 0) {
return Holders.of();
} else {
return Holders.of(entries[realIndex(bitmask, bit)]);
}
}
@Nonnull
@SuppressWarnings("unchecked")
public Bit32Array assign(int index,
@Nullable T value)
{
checkIndex(index);
final int bit = 1 << index;
final int bitmask = this.bitmask;
final int arrayIndex = realIndex(bitmask, bit);
final T[] entries = this.entries;
if ((bitmask & bit) == 0) {
final int oldLength = entries.length;
final T[] newEntries = (T[])new Object[oldLength + 1];
if (bitmask != 0) {
System.arraycopy(entries, 0, newEntries, 0, arrayIndex);
System.arraycopy(entries, arrayIndex, newEntries, arrayIndex + 1, oldLength - arrayIndex);
}
newEntries[arrayIndex] = value;
if (newEntries.length == 32) {
return new FullBit32Array(newEntries);
} else {
return new StandardBit32Array(bitmask | bit, newEntries);
}
} else if (entries[arrayIndex] == value) {
return this;
} else {
final T[] newEntries = entries.clone();
newEntries[arrayIndex] = value;
return new StandardBit32Array(bitmask, newEntries);
}
}
@Nonnull
@SuppressWarnings("unchecked")
public Bit32Array delete(int index)
{
checkIndex(index);
final int bit = 1 << index;
final int bitmask = this.bitmask;
final T[] entries = this.entries;
if ((bitmask & bit) == 0) {
return this;
} else {
switch (entries.length) {
case 1:
return Bit32Array.of();
case 2: {
final int newBitmask = bitmask & ~bit;
final int remainingIndex = Integer.numberOfTrailingZeros(newBitmask);
return new SingleBit32Array(remainingIndex, entries[realIndex(bitmask, 1 << remainingIndex)]);
}
default: {
int skipIndex = realIndex(bitmask, bit);
final int newLength = entries.length - 1;
final T[] newArray = (T[])new Object[newLength];
System.arraycopy(entries, 0, newArray, 0, skipIndex);
System.arraycopy(entries, skipIndex + 1, newArray, skipIndex, newLength - skipIndex);
return new StandardBit32Array(bitmask & ~bit, newArray);
}
}
}
}
public int size()
{
return entries.length;
}
@Override
public int firstIndex()
{
return Integer.numberOfTrailingZeros(bitmask);
}
@Override
@Nonnull
public Cursor> cursor()
{
return StandardCursor.of(new CursorSource(bitmask));
}
@Override
public void checkInvariants()
{
//TODO: fix empty checkInvariants()
}
private class CursorSource
implements StandardCursor.Source>
{
private final int remainingMask;
private final int index;
private CursorSource(int remainingMask)
{
this.remainingMask = remainingMask;
this.index = Integer.numberOfTrailingZeros(remainingMask);
}
@Override
public boolean atEnd()
{
return remainingMask == 0;
}
@Override
public JImmutableMap.Entry currentValue()
{
return MapEntry.of(index, find(index).getValue());
}
@Override
public StandardCursor.Source> advance()
{
if (remainingMask == 0) {
return this;
} else {
final int bit = 1 << index;
return new CursorSource(remainingMask & ~bit);
}
}
}
private static int realIndex(int bitmask,
int bit)
{
return Integer.bitCount(bitmask & (bit - 1));
}
}