it.unimi.dsi.fastutil.bytes.ByteIterators Maven / Gradle / Ivy
/*
* Copyright (C) 2002-2017 Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.bytes;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
/** A class providing static methods and objects that do useful things with type-specific iterators.
*
* @see Iterator
*/
public class ByteIterators {
private ByteIterators() {}
/** A class returning no elements and a type-specific iterator interface.
*
* This class may be useful to implement your own in case you subclass
* a type-specific iterator.
*/
public static class EmptyIterator extends AbstractByteListIterator implements java.io.Serializable, Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected EmptyIterator() {}
@Override
public boolean hasNext() { return false; }
@Override
public boolean hasPrevious() { return false; }
@Override
public byte nextByte() { throw new NoSuchElementException(); }
@Override
public byte previousByte() { throw new NoSuchElementException(); }
@Override
public int nextIndex() { return 0; }
@Override
public int previousIndex() { return -1; }
@Override
public int skip(int n) { return 0; };
@Override
public int back(int n) { return 0; };
@Override
public Object clone() { return EMPTY_ITERATOR; }
private Object readResolve() { return EMPTY_ITERATOR; }
}
/** An empty iterator. It is serializable and cloneable.
*
*
The class of this objects represent an abstract empty iterator
* that can iterate as a type-specific (list) iterator.
*/
public final static EmptyIterator EMPTY_ITERATOR = new EmptyIterator();
/** An iterator returning a single element. */
private static class SingletonIterator extends AbstractByteListIterator {
private final byte element;
private int curr;
public SingletonIterator(final byte element) {
this.element = element;
}
@Override
public boolean hasNext() { return curr == 0; }
@Override
public boolean hasPrevious() { return curr == 1; }
@Override
public byte nextByte() {
if (! hasNext()) throw new NoSuchElementException();
curr = 1;
return element;
}
@Override
public byte previousByte() {
if (! hasPrevious()) throw new NoSuchElementException();
curr = 0;
return element;
}
@Override
public int nextIndex() {
return curr;
}
@Override
public int previousIndex() {
return curr - 1;
}
}
/** Returns an immutable iterator that iterates just over the given element.
*
* @param element the only element to be returned by a type-specific list iterator.
* @return an immutable iterator that iterates just over element.
*/
public static ByteListIterator singleton(final byte element) {
return new SingletonIterator (element);
}
/** A class to wrap arrays in iterators. */
private static class ArrayIterator extends AbstractByteListIterator {
private final byte[] array;
private final int offset, length;
private int curr;
public ArrayIterator(final byte[] array, final int offset, final int length) {
this.array = array;
this.offset = offset;
this.length = length;
}
@Override
public boolean hasNext() { return curr < length; }
@Override
public boolean hasPrevious() { return curr > 0; }
@Override
public byte nextByte() {
if (! hasNext()) throw new NoSuchElementException();
return array[offset + curr++];
}
@Override
public byte previousByte() {
if (! hasPrevious()) throw new NoSuchElementException();
return array[offset + --curr];
}
@Override
public int skip(int n) {
if (n <= length - curr) {
curr += n;
return n;
}
n = length - curr;
curr = length;
return n;
}
@Override
public int back(int n) {
if (n <= curr) {
curr -= n;
return n;
}
n = curr;
curr = 0;
return n;
}
@Override
public int nextIndex() {
return curr;
}
@Override
public int previousIndex() {
return curr - 1;
}
}
/** Wraps the given part of an array into a type-specific list iterator.
*
*
The type-specific list iterator returned by this method will iterate
* length times, returning consecutive elements of the given
* array starting from the one with index offset.
*
* @param array an array to wrap into a type-specific list iterator.
* @param offset the first element of the array to be returned.
* @param length the number of elements to return.
* @return an iterator that will return length elements of array starting at position offset.
*/
public static ByteListIterator wrap(final byte[] array, final int offset, final int length) {
ByteArrays.ensureOffsetLength(array, offset, length);
return new ArrayIterator (array, offset, length);
}
/** Wraps the given array into a type-specific list iterator.
*
*
The type-specific list iterator returned by this method will return
* all elements of the given array.
*
* @param array an array to wrap into a type-specific list iterator.
* @return an iterator that will the elements of array.
*/
public static ByteListIterator wrap(final byte[] array) {
return new ArrayIterator (array, 0, array.length);
}
/** Unwraps an iterator into an array starting at a given offset for a given number of elements.
*
*
This method iterates over the given type-specific iterator and stores the elements
* returned, up to a maximum of length, in the given array starting at offset.
