/*
    * Copyright 2022 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.driver.linux.proc;
   
   import java.nio.ByteBuffer;
   import java.util.HashMap;
   import java.util.Map;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.util.FileUtil;
  import oshi.util.platform.linux.ProcPath;
  
  /**
   * Utility to read auxiliary vector from {@code /proc/self/auxv}
   */
  @ThreadSafe
  public final class Auxv {
  
      private Auxv() {
      }
  
      public static final int AT_PAGESZ = 6; // system page size
      public static final int AT_HWCAP = 16; // arch dependent hints at CPU capabilities
      public static final int AT_CLKTCK = 17; // frequency at which times() increments
  
      /**
       * Retrieve the auxiliary vector for the current process
       *
       * @return A map of auxiliary vector keys to their respective values
       * @see <a href= "https://github.com/torvalds/linux/blob/v3.19/include/uapi/linux/auxvec.h">auxvec.h</a>
       */
      public static Map<Integer, Long> queryAuxv() {
          ByteBuffer buff = FileUtil.readAllBytesAsBuffer(ProcPath.AUXV);
          Map<Integer, Long> auxvMap = new HashMap<>();
          int key;
          do {
              key = FileUtil.readNativeLongFromBuffer(buff).intValue();
              if (key > 0) {
                  auxvMap.put(key, FileUtil.readNativeLongFromBuffer(buff).longValue());
              }
          } while (key > 0);
          return auxvMap;
  
      }
  }