/*
    * Copyright 2020-2022 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.driver.unix.aix.perfstat;
   
   import com.sun.jna.platform.unix.aix.Perfstat;
   import com.sun.jna.platform.unix.aix.Perfstat.perfstat_disk_t;
   import com.sun.jna.platform.unix.aix.Perfstat.perfstat_id_t;
  
  import oshi.annotation.concurrent.ThreadSafe;
  
  /**
   * Utility to query performance stats for disk_stats
   */
  @ThreadSafe
  public final class PerfstatDisk {
  
      private static final Perfstat PERF = Perfstat.INSTANCE;
  
      private PerfstatDisk() {
      }
  
      /**
       * Queries perfstat_disk for per-disk usage statistics
       *
       * @return an array of usage statistics
       */
      public static perfstat_disk_t[] queryDiskStats() {
          perfstat_disk_t diskStats = new perfstat_disk_t();
          // With null, null, ..., 0, returns total # of elements
          int total = PERF.perfstat_disk(null, null, diskStats.size(), 0);
          if (total > 0) {
              perfstat_disk_t[] statp = (perfstat_disk_t[]) diskStats.toArray(total);
              perfstat_id_t firstdiskStats = new perfstat_id_t(); // name is ""
              int ret = PERF.perfstat_disk(firstdiskStats, statp, diskStats.size(), total);
              if (ret > 0) {
                  return statp;
              }
          }
          return new perfstat_disk_t[0];
      }
  }