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265 lines
8.9 KiB
265 lines
8.9 KiB
/*
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* Minio Cloud Storage, (C) 2016 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package cmd
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import (
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"context"
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"sort"
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"strings"
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)
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// Tree walk result carries results of tree walking.
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type treeWalkResult struct {
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entry string
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err error
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end bool
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}
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// posix.ListDir returns entries with trailing "/" for directories. At the object layer
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// we need to remove this trailing "/" for objects and retain "/" for prefixes before
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// sorting because the trailing "/" can affect the sorting results for certain cases.
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// Ex. lets say entries = ["a-b/", "a/"] and both are objects.
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// sorting with out trailing "/" = ["a", "a-b"]
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// sorting with trailing "/" = ["a-b/", "a/"]
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// Hence if entries[] does not have a case like the above example then isLeaf() check
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// can be delayed till the entry is pushed into the treeWalkResult channel.
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// delayIsLeafCheck() returns true if isLeaf can be delayed or false if
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// isLeaf should be done in listDir()
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func delayIsLeafCheck(entries []string) bool {
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for i, entry := range entries {
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if i == len(entries)-1 {
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break
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}
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// If any byte in the "entry" string is less than '/' then the
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// next "entry" should not contain '/' at the same same byte position.
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for j := 0; j < len(entry); j++ {
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if entry[j] < '/' {
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if len(entries[i+1]) > j {
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if entries[i+1][j] == '/' {
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return false
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}
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}
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}
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}
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}
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return true
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}
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// Return entries that have prefix prefixEntry.
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// Note: input entries are expected to be sorted.
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func filterMatchingPrefix(entries []string, prefixEntry string) []string {
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start := 0
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end := len(entries)
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for {
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if start == end {
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break
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}
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if hasPrefix(entries[start], prefixEntry) {
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break
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}
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start++
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}
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for {
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if start == end {
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break
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}
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if hasPrefix(entries[end-1], prefixEntry) {
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break
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}
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end--
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}
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return entries[start:end]
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}
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// "listDir" function of type listDirFunc returned by listDirFactory() - explained below.
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type listDirFunc func(bucket, prefixDir, prefixEntry string) (entries []string, delayIsLeaf bool, err error)
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// A function isLeaf of type isLeafFunc is used to detect if an entry is a leaf entry. There are four scenarios
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// where isLeaf should behave differently:
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// 1. FS backend object listing - isLeaf is true if the entry has a trailing "/"
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// 2. FS backend multipart listing - isLeaf is true if the entry is a directory and contains uploads.json
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// 3. XL backend object listing - isLeaf is true if the entry is a directory and contains xl.json
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// 4. XL backend multipart listing - isLeaf is true if the entry is a directory and contains uploads.json
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type isLeafFunc func(string, string) bool
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// A function isLeafDir of type isLeafDirFunc is used to detect if an entry represents an empty directory.
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type isLeafDirFunc func(string, string) bool
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func filterListEntries(bucket, prefixDir string, entries []string, prefixEntry string, isLeaf isLeafFunc) ([]string, bool) {
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// Listing needs to be sorted.
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sort.Strings(entries)
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// Filter entries that have the prefix prefixEntry.
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entries = filterMatchingPrefix(entries, prefixEntry)
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// Can isLeaf() check be delayed till when it has to be sent down the
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// treeWalkResult channel?
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delayIsLeaf := delayIsLeafCheck(entries)
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if delayIsLeaf {
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return entries, true
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}
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// isLeaf() check has to happen here so that trailing "/" for objects can be removed.
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for i, entry := range entries {
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if isLeaf(bucket, pathJoin(prefixDir, entry)) {
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entries[i] = strings.TrimSuffix(entry, slashSeparator)
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}
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}
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// Sort again after removing trailing "/" for objects as the previous sort
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// does not hold good anymore.
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sort.Strings(entries)
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return entries, false
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}
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// treeWalk walks directory tree recursively pushing treeWalkResult into the channel as and when it encounters files.
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func doTreeWalk(ctx context.Context, bucket, prefixDir, entryPrefixMatch, marker string, recursive bool, listDir listDirFunc, isLeaf isLeafFunc, isLeafDir isLeafDirFunc, resultCh chan treeWalkResult, endWalkCh chan struct{}, isEnd bool) error {
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// Example:
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// if prefixDir="one/two/three/" and marker="four/five.txt" treeWalk is recursively
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// called with prefixDir="one/two/three/four/" and marker="five.txt"
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var markerBase, markerDir string
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if marker != "" {
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// Ex: if marker="four/five.txt", markerDir="four/" markerBase="five.txt"
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markerSplit := strings.SplitN(marker, slashSeparator, 2)
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markerDir = markerSplit[0]
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if len(markerSplit) == 2 {
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markerDir += slashSeparator
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markerBase = markerSplit[1]
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}
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}
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entries, delayIsLeaf, err := listDir(bucket, prefixDir, entryPrefixMatch)
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if err != nil {
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select {
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case <-endWalkCh:
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return errWalkAbort
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case resultCh <- treeWalkResult{err: err}:
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return err
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}
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}
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// When isleaf check is delayed, make sure that it is set correctly here.
