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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2020 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.om;
import net.sf.saxon.event.Outputter;
import net.sf.saxon.event.ReceiverOption;
import net.sf.saxon.expr.*;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.functions.Count;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.EmptyIterator;
import net.sf.saxon.tree.iter.UnfailingIterator;
import net.sf.saxon.tree.util.FastStringBuffer;
import net.sf.saxon.tree.wrapper.VirtualNode;
import net.sf.saxon.type.*;
import net.sf.saxon.value.*;
/**
* Utility class for manipulating sequences. Some of these methods should be regarded
* as temporary scaffolding while the model is in transition.
*/
public class SequenceTool {
/**
* Constant returned by compareTo() method to indicate an indeterminate ordering between two values
*/
public static final int INDETERMINATE_ORDERING = Integer.MIN_VALUE;
/**
* Produce a GroundedValue containing the same values as a supplied sequence.
*
* @param iterator the supplied sequence. The iterator may or may not be consumed as a result of
* passing it to this method.
* @return a GroundedValue containing the same items
* @throws XPathException if a failure occurs reading the input iterator
*/
public static GroundedValue toGroundedValue(SequenceIterator iterator) throws XPathException {
return iterator.materialize();
}
/**
* Produce a Sequence containing the same values as a supplied sequence; the input is
* read progressively as required, and saved in a buffer as it is read in case it is needed
* again. But if the iterator is already backed by a grounded value, we return that value.
*
* @param iterator the supplied sequence. The iterator may or may not be consumed as a result of
* passing it to this method.
* @return a Sequence containing the same items
* @throws XPathException if a failure occurs reading the input iterator
*/
public static Sequence toMemoSequence(SequenceIterator iterator) throws XPathException {
if (iterator instanceof EmptyIterator) {
return EmptySequence.getInstance();
} else if (iterator.getProperties().contains(SequenceIterator.Property.GROUNDED)) {
return iterator.materialize();
} else {
return new MemoSequence(iterator);
}
}
/**
* Construct a sequence capable of returning the same items as an iterator,
* without incurring the cost of evaluating the iterator and storing all
* the items.
*
* @param iterator the supplied sequence. The iterator may or may not be consumed as a result of
* passing it to this method.
* @return a Sequence containing the same items as the supplied iterator
* @throws XPathException if a failure occurs reading the input iterator
*/
public static Sequence toLazySequence(SequenceIterator iterator) throws XPathException {
if (iterator.getProperties().contains(SequenceIterator.Property.GROUNDED) &&
!(iterator instanceof RangeIterator) &&
!(iterator instanceof ReverseRangeIterator)) {
return iterator.materialize();
} else {
return new LazySequence(iterator);
}
}
public static Sequence toLazySequence2(SequenceIterator iterator) throws XPathException {
if (iterator.getProperties().contains(SequenceIterator.Property.GROUNDED) &&
!(iterator instanceof RangeIterator) &&
!(iterator instanceof ReverseRangeIterator)) {
return iterator.materialize();
} else {
return new LazySequence(iterator);
}
}
public static boolean isUnrepeatable(Sequence seq) {
return seq instanceof LazySequence ||
(seq instanceof Closure && !(seq instanceof MemoClosure || seq instanceof SingletonClosure));
}
/**
* Get the length of a sequence (the number of items it contains)
*
* @param sequence the sequence
* @return the length in items
* @throws XPathException if an error occurs (due to lazy evaluation)
*/
public static int getLength(Sequence sequence) throws XPathException {
if (sequence instanceof GroundedValue) {
return ((GroundedValue) sequence).getLength();
}
return Count.count(sequence.iterate());
}
/**
* Ask whether the length of a sequence is exactly N
*
* @param iter an iterator over the sequence in question (which is typically consumed)
* @param length the supposed length
* @return true if and only if the length of the sequence is the supposed length
*/
public static boolean hasLength(SequenceIterator iter, int length) throws XPathException {
if (iter.getProperties().contains(SequenceIterator.Property.LAST_POSITION_FINDER)) {
return ((LastPositionFinder) iter).getLength() == length;
} else {
int n = 0;
while (iter.next() != null) {
if (n++ == length) {
iter.close();
return false;
}
}
return length == 0;
}
}
/**
* Determine whether two sequences have the same number of items. This is more efficient
* than comparing the counts, because the longer sequence is evaluated only as far as the
* length of the shorter sequence. The method consumes the supplied iterators.
