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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.functions;
import net.sf.saxon.expr.*;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.SequenceTool;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.EmptyIterator;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.NumericValue;
/**
* Implements the XPath 2.0 subsequence() function with three arguments
*/
public class Subsequence_3 extends SystemFunction implements Callable {
/**
* Get the static properties of this expression (other than its type). The result is
* bit-significant. These properties are used for optimizations. In general, if
* property bit is set, it is true, but if it is unset, the value is unknown.
* @param arguments the actual arguments to the function call
*/
@Override
public int getSpecialProperties(Expression[] arguments) {
return arguments[0].getSpecialProperties();
}
/**
* Call the function
* @param context the dynamic evaluation context
* @param arguments the values of the arguments, supplied as Sequences.
* Generally it is advisable, if calling iterate() to process a supplied sequence, to
* call it only once; if the value is required more than once, it should first be converted
* to a {@link net.sf.saxon.om.GroundedValue} by calling the utility methd
* SequenceTool.toGroundedValue().
* If the expected value is a single item, the item should be obtained by calling
* Sequence.head(): it cannot be assumed that the item will be passed as an instance of
* {@link net.sf.saxon.om.Item} or {@link net.sf.saxon.value.AtomicValue}.
* It is the caller's responsibility to perform any type conversions required
* to convert arguments to the type expected by the callee. An exception is where
* this Callable is explicitly an argument-converting wrapper around the original
* Callable.
* @return the result of the function call
* @throws XPathException if evaluation of the arguments fails
*/
@Override
public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
return SequenceTool.toLazySequence(subSequence(
arguments[0].iterate(),
(NumericValue) arguments[1].head(),
(NumericValue) arguments[2].head(),
context));
}
public static SequenceIterator subSequence(
SequenceIterator seq, NumericValue startVal, NumericValue lengthVal, XPathContext context)
throws XPathException {
if (startVal instanceof Int64Value && lengthVal instanceof Int64Value) {
// Fast path where the second and third arguments evaluate to integers
long lstart = startVal.longValue();
if (lstart > Integer.MAX_VALUE) {
return EmptyIterator.getInstance();
}
long llength = lengthVal.longValue();
if (llength > Integer.MAX_VALUE) {
llength = Integer.MAX_VALUE;
}
if (llength < 1) {
return EmptyIterator.getInstance();
}
long lend = lstart + llength - 1;
if (lend < 1) {
return EmptyIterator.getInstance();
}
int start = lstart < 1 ? 1 : (int) lstart;
return SubsequenceIterator.make(seq, start, (int) lend);
} else {
if (startVal.isNaN()) {
return EmptyIterator.getInstance();
}
if (startVal.compareTo(Int64Value.MAX_LONG) > 0) {
return EmptyIterator.getInstance();
}
startVal = startVal.round(0);
if (lengthVal.isNaN()) {
return EmptyIterator.getInstance();
}
lengthVal = lengthVal.round(0);
if (lengthVal.compareTo(Int64Value.ZERO) <= 0) {
return EmptyIterator.getInstance();
}
NumericValue rend = (NumericValue) ArithmeticExpression.compute(
startVal, Calculator.PLUS, lengthVal, context);
if (rend.isNaN()) {
// Can happen when start = -INF, length = +INF
return EmptyIterator.getInstance();
}
rend = (NumericValue) ArithmeticExpression.compute(
rend, Calculator.MINUS, Int64Value.PLUS_ONE, context);
if (rend.compareTo(Int64Value.ZERO) <= 0) {
return EmptyIterator.getInstance();
}
long lstart;
if (startVal.compareTo(Int64Value.PLUS_ONE) <= 0) {
lstart = 1;
} else {
lstart = startVal.longValue();
}
if (lstart > Integer.MAX_VALUE) {
return EmptyIterator.getInstance();
}
long lend;
if (rend.compareTo(Int64Value.MAX_LONG) >= 0) {
lend = Integer.MAX_VALUE;
} else {
lend = rend.longValue();
}
return SubsequenceIterator.make(seq, (int) lstart, (int) lend);
}
}
@Override
public String getStreamerName() {
return "Subsequence";
}
}