Application: gvSIG desktop

package org.gvsig.expressionevaluator.impl.function.string;

import org.apache.commons.lang3.Range;

import org.apache.commons.lang3.StringUtils;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.spi.AbstractFunction;

public class SubstringFunction extends AbstractFunction {

    public SubstringFunction() {

        super("String", "SUBSTRING", Range.between(2, 3));

        this.addAlias("SUBSTR");

    }

    @Override

    public boolean allowConstantFolding() {

        return true;

    }

    @Override

    public Object call(Interpreter interpreter, Object[] args) throws Exception {

        /*

            http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt

            section 4.2.2.1

        */

        String str = getStr(args,0);

        int start = getInt(args, 1);

        int len = 0;

        if( args.length == 3 ) {

            len = getInt(args, 2);

            if(len < 0) {

                throw new IllegalArgumentException("Length must be greater than or equal to 0");

            }

        }

        if(start < 1) {

            len = len + start - 1;

            start = 1;

        }

        String r = StringUtils.substring(str, start-1);

        if( args.length == 3 ) {

            r = StringUtils.left(r, len);

        }

        return r;

    }

}