*
* @param a iterator over the first sequence
* @param b iterator over the second sequece
* @return true if the lengths of the two sequences are the same
*/
public static boolean sameLength(SequenceIterator a, SequenceIterator b) throws XPathException {
if (a.getProperties().contains(SequenceIterator.Property.LAST_POSITION_FINDER)) {
return hasLength(b, ((LastPositionFinder) a).getLength());
} else if (b.getProperties().contains(SequenceIterator.Property.LAST_POSITION_FINDER)) {
return hasLength(a, ((LastPositionFinder) b).getLength());
} else {
while (true) {
Item itA = a.next();
Item itB = b.next();
if (itA == null || itB == null) {
if (itA != null) {
a.close();
}
if (itB != null) {
b.close();
}
return itA == null && itB == null;
}
}
}
}
/**
* Get the item at a given offset in a sequence. Uses zero-base indexing
*
* @param sequence the input sequence
* @param index the 0-based subscript
* @return the n'th item if it exists, or null otherwise
* @throws XPathException for example if the value is a closure that needs to be
* evaluated, and evaluation fails
*/
public static Item itemAt(Sequence sequence, int index) throws XPathException {
if (sequence instanceof Item && index == 0) {
return (Item)sequence;
}
return sequence.materialize().itemAt(index);
}
/**
* Static method to make an Item from a Value
*
* @param sequence the value to be converted
* @return null if the value is an empty sequence; or the only item in the value
* if it is a singleton sequence
* @throws net.sf.saxon.trans.XPathException if the supplied Sequence contains multiple items
*/
/*@Nullable*/
public static Item asItem(Sequence sequence) throws XPathException {
if (sequence instanceof Item) {
return (Item) sequence;
}
SequenceIterator iter = sequence.iterate();
Item first = iter.next();
if (first == null) {
return null;
}
if (iter.next() != null) {
throw new XPathException("Sequence contains more than one item");
}
return first;
}
/**
* Convert an XPath value to a Java object.
* An atomic value is returned as an instance
* of the best available Java class. If the item is a node, the node is "unwrapped",
* to return the underlying node in the original model (which might be, for example,
* a DOM or JDOM node).
*
* @param item the item to be converted
* @return the value after conversion
* @throws net.sf.saxon.trans.XPathException if an error occurs: for example, if the XPath value is
* an integer and is too big to fit in a Java long
*/
public static Object convertToJava(/*@NotNull*/ Item item) throws XPathException {
if (item instanceof NodeInfo) {
Object node = item;
while (node instanceof VirtualNode) {
// strip off any layers of wrapping
node = ((VirtualNode) node).getRealNode();
}
return node;
} else if (item instanceof Function) {
return item;
} else if (item instanceof ExternalObject) {
return ((ExternalObject) item).getObject();
} else {
AtomicValue value = (AtomicValue) item;
switch (value.getItemType().getPrimitiveType()) {
case StandardNames.XS_STRING:
case StandardNames.XS_UNTYPED_ATOMIC:
case StandardNames.XS_ANY_URI:
case StandardNames.XS_DURATION:
return value.getStringValue();
case StandardNames.XS_BOOLEAN:
return ((BooleanValue) value).getBooleanValue() ? Boolean.TRUE : Boolean.FALSE;
case StandardNames.XS_DECIMAL:
return ((BigDecimalValue) value).getDecimalValue();
case StandardNames.XS_INTEGER:
return ((NumericValue) value).longValue();
case StandardNames.XS_DOUBLE:
return ((DoubleValue) value).getDoubleValue();
case StandardNames.XS_FLOAT:
return ((FloatValue) value).getFloatValue();
case StandardNames.XS_DATE_TIME:
return ((DateTimeValue) value).getCalendar().getTime();
case StandardNames.XS_DATE:
return ((DateValue) value).getCalendar().getTime();
case StandardNames.XS_TIME:
return value.getStringValue();
case StandardNames.XS_BASE64_BINARY:
return ((Base64BinaryValue) value).getBinaryValue();
case StandardNames.XS_HEX_BINARY:
return ((HexBinaryValue) value).getBinaryValue();
default:
return item;
}
}
}
/**
* Get the string value of a sequence. For an item, this is same as the result
* of calling the XPath string() function. For a sequence of more than one item,
* it is the concatenation of the individual string values of the items in the sequence,
* space-separated.