* The number of actually unwrapped elements is returned (it may be less than max if
* the iterator emits less than max elements).
*
* @param i a type-specific iterator.
* @param array an array to contain the output of the iterator.
* @param offset the first element of the array to be returned.
* @param max the maximum number of elements to unwrap.
* @return the number of elements unwrapped.
*/
public static int unwrap(final ByteIterator i, final byte array[], int offset, final int max) {
if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
if (offset < 0 || offset + max > array.length) throw new IllegalArgumentException();
int j = max;
while(j-- != 0 && i.hasNext()) array[offset++] = i.nextByte();
return max - j - 1;
}
/** Unwraps an iterator into an array.
*
*
This method iterates over the given type-specific iterator and stores the
* elements returned in the given array. The iteration will stop when the
* iterator has no more elements or when the end of the array has been reached.
*
* @param i a type-specific iterator.
* @param array an array to contain the output of the iterator.
* @return the number of elements unwrapped.
*/
public static int unwrap(final ByteIterator i, final byte array[]) {
return unwrap(i, array, 0, array.length);
}
/** Unwraps an iterator, returning an array, with a limit on the number of elements.
*
*
This method iterates over the given type-specific iterator and returns an array
* containing the elements returned by the iterator. At most max elements
* will be returned.
*
* @param i a type-specific iterator.
* @param max the maximum number of elements to be unwrapped.
* @return an array containing the elements returned by the iterator (at most max).
*/
public static byte[] unwrap(final ByteIterator i, int max) {
if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
byte array[] = new byte[16];
int j = 0;
while(max-- != 0 && i.hasNext()) {
if (j == array.length) array = ByteArrays.grow(array, j + 1);
array[j++] = i.nextByte();
}
return ByteArrays.trim(array, j);
}
/** Unwraps an iterator, returning an array.
*
*
This method iterates over the given type-specific iterator and returns an array
* containing the elements returned by the iterator.
*
* @param i a type-specific iterator.
* @return an array containing the elements returned by the iterator.
*/
public static byte[] unwrap(final ByteIterator i) {
return unwrap(i, Integer.MAX_VALUE);
}
/** Unwraps an iterator into a type-specific collection, with a limit on the number of elements.
*
*
This method iterates over the given type-specific iterator and stores the elements
* returned, up to a maximum of max, in the given type-specific collection.
* The number of actually unwrapped elements is returned (it may be less than max if
* the iterator emits less than max elements).
*
* @param i a type-specific iterator.
* @param c a type-specific collection array to contain the output of the iterator.
* @param max the maximum number of elements to unwrap.
* @return the number of elements unwrapped. Note that
* this is the number of elements returned by the iterator, which is not necessarily the number
* of elements that have been added to the collection (because of duplicates).
*/
public static int unwrap(final ByteIterator i, final ByteCollection c, final int max) {
if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
int j = max;
while(j-- != 0 && i.hasNext()) c.add(i.nextByte());
return max - j - 1;
}
/** Unwraps an iterator into a type-specific collection.
*
*
This method iterates over the given type-specific iterator and stores the
* elements returned in the given type-specific collection. The returned count on the number
* unwrapped elements is a long, so that it will work also with very large collections.
*
* @param i a type-specific iterator.
* @param c a type-specific collection to contain the output of the iterator.
* @return the number of elements unwrapped. Note that
* this is the number of elements returned by the iterator, which is not necessarily the number
* of elements that have been added to the collection (because of duplicates).
*/
public static long unwrap(final ByteIterator i, final ByteCollection c) {
long n = 0;
while(i.hasNext()) {
c.add(i.nextByte());
n++;
}
return n;
}
/** Pours an iterator into a type-specific collection, with a limit on the number of elements.
*
*
This method iterates over the given type-specific iterator and adds
* the returned elements to the given collection (up to max).
*
* @param i a type-specific iterator.
* @param s a type-specific collection.
* @param max the maximum number of elements to be poured.
* @return the number of elements poured. Note that
* this is the number of elements returned by the iterator, which is not necessarily the number
* of elements that have been added to the collection (because of duplicates).
*/
public static int pour(final ByteIterator i, final ByteCollection s, final int max) {
if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
int j = max;
while(j-- != 0 && i.hasNext()) s.add(i.nextByte());
return max - j - 1;
}
/** Pours an iterator into a type-specific collection.
*
*
This method iterates over the given type-specific iterator and adds
* the returned elements to the given collection.
*
* @param i a type-specific iterator.
* @param s a type-specific collection.
