}
    return fromHashers(hashers);
  }

  private Hasher fromHashers(Hasher[] hashers) {
    return new Hasher() {
      @Override
      public Hasher putByte(byte b) {
        for (Hasher hasher : hashers) {
          hasher.putByte(b);
        }
        return this;
      }

      @Override
      public Hasher putBytes(byte[] bytes) {
        for (Hasher hasher : hashers) {
          hasher.putBytes(bytes);
        }

            function.bits(),
            function);
      }
    }

    @Override
    HashCode makeHash(Hasher[] hashers) {
      byte[] bytes = new byte[bits() / 8];
      int i = 0;
      for (Hasher hasher : hashers) {
        HashCode newHash = hasher.hash();
        i += newHash.writeBytesTo(bytes, i, newHash.bits() / 8);
      }
      return HashCode.fromBytesNoCopy(bytes);
    }

}

// Borrow a single hasher.
func (h *HashBorrower) Borrow() hash.Hash {
	hasher := h.pool.Get()
	h.borrowed = append(h.borrowed, hasher)
	hasher.Reset()
	return hasher
}

// ReturnAll will return all borrowed hashes.
func (h *HashBorrower) ReturnAll() {
	for _, hasher := range h.borrowed {
		h.pool.Put(hasher)
	}
	h.borrowed = nil
}

// StandardClaims are basically standard claims with "accessKey"

 * @since 11.0
 */
@Beta
public interface Hasher extends PrimitiveSink {
  @CanIgnoreReturnValue
  @Override
  Hasher putByte(byte b);

  @CanIgnoreReturnValue
  @Override
  Hasher putBytes(byte[] bytes);

  @CanIgnoreReturnValue
  @Override
  Hasher putBytes(byte[] bytes, int off, int len);

  @CanIgnoreReturnValue
  @Override
  Hasher putBytes(ByteBuffer bytes);

  @CanIgnoreReturnValue

    Random random2 = new Random(2L);
    Hasher hasher1 = hashFunction.newHasher();
    Hasher hasher2 = hashFunction.newHasher();
    for (int i = 0; i < numActions; i++) {
      RandomHasherAction.pickAtRandom(random1).performAction(random1, ImmutableSet.of(hasher1));
      RandomHasherAction.pickAtRandom(random2).performAction(random2, ImmutableSet.of(hasher2));
    }

    Assert.assertEquals(expected1, hasher1.hash());

 *
 * @author Qian Huang
 * @since 16.0
 */
@Beta
public final class HashingInputStream extends FilterInputStream {
  private final Hasher hasher;

  /**
   * Creates an input stream that hashes using the given {@link HashFunction} and delegates all data
   * read from it to the underlying {@link InputStream}.
   *

 *
 * @author Zoe Piepmeier
 * @since 16.0
 */
@Beta
public final class HashingOutputStream extends FilterOutputStream {
  private final Hasher hasher;

  /**
   * Creates an output stream that hashes using the given {@link HashFunction}, and forwards all
   * data written to it to the underlying {@link OutputStream}.
   *

If your database is stolen, the thief won't have your users' plaintext passwords, only the hashes.

So, the thief won't be able to try to use that password in another system (as many users use the same password everywhere, this would be dangerous).

## Install `pwdlib` { #install-pwdlib }

pwdlib is a great Python package to handle password hashes.

It supports many secure hashing algorithms and utilities to work with them.

import org.jspecify.annotations.Nullable;

/**
 * An abstract implementation of {@link Hasher}, which only requires subtypes to implement {@link
 * #putByte}. Subtypes may provide more efficient implementations, however.
 *
 * @author Dimitris Andreou
 */
abstract class AbstractHasher implements Hasher {
  @Override
  @CanIgnoreReturnValue
  public final Hasher putBoolean(boolean b) {
    return putByte(b ? (byte) 1 : (byte) 0);
  }

    assertThrows(IllegalStateException.class, () -> hasher.putInt(42));
  }

  public void testHashTwice() {
    Hasher hasher = sha512().newHasher();

    assertThat(
            hasher
                .putString("The quick brown fox jumps over the lazy dog", UTF_8)
                .hash()
                .toString())