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 com.alibaba.druid.util.HexBin;
  
  import java.nio.charset.StandardCharsets;
  
  import static com.alibaba.druid.sql.visitor.SQLEvalVisitor.EVAL_EXPR;
  import static com.alibaba.druid.sql.visitor.SQLEvalVisitor.EVAL_VALUE;
  
  public class Unhex implements Function {
      public static final Unhex instance = new Unhex();
  
      public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
          if (x.getArguments().size() != 1) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          SQLExpr param0 = x.getArguments().get(0);
  
          if (param0 instanceof SQLMethodInvokeExpr) {
              SQLMethodInvokeExpr paramMethodExpr = (SQLMethodInvokeExpr) param0;
              if (paramMethodExpr.getMethodName().equalsIgnoreCase("hex")) {
                  SQLExpr subParamExpr = paramMethodExpr.getArguments().get(0);
                  subParamExpr.accept(visitor);
  
                  Object param0Value = subParamExpr.getAttributes().get(EVAL_VALUE);
                  if (param0Value == null) {
                      x.putAttribute(EVAL_EXPR, subParamExpr);
                      return SQLEvalVisitor.EVAL_ERROR;
                  }
  
                  return param0Value;
              }
          }
  
          param0.accept(visitor);
  
          Object param0Value = param0.getAttributes().get(EVAL_VALUE);
          if (param0Value == null) {
              return SQLEvalVisitor.EVAL_ERROR;
          }
  
          if (param0Value instanceof String) {
              byte[] bytes = HexBin.decode((String) param0Value);
              if (bytes == null) {
                  return SQLEvalVisitor.EVAL_VALUE_NULL;
              }
  
              String result = new String(bytes, StandardCharsets.UTF_8);
              return result;
          }
  
          return SQLEvalVisitor.EVAL_ERROR;
      }
  }
  