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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 org.apache.hadoop.hive.ql.udf.generic;

import org.apache.hadoop.hive.ql.exec.Description;

/**
 * UDFLpad.
 *
 */
@Description(name = "lpad",
    value = "_FUNC_(str, len, pad) - Returns str, left-padded with pad to a length of len",
    extended = "If str is longer than len, the return value is shortened to "
    + "len characters.\n"
    + "In case of empty pad string, the return value is null.\n"
    + "Example:\n"
    + "  > SELECT _FUNC_('hi', 5, '??') FROM src LIMIT 1;\n"
    + "  '???hi'\n"
    + "  > SELECT _FUNC_('hi', 1, '??') FROM src LIMIT 1;\n"
    + "  'h'\n"
    + "  > SELECT _FUNC_('hi', 5, '') FROM src LIMIT 1;\n"
    + "  null")
public class GenericUDFLpad extends GenericUDFBasePad {
  public GenericUDFLpad() {
    super("lpad");
  }

  @Override
  protected void performOp(
      StringBuilder builder, int len, String str, String pad) {
    int pos = Math.max(len - str.length(), 0);

    for (int i = 0; i < pos; i += pad.length()) {
      builder.append(pad);
    }
    builder.setLength(pos);

    // Copy the text
    builder.append(str, 0, str.length());
    builder.setLength(len);
  }
}