@ElementTypesAreNonnullByDefault
final class SingletonImmutableSet<E> extends ImmutableSet<E> {
  // We deliberately avoid caching the asList and hashCode here, to ensure that with
  // compressed oops, a SingletonImmutableSet packs all the way down to the optimal 16 bytes.

  final transient E element;

  SingletonImmutableSet(E element) {
    this.element = Preconditions.checkNotNull(element);
  }

///

## Use cases

Some use cases include:

* Converting non-JSON request bodies to JSON (e.g. <a href="https://msgpack.org/index.html" class="external-link" target="_blank">`msgpack`</a>).
* Decompressing gzip-compressed request bodies.
* Automatically logging all request bodies.

## Handling custom request body encodings

Let's see how to make use of a custom `Request` subclass to decompress gzip requests.

	// predicted date/time of transition
	MinIOTransition            = "X-Minio-Transition"
	MinIOLifecycleCfgUpdatedAt = "X-Minio-LifecycleConfig-UpdatedAt"
	// MinIOCompressed is returned when object is compressed
	MinIOCompressed = "X-Minio-Compressed"

	// SUBNET related
	SubnetAPIKey = "x-subnet-api-key"
)

// Common http query params S3 API
const (
	VersionID = "versionId"

	PartNumber = "partNumber"

@ElementTypesAreNonnullByDefault
final class SingletonImmutableSet<E> extends ImmutableSet<E> {
  // We deliberately avoid caching the asList and hashCode here, to ensure that with
  // compressed oops, a SingletonImmutableSet packs all the way down to the optimal 16 bytes.

  final transient E element;

  SingletonImmutableSet(E element) {
    this.element = Preconditions.checkNotNull(element);
  }

			// the file needs a zip64 header. store maxint in both
			// 32 bit size fields (and offset later) to signal that the
			// zip64 extra header should be used.
			b.uint32(uint32max) // compressed size
			b.uint32(uint32max) // uncompressed size

			// append a zip64 extra block to Extra
			var buf [28]byte // 2x uint16 + 3x uint64
			eb := writeBuf(buf[:])
			eb.uint16(zip64ExtraID)

		return io.ErrUnexpectedEOF
	}
	ver := int(b[0])
	switch ver {
	case dataUsageCacheVerV1:
		return errors.New("cache version deprecated (will autoupdate)")
	case dataUsageCacheVerV2:
		// Zstd compressed.
		dec, err := zstd.NewReader(r, zstd.WithDecoderConcurrency(2))
		if err != nil {
			return err
		}
		defer dec.Close()

		dold := &dataUsageCacheV2{}

		index = opts.IndexCB()
	}

	actualSize := data.ActualSize()
	if actualSize < 0 {
		_, encrypted := crypto.IsEncrypted(fi.Metadata)
		compressed := fi.IsCompressed()
		switch {
		case compressed:
			// ... nothing changes for compressed stream.
			// if actualSize is -1 we have no known way to
			// determine what is the actualSize.
		case encrypted:
			decSize, err := sio.DecryptedSize(uint64(n))

	// Refer to https://cloud.google.com/storage/docs/transcoding#decompressive_transcoding
	// Need to set `Accept-Encoding` header to `gzip` when issuing a GetObject call, to be able
	// to download the object in compressed state.
	// Calling ReadCompressed with true accomplishes that.
	object := gcs.client.Bucket(gcs.Bucket).Object(gcs.getDest(key)).ReadCompressed(true)

	r, err = object.NewRangeReader(ctx, opts.startOffset, opts.length)

	@env bash $(PWD)/docs/distributed/decom.sh
	@env bash $(PWD)/docs/distributed/decom-encrypted.sh
	@env bash $(PWD)/docs/distributed/decom-encrypted-sse-s3.sh
	@env bash $(PWD)/docs/distributed/decom-compressed-sse-s3.sh
	@env bash $(PWD)/docs/distributed/decom-encrypted-kes.sh

test-versioning: install-race
	@echo "Running minio versioning tests"
	@env bash $(PWD)/docs/bucket/versioning/versioning-tests.sh

			}

			// If metadata says encrypted, ask for it in quorum.
			if etyp, ok := crypto.IsEncrypted(meta.Metadata); ok {
				fmt.Fprint(h, etyp)
			}

			// If compressed, look for compressed FileInfo only
			if meta.IsCompressed() {
				fmt.Fprint(h, meta.Metadata[ReservedMetadataPrefix+"compression"])
			}

			metaHashes[i] = hex.EncodeToString(h.Sum(nil))
			h.Reset()
		}
	}