Execute the function. The function must return
a valid object.
XMLString s1 = m_arg0.execute(xctxt).xstr();
double start = m_arg1.execute(xctxt).num();
int lenOfS1 = s1.length();
XMLString substr;
if (lenOfS1 <= 0)
return XString.EMPTYSTRING;
else
{
int startIndex;
if (Double.isNaN(start))
{
// Double.MIN_VALUE doesn't work with math below
// so just use a big number and hope I never get caught.
start = -1000000;
startIndex = 0;
}
else
{
start = Math.round(start);
startIndex = (start > 0) ? (int) start - 1 : 0;
}
if (null != m_arg2)
{
double len = m_arg2.num(xctxt);
int end = (int) (Math.round(len) + start) - 1;
// Normalize end index.
if (end < 0)
end = 0;
else if (end > lenOfS1)
end = lenOfS1;
if (startIndex > lenOfS1)
startIndex = lenOfS1;
substr = s1.substring(startIndex, end);
}
else
{
if (startIndex > lenOfS1)
startIndex = lenOfS1;
substr = s1.substring(startIndex);
}
}
return (XString)substr; // cast semi-safe
