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package com.jclark.xsl.expr;
import com.jclark.xsl.om.*;
class SubstringFunction implements Function {
public ConvertibleExpr makeCallExpr(ConvertibleExpr[] args,
Node exprNode) throws ParseException {
if (args.length < 2 || args.length > 3)
throw new ParseException("expected 2 or 3 arguments");
final StringExpr se = args[0].makeStringExpr();
final NumberExpr ne1 = args[1].makeNumberExpr();
final NumberExpr ne2 = (args.length == 2
? new NumberConstantExpr(1.0/0.0)
: args[2].makeNumberExpr());
return new ConvertibleStringExpr() {
public String eval(Node node, ExprContext context) throws XSLException {
return substring(se.eval(node, context),
ne1.eval(node, context),
ne2.eval(node, context));
}
};
}
static final private String substring(String str, double start, double len) {
start = Math.floor(start + 0.5);
double end = start + Math.floor(len + 0.5);
int strLen = str.length();
int pos = 1;
int firstIndex = -1;
int lastIndex = -1;
for (int i = 0; i < strLen; i++, pos++) {
if (pos >= start && pos < end) {
if (firstIndex < 0)
firstIndex = i;
if (isLowSurrogate(str.charAt(i)))
++i;
lastIndex = i;
}
else if (isLowSurrogate(str.charAt(i)))
++i;
}
if (firstIndex >= 0)
return str.substring(firstIndex, lastIndex + 1);
return "";
}
private final static boolean isLowSurrogate(char c) {
return (c & 0xFC00) == 0xD800;
}
}
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