* <p>Implementations should be collections of pure functions (i.e. stateless).
   */
  interface Strategy extends java.io.Serializable {

    /**
     * Sets {@code numHashFunctions} bits of the given bit array, by hashing a user element.
     *
     * <p>Returns whether any bits changed as a result of this operation.
     */
    <T extends @Nullable Object> boolean put(
        @ParametricNullness T object,

* **出力モデル**はパスワードをもつべきではありません。
* **データベースモデル**はおそらくハッシュ化されたパスワードが必要になるでしょう。

/// danger | "危険"

ユーザーの平文のパスワードは絶対に保存しないでください。常に認証に利用可能な「安全なハッシュ」を保存してください。

知らない方は、[セキュリティの章](security/simple-oauth2.md#password-hashing){.internal-link target=_blank}で「パスワードハッシュ」とは何かを学ぶことができます。

///

## 複数のモデル

ここでは、パスワードフィールドをもつモデルがどのように見えるのか、また、どこで使われるのか、大まかなイメージを紹介します:

```Python hl_lines="9  11  16  22  24  29-30  33-35  40-41"

   * holds the lock. If a hashed slot is empty, and lock is
   * available, a new Cell is created. Otherwise, if the slot
   * exists, a CAS is tried.  Retries proceed by "double hashing",
   * using a secondary hash (Marsaglia XorShift) to try to find a
   * free slot.
   *
   * The table size is capped because, when there are more threads
   * than CPUs, supposing that each thread were bound to a CPU,

      LinkedHashMultimap<String, Integer>.ValueSet valueSet =
          (LinkedHashMultimap.ValueSet) multimap.backingMap().get("a");
      assertEquals(z, valueSet.size());
      assertFalse(
          Hashing.needsResizing(
              valueSet.size(),
              valueSet.hashTable.length,
              LinkedHashMultimap.VALUE_SET_LOAD_FACTOR));
    }
  }

 */

package com.google.common.collect;

import static com.google.common.collect.CollectPreconditions.checkRemove;
import static com.google.common.collect.CompactHashing.UNSET;
import static com.google.common.collect.Hashing.smearedHash;
import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtIncompatible;

  @Override
  public int bits() {
    return 32;
  }

  @Override
  public Hasher newHasher() {
    return new Crc32cHasher();
  }

  @Override
  public String toString() {
    return "Hashing.crc32c()";
  }

  static final class Crc32cHasher extends AbstractStreamingHasher {

    /*
     * The striding algorithm works roughly as follows: it is universally the case that

   *
   * As of 2010/06/11, this method is identical to the (package private) hash method in OpenJDK 7's
   * java.util.HashMap class.
   */
  // Copied from java/com/google/common/collect/Hashing.java
  private static int smear(int hashCode) {
    hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12);
    return hashCode ^ (hashCode >>> 7) ^ (hashCode >>> 4);
  }

Für OAuth2 sind es einfach nur Strings.

///

## Gesamtübersicht

Sehen wir uns zunächst kurz die Teile an, die sich gegenüber den Beispielen im Haupt-**Tutorial – Benutzerhandbuch** für [OAuth2 mit Password (und Hashing), Bearer mit JWT-Tokens](../../tutorial/security/oauth2-jwt.md){.internal-link target=_blank} ändern. Diesmal verwenden wir OAuth2-Scopes:

//// tab | Python 3.10+

     * {@code " x "} (space, letter x, space), followed by the count.
     */
    @Override
    String toString();
  }

  // Comparison and hashing

  /**
   * Compares the specified object with this multiset for equality. Returns {@code true} if the
   * given object is also a multiset and contains equal elements with equal counts, regardless of
   * order.

import static com.google.common.collect.CollectPreconditions.checkRemove;
import static com.google.common.collect.CompactHashing.UNSET;
import static com.google.common.collect.Hashing.smearedHash;
import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtIncompatible;