Factor out hard link code for cross platform build

Move system specific code out of entry so the build continues to work on
Windows. Hard links are not currently supported on Windows, the behavior
is a no-op.

src/duplicacy_entry.go

@@ -18,7 +18,6 @@ import (
 	"sort"
 	"strconv"
 	"strings"
-	"syscall"
 	"time"
 
 	"github.com/vmihailenco/msgpack"
@@ -752,11 +751,6 @@ func (files FileInfoCompare) Less(i, j int) bool {
 	}
 }
 
-type listEntryLinkKey struct {
-	dev uint64
-	ino uint64
-}
-
 type ListingState struct {
 	linkIndex int
 	linkTable map[listEntryLinkKey]int // map unique inode details to initially found path
@@ -816,16 +810,14 @@ func ListEntries(top string, path string, patterns []string, nobackupFile string
 			continue
 		}
 
-		var linkKey *listEntryLinkKey
-
-		if runtime.GOOS != "windows" && !entry.IsDir() {
-			if stat := f.Sys().(*syscall.Stat_t); stat != nil && stat.Nlink > 1 {
-				k := listEntryLinkKey{dev: uint64(stat.Dev), ino: uint64(stat.Ino)}
-				if linkIndex, seen := listingState.linkTable[k]; seen {
+		linkKey, isHardLinked := entry.getHardLinkKey(f)
+		if isHardLinked {
+			if linkIndex, seen := listingState.linkTable[linkKey]; seen {
 				if linkIndex == -1 {
-						LOG_DEBUG("LIST_EXCLUDE", "%s is excluded by attribute (hard link)", entry.Path)
+					LOG_DEBUG("LIST_EXCLUDE", "%s was excluded or skipped (hard link)", entry.Path)
 					continue
 				}
+
 				entry.Size = 0
 				if entry.IsFile() {
 					entry.Link = strconv.FormatInt(int64(linkIndex), 16)
@@ -841,9 +833,7 @@ func ListEntries(top string, path string, patterns []string, nobackupFile string
 				} else {
 					entry.EndChunk = entryHardLinkRootChunkMarker
 				}
-					listingState.linkTable[k] = -1
-					linkKey = &k
-				}
+				listingState.linkTable[linkKey] = -1
 			}
 		}
 
@@ -892,8 +882,8 @@ func ListEntries(top string, path string, patterns []string, nobackupFile string
 			continue
 		}
 
-		if linkKey != nil {
-			listingState.linkTable[*linkKey] = listingState.linkIndex
+		if isHardLinked {
+			listingState.linkTable[linkKey] = listingState.linkIndex
 			listingState.linkIndex++
 		}
 

src/duplicacy_utils_others.go

@@ -47,6 +47,25 @@ func SetOwner(fullPath string, entry *Entry, fileInfo *os.FileInfo) bool {
 	return true
 }
 
+type listEntryLinkKey struct {
+	dev uint64
+	ino uint64
+}
+
+func (entry *Entry) getHardLinkKey(f os.FileInfo) (key listEntryLinkKey, linked bool) {
+	if entry.IsDir() {
+		return
+	}
+	stat := f.Sys().(*syscall.Stat_t)
+	if stat == nil || stat.Nlink < 2 {
+		return
+	}
+	key.dev = uint64(stat.Dev)
+	key.ino = uint64(stat.Ino)
+	linked = true
+	return
+}
+
 func (entry *Entry) ReadSpecial(fileInfo os.FileInfo) bool {
 	if fileInfo.Mode()&(os.ModeDevice|os.ModeCharDevice) == 0 {
 		return true

src/duplicacy_utils_windows.go

@@ -110,6 +110,12 @@ func SetOwner(fullPath string, entry *Entry, fileInfo *os.FileInfo) bool {
 	return true
 }
 
+type listEntryLinkKey struct{}
+
+func (entry *Entry) getHardLinkKey(f os.FileInfo) (key listEntryLinkKey, linked bool) {
+	return
+}
+
 func (entry *Entry) ReadAttributes(top string) {
 }