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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.evernote.thrift.protocol;

import com.evernote.thrift.TException;

/**
 * Utility class with static methods for interacting with protocol data
 * streams.
 *
 */
public class TProtocolUtil {

  /**
   * The maximum recursive depth the skip() function will traverse before
   * throwing a TException.
   */
  private static int maxSkipDepth = Integer.MAX_VALUE;

  /**
   * Specifies the maximum recursive depth that the skip function will
   * traverse before throwing a TException.  This is a global setting, so
   * any call to skip in this JVM will enforce this value.
   *
   * @param depth  the maximum recursive depth.  A value of 2 would allow
   *    the skip function to skip a structure or collection with basic children,
   *    but it would not permit skipping a struct that had a field containing
   *    a child struct.  A value of 1 would only allow skipping of simple
   *    types and empty structs/collections.
   */
  public static void setMaxSkipDepth(int depth) {
    maxSkipDepth = depth;
  }

  /**
   * Skips over the next data element from the provided input TProtocol object.
   *
   * @param prot  the protocol object to read from
   * @param type  the next value will be intepreted as this TType value.
   */
  public static void skip(TProtocol prot, byte type)
    throws TException {
    skip(prot, type, maxSkipDepth);
  }

  /**
   * Skips over the next data element from the provided input TProtocol object.
   *
   * @param prot  the protocol object to read from
   * @param type  the next value will be intepreted as this TType value.
   * @param maxDepth  this function will only skip complex objects to this
   *   recursive depth, to prevent Java stack overflow.
   */
  public static void skip(TProtocol prot, byte type, int maxDepth)
  throws TException {
    if (maxDepth <= 0) {
      throw new TException("Maximum skip depth exceeded");
    }
    switch (type) {
    case TType.BOOL:
      {
        prot.readBool();
        break;
      }
    case TType.BYTE:
      {
        prot.readByte();
        break;
      }
    case TType.I16:
      {
        prot.readI16();
        break;
      }
    case TType.I32:
      {
        prot.readI32();
        break;
      }
    case TType.I64:
      {
        prot.readI64();
        break;
      }
    case TType.DOUBLE:
      {
        prot.readDouble();
        break;
      }
    case TType.STRING:
      {
        prot.readBinary();
        break;
      }
    case TType.STRUCT:
      {
        prot.readStructBegin();
        while (true) {
          TField field = prot.readFieldBegin();
          if (field.type == TType.STOP) {
            break;
          }
          skip(prot, field.type, maxDepth - 1);
          prot.readFieldEnd();
        }
        prot.readStructEnd();
        break;
      }
    case TType.MAP:
      {
        TMap map = prot.readMapBegin();
        for (int i = 0; i < map.size; i++) {
          skip(prot, map.keyType, maxDepth - 1);
          skip(prot, map.valueType, maxDepth - 1);
        }
        prot.readMapEnd();
        break;
      }
    case TType.SET:
      {
        TSet set = prot.readSetBegin();
        for (int i = 0; i < set.size; i++) {
          skip(prot, set.elemType, maxDepth - 1);
        }
        prot.readSetEnd();
        break;
      }
    case TType.LIST:
      {
        TList list = prot.readListBegin();
        for (int i = 0; i < list.size; i++) {
          skip(prot, list.elemType, maxDepth - 1);
        }
        prot.readListEnd();
        break;
      }
    default:
      break;
    }
  }
}