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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.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 two arguments
*/
public class Subsequence_2 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();
}
/**
* Determine the cardinality of the function.
*/
@Override
public int getCardinality(Expression[] arguments) {
return arguments[0].getCardinality() | StaticProperty.ALLOWS_ZERO_OR_ONE;
}
/**
* 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 a dynamic error occurs
*/
@Override
public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
return SequenceTool.toLazySequence(
subSequence(arguments[0].iterate(), (NumericValue) arguments[1].head()));
}
public static SequenceIterator subSequence(
SequenceIterator seq, NumericValue startVal)
throws XPathException {
long lstart;
if (startVal instanceof Int64Value) {
lstart = startVal.longValue();
if (lstart <= 1) {
return seq;
}
} else if (startVal.isNaN()) {
return EmptyIterator.emptyIterator();
} else {
startVal = startVal.round(0);
if (startVal.compareTo(Int64Value.PLUS_ONE) <= 0) {
return seq;
} else if (startVal.compareTo(Int64Value.MAX_LONG) > 0) {
return EmptyIterator.emptyIterator();
} else {
lstart = startVal.longValue();
}
}
if (lstart > Integer.MAX_VALUE) {
// we don't allow sequences longer than an this
return EmptyIterator.emptyIterator();
}
return TailIterator.make(seq, (int) lstart);
}
/**
* Make an expression that either calls this function, or that is equivalent to a call
* on this function
*
* @param arguments the supplied arguments to the function call
* @return either a function call on this function, or an expression that delivers
* the same result
*/
@Override
public Expression makeFunctionCall(Expression[] arguments) {
// Handle the case where the second argument is known statically
try {
if (Literal.isAtomic(arguments[1]) && !(arguments[0] instanceof ErrorExpression)) {
NumericValue start = (NumericValue) ((Literal) arguments[1]).getGroundedValue();
start = start.round(0);
long intStart = start.longValue();
if (intStart > Integer.MAX_VALUE) {
// Handle this case dynamically. Test case cbcl-subsequence-012
return super.makeFunctionCall(arguments);
}
if (intStart <= 0) {
return arguments[0];
}
return new TailExpression(arguments[0], (int) intStart);
}
} catch (Exception e) {
// fall through (for example, in 1.0 mode start can be a StringValue ...)
}
return super.makeFunctionCall(arguments);
}
@Override
public String getStreamerName() {
return "Subsequence";
}
}