content: /*
   * Copyright 1999-2017 Alibaba Group Holding Ltd.
   *
   * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.druid.sql.visitor.functions;
  
  import com.alibaba.druid.sql.ast.SQLExpr;
  import com.alibaba.druid.sql.ast.expr.SQLMethodInvokeExpr;
  import com.alibaba.druid.sql.visitor.SQLEvalVisitor;
  
  import java.math.BigDecimal;
  
  import static com.alibaba.druid.sql.visitor.SQLEvalVisitor.EVAL_VALUE;
  
  public class Char implements Function {
      public static final Char instance = new Char();
  
      public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
          if (x.getArguments().isEmpty()) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          StringBuilder buf = new StringBuilder(x.getArguments().size());
          for (SQLExpr param : x.getArguments()) {
              param.accept(visitor);
  
              Object paramValue = param.getAttributes().get(EVAL_VALUE);
  
              if (paramValue instanceof Number) {
                  int charCode = ((Number) paramValue).intValue();
                  buf.append((char) charCode);
              } else if (paramValue instanceof String) {
                  try {
                      int charCode = new BigDecimal((String) paramValue).intValue();
                      buf.append((char) charCode);
                  } catch (NumberFormatException e) {
                  }
              } else {
                  return SQLEvalVisitor.EVAL_ERROR;
              }
          }
  
          return buf.toString();
      }
  }
  