* @return the number of elements poured. Note that
* this is the number of elements returned by the iterator, which is not necessarily the number
* of elements that have been added to the collection (because of duplicates).
*/
public static int pour(final ByteIterator i, final ByteCollection s) {
return pour(i, s, Integer.MAX_VALUE);
}
/** Pours an iterator, returning a type-specific list, with a limit on the number of elements.
*
*
This method iterates over the given type-specific iterator and returns
* a type-specific list containing the returned elements (up to max). Iteration
* on the returned list is guaranteed to produce the elements in the same order
* in which they appeared in the iterator.
*
*
* @param i a type-specific iterator.
* @param max the maximum number of elements to be poured.
* @return a type-specific list containing the returned elements, up to max.
*/
public static ByteList pour(final ByteIterator i, int max) {
final ByteArrayList l = new ByteArrayList ();
pour(i, l, max);
l.trim();
return l;
}
/** Pours an iterator, returning a type-specific list.
*
*
This method iterates over the given type-specific iterator and returns
* a list containing the returned elements. Iteration
* on the returned list is guaranteed to produce the elements in the same order
* in which they appeared in the iterator.
*
* @param i a type-specific iterator.
* @return a type-specific list containing the returned elements.
*/
public static ByteList pour(final ByteIterator i) {
return pour(i, Integer.MAX_VALUE);
}
private static class IteratorWrapper extends AbstractByteIterator {
final Iterator i;
public IteratorWrapper(final Iterator i) {
this.i = i;
}
public boolean hasNext() { return i.hasNext(); }
public void remove() { i.remove(); }
public byte nextByte() { return ((i.next()).byteValue()); }
}
/** Wraps a standard iterator into a type-specific iterator.
*
* This method wraps a standard iterator into a type-specific one which will handle the
* type conversions for you. Of course, any attempt to wrap an iterator returning the
* instances of the wrong class will generate a {@link ClassCastException}. The
* returned iterator is backed by i: changes to one of the iterators
* will affect the other, too.
*
*
If i is already type-specific, it will returned and no new object
* will be generated.
*
* @param i an iterator.
* @return a type-specific iterator backed by i.
*/
@SuppressWarnings({"unchecked","rawtypes"})
public static ByteIterator asByteIterator(final Iterator i) {
if (i instanceof ByteIterator) return (ByteIterator )i;
return new IteratorWrapper (i);
}
private static class ListIteratorWrapper extends AbstractByteListIterator {
final ListIterator i;
public ListIteratorWrapper(final ListIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public int nextIndex() { return i.nextIndex(); }
@Override
public int previousIndex() { return i.previousIndex(); }
@Override
public void set(byte k) { i.set((Byte.valueOf(k))); }
@Override
public void add(byte k) { i.add((Byte.valueOf(k))); }
@Override
public void remove() { i.remove(); }
@Override
public byte nextByte() { return ((i.next()).byteValue()); }
@Override
public byte previousByte() { return ((i.previous()).byteValue()); }
}
/** Wraps a standard list iterator into a type-specific list iterator.
*
* This method wraps a standard list iterator into a type-specific one
* which will handle the type conversions for you. Of course, any attempt
* to wrap an iterator returning the instances of the wrong class will
* generate a {@link ClassCastException}. The
* returned iterator is backed by i: changes to one of the iterators
* will affect the other, too.
*
*
If i is already type-specific, it will returned and no new object
* will be generated.
*
* @param i a list iterator.
* @return a type-specific list iterator backed by i.
*/
@SuppressWarnings({"unchecked","rawtypes"})
public static ByteListIterator asByteIterator(final ListIterator i) {
if (i instanceof ByteListIterator) return (ByteListIterator )i;
return new ListIteratorWrapper (i);
}
private static class IntervalIterator extends AbstractByteListIterator {
private final byte from, to;
byte curr;
public IntervalIterator(final byte from, final byte to) {
this.from = this.curr = from;
this.to = to;
}
@Override
public boolean hasNext() { return curr < to; }
@Override
public boolean hasPrevious() { return curr > from; }
@Override
public byte nextByte() {
if (! hasNext()) throw new NoSuchElementException();
return curr++;
}
@Override
public byte previousByte() {
if (! hasPrevious()) throw new NoSuchElementException();
return --curr;
}
@Override
public int nextIndex() { return curr - from; }
@Override
public int previousIndex() { return curr - from - 1; }
@Override
public int skip(int n) {
if (curr + n <= to) {
curr += n;
return n;
}
n = to - curr;
curr = to;
return n;
}
@Override
public int back(int n) {
if (curr - n >= from) {
curr -= n;
return n;
}
n = curr - from ;
curr = from;
return n;
}
}
/** Creates a type-specific list iterator over an interval.
