// Buckets meta prefix.
	bucketMetaPrefix = "buckets"

	// Deleted Buckets prefix.
	deletedBucketsPrefix = ".deleted"

	// ETag (hex encoded md5sum) of empty string.
	emptyETag = "d41d8cd98f00b204e9800998ecf8427e"
)

// Global object layer mutex, used for safely updating object layer.
var globalObjLayerMutex sync.RWMutex

// Global object layer, only accessed by globalObjectAPI.
var globalObjectAPI ObjectLayer

	Header     http.Header
	ETag       ETag
	ShouldFail bool
}{
	{Header: http.Header{}, ETag: nil}, // 0
	{Header: http.Header{"Content-Md5": []string{"1B2M2Y8AsgTpgAmY7PhCfg=="}}, ETag: must("d41d8cd98f00b204e9800998ecf8427e")},                             // 1
	{Header: http.Header{"Content-Md5": []string{"sQqNsWTgdUEFt6mb5y4/5Q=="}}, ETag: must("b10a8db164e0754105b7a99be72e3fe5")},                             // 2

		6: {
			bucketName: bucket, objName: object, inputData: []byte(""),
			inputMeta:     map[string]string{"etag": "d41d8cd98f00b204e9800998ecf8427f"},
			expectedError: hash.BadDigest{ExpectedMD5: "d41d8cd98f00b204e9800998ecf8427f", CalculatedMD5: "d41d8cd98f00b204e9800998ecf8427e"},
		},

		// With incorrect sha256.
		7: {
			bucketName: bucket, objName: object, inputData: []byte("abcd"),

			actualSize: 4,
		},
		{
			desc:       "Failure md5 mismatch.",
			src:        bytes.NewReader([]byte("abcd")),
			size:       4,
			actualSize: 4,
			md5hex:     "d41d8cd98f00b204e9800998ecf8427f",
			err: BadDigest{
				"d41d8cd98f00b204e9800998ecf8427f",
				"e2fc714c4727ee9395f324cd2e7f331f",
			},
		},
		{
			desc:       "Failure sha256 mismatch.",
			src:        bytes.NewReader([]byte("abcd")),
			size:       4,

          .put(Hashing.adler32(), "", "01000000")
          .put(Hashing.adler32(), TQBFJOTLD, "da0fdc5b")
          .put(Hashing.adler32(), TQBFJOTLDP, "0810e46b")
          .put(Hashing.md5(), "", "d41d8cd98f00b204e9800998ecf8427e")
          .put(Hashing.md5(), TQBFJOTLD, "9e107d9d372bb6826bd81d3542a419d6")
          .put(Hashing.md5(), TQBFJOTLDP, "e4d909c290d0fb1ca068ffaddf22cbd0")

		// Test case - 12.
		// Input to replicate Md5 mismatch.
		{
			bucketName: bucket, objName: object, uploadID: uploadID, PartID: 1, inputMd5: "d41d8cd98f00b204e9800998ecf8427f",
			expectedError: hash.BadDigest{ExpectedMD5: "d41d8cd98f00b204e9800998ecf8427f", CalculatedMD5: "d41d8cd98f00b204e9800998ecf8427e"},
		},
		// Test case - 13.
		// When incorrect sha256 is provided.
		{