function.java

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        for (; i < iArgCount; i++) {
            Expression e = eArg[i];
            Object     o = null;

            if (e != null) {

                // no argument: null
                o = e.getValue(session, iArgType[i]);
            }

            if ((o == null) &&!bArgNullable[i]) {

                // null argument for primitive datatype: don't call
                return null;
            }

            if (o instanceof JavaObject) {
                o = ((JavaObject) o).getObject();
            } else if (o instanceof Binary) {
                o = ((Binary) o).getBytes();
            }

            oArg[i] = o;
        }

        return oArg;
    }

    /**
     * returns null if any non-nullable element of values is null
     */
    private Object[] getNotNull(Object[] values) throws HsqlException {

        int i = bConnection ? 1
                            : 0;

        for (; i < iArgCount; i++) {
            Object o = values[i];

            if (o == null &&!bArgNullable[i]) {

                // null argument for primitive datatype: don't call
                return null;
            }
        }

        return values;
    }

    void collectInGroupByExpressions(HsqlArrayList colExps) {

        for (int i = 0; i < iArgCount; i++) {
            Expression e = eArg[i];

            if (e != null) {
                e.collectInGroupByExpressions(colExps);
            }
        }
    }

    Object getAggregatedValue(Session session,
                              Object currValue) throws HsqlException {

        Object[] valueArray = (Object[]) currValue;

        if (valueArray == null) {
            valueArray = new Object[iArgCount];
        }

        for (int i = 0; i < iArgCount; i++) {
            Expression e = eArg[i];

            if (eArg[i] != null) {
                if (eArg[i].isAggregate()) {
                    valueArray[i] = Column.convertObject(
                        e.getAggregatedValue(session, valueArray[i]),
                        iArgType[i]);
                } else {
                    valueArray[i] = e.getValue(session, iArgType[i]);
                }
            }
        }

        valueArray = getNotNull(valueArray);

        if (valueArray == null) {
            return null;
        }

        return getValue(session, valueArray);
    }

    Object updateAggregatingValue(Session session,
                                  Object currValue) throws HsqlException {

        Object[] valueArray = (Object[]) currValue;

        if (valueArray == null) {
            valueArray = new Object[iArgCount];
        }

        for (int i = 0; i < iArgCount; i++) {
            Expression e = eArg[i];

            if (eArg[i] != null) {
                valueArray[i] = e.updateAggregatingValue(session,
                        valueArray[i]);
            }
        }

        return valueArray;
    }

    /**
     * Returns the number of parameters that must be supplied to evaluate
     * this Function object from SQL.  <p>
     *
     * This value may be different than the number of parameters of the
     * underlying Java method.  This is because HSQLDB automatically detects
     * if the first parameter is of type java.sql.Connection, and supplies a
     * live Connection object constructed from the evaluating session context
     * if so.
     */
    int getArgCount() {
        return iSqlArgCount;
    }

    /**
     * Remnoves the Table filters from Expression parameters to this Function.
     *
     * @throws HsqlException if there is a problem resolving a parameter
     * against the specified TableFilter
     */
/*
    void removeFilters() throws HsqlException {

        Expression e;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            e = eArg[i];

            if (e != null) {
                e.removeFilters();
            }
        }
    }
*/
    void replaceAliases(Expression[] columns,
                        int length) throws HsqlException {

        Expression e;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            e = eArg[i];

            if (e != null) {
                if (e.exprType == Expression.COLUMN) {
                    eArg[i] = e.getExpressionForAlias(columns, length);
                } else {
                    e.replaceAliases(columns, length);
                }
            }
        }
    }

    /**
     * Checks the Expresion parameters to this Function object against the
     * set of TableFilter.
     */
    void checkTables(HsqlArrayList fa) throws HsqlException {

        Expression e;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            e = eArg[i];

            if (e != null) {
                e.checkTables(fa);
            }
        }
    }

    /**
     * Resolves the Expression parameters to this Function object against the
     * specified TableFilter.
     */
    void resolveTables(TableFilter f) throws HsqlException {

