/*
* Javolution - Java(TM) Solution for Real-Time and Embedded Systems
* Copyright (C) 2012 - Javolution (http://javolution.org/)
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software is
* freely granted, provided that this notice is preserved.
*/
package javolution.util.internal.table;
import javolution.lang.MathLib;
/**
* A fractal-based table with fast insertion/deletion capabilities regardless
* of the collection size. It is based on a fractal structure with self-similar
* patterns at any scale (large tables have the same structure as smaller tables
* which have similar structure as even smaller tables and so on).
*/
final class FractalTableImpl {
static final int BASE_CAPACITY_MIN = 16;
static final int SHIFT = 8;
private static final int BASE_CAPACITY_MAX = 1 << SHIFT;
/** Offset value, it is the index of the first element (modulo data.length). */
int offset;
/** An array of data elements or fractal tables (recursion).
Data length varies from 2 to BASE_CAPACITY_MAX */
private Object[] data;
/** The index shift, zero if base table. */
private final int shift;
public FractalTableImpl() {
this.shift = 0;
data = new Object[BASE_CAPACITY_MIN];
}
public FractalTableImpl(int shift) {
this.shift = shift;
data = new Object[2];
}
public FractalTableImpl(int shift, Object[] data, int offset) {
this.shift = shift;
this.data = data;
this.offset = offset;
}
public int capacity() {
// Reports lower capacity to ensure that there is no fractal holding
// wrapping data (head and tail in the same fractal).
return (data.length - 1) << shift;
}
public Object get(int index) {
Object fractal = data[((index + offset) >> shift) & (data.length - 1)];
return (shift == 0) ? fractal : ((FractalTableImpl) fractal).get(index
+ offset);
}
public Object set(int index, Object element) {
int i = ((index + offset) >> shift) & (data.length - 1);
if (shift != 0) return F(i).set(index + offset, element);
Object previous = data[i];
data[i] = element;
return previous;
}
/** Shifts the specified elements(]last - length, last] modulo capacity)
one position to the left. No shift if length (modulo capacity) is zero. */
public void shiftLeft(Object inserted, int last, int length) {
int mask = (data.length << shift) - 1;
int tail = (last + offset) & mask;
int head = (last + offset - length) & mask;
if (shift == 0) {
int n = tail - head;
if (head > tail) { // Wrapping
System.arraycopy(data, head + 1, data, head, mask - head);
data[mask] = data[0];
n = tail;
}
System.arraycopy(data, tail - n + 1, data, tail - n, n);
data[tail] = inserted;
} else if ((head <= tail) && ((head >> shift) == (tail >> shift))) { // Shift local to inner table.
F(head >> shift).shiftLeft(inserted, tail, length); // (no wrapping).
} else {
int low = head >> shift;
int high = (low != data.length - 1) ? low + 1 : 0;
F(low).shiftLeft(F(high).get(0), -1, mask - head);
while (high != (tail >> shift)) {
low = high;
high = (low != data.length - 1) ? low + 1 : 0;
F(low).offset++; // Full shift left.
F(low).set(-1, F(high).get(0));
}
F(high).shiftLeft(inserted, tail, tail);
}
}
/** Shifts the specified element ([first, first + length[ modulo capacity)
one position to the right. No shift if length (modulo capacity) is zero. */
public void shiftRight(Object inserted, int first, int length) {
int mask = (data.length << shift) - 1;
int head = (first + offset) & mask;
int tail = (first + offset + length) & mask;
if (shift == 0) {
int n = tail - head;
if (head > tail) { // Wrapping
System.arraycopy(data, 0, data, 1, tail);
data[0] = data[mask];
n = mask - head;
}
System.arraycopy(data, head, data, head + 1, n);
data[head] = inserted;
} else if ((head <= tail) && ((head >> shift) == (tail >> shift))) { // Shift local to inner table.
F(head >> shift).shiftRight(inserted, head, length); // (no wrapping).
} else {
int high = tail >> shift;
int low = (high != 0) ? high - 1 : data.length - 1;
F(high).shiftRight(F(low).get(-1), 0, tail);
while (low != (head >> shift)) {
high = low;
low = (high != 0) ? high - 1 : data.length - 1;
F(high).offset--; // Full shift right.
F(high).set(0, F(low).get(-1));
}
F(low).shiftRight(inserted, head, mask - head);
}
}
public FractalTableImpl upsize() {
if (data.length >= BASE_CAPACITY_MAX) { // Creates outer fractal.
FractalTableImpl table = new FractalTableImpl(shift + SHIFT);
copyTo(table.F(0));
return table;
} else {
FractalTableImpl table = new FractalTableImpl(shift,
new Object[data.length << 1], 0);
copyTo(table);
return table;
}
}
private FractalTableImpl allocate(int i) {
FractalTableImpl fractal = new FractalTableImpl(shift - SHIFT,
new Object[1 << SHIFT], 0);
data[i] = fractal;
return fractal;
}
// Copy to the specified table.
private void copyTo(FractalTableImpl that) {
int n = MathLib.min(this.data.length, that.data.length);
offset &= (data.length << shift) - 1; // Makes it positive.
int o = offset >> shift;
if ((o + n) > data.length) { // Wrapping.
int w = (o + n) - data.length;
n -= w;
System.arraycopy(data, 0, that.data, n, w);
}
System.arraycopy(data, o, that.data, 0, n);
that.offset = offset - (o << shift);
}
private FractalTableImpl F(int i) {
FractalTableImpl table = (FractalTableImpl) data[i];
return (table != null) ? table : allocate(i);
}
}