Makes sure folders are created when files are added

Added some comments

writer.go

@@ -87,7 +87,7 @@ type fileHolder struct {
 	blockSizes  []uint32
 	GUID        int
 	perm        int
-	size        uint64
+	size        uint64 //when folder, size is of the directory entry(s) in the Directory Table.
 	UID         int
 	folder      bool
 	symlink     bool
@@ -145,19 +145,22 @@ func (w *Writer) AddFileTo(filepath string, file *os.File) error {
 	}
 	if holder.symlink {
 		holder.reader = file
-		target, err := os.Readlink(file.Name())
+		var target string
+		target, err = os.Readlink(file.Name())
 		if err != nil {
 			return err
 		}
 		holder.symLocation = target
 	} else if holder.folder {
-		subDirNames, err := file.Readdirnames(-1)
+		var subDirNames []string
+		subDirNames, err = file.Readdirnames(-1)
 		if err != nil {
 			return err
 		}
 		dirsAdded := make([]string, 0)
 		for _, subDir := range subDirNames {
-			fil, err := os.Open(file.Name() + subDir)
+			var fil *os.File
+			fil, err = os.Open(file.Name() + subDir)
 			if err != nil {
 				return err
 			}
@@ -181,6 +184,12 @@ func (w *Writer) AddFileTo(filepath string, file *os.File) error {
 		return errors.New("Unsupported file type " + file.Name())
 	}
 	if _, ok := w.structure[holder.path]; ok {
+		if !w.Contains(holder.path) {
+			err = w.AddFolderTo(holder.path, fs.ModePerm)
+			if err != nil {
+				return err
+			}
+		}
 		w.folders = append(w.folders, holder.path)
 		sort.Strings(w.folders)
 	}
@@ -205,6 +214,12 @@ func (w *Writer) AddReaderTo(filepath string, reader io.Reader, size uint64) err
 	holder.size = size
 	holder.reader = reader
 	if _, ok := w.structure[holder.path]; ok {
+		if !w.Contains(holder.path) {
+			err := w.AddFolderTo(holder.path, fs.ModePerm)
+			if err != nil {
+				return err
+			}
+		}
 		w.folders = append(w.folders, holder.path)
 		sort.Strings(w.folders)
 	}
@@ -227,9 +242,19 @@ func (w *Writer) AddFolderTo(folderpath string, permission fs.FileMode) error {
 	file := fileHolder{
 		path:   path.Dir(folderpath),
 		name:   path.Base(folderpath),
-		perm:   int(permission | fs.ModePerm),
+		perm:   int(permission.Perm()),
 		folder: true,
 	}
+	if _, ok := w.structure[file.path]; ok {
+		if !w.Contains(file.path) {
+			err := w.AddFolderTo(file.path, fs.ModePerm)
+			if err != nil {
+				return err
+			}
+		}
+		w.folders = append(w.folders, file.path)
+		sort.Strings(w.folders)
+	}
 	w.structure[file.path] = append(w.structure[file.path], &file)
 	return nil
 }

writer_fragment.go

@@ -64,6 +64,8 @@ func (w *Writer) addToFragments(fil *fileHolder) {
 	fragSize := fil.blockSizes[len(fil.blockSizes)-1]
 	//only fragment if the final block is less then 80% of a full block or AlwaysFragment
 	if w.Flags.AlwaysFragment || fragSize < uint32(float32(w.BlockSize)*0.8) {
+		//Try to slot the fragment into a fragment that has the perfect size left. If not, just pick the first one.
+		//TODO: possibly make this more efficient, possibly by calculating fragments all at once and seeing which combos match BlockSize perfectly.
 		var possibleFrags []int
 		for i := range w.frags {
 			left := w.frags[i].sizeLeft()

writer_write.go

@@ -3,34 +3,14 @@ package squashfs
 import (
 	"errors"
 	"io"
-	"io/fs"
 	"math"
 	"time"
 )
 
-func (w *Writer) fixFolders() error {
-	for folder := range w.structure {
-		if folder == "/" || w.Contains(folder) {
-			continue
-		}
-		err := w.AddFolderTo(folder, fs.ModePerm)
-		if err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 //WriteTo attempts to write the archive to the given io.Writer.
-//Folder that aren't present (such as if you add a file at /folder/file, but not the folder /folder)
-//are added with full permission (777).
 //
 //Not working. Yet.
 func (w *Writer) WriteTo(write io.Writer) (int64, error) {
-	err := w.fixFolders()
-	if err != nil {
-		return 0, err
-	}
 	if w.BlockSize > 1048576 {
 		w.BlockSize = 1048576
 	} else if w.BlockSize < 4096 {