server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/xl-v1-common.go

@@ -0,0 +1,71 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import (
+	"path"
+	"time"
+)
+
+// getLoadBalancedDisks - fetches load balanced (sufficiently randomized) disk slice.
+func (xl xlObjects) getLoadBalancedDisks() (disks []StorageAPI) {
+	// Based on the random shuffling return back randomized disks.
+	for _, i := range hashOrder(time.Now().UTC().String(), len(xl.storageDisks)) {
+		disks = append(disks, xl.storageDisks[i-1])
+	}
+	return disks
+}
+
+// This function does the following check, suppose
+// object is "a/b/c/d", stat makes sure that objects ""a/b/c""
+// "a/b" and "a" do not exist.
+func (xl xlObjects) parentDirIsObject(bucket, parent string) bool {
+	var isParentDirObject func(string) bool
+	isParentDirObject = func(p string) bool {
+		if p == "." {
+			return false
+		}
+		if xl.isObject(bucket, p) {
+			// If there is already a file at prefix "p" return error.
+			return true
+		}
+		// Check if there is a file as one of the parent paths.
+		return isParentDirObject(path.Dir(p))
+	}
+	return isParentDirObject(parent)
+}
+
+// isObject - returns `true` if the prefix is an object i.e if
+// `xl.json` exists at the leaf, false otherwise.
+func (xl xlObjects) isObject(bucket, prefix string) (ok bool) {
+	for _, disk := range xl.getLoadBalancedDisks() {
+		if disk == nil {
+			continue
+		}
+		// Check if 'prefix' is an object on this 'disk', else continue the check the next disk
+		_, err := disk.StatFile(bucket, path.Join(prefix, xlMetaJSONFile))
+		if err == nil {
+			return true
+		}
+		// Ignore for file not found,  disk not found or faulty disk.
+		if isErrIgnored(err, walkResultIgnoredErrs) {
+			continue
+		}
+		errorIf(err, "Unable to stat a file %s/%s/%s", bucket, prefix, xlMetaJSONFile)
+	} // Exhausted all disks - return false.
+	return false
+}