package net.sf.saxon.functions;
import net.sf.saxon.expr.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
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 SystemFunction {
/**
* 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.
*/
public Expression typeCheck(ExpressionVisitor visitor, ItemType 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 Item 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 CharSequence substring(StringValue sv, NumericValue start) {
CharSequence s = sv.getStringValueCS();
int slength = s.length();
long lstart;
if (start instanceof Int64Value) {
//noinspection RedundantCast
lstart = ((Int64Value)start).longValue();
if (lstart > slength) {
return "";
} 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 "";
} 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 "";
} else {
lstart = Math.round(start.getDoubleValue());
}
}
if (!sv.containsSurrogatePairs()) {
return s.subSequence((int)lstart-1, s.length());
}
int pos=1;
int cpos=0;
while (cpos<slength) {
if (pos >= lstart) {
return s.subSequence(cpos, s.length());
}
int ch = (int)s.charAt(cpos++);
if (ch<55296 || ch>56319) {
pos++; // don't count high surrogates, i.e. D800 to DBFF
}
}
return "";
}
/**
* 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 CharSequence substring(StringValue sv, NumericValue start, 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 "";
}
} else {
start = start.round();
// 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 "";
} 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 "";
} 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(), 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 "";
} else if (end.signum() <= 0) {
return "";
} 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 "";
}
if (!sv.containsSurrogatePairs()) {
return s.subSequence(Math.max((int)lstart-1, 0), Math.min(slength, (int)lend-1));
}
int jstart=-1;
int jend=-1;
int pos=1;
int cpos=0;
while (cpos<slength) {
if (pos >= lstart) {
if (pos < lend) {
if (jstart<0) {
jstart = cpos;
}
} else {
jend = cpos;
break;
}
}
int ch = (int)s.charAt(cpos++);
if (ch<55296 || ch>56319) pos++; // don't count high surrogates, i.e. D800 to DBFF
}
if (jstart<0 || jstart==jend) {
return "";
} else if (jend<0) {
return s.subSequence(jstart, s.length());
} else {
return s.subSequence(jstart, jend);
}
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//