        Expression e;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            e = eArg[i];

            if (e != null) {
                e.resolveTables(f);
            }
        }
    }

    /**
     * Resolves the type of this expression and performs certain
     * transformations and optimisations of the expression tree.
     */
    void resolveType(Session session) throws HsqlException {

        Expression e;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            e = eArg[i];

            if (e != null) {
                if (e.isParam()) {
                    e.setDataType(iArgType[i]);

                    e.nullability    = getArgNullability(i);
                    e.valueClassName = getArgClass(i).getName();
                } else {
                    e.resolveTypes(session);
                }
            }
        }
    }

    /**
     * Checks each of this object's arguments for resolution, throwing an
     * HsqlException if any arguments have not yet been resolved. <p>
     * The check boolean argument is passed on to further check calls.<p>
     */
    boolean checkResolved(boolean check) throws HsqlException {

        boolean result = true;

        for (int i = iSqlArgStart; i < iArgCount; i++) {
            if (eArg[i] != null) {
                result = result && eArg[i].checkResolved(check);
            }
        }

        return result;
    }

    /**
     * Returns the type of the argument at the specified
     * offset in this Function object's paramter list. <p>
     */
    int getArgType(int i) {
        return iArgType[i];
    }

    /**
     * Returns the type of this Function
     * object's return type. <p>
     */
    int getReturnType() {
        return iReturnType;
    }

    /**
     * Binds the specified expression to the specified position in this
     * Function object's parameter list. <p>
     */
    void setArgument(int i, Expression e) {

        if (bConnection) {
            i++;
        }

        eArg[i]      = e;
        hasAggregate = hasAggregate || (e != null && e.isAggregate());
    }

    /**
     * Returns a DDL representation of this object. <p>
     */
    String getDLL() throws HsqlException {

        StringBuffer sb = new StringBuffer();

        // get the name as used by the CHECK statement
        String ddlName = name;

        if (isSimple) {
            return name;
        } else if (Token.T_TRIM.equals(name)) {

            // special case for TRIM
            sb.append(name).append('(');

            boolean leading  = eArg[2].testCondition(null);
            boolean trailing = eArg[3].testCondition(null);

            if (leading && trailing) {
                sb.append(Token.T_BOTH);
            } else {
                sb.append(leading ? Token.T_LEADING
                                  : Token.T_TRAILING);
            }

            // to do change to string
            sb.append(' ');

            String charval = (String) eArg[1].getValue(null);

            sb.append(Column.createSQLString(charval)).append(' ');
            sb.append(Token.T_FROM).append(' ');
            sb.append(eArg[0].getDDL()).append(')');

            return sb.toString();
        }

        if (sFunction.equals(name)) {
            ddlName = StringConverter.toQuotedString(name, '"', true);
        }

        sb.append(ddlName).append('(');

        for (int i = iSqlArgStart; i < eArg.length; i++) {
            sb.append(eArg[i].getDDL());

            if (i < eArg.length - 1) {
                sb.append(',');
            }
        }

        sb.append(')');

        return sb.toString();
    }

    /**
     * Returns a String representation of this object. <p>
     */
    public String describe(Session session) {

        StringBuffer sb = new StringBuffer();

        sb.append(super.toString()).append("=[\n");
        sb.append(sFunction).append("(");

        for (int i = iSqlArgStart; i < eArg.length; i++) {
            sb.append("[").append(eArg[i].describe(session)).append("]");
        }

        sb.append(") returns ").append(Types.getTypeString(getReturnType()));
        sb.append("]\n");

        return sb.toString();
    }

    /**
     * Returns the Java Class of the object returned by getValue(). <p>
     */
    String getReturnClassName() {
        return returnClassName;
    }

    /**
     * Returns the Java Class of the i'th argument. <p>
     */
    Class getArgClass(int i) {
        return aArgClasses[i];
    }

    /**
     * Returns the SQL nullability code of the i'th argument. <p>
     */
    int getArgNullability(int i) {
        return bArgNullable[i] ? Expression.NULLABLE
                               : Expression.NO_NULLS;
    }

    Method getMethod() {
        return mMethod;
    }
}