XL: Cleanup and add more comments. (#1807)

xl-v1-utils.go

@@ -1,85 +1,59 @@
+/*
+ * 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 main
 
 import (
-	"path"
-	"sync"
+	"bytes"
+	"io"
+	"math/rand"
+	"time"
 )
 
-// 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))
+// randInts - uses Knuth Fisher-Yates shuffle algorithm for generating uniform shuffling.
+func randInts(count int) []int {
+	rand.Seed(time.Now().UTC().UnixNano()) // Seed with current time.
+	ints := make([]int, count)
+	for i := 0; i < count; i++ {
+		ints[i] = i + 1
 	}
-	return isParentDirObject(parent)
+	for i := 0; i < count; i++ {
+		// Choose index uniformly in [i, count-1]
+		r := i + rand.Intn(count-i)
+		ints[r], ints[i] = ints[i], ints[r]
+	}
+	return ints
 }
 
-func (xl xlObjects) isObject(bucket, prefix string) bool {
-	// Create errs and volInfo slices of storageDisks size.
-	var errs = make([]error, len(xl.storageDisks))
-
-	// Allocate a new waitgroup.
-	var wg = &sync.WaitGroup{}
-	for index, disk := range xl.storageDisks {
-		wg.Add(1)
-		// Stat file on all the disks in a routine.
-		go func(index int, disk StorageAPI) {
-			defer wg.Done()
-			_, err := disk.StatFile(bucket, path.Join(prefix, xlMetaJSONFile))
-			if err != nil {
-				errs[index] = err
-				return
-			}
-			errs[index] = nil
-		}(index, disk)
-	}
-
-	// Wait for all the Stat operations to finish.
-	wg.Wait()
-
-	var errFileNotFoundCount int
-	for _, err := range errs {
-		if err != nil {
-			if err == errFileNotFound {
-				errFileNotFoundCount++
-				// If we have errors with file not found greater than allowed read
-				// quorum we return err as errFileNotFound.
-				if errFileNotFoundCount > len(xl.storageDisks)-xl.readQuorum {
-					return false
-				}
-				continue
-			}
-			errorIf(err, "Unable to access file "+path.Join(bucket, prefix))
-			return false
+// readAll reads from bucket, object until an error or returns the data it read until io.EOF.
+func readAll(disk StorageAPI, bucket, object string) ([]byte, error) {
+	var writer = new(bytes.Buffer)
+	startOffset := int64(0)
+	// Read until io.EOF.
+	for {
+		buf := make([]byte, blockSizeV1)
+		n, err := disk.ReadFile(bucket, object, startOffset, buf)
+		if err == io.EOF {
+			break
 		}
-	}
-	return true
-}
-
-// statPart - stat a part file.
-func (xl xlObjects) statPart(bucket, objectPart string) (fileInfo FileInfo, err error) {
-	// Count for errors encountered.
-	var xlJSONErrCount = 0
-
-	// Return the first success entry based on the selected random disk.
-	for xlJSONErrCount < len(xl.storageDisks) {
-		// Choose a random disk on each attempt.
-		disk := xl.getRandomDisk()
-		fileInfo, err = disk.StatFile(bucket, objectPart)
-		if err == nil {
-			return fileInfo, nil
+		if err != nil && err != io.EOF {
+			return nil, err
 		}
-		xlJSONErrCount++ // Update error count.
+		writer.Write(buf[:n])
+		startOffset += n
 	}
-	return FileInfo{}, err
+	return writer.Bytes(), nil
 }