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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 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.Expression;
import net.sf.saxon.expr.StaticProperty;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.parser.ContextItemStaticInfo;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.ZeroOrOne;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.util.FastStringBuffer;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.StringValue;
/**
* fn:string-join(string* $sequence, string $separator)
*/
public class StringJoin extends FoldingFunction {
private boolean returnEmptyIfEmpty;
/**
* Indicate that when the input sequence (first argument) is empty, the function should return
* an empty sequence rather than an empty string
*
* @param option true if an empty sequence should be returned when the input is an empty sequence.
*/
public void setReturnEmptyIfEmpty(boolean option) {
returnEmptyIfEmpty = option;
}
public boolean isReturnEmptyIfEmpty() {
return returnEmptyIfEmpty;
}
/**
* Determine the cardinality of the function.
*/
@Override
public int getCardinality(Expression[] arguments) {
if (returnEmptyIfEmpty) {
return StaticProperty.ALLOWS_ZERO_OR_ONE;
} else {
return StaticProperty.EXACTLY_ONE;
}
}
/**
* Determine whether two expressions are equivalent
*/
@Override
public boolean equals(Object o) {
return (o instanceof StringJoin) &&
super.equals(o) &&
returnEmptyIfEmpty == ((StringJoin) o).returnEmptyIfEmpty;
}
/**
* Allow the function to create an optimized call based on the values of the actual arguments
*
* @param visitor the expression visitor
* @param contextInfo information about the context item
* @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, or null indicating that no optimization has taken place
* @throws net.sf.saxon.trans.XPathException if an error is detected
*/
@Override
public Expression makeOptimizedFunctionCall(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo, Expression... arguments) throws XPathException {
Expression e2 = super.makeOptimizedFunctionCall(visitor, contextInfo, arguments);
if (e2 != null) {
return e2;
}
int card = arguments[0].getCardinality();
if (!Cardinality.allowsMany(card)) {
if (Cardinality.allowsZero(card)) {
return SystemFunction.makeCall("string", getRetainedStaticContext(), arguments[0]);
} else {
return arguments[0];
}
}
return null;
}
@Override
public Fold getFold(XPathContext context, Sequence... additionalArguments) throws XPathException {
CharSequence separator = "";
if (additionalArguments.length > 0) {
separator = additionalArguments[0].head().getStringValueCS();
}
return new StringJoinFold(separator);
}
private class StringJoinFold implements Fold {
private int position = 0;
private CharSequence separator;
private FastStringBuffer data;
public StringJoinFold(CharSequence separator) {
this.separator = separator;
this.data = new FastStringBuffer(FastStringBuffer.C64);
}
/**
* Process one item in the input sequence, returning a new copy of the working data
*
* @param item the item to be processed from the input sequence
* @throws net.sf.saxon.trans.XPathException if a dynamic error occurs
*/
public void processItem(Item item) throws XPathException {
if (position == 0) {
data.append(item.getStringValueCS());
position = 1;
} else {
data.append(separator);
data.append(item.getStringValueCS());
}
}
/**
* Ask whether the computation has completed. A function that can deliver its final
* result without reading the whole input should return true; this will be followed
* by a call on result() to deliver the final result.
*/
public boolean isFinished() {
return false;
}
/**
* Compute the final result of the function, when all the input has been processed
* @return the result of the function
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
public ZeroOrOne result() throws XPathException {
if (position == 0 && returnEmptyIfEmpty) {
return ZeroOrOne.empty();
} else {
return new ZeroOrOne(new StringValue(data));
}
}
}
// /**
// * Process the instruction in push mode. This avoids constructing the concatenated string
// * in memory, instead its parts can be sent straight to the serializer.
// *
// * @param context The dynamic context, giving access to the current node,
// * the current variables, etc.
// */
//
// public void process(XPathContext context) throws XPathException {
// // This rather tortuous code is designed to ensure that we don't evaluate the
// // separator argument unless there are at least two items in the sequence.
//
// SequenceReceiver out = context.getReceiver();
// if (out instanceof ComplexContentOutputter) {
// // Optimization is only safe if evaluated as part of a complex content constructor
// // Start and end with an empty string to force space separation from any previous or following outputs
// out.append(StringValue.EMPTY_STRING, 0, 0);
//
// SequenceIterator iter = getArg(0).iterate(context);
// Item it = iter.next();
// if (it == null) {
// return;
// }
//
// CharSequence first = it.getStringValueCS();
// out.characters(first, 0, 0);
//
// it = iter.next();
// if (it == null) {
// out.append(StringValue.EMPTY_STRING, 0, 0);
// return;
// }
//
// // Type checking ensures that the separator is not an empty sequence
// if (getArity() == 1) {
// out.characters(it.getStringValueCS(), 0, 0);
// while ((it = iter.next()) != null) {
// out.characters(it.getStringValueCS(), 0, 0);
// }
// } else {
// Item sepItem = getArg(1).evaluateItem(context);
// assert sepItem != null;
// CharSequence sep = sepItem.getStringValueCS();
// out.characters(sep, 0, 0);
// out.characters(it.getStringValueCS(), 0, 0);
//
// while ((it = iter.next()) != null) {
// out.characters(sep, 0, 0);
// out.characters(it.getStringValueCS(), 0, 0);
// }
//
// }
// out.append(StringValue.EMPTY_STRING, 0, 0);
// } else {
// out.append(evaluateItem(context), 0, 0);
// }
// }
}
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