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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.tree.iter;
import net.sf.saxon.expr.LastPositionFinder;
import net.sf.saxon.functions.Reverse;
import net.sf.saxon.om.*;
import net.sf.saxon.value.SequenceExtent;
import java.util.Arrays;
import java.util.List;
/**
* ArrayIterator is used to enumerate items held in an array.
* The items are always held in the correct sorted order for the sequence.
*
* The challenge here is getting the generics right, especially in a way
* that works for C#, which is less tolerant of generic abuse. The solution
* is to have a non-generic {@code ArrayIterator} class, with
* {@code ArrayIterator.Of} as a subclass. A further subtlety
* is that we need an ArrayIterator of nodes to implement {@code AxisIterator},
* so we have another subclass {@code ArrayIterator.OfNodes}
* for that purpose.
*/
public abstract class ArrayIterator implements SequenceIterator,
LastPositionFinder, LookaheadIterator, GroundedIterator, ReversibleIterator {
protected int index; // position in array of current item, zero-based
// set equal to end+1 when all the items required have been read.
protected int start; // position of first item to be returned, zero-based
protected int end; // position of first item that is NOT returned, zero-based
/**
* Create a new ArrayIterator over the same items,
* with a different start point and end point
*
* @param min the start position (1-based) of the new ArrayIterator
* relative to the original
* @param max the end position (1-based) of the last item to be delivered
* by the new ArrayIterator, relative to the original. For example, min=2, max=3
* delivers the two items ($base[2], $base[3]). Set this to Integer.MAX_VALUE if
* there is no end limit.
* @return an iterator over the items between the min and max positions
*/
public abstract SequenceIterator makeSliceIterator(int min, int max);
public boolean isActuallyGrounded() {
return true;
}
@Override
public boolean supportsHasNext() {
return true;
}
/**
* Parameterised subclass to accept items of a particular item type
* @param the item type of the items returned by the ArrayIterator
*/
public static class Of extends ArrayIterator {
protected T[] items;
public Of(T[] items) {
this.items = items;
start = 0;
end = items.length;
index = 0;
}
/**
* Create an iterator over a range of an array. Note that the start position is zero-based
*
* @param items the array (of nodes or simple values) to be processed by
* the iterator
* @param start the position of the first item to be processed
* (numbering from zero). Must be between zero and nodes.length-1; if not,
* undefined exceptions are likely to occur.
* @param end position of first item that is NOT returned, zero-based. Must be
* between 1 and nodes.length; if not, undefined exceptions are likely to occur.
*/
public Of(T[] items, int start, int end) {
this.items = items;
this.end = end;
this.start = start;
index = start;
}
/**
* Create a new ArrayIterator over the same items,
* with a different start point and end point
*
* @param min the start position (1-based) of the new ArrayIterator
* relative to the original
* @param max the end position (1-based) of the last item to be delivered
* by the new ArrayIterator, relative to the original. For example, min=2, max=3
* delivers the two items ($base[2], $base[3]). Set this to Integer.MAX_VALUE if
* there is no end limit.
* @return an iterator over the items between the min and max positions
*/
public SequenceIterator makeSliceIterator(int min, int max) {
T[] items = getArray();
int currentStart = getStartPosition();
int currentEnd = getEndPosition();
if (min < 1) {
min = 1;
}
int newStart = currentStart + (min - 1);
if (newStart < currentStart) {
newStart = currentStart;
}
int newEnd = max == Integer.MAX_VALUE ? currentEnd : newStart + max - min + 1;
if (newEnd > currentEnd) {
newEnd = currentEnd;
}
if (newEnd <= newStart) {
return EmptyIterator.emptyIterator();
}
return new Of(items, newStart, newEnd);
}
/**
* Test whether there are any more items
*
* @return true if there are more items
*/
@Override
public boolean hasNext() {
return index < end;
}
/**
* Get the next item in the array
*
* @return the next item in the array
*/
/*@Nullable*/
@Override
public Item next() {
if (index >= end) {
index = end + 1;
return null;
}
return items[index++];
}
@Override
public boolean supportsGetLength() {
return true;
}
/**
* Get the number of items in the part of the array being processed
*
* @return the number of items; equivalently, the position of the last
* item
*/
@Override
public int getLength() {
return end - start;
}
/**
* Get the underlying array
*
* @return the underlying array being processed by the iterator
*/
public T[] getArray() {
return items;
}
/**
* Get the initial start position
*
* @return the start position of the iterator in the array (zero-based)
*/
public int getStartPosition() {
return start;
}
/**
* Get the end position in the array
*
* @return the position in the array (zero-based) of the first item not included
* in the iteration
*/
public int getEndPosition() {
return end;
}
/**
* Return a SequenceValue containing all the items in the sequence returned by this
* SequenceIterator
*
* @return the corresponding SequenceValue
*/
/*@NotNull*/
@Override
public GroundedValue materialize() {
SequenceExtent.Of seq;
if (start == 0 && end == items.length) {
seq = new SequenceExtent.Of<>(items);
} else {
List sublist = Arrays.asList(items).subList(start, end);
seq = new SequenceExtent.Of<>(sublist);
}
return seq.reduce();
}
@Override
public GroundedValue getResidue() {
SequenceExtent seq;
if (start == 0 && index == 0 && end == items.length) {
seq = new SequenceExtent.Of<>(items);
} else {
List sublist = Arrays.asList(items).subList(start + index, end);
seq = new SequenceExtent.Of<>(sublist);
}
return seq.reduce();
}
@Override
public SequenceIterator getReverseIterator() {
if (start == 0 && end == items.length) {
return Reverse.reverseIterator(Arrays.asList(items));
} else {
List sublist = Arrays.asList(items).subList(start, end);
return Reverse.reverseIterator(sublist);
}
}
}
/**
* ArrayIterator.OfNodes is a subclass of ArrayIterator where the array always
* contains Nodes; it therefore implements the AxisIterator interface.
*/
public static class OfNodes extends ArrayIterator.Of implements AxisIterator {
public OfNodes(N[] nodes) {
super(nodes);
}
public NodeInfo next() {
return (NodeInfo)super.next();
}
}
}