// functionality to handle SSE-C copy requests.
var SSECopy = ssecCopy{}

type ssecCopy struct{}

// IsRequested returns true if the HTTP headers contains
// at least one SSE-C copy header. Regular SSE-C headers
// are ignored.
func (ssecCopy) IsRequested(h http.Header) bool {
	if _, ok := h[xhttp.AmzServerSideEncryptionCopyCustomerAlgorithm]; ok {
		return true
	}

)

var magicHeaders = []struct {
	header []byte
	f      format
}{
	{
		header: []byte{0x1f, 0x8b, 8},
		f:      formatGzip,
	},
	{
		// Zstd default header.
		header: []byte{0x28, 0xb5, 0x2f, 0xfd},
		f:      formatZstd,
	},
	{
		// Zstd skippable frame header.
		header: []byte{0x2a, 0x4d, 0x18},
		f:      formatZstd,
	},
	{
		// LZ4
		header: []byte{0x4, 0x22, 0x4d, 0x18},

	var idxCb func() []byte
	if isCompressed {
		wantEncryption := crypto.Requested(r.Header) || isEncrypted
		s2c, cb := newS2CompressReader(reader, actualPartSize, wantEncryption)
		idxCb = cb
		defer s2c.Close()
		reader = etag.Wrap(s2c, reader)
		length = -1
	}

	srcInfo.Reader, err = hash.NewReader(ctx, reader, length, "", "", actualPartSize)
	if err != nil {

				w.Header().Set(xhttp.AmzServerSideEncryptionKmsContext, kmsCtx)
			}
		case crypto.SSEC:
			w.Header().Set(xhttp.AmzServerSideEncryptionCustomerAlgorithm, r.Header.Get(xhttp.AmzServerSideEncryptionCustomerAlgorithm))
			w.Header().Set(xhttp.AmzServerSideEncryptionCustomerKeyMD5, r.Header.Get(xhttp.AmzServerSideEncryptionCustomerKeyMD5))
		}
		objInfo.ETag = getDecryptedETag(r.Header, objInfo, false)
	}

	}
}

var isHTTPHeaderSizeTooLargeTests = []struct {
	header     http.Header
	shouldFail bool
}{
	{header: generateHeader(0, 0), shouldFail: false},
	{header: generateHeader(1024, 0), shouldFail: false},
	{header: generateHeader(2048, 0), shouldFail: false},
	{header: generateHeader(8*1024+1, 0), shouldFail: true},
	{header: generateHeader(0, 1024), shouldFail: false},
	{header: generateHeader(0, 2048), shouldFail: true},

	}
	extractedSignedHeaders := make(http.Header)
	for _, header := range signedHeaders {
		// `host` will not be found in the headers, can be found in r.Host.
		// but its always necessary that the list of signed headers containing host in it.
		val, ok := reqHeaders[http.CanonicalHeaderKey(header)]
		if !ok {
			// try to set headers from Query String
			val, ok = reqQueries[header]
		}
		if ok {

			}
		}
	} else if _, ok := r.Header[xhttp.AmzContentSha256]; !skipSHA256 && ok {
		contentSHA256, err = hex.DecodeString(r.Header.Get(xhttp.AmzContentSha256))
		if err != nil || len(contentSHA256) == 0 {
			return ErrContentSHA256Mismatch
		}
	}

	// Verify 'Content-Md5' and/or 'X-Amz-Content-Sha256' if present.
	// The verification happens implicit during reading.

	c, err := GetContentChecksum(r.Header)
	if err != nil || c == nil {
		return
	}
	t, s := c.Type, c.Encoded
	if !c.Type.IsSet() {
		return
	}
	if c.Type.Is(ChecksumTrailing) {
		val := r.Trailer.Get(t.Key())
		if val != "" {
			w.Header().Set(t.Key(), val)
		}
		return
	}
	w.Header().Set(t.Key(), s)
}

		// If server is in shutdown.
		if atomic.LoadUint32(&srv.inShutdown) != 0 {
			// To indicate disable keep-alive, server is shutting down.
			w.Header().Set("Connection", "close")

			// Add 1 minute retry header, incase-client wants to honor it
			w.Header().Set(RetryAfter, "60")

			w.WriteHeader(http.StatusServiceUnavailable)
			w.Write([]byte(http.ErrServerClosed.Error()))
			return
		}

				}
				type version struct {
					Idx      int
					Header   json.RawMessage
					Metadata json.RawMessage
				}
				versions := make([]version, hdr.versions)
				headerVer := hdr.headerVer
				err = decodeVersions(v, hdr.versions, func(idx int, hdr, meta []byte) error {
					var header xlMetaV2VersionHeaderV2
					if _, err := header.UnmarshalMsg(hdr, headerVer); err != nil {
						return err
					}