platform/vcs-log/graph/src/com/intellij/vcs/log/graph/utils/impl/ByteArrayUtils.java

/*
 * Copyright 2000-2014 JetBrains s.r.o.
 *
 * 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.intellij.vcs.log.graph.utils.impl;

import com.intellij.vcs.log.graph.utils.IntList;
import org.jetbrains.annotations.NotNull;

class ByteArrayUtils {
  private static final int BYTE_OFFSET = 8;
  private static final int BYTE_MASK = 0xff;

  public static int countBytesAfterCompression(@NotNull IntList deltaList) {
    int count = 0;
    for (int i = 0; i < deltaList.size(); i++) {
      count += sizeOf(deltaList.get(i));
    }
    return count;
  }

  // return count of byte after compression
  public static int sizeOf(int value) {
    if (value < 0) value = ~value;

    value >>= BYTE_OFFSET - 1;
    for (int  i = 1; i < 4; i++) {
      if (value == 0)
        return i;
      value >>= BYTE_OFFSET;
    }
    return 4;
  }

  public static void writeDelta(int startIndex, int value, int sizeOf, byte[] bytes) {
    for (int i = sizeOf - 1; i >= 0; i--) {
      bytes[startIndex + i] = (byte) value;
      value >>= BYTE_OFFSET;
    }
  }

  public static int readDelta(int startIndex, int sizeOf, byte[] bytes) {
    int result = 0;

    boolean isNegative = bytes[startIndex] < 0;
    if (isNegative) {
      for (int i = 0; i < 4 - sizeOf; i++) {
        result <<= BYTE_OFFSET;
        result |= BYTE_MASK;
      }
    }

    for (int i = startIndex; i < startIndex + sizeOf; i++) {
      result <<= BYTE_OFFSET;
      result |= bytes[i] & BYTE_MASK;
    }
    return result;
  }

  public static int groundPointCount(int arraySize, int blockSize) {
    if (arraySize == 0)
      return 1;

    return (arraySize - 1) / blockSize + 1;
  }
}