*
*
The type-specific list iterator returned by this method will return the
* elements from, from+1,…, to-1.
*
* @param from the starting element (inclusive).
* @param to the ending element (exclusive).
* @return a type-specific list iterator enumerating the elements from from to to.
*/
public static ByteListIterator fromTo(final byte from, final byte to) {
return new IntervalIterator(from, to);
}
private static class IteratorConcatenator extends AbstractByteIterator {
final ByteIterator a[];
int offset, length, lastOffset = -1;
public IteratorConcatenator(final ByteIterator a[], int offset, int length) {
this.a = a;
this.offset = offset;
this.length = length;
advance();
}
private void advance() {
while(length != 0) {
if (a[offset].hasNext()) break;
length--;
offset++;
}
return;
}
@Override
public boolean hasNext() {
return length > 0;
}
@Override
public byte nextByte() {
if (! hasNext()) throw new NoSuchElementException();
byte next = a[lastOffset = offset].nextByte();
advance();
return next;
}
@Override
public void remove() {
if (lastOffset == -1) throw new IllegalStateException();
a[lastOffset].remove();
}
@Override
public int skip(int n) {
lastOffset = -1;
int skipped = 0;
while(skipped < n && length != 0) {
skipped += a[offset].skip(n - skipped);
if (a[offset].hasNext()) break;
length--;
offset++;
}
return skipped;
}
}
/** Concatenates all iterators contained in an array.
*
*
This method returns an iterator that will enumerate in order the elements returned
* by all iterators contained in the given array.
*
* @param a an array of iterators.
* @return an iterator obtained by concatenation.
*/
public static ByteIterator concat(final ByteIterator a[]) {
return concat(a, 0, a.length);
}
/** Concatenates a sequence of iterators contained in an array.
*
*
This method returns an iterator that will enumerate in order the elements returned
* by a[offset], then those returned
* by a[offset + 1], and so on up to
* a[offset + length - 1].
*
* @param a an array of iterators.
* @param offset the index of the first iterator to concatenate.
* @param length the number of iterators to concatenate.
* @return an iterator obtained by concatenation of length elements of a starting at offset.
*/
public static ByteIterator concat(final ByteIterator a[], final int offset, final int length) {
return new IteratorConcatenator (a, offset, length);
}
/** An unmodifiable wrapper class for iterators. */
public static class UnmodifiableIterator extends AbstractByteIterator {
final protected ByteIterator i;
public UnmodifiableIterator(final ByteIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public byte nextByte() { return i.nextByte(); }
}
/** Returns an unmodifiable iterator backed by the specified iterator.
*
* @param i the iterator to be wrapped in an unmodifiable iterator.
* @return an unmodifiable view of the specified iterator.
*/
public static ByteIterator unmodifiable(final ByteIterator i) { return new UnmodifiableIterator (i); }
/** An unmodifiable wrapper class for bidirectional iterators. */
public static class UnmodifiableBidirectionalIterator extends AbstractByteBidirectionalIterator {
final protected ByteBidirectionalIterator i;
public UnmodifiableBidirectionalIterator(final ByteBidirectionalIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public byte nextByte() { return i.nextByte(); }
@Override
public byte previousByte() { return i.previousByte(); }
}
/** Returns an unmodifiable bidirectional iterator backed by the specified bidirectional iterator.
*
* @param i the bidirectional iterator to be wrapped in an unmodifiable bidirectional iterator.
* @return an unmodifiable view of the specified bidirectional iterator.
*/
public static ByteBidirectionalIterator unmodifiable(final ByteBidirectionalIterator i) { return new UnmodifiableBidirectionalIterator (i); }
/** An unmodifiable wrapper class for list iterators. */
public static class UnmodifiableListIterator extends AbstractByteListIterator {
final protected ByteListIterator i;
public UnmodifiableListIterator(final ByteListIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public byte nextByte() { return i.nextByte(); }
@Override
public byte previousByte() { return i.previousByte(); }
@Override
public int nextIndex() { return i.nextIndex(); }
@Override
public int previousIndex() { return i.previousIndex(); }
}
/** Returns an unmodifiable list iterator backed by the specified list iterator.
*
* @param i the list iterator to be wrapped in an unmodifiable list iterator.
* @return an unmodifiable view of the specified list iterator.
*/
public static ByteListIterator unmodifiable(final ByteListIterator i) { return new UnmodifiableListIterator (i); }
}