Added uid/guid support.

Added permission support.

compress.go

@@ -0,0 +1,17 @@
+package squashfs
+
+import "reflect"
+
+func (w *Writer) compressData(data []byte) ([]byte, error) {
+	if reflect.DeepEqual(data, make([]byte, len(data))) {
+		return nil, nil
+	}
+	compressedData, err := w.compressor.Compress(data)
+	if err != nil {
+		return nil, err
+	}
+	if len(data) <= len(compressedData) {
+		return data, nil
+	}
+	return compressedData, nil
+}

internal/compression/gzip.go

@@ -50,9 +50,11 @@ func (g *Gzip) Decompress(r io.Reader) ([]byte, error) {
 //Compress compresses the given data (as a byte array) and returns the compressed data.
 func (g *Gzip) Compress(data []byte) ([]byte, error) {
 	var buf bytes.Buffer
-	wrt := zlib.NewWriter(&buf)
-	defer wrt.Close()
-	_, err := wrt.Write(data)
+	wrt, err := zlib.NewWriterLevel(&buf, int(g.CompressionLevel))
+	if err != nil {
+		return nil, err
+	}
+	_, err = wrt.Write(data)
 	if err != nil {
 		return nil, err
 	}

writer.go

@@ -6,7 +6,9 @@ import (
 	"log"
 	"os"
 	"path"
+	"sort"
 	"strings"
+	"syscall"
 
 	"github.com/CalebQ42/squashfs/internal/compression"
 )
@@ -18,6 +20,7 @@ type fileHolder struct {
 	symLocation string
 	UID         int
 	GUID        int
+	perm        int
 	folder      bool
 	symlink     bool
 }
@@ -28,7 +31,7 @@ type Writer struct {
 	compressor      compression.Compressor
 	structure       map[string][]*fileHolder
 	symlinkTable    map[string]string //[oldpath]newpath
-	superblock      superblock
+	uidGUIDTable    []int
 	compressionType int
 	allowErrors     bool
 }
@@ -87,6 +90,20 @@ func (w *Writer) AddFileTo(filepath string, file *os.File) error {
 	}
 	holder.folder = stat.IsDir()
 	holder.symlink = (stat.Mode()&os.ModeSymlink == os.ModeSymlink)
+	holder.perm = int(stat.Mode().Perm())
+	//Thanks to https://stackoverflow.com/questions/58179647/getting-uid-and-gid-of-a-file for uid and guid getting
+	if stat, ok := stat.Sys().(*syscall.Stat_t); ok {
+		holder.UID = int(stat.Uid)
+		holder.GUID = int(stat.Gid)
+	}
+	if sort.SearchInts(w.uidGUIDTable, holder.UID) == len(w.uidGUIDTable) {
+		w.uidGUIDTable = append(w.uidGUIDTable, holder.UID)
+		sort.Ints(w.uidGUIDTable)
+	}
+	if sort.SearchInts(w.uidGUIDTable, holder.GUID) == len(w.uidGUIDTable) {
+		w.uidGUIDTable = append(w.uidGUIDTable, holder.GUID)
+		sort.Ints(w.uidGUIDTable)
+	}
 	if holder.symlink {
 		target, err := os.Readlink(file.Name())
 		if err != nil {