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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.expr.parser.ExpressionVisitor;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.regex.UnicodeString;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.NumericValue;
import net.sf.saxon.value.StringValue;
/**
* This class implements the XPath substring() function
*/
public class Substring extends SystemFunctionCall implements Callable {
/**
* Type-check the expression. This also calls preEvaluate() to evaluate the function
* if all the arguments are constant; functions that do not require this behavior
* can override the preEvaluate method.
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
Expression e2 = super.typeCheck(visitor, contextItemType);
if (e2 != this) {
return e2;
}
TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (argument[1] instanceof NumberFn) {
Expression a1 = ((NumberFn)argument[1]).getArguments()[0];
if (th.isSubType(a1.getItemType(th), BuiltInAtomicType.INTEGER)) {
argument[1] = a1;
}
}
if (argument.length > 2 && argument[2] instanceof NumberFn) {
Expression a2 = ((NumberFn)argument[2]).getArguments()[0];
if (th.isSubType(a2.getItemType(th), BuiltInAtomicType.INTEGER)) {
argument[2] = a2;
}
}
return this;
}
/**
* Evaluate the function
*/
public StringValue evaluateItem(XPathContext context) throws XPathException {
AtomicValue av = (AtomicValue)argument[0].evaluateItem(context);
if (av==null) {
return StringValue.EMPTY_STRING;
}
StringValue sv = (StringValue)av;
if (sv.isZeroLength()) {
return StringValue.EMPTY_STRING;
}
AtomicValue a1 = (AtomicValue)argument[1].evaluateItem(context);
NumericValue a = (NumericValue)a1;
if (argument.length==2) {
StringValue result = StringValue.makeStringValue(substring(sv, a));
if (sv.isKnownToContainNoSurrogates()) {
result.setContainsNoSurrogates();
}
return result;
} else {
AtomicValue b2 = (AtomicValue)argument[2].evaluateItem(context);
NumericValue b = (NumericValue)b2;
StringValue result = StringValue.makeStringValue(substring(sv, a, b, context));
if (sv.isKnownToContainNoSurrogates()) {
result.setContainsNoSurrogates();
}
return result;
}
}
/**
* Implement the substring function with two arguments.
* @param sv the string value
* @param start the numeric offset (1-based) of the first character to be included in the result
* (if not an integer, the XPath rules apply)
* @return the substring starting at this position.
*/
public static UnicodeString substring(StringValue sv, NumericValue start) {
UnicodeString s = sv.getUnicodeString();
int slength = s.length();
long lstart;
if (start instanceof Int64Value) {
//noinspection RedundantCast
lstart = ((Int64Value)start).longValue();
if (lstart > slength) {
return UnicodeString.EMPTY_STRING;
} else if (lstart <= 0) {
lstart = 1;
}
} else {
//NumericValue rstart = start.round();
// We need to be careful to handle cases such as plus/minus infinity
if (start.isNaN()) {
return UnicodeString.EMPTY_STRING;
} else if (start.signum() <= 0) {
return s;
} else if (start.compareTo(slength) > 0) {
// this works even where the string contains surrogate pairs,
// because the Java length is always >= the XPath length
return UnicodeString.EMPTY_STRING;
} else {
lstart = Math.round(start.getDoubleValue());
}
}
if (lstart > s.length()) {
return UnicodeString.EMPTY_STRING;
}
return s.substring((int)lstart-1, s.length());
}
/**
* Implement the substring function with three arguments.
* @param sv the string value
* @param start the numeric offset (1-based) of the first character to be included in the result
* (if not an integer, the XPath rules apply)
* @param len the length of the required substring (again, XPath rules apply)
* @param context the XPath dynamic context. Provided because some arithmetic computations require it
* @return the substring starting at this position.
*/
public static UnicodeString substring(StringValue sv, NumericValue start, /*@NotNull*/ NumericValue len, XPathContext context) {
CharSequence s = sv.getStringValueCS();
int slength = s.length();
long lstart;
if (start instanceof Int64Value) {
//noinspection RedundantCast
lstart = ((Int64Value)start).longValue();
if (lstart > slength) {
return UnicodeString.EMPTY_STRING;
}
} else {
start = start.round(0);
// TODO: convert directly to a long using Math.round, as in the 2-argument case
// We need to be careful to handle cases such as plus/minus infinity and NaN
if (start.isNaN()) {
return UnicodeString.EMPTY_STRING;
} else if (start.signum() <= 0) {
lstart = 0;
} else if (start.compareTo(slength) > 0) {
// this works even where the string contains surrogate pairs,
// because the Java length is always >= the XPath length
return UnicodeString.EMPTY_STRING;
} else {
try {
lstart = start.longValue();
} catch (XPathException err) {
// this shouldn't happen unless the string length exceeds the bounds
// of a long
throw new AssertionError("string length out of permissible range");
}
}
}
NumericValue end;
try {
//end = start.arithmetic(Token.PLUS, len.round(), context);
end = (NumericValue)ArithmeticExpression.compute(start, Calculator.PLUS, len.round(0), context);
} catch (XPathException e) {
throw new AssertionError("Unexpected arithmetic failure in substring");
}
long lend;
if (end instanceof Int64Value) {
//noinspection RedundantCast
lend = ((Int64Value)end).longValue();
} else {
// We need to be careful to handle cases such as plus/minus infinity and NaN
if (end.isNaN()) {
return UnicodeString.EMPTY_STRING;
} else if (end.signum() <= 0) {
return UnicodeString.EMPTY_STRING;
} else if (end.compareTo(slength) > 0) {
// this works even where the string contains surrogate pairs,
// because the Java length is always >= the XPath length
lend = slength+1;
} else {
try {
lend = end.ceiling().longValue();
} catch (XPathException err) {
// this shouldn't happen unless the string length exceeds the bounds
// of a long
throw new AssertionError("string length out of permissible range");
}
}
}
if (lend < lstart) {
return UnicodeString.EMPTY_STRING;
}
UnicodeString us = sv.getUnicodeString();
int clength = us.length();
int a1 = (int)lstart - 1;
if (a1 >= clength) {
return UnicodeString.EMPTY_STRING;
}
int a2 = Math.min(clength, (int)lend - 1);
if (a1 < 0) {
if (a2 < 0) {
return UnicodeString.EMPTY_STRING;
} else {
a1 = 0;
}
}
return us.substring(a1, a2);
}
/**
* Evaluate the expression
*
* @param context the dynamic evaluation context
* @param arguments the values of the arguments, supplied as Sequences
* @return the result of the evaluation, in the form of a Sequence
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs during the evaluation of the expression
*/
public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
StringValue arg0 = (StringValue)arguments[0].head();
NumericValue arg1 = (NumericValue)arguments[1].head();
if (arguments.length == 2) {
return StringValue.makeStringValue(substring(arg0, arg1));
} else {
NumericValue arg2 = (NumericValue)arguments[2].head();
return StringValue.makeStringValue(substring(arg0, arg1, arg2, context));
}
}
}
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