core/src/main/java/org/apache/accumulo/core/util/FastFormat.java

/*
 * 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.accumulo.core.util;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.common.base.Preconditions;

public class FastFormat {

  // this 7 to 8 times faster than String.format("%s%06d",prefix, num)
  public static byte[] toZeroPaddedString(long num, int width, int radix, byte[] prefix) {
    Preconditions.checkArgument(num >= 0);
    String strNum = Long.toString(num, radix);
    byte[] ret = new byte[Math.max(strNum.length(), width) + prefix.length];
    if (toZeroPaddedString(ret, 0, strNum, width, prefix) != ret.length)
      throw new RuntimeException(" Did not format to expected width " + num + " " + width + " "
          + radix + " " + new String(prefix, UTF_8));
    return ret;
  }

  public static int toZeroPaddedString(byte[] output, int outputOffset, long num, int width,
      int radix, byte[] prefix) {
    Preconditions.checkArgument(num >= 0);

    String strNum = Long.toString(num, radix);

    return toZeroPaddedString(output, outputOffset, strNum, width, prefix);
  }

  private static int toZeroPaddedString(byte[] output, int outputOffset, String strNum, int width,
      byte[] prefix) {

    int index = outputOffset;

    for (byte b : prefix) {
      output[index++] = b;
    }

    int end = width - strNum.length() + index;

    while (index < end)
      output[index++] = '0';

    for (int i = 0; i < strNum.length(); i++) {
      output[index++] = (byte) strNum.charAt(i);
    }

    return index - outputOffset;
  }
}