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if delayIsLeaf && isLeaf == nil {
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return errInvalidArgument
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}
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// For an empty list return right here.
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if len(entries) == 0 {
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return nil
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}
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// example:
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// If markerDir="four/" Search() returns the index of "four/" in the sorted
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// entries list so we skip all the entries till "four/"
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idx := sort.Search(len(entries), func(i int) bool {
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return entries[i] >= markerDir
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})
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entries = entries[idx:]
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// For an empty list after search through the entries, return right here.
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if len(entries) == 0 {
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return nil
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}
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for i, entry := range entries {
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var leaf, leafDir bool
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// Decision to do isLeaf check was pushed from listDir() to here.
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if delayIsLeaf {
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leaf = isLeaf(bucket, pathJoin(prefixDir, entry))
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if leaf {
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entry = strings.TrimSuffix(entry, slashSeparator)
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}
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} else {
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leaf = !strings.HasSuffix(entry, slashSeparator)
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}
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if strings.HasSuffix(entry, slashSeparator) {
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leafDir = isLeafDir(bucket, pathJoin(prefixDir, entry))
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}
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isDir := !leafDir && !leaf
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if i == 0 && markerDir == entry {
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if !recursive {
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// Skip as the marker would already be listed in the previous listing.
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continue
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}
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if recursive && !isDir {
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// We should not skip for recursive listing and if markerDir is a directory
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// for ex. if marker is "four/five.txt" markerDir will be "four/" which
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// should not be skipped, instead it will need to be treeWalk()'ed into.
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// Skip if it is a file though as it would be listed in previous listing.
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continue
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}
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}
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if recursive && isDir {
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// If the entry is a directory, we will need recurse into it.
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markerArg := ""
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if entry == markerDir {
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// We need to pass "five.txt" as marker only if we are
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// recursing into "four/"
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markerArg = markerBase
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}
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prefixMatch := "" // Valid only for first level treeWalk and empty for subdirectories.
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// markIsEnd is passed to this entry's treeWalk() so that treeWalker.end can be marked
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// true at the end of the treeWalk stream.
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markIsEnd := i == len(entries)-1 && isEnd
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if tErr := doTreeWalk(ctx, bucket, pathJoin(prefixDir, entry), prefixMatch, markerArg, recursive, listDir, isLeaf, isLeafDir, resultCh, endWalkCh, markIsEnd); tErr != nil {
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return tErr
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}
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continue
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}
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// EOF is set if we are at last entry and the caller indicated we at the end.
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isEOF := ((i == len(entries)-1) && isEnd)
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select {
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case <-endWalkCh:
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return errWalkAbort
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case resultCh <- treeWalkResult{entry: pathJoin(prefixDir, entry), end: isEOF}:
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}
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}
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// Everything is listed.
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return nil
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}
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// Initiate a new treeWalk in a goroutine.
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func startTreeWalk(ctx context.Context, bucket, prefix, marker string, recursive bool, listDir listDirFunc, isLeaf isLeafFunc, isLeafDir isLeafDirFunc, endWalkCh chan struct{}) chan treeWalkResult {
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// Example 1
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// If prefix is "one/two/three/" and marker is "one/two/three/four/five.txt"
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// treeWalk is called with prefixDir="one/two/three/" and marker="four/five.txt"
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// and entryPrefixMatch=""
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// Example 2
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// if prefix is "one/two/th" and marker is "one/two/three/four/five.txt"
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// treeWalk is called with prefixDir="one/two/" and marker="three/four/five.txt"
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// and entryPrefixMatch="th"
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resultCh := make(chan treeWalkResult, maxObjectList)
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entryPrefixMatch := prefix
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prefixDir := ""
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lastIndex := strings.LastIndex(prefix, slashSeparator)
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if lastIndex != -1 {
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entryPrefixMatch = prefix[lastIndex+1:]
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prefixDir = prefix[:lastIndex+1]
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}
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marker = strings.TrimPrefix(marker, prefixDir)
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go func() {
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isEnd := true // Indication to start walking the tree with end as true.
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doTreeWalk(ctx, bucket, prefixDir, entryPrefixMatch, marker, recursive, listDir, isLeaf, isLeafDir, resultCh, endWalkCh, isEnd)
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close(resultCh)
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}()
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return resultCh
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}
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