package once

// Singleton contains a pointer to T that must be set once.
// Until the value is set all Get() calls will block.
type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v

        | ((source[offset + 3] & 0xFF) << 24);
  }

  /**
   * Indicates that the loading of Unsafe was successful and the load and store operations will be
   * very efficient. May be useful for calling code to fall back on an alternative implementation
   * that is slower than Unsafe.get/store but faster than the pure-Java mask-and-shift.
   */
  static boolean usingUnsafe() {
    return (byteArray instanceof UnsafeByteArray);
  }

import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Serializes execution of tasks, somewhat like an "asynchronous {@code synchronized} block." Each
 * {@linkplain #submit enqueued} callable will not be submitted to its associated executor until the
 * previous callable has returned -- and, if the previous callable was an {@link AsyncCallable}, not

	// Tolerance is not set, defaults to half of the locker clients.
	tolerance := len(restClnts) / 2

	isReadLock := false
	started := time.Now()
	// Do async unlocking.
	// This means unlock will no longer block on the network or missing quorum.
	go func() {
		ctx, done := context.WithTimeout(ctx, drwMutexUnlockCallTimeout)
		defer done()
		for !releaseAll(ctx, dm.clnt, tolerance, owner, &locks, isReadLock, restClnts, dm.Names...) {

/*
 * Copyright (c) 2022 Block, Inc.
 *
 * 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,

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"os"
	"syscall"
)

var (
	// Disallow updating access times
	// Add non-block to avoid syscall to attempt to set epoll on files.
	readMode = os.O_RDONLY | 0x40000 | syscall.O_NONBLOCK // O_NOATIME

	// Write with data sync only used only for `xl.meta` writes

/*
 * Copyright (C) 2023 Block, Inc.
 *
 * 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,

/*
 * Copyright (c) 2022 Block, Inc.
 *
 * 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,

			mu.Unlock()
		}()
	}
	wg.Wait()
	return newDisks
}

func (er erasureObjects) getOnlineLocalDisks() (newDisks []StorageAPI) {
	disks := er.getOnlineDisks()

	// Based on the random shuffling return back randomized disks.
	r := rand.New(rand.NewSource(time.Now().UnixNano()))

	for _, i := range r.Perm(len(disks)) {
		if disks[i] != nil && disks[i].IsLocal() {
			newDisks = append(newDisks, disks[i])
		}
	}

/*
 * Copyright (C) 2022 Block, Inc.
 *
 * 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,