/*
    * Copyright (C) 2011 The Guava Authors
    *
    * 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.google.common.base;
  
  import com.google.caliper.BeforeExperiment;
  import com.google.caliper.Benchmark;
  import com.google.caliper.Param;
  import com.google.common.base.Strings;
  
  /**
   * Microbenchmark for {@link Strings#repeat}
   *
   * @author Mike Cripps
   */
  public class StringsRepeatBenchmark {
    @Param({"1", "5", "25", "125"}) int count;
    @Param({"1", "10"}) int length;
  
    private String originalString;
  
    @BeforeExperiment void setUp() {
      originalString = Strings.repeat("x", length);
    }
  
    @Benchmark void oldRepeat(int reps) {
      for (int i = 0; i < reps; i++) {
        String x = oldRepeat(originalString, count);
        if (x.length() != (originalString.length() * count)) {
          throw new RuntimeException("Wrong length: "+x);
        }
      }
    }
    @Benchmark void mikeRepeat(int reps) {
      for (int i = 0; i < reps; i++) {
        String x = mikeRepeat(originalString, count);
        if (x.length() != (originalString.length() * count)) {
          throw new RuntimeException("Wrong length: "+x);
        }
      }
    }
    @Benchmark void martinRepeat(int reps) {
      for (int i = 0; i < reps; i++) {
        String x = martinRepeat(originalString, count);
        if (x.length() != (originalString.length() * count)) {
          throw new RuntimeException("Wrong length: "+x);
        }
      }
    }
  
    private static String mikeRepeat(String string, int count) {
      final int len = string.length();
      char[] strCopy = new char[len * Integer.highestOneBit(count)];
      string.getChars(0, len, strCopy, 0);
  
      char[] array = new char[len * count];
  
      int strCopyLen = len;
      int pos = 0;
      while (count != 0) {
        if ((count & 1) != 0) {
          System.arraycopy(strCopy, 0, array, pos,strCopyLen);
          pos += strCopyLen;
        }
        count >>= 1;
        if (count != 0) {
          System.arraycopy(strCopy, 0, strCopy, strCopyLen, strCopyLen);
          strCopyLen <<= 1;
        }
      }
      return new String(array);
    }
  
    private static String oldRepeat(String string, int count) {
      // If this multiplication overflows, a NegativeArraySizeException or
      // OutOfMemoryError is not far behind
      final int len = string.length();
      final int size = len * count;
      char[] array = new char[size];
      for (int i = 0; i < size; i+=len) {
        string.getChars(0, len, array, i);
      }
      return new String(array);
    }
  
    private static String martinRepeat(String string, int count) {
     final int len = string.length();
     final int size = len * count;
     final char[] array = new char[size];
     string.getChars(0, len, array, 0);
     int n;
     for (n = len; n < size - n; n <<= 1) {
       System.arraycopy(array, 0, array, n, n);
     }
     System.arraycopy(array, 0, array, n, size - n);
     return new String(array);
   }
 }