api: ListObjectsV1 compliance with AWS S3. (#2856)

XSD - xml schema definition for SOAP operations
on S3 provides positional restrictions on XML
output.

Fix the response by re-arranging the positions in
accordance with S3 behavior.

Fixes #2849

cmd/api-response.go

@@ -40,20 +40,9 @@ type LocationResponse struct {
 type ListObjectsResponse struct {
 	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListBucketResult" json:"-"`
 
-	CommonPrefixes []CommonPrefix
-	Contents       []Object
-
-	Delimiter string
-
-	// Encoding type used to encode object keys in the response.
-	EncodingType string
-
-	// A flag that indicates whether or not ListObjects returned all of the results
-	// that satisfied the search criteria.
-	IsTruncated bool
-	Marker      string
-	MaxKeys     int
 	Name   string
+	Prefix string
+	Marker string
 
 	// When response is truncated (the IsTruncated element value in the response
 	// is true), you can use the key name in this field as marker in the subsequent
@@ -62,29 +51,28 @@ type ListObjectsResponse struct {
 	// specified. If response does not include the NextMaker and it is truncated,
 	// you can use the value of the last Key in the response as the marker in the
 	// subsequent request to get the next set of object keys.
-	NextMarker string
-	Prefix     string
+	NextMarker string `xml:"NextMarker,omitempty"`
+
+	MaxKeys   int
+	Delimiter string
+	// A flag that indicates whether or not ListObjects returned all of the results
+	// that satisfied the search criteria.
+	IsTruncated bool
+
+	Contents       []Object
+	CommonPrefixes []CommonPrefix
+
+	// Encoding type used to encode object keys in the response.
+	EncodingType string `xml:"EncodingType,omitempty"`
 }
 
 // ListObjectsV2Response - format for list objects response.
 type ListObjectsV2Response struct {
 	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListBucketResult" json:"-"`
 
-	CommonPrefixes []CommonPrefix
-	Contents       []Object
-
-	Delimiter string
-
-	// Encoding type used to encode object keys in the response.
-	EncodingType string
-
-	// A flag that indicates whether or not ListObjects returned all of the results
-	// that satisfied the search criteria.
-	IsTruncated bool
-	StartAfter  string
-	MaxKeys     int
 	Name       string
-
+	Prefix     string
+	StartAfter string `xml:"StartAfter,omitempty"`
 	// When response is truncated (the IsTruncated element value in the response
 	// is true), you can use the key name in this field as marker in the subsequent
 	// request to get next set of objects. Server lists objects in alphabetical
@@ -92,16 +80,28 @@ type ListObjectsV2Response struct {
 	// specified. If response does not include the NextMaker and it is truncated,
 	// you can use the value of the last Key in the response as the marker in the
 	// subsequent request to get the next set of object keys.
-	ContinuationToken     string
-	NextContinuationToken string
-	Prefix                string
+	ContinuationToken     string `xml:"ContinuationToken,omitempty"`
+	NextContinuationToken string `xml:"NextContinuationToken,omitempty"`
+
+	KeyCount  int
+	MaxKeys   int
+	Delimiter string
+	// A flag that indicates whether or not ListObjects returned all of the results
+	// that satisfied the search criteria.
+	IsTruncated bool
+
+	Contents       []Object
+	CommonPrefixes []CommonPrefix
+
+	// Encoding type used to encode object keys in the response.
+	EncodingType string `xml:"EncodingType,omitempty"`
 }
 
 // Part container for part metadata.
 type Part struct {
 	PartNumber   int
-	ETag         string
 	LastModified string
+	ETag         string
 	Size         int64
 }
 
@@ -137,23 +137,29 @@ type ListMultipartUploadsResponse struct {
 	UploadIDMarker     string `xml:"UploadIdMarker"`
 	NextKeyMarker      string
 	NextUploadIDMarker string `xml:"NextUploadIdMarker"`
-	EncodingType       string
+	Delimiter          string
+	Prefix             string
+	EncodingType       string `xml:"EncodingType,omitempty"`
 	MaxUploads         int
 	IsTruncated        bool
+
+	// List of pending uploads.
 	Uploads []Upload `xml:"Upload"`
-	Prefix             string
-	Delimiter          string
+
+	// Delimed common prefixes.
 	CommonPrefixes []CommonPrefix
 }
 
 // ListBucketsResponse - format for list buckets response
 type ListBucketsResponse struct {
 	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListAllMyBucketsResult" json:"-"`
+
+	Owner Owner
+
 	// Container for one or more buckets.
 	Buckets struct {
 		Buckets []Bucket `xml:"Bucket"`
 	} // Buckets are nested
-	Owner Owner
 }
 
 // Upload container for in progress multipart upload
@@ -179,23 +185,23 @@ type Bucket struct {
 
 // Object container for object metadata
 type Object struct {
-	ETag         string
 	Key          string
 	LastModified string // time string of format "2006-01-02T15:04:05.000Z"
+	ETag         string
 	Size         int64
 
+	// Owner of the object.
 	Owner Owner
 
 	// The class of storage used to store the object.
 	StorageClass string
 }
 
-// CopyObjectResponse container returns ETag and LastModified of the
-// successfully copied object
+// CopyObjectResponse container returns ETag and LastModified of the successfully copied object
 type CopyObjectResponse struct {
 	XMLName      xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ CopyObjectResult" json:"-"`
-	ETag         string
 	LastModified string   // time string of format "2006-01-02T15:04:05.000Z"
+	ETag         string   // md5sum of the copied object.
 }
 
 // Initiator inherit from Owner struct, fields are same
@@ -370,6 +376,7 @@ func generateListObjectsV2Response(bucket, prefix, token, startAfter, delimiter
 		prefixes = append(prefixes, prefixItem)
 	}
 	data.CommonPrefixes = prefixes
+	data.KeyCount = len(data.Contents) + len(data.CommonPrefixes)
 	return data
 }