*
* @param sequence the input sequence
* @return a string representation of the items in the supplied sequence
* @throws XPathException if the sequence contains an item with no string value,
* for example a function item
*/
public static String getStringValue(Sequence sequence) throws XPathException {
FastStringBuffer fsb = new FastStringBuffer(FastStringBuffer.C64);
sequence.iterate().forEachOrFail(item -> {
if (!fsb.isEmpty()) {
fsb.cat(' ');
}
fsb.cat(item.getStringValueCS());
});
return fsb.toString();
}
/**
* Get the item type of the items in a sequence. If the sequence is heterogeneous,
* the method returns the lowest common supertype. If the sequence is empty, it returns
* ErrorType (the type to which no instance can belong)
*
* @param sequence the input sequence
* @param th the Type Hierarchy cache
* @return the lowest common supertype of the types of the items in the sequence
*/
public static ItemType getItemType(Sequence sequence, TypeHierarchy th) {
if (sequence instanceof Item) {
return Type.getItemType((Item) sequence, th);
} else if (sequence instanceof GroundedValue) {
try {
ItemType type = null;
SequenceIterator iter = sequence.iterate();
Item item;
while ((item = iter.next()) != null) {
if (type == null) {
type = Type.getItemType(item, th);
} else {
type = Type.getCommonSuperType(type, Type.getItemType(item, th), th);
}
if (type == AnyItemType.getInstance()) {
break;
}
}
return type == null ? ErrorType.getInstance() : type;
} catch (XPathException err) {
return AnyItemType.getInstance();
}
} else {
return AnyItemType.getInstance();
}
}
/**
* Get the UType of the items in a sequence. If the sequence is heterogeneous,
* the method returns the lowest common supertype. If the sequence is empty, it returns
* ErrorType (the type to which no instance can belong)
*
* @param sequence the input sequence
* @return the lowest common supertype of the types of the items in the sequence
*/
public static UType getUType(Sequence sequence) {
if (sequence instanceof Item) {
return UType.getUType((Item) sequence);
} else if (sequence instanceof GroundedValue) {
UType type = UType.VOID;
UnfailingIterator iter = ((GroundedValue) sequence).iterate();
Item item;
while ((item = iter.next()) != null) {
type = type.union(UType.getUType(item));
if (type == UType.ANY) {
break;
}
}
return type;
} else {
return UType.ANY;
}
}
/**
* Get the cardinality of a sequence
*
* @param sequence the supplied sequence
* @return the cardinality, as one of the constants {@link StaticProperty#ALLOWS_ZERO} (for an empty sequence)
* {@link StaticProperty#EXACTLY_ONE} (for a singleton), or {@link StaticProperty#ALLOWS_ONE_OR_MORE} (for
* a sequence with more than one item)
*/
public static int getCardinality(Sequence sequence) {
if (sequence instanceof Item) {
return StaticProperty.EXACTLY_ONE;
}
if (sequence instanceof GroundedValue) {
int len = ((GroundedValue) sequence).getLength();
switch (len) {
case 0:
return StaticProperty.ALLOWS_ZERO;
case 1:
return StaticProperty.EXACTLY_ONE;
default:
return StaticProperty.ALLOWS_ONE_OR_MORE;
}
}
try {
SequenceIterator iter = sequence.iterate();
Item item = iter.next();
if (item == null) {
return StaticProperty.ALLOWS_ZERO;
}
item = iter.next();
return item == null ? StaticProperty.EXACTLY_ONE : StaticProperty.ALLOWS_ONE_OR_MORE;
} catch (XPathException err) {
return StaticProperty.ALLOWS_ONE_OR_MORE;
}
}
/**
* Process a supplied value by copying it to the current output destination
*
* @param value the sequence to be processed
* @param output the destination for the result
* @param locationId (can be set to -1 if absent) information about the location of the value,
* which can be resolved by reference to the PipelineConfiguration of the current output
* destination
* @throws net.sf.saxon.trans.XPathException if an error occurs (for example if the value is
* a closure that needs to be evaluated)
*/
public static void process(Sequence value, Outputter output, Location locationId) throws XPathException {
value.iterate().forEachOrFail(it -> output.append(it, locationId, ReceiverOption.ALL_NAMESPACES));
}
/**
* Make an array of general-purpose Sequence objects of a given length
* @param length the length of the returned array
*/
public static Sequence[] makeSequenceArray(int length) {
return (Sequence[])new Sequence[length];
}
/**
* Make an array of general-purpose Sequence objects with supplied contents
*/
public static Sequence[] fromItems(Item... items) {
Sequence[] seq = (Sequence[]) new Sequence[items.length];
System.arraycopy(items, 0, seq, 0, items.length);
return seq;
}
}
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