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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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.om;
import net.sf.saxon.event.Outputter;
import net.sf.saxon.event.ReceiverOption;
import net.sf.saxon.expr.AscendingRangeIterator;
import net.sf.saxon.expr.DescendingRangeIterator;
import net.sf.saxon.expr.LastPositionFinder;
import net.sf.saxon.expr.StaticProperty;
import net.sf.saxon.functions.Count;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.str.UnicodeBuilder;
import net.sf.saxon.str.UnicodeString;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.EmptyIterator;
import net.sf.saxon.tree.iter.GroundedIterator;
import net.sf.saxon.tree.wrapper.VirtualNode;
import net.sf.saxon.type.*;
import net.sf.saxon.value.*;
import java.util.List;
/**
* 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 UncheckedXPathException if a failure occurs reading the input iterator
*/
public static GroundedValue toGroundedValue(SequenceIterator iterator) {
if (iterator instanceof GroundedIterator && ((GroundedIterator)iterator).isActuallyGrounded()) {
return ((GroundedIterator) iterator).materialize();
} else {
return SequenceExtent.from(iterator).reduce();
}
}
/**
* 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 instanceof GroundedIterator && ((GroundedIterator) iterator).isActuallyGrounded()) {
return toGroundedValue(iterator);
} 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 instanceof GroundedIterator && ((GroundedIterator) iterator).isActuallyGrounded() &&
!(iterator instanceof AscendingRangeIterator) &&
!(iterator instanceof DescendingRangeIterator)) {
return toGroundedValue(iterator);
} else {
return new LazySequence(iterator);
}
}
/**
* Ask whether a SequenceIterator supports the capability to call {@code getLength()} to establish
* the number of items in the sequence.
* @param iterator the iterator we are asking about
* @return true if the iterator is a {@link LastPositionFinder} with this
* capability. Note that some iterators implement this interface, but do not actually have the
* capability to determine the length, because they delegate to another iterator.
*/
public static boolean supportsGetLength(SequenceIterator iterator) {
return iterator instanceof LastPositionFinder && ((LastPositionFinder)iterator).supportsGetLength();
}
/**
* Get the number of items in the sequence identified by a {@link SequenceIterator}.
* This method can only be used if {@link #supportsGetLength(SequenceIterator)} has been called
* and returns true. The length is returned regardless of the current position of the iterator.
* The state of the iterator is not changed
*
* @param iterator the iterator we are asking about
* @return the number of items in the sequence
* @throws UnsupportedOperationException if the iterator does not have this capability
*/
public static int getLength(SequenceIterator iterator) {
try {
return ((LastPositionFinder)iterator).getLength();
} catch (ClassCastException e) {
throw new UnsupportedOperationException("getLength() not available");
}
}
/**
* Supply the (remaining) items in a sequence to a consumer of items
* @param iter a sequence iterator, which will be consumed by calling this method
* @param consumer the consumer which will be called to process the remaining items
* in the sequence, in turn
* @throws UncheckedXPathException if the computation of the input sequence reports an XPathException,
* or if the consymer throws an XPathException
*/
public static void supply(SequenceIterator iter, ItemConsumer consumer) {
Item item;
try {
while ((item = iter.next()) != null) {
consumer.accept(item);
}
} catch (XPathException e) {
throw new UncheckedXPathException(e);
}
}
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
*
* Note: this is more efficient than counting the items and testing whether the result is
* N, because the sequence only needs to be read as far as the Nth item.
*
* @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
* @throws XPathException if an error is detected
*/
public static boolean hasLength(SequenceIterator iter, int length) throws XPathException {
if (SequenceTool.supportsGetLength(iter)) {
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 sequence
* @return true if the lengths of the two sequences are the same
* @throws XPathException if an error is detected
*/
public static boolean sameLength(SequenceIterator a, SequenceIterator b) throws XPathException {
if (SequenceTool.supportsGetLength(a)) {
return hasLength(b, ((LastPositionFinder) a).getLength());
} else if (SequenceTool.supportsGetLength(b)) {
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 UncheckedXPathException for example if the value is a closure that needs to be
* evaluated, and evaluation fails
*/
public static Item itemAt(Sequence sequence, int index) {
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 {
switch (item.getGenre()) {
case NODE:
Object node = item;
while (node instanceof VirtualNode) {
// strip off any layers of wrapping
node = ((VirtualNode) node).getRealNode();
}
return node;
case FUNCTION:
case ARRAY:
case MAP:
return item;
case EXTERNAL:
return ((AnyExternalObject) item).getWrappedObject();
case ATOMIC:
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:
case StandardNames.XS_TIME:
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_BASE64_BINARY:
return ((Base64BinaryValue) value).getBinaryValue();
case StandardNames.XS_HEX_BINARY:
return ((HexBinaryValue) value).getBinaryValue();
default:
return item;
}
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 UnicodeString getStringValue(Sequence sequence) throws XPathException {
UnicodeBuilder ub = new UnicodeBuilder();
supply(sequence.iterate(), (ItemConsumer) item -> {
if (!ub.isEmpty()) {
ub.append(' ');
}
ub.accept(item.getUnicodeStringValue());
});
return ub.toUnicodeString();
}
/**
* 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 stringify(Sequence sequence) throws XPathException {
StringBuilder sb = new StringBuilder(64);
supply(sequence.iterate(), (ItemConsumer) item -> {
if (sb.length() != 0) {
sb.append(' ');
}
sb.append(item.getStringValue());
});
return sb.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 (UncheckedXPathException 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;
SequenceIterator 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 (UncheckedXPathException 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 {
supply(value.iterate(), (ItemConsumer) 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
* @return the new array
*/
public static Sequence[] makeSequenceArray(int length) {
return new Sequence[length];
}
/**
* Make an array of general-purpose Sequence objects with supplied contents
* @param items the contents for the array
* @return the new array
*/
public static Sequence[] fromItems(Item... items) {
Sequence[] seq = new Sequence[items.length];
System.arraycopy(items, 0, seq, 0, items.length);
return seq;
}
/**
* Construct an AttributeMap given a list of {@link AttributeInfo} objects
* representing the individual attributes.
* @param list the list of attributes. It is the caller's responsibility
* to ensure that this list contains no duplicates. The method
* may detect this, but is not guaranteed to do so. Calling
* {@link AttributeMap#verify} after constructing the attribute map verifies
* that there are no duplicates. The order of items in the input
* list is not necessarily preserved.
* @return an AttributeMap containing the specified attributes.
* @throws IllegalArgumentException if duplicate attributes are detected
*/
public static AttributeMap attributeMapFromList(List list) {
int n = list.size();
if (n == 0) {
return EmptyAttributeMap.getInstance();
} else if (n == 1) {
return SingletonAttributeMap.of(list.get(0));
} else if (n <= SmallAttributeMap.LIMIT) {
return new SmallAttributeMap(list);
} else {
return new LargeAttributeMap(list);
}
}
/**
* Helper method to convert an Item or null to a Sequence
* @param item the item to convert
* @return the converted sequence
*/
public static GroundedValue itemOrEmpty(Item item) {
if (item == null) {
return EmptySequence.getInstance();
} else {
return item;
}
}
}