diff --git a/superblock.go b/superblock.go
index 0f846b8..8a46007 100644
--- a/superblock.go
+++ b/superblock.go
@@ -45,7 +45,7 @@ type SuperblockFlags struct {
 	//If true, ALL data is stored in sequential data blocks instead of utilizing fragments.
 	NoFragments bool
 	//If true, the last block of data will always be stored as a fragment if it's less then the block size.
-	AlwaysFragments bool
+	AlwaysFragment bool
 	//If true, duplicate files are only stored once. (Currently unsupported)
 	RemoveDuplicates bool
 	//If true, the export table is populated. (Currently unsupported)
@@ -73,7 +73,7 @@ func (s *superblock) GetFlags() SuperblockFlags {
 		check:                 s.Flags&0x4 == 0x4,
 		UncompressedFragments: s.Flags&0x8 == 0x8,
 		NoFragments:           s.Flags&0x10 == 0x10,
-		AlwaysFragments:       s.Flags&0x20 == 0x20,
+		AlwaysFragment:        s.Flags&0x20 == 0x20,
 		RemoveDuplicates:      s.Flags&0x40 == 0x40,
 		Exportable:            s.Flags&0x80 == 0x80,
 		UncompressedXattr:     s.Flags&0x100 == 0x100,
@@ -101,7 +101,7 @@ func (s *SuperblockFlags) ToUint() uint16 {
 	if s.NoFragments {
 		out = out | 0x10
 	}
-	if s.AlwaysFragments {
+	if s.AlwaysFragment {
 		out = out | 0x20
 	}
 	if s.RemoveDuplicates {
diff --git a/writer.go b/writer.go
index 7a7bbb9..ba0fe2d 100644
--- a/writer.go
+++ b/writer.go
@@ -19,9 +19,11 @@ import (
 type Writer struct {
 	compressor      compression.Compressor
 	structure       map[string][]*fileHolder
-	symlinkTable    map[string]string //[oldpath]newpath
+	symlinkTable    map[string]string
 	folders         []string
 	uidGUIDTable    []int
+	frags           []fragment
+	superblock      superblock
 	compressionType int
 	//BlockSize is how large the data blocks are. Can be between 4096 (4KB) and 1048576 (1 MB).
 	//If BlockSize is not inside that range, it will be set to within the range before writing.
@@ -31,10 +33,6 @@ type Writer struct {
 	//Currently Duplicates, Exportable, UncompressedXattr, NoXattr values are ignored
 	Flags       SuperblockFlags
 	allowErrors bool
-
-	//variables used when actually writing.
-	superblock superblock
-	frags      []fragment
 }
 
 //NewWriter creates a new with the default options (Gzip compression and allow errors)
@@ -52,7 +50,7 @@ func NewWriterWithOptions(compressionType int, allowErrors bool) (*Writer, error
 	if compressionType == 3 {
 		return nil, errors.New("Lzo compression is not (currently) supported")
 	}
-	return &Writer{
+	writer := &Writer{
 		structure: map[string][]*fileHolder{
 			"/": make([]*fileHolder, 0),
 		},
@@ -64,7 +62,20 @@ func NewWriterWithOptions(compressionType int, allowErrors bool) (*Writer, error
 		allowErrors:     allowErrors,
 		BlockSize:       uint32(1048576),
 		Flags:           DefaultFlags,
-	}, nil
+	}
+	switch compressionType {
+	case 1:
+		writer.compressor = &compression.Gzip{}
+	case 2:
+		writer.compressor = &compression.Lzma{}
+	case 4:
+		writer.compressor = &compression.Xz{}
+	case 5:
+		writer.compressor = &compression.Lz4{}
+	case 6:
+		writer.compressor = &compression.Zstd{}
+	}
+	return writer, nil
 }
 
 //fileHolder holds the necessary information about a given file inside of a squashfs
@@ -80,6 +91,9 @@ type fileHolder struct {
 	UID         int
 	folder      bool
 	symlink     bool
+
+	fragIndex  int
+	fragOffset int
 }
 
 //AddFile attempts to add an os.File to the archive's root directory.
diff --git a/writer_fragment.go b/writer_fragment.go
index 165be64..b0ea9eb 100644
--- a/writer_fragment.go
+++ b/writer_fragment.go
@@ -16,6 +16,54 @@ func (f *fragment) SizeLeft() uint32 {
 
 func (f *fragment) AddFragment(fil *fileHolder) {
 	//SizeLeft should already be checked
+	fil.fragOffset = len(f.files)
 	f.files = append(f.files, fil)
 	f.sizes = append(f.sizes, fil.blockSizes[len(fil.blockSizes)-1])
 }
+
+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) {
+		var possibleFrags []int
+		for i := range w.frags {
+			left := w.frags[i].SizeLeft()
+			if left == fragSize {
+				fil.fragIndex = i
+				w.frags[i].AddFragment(fil)
+				return
+			} else if left > fragSize {
+				possibleFrags = append(possibleFrags, i)
+			}
+		}
+		if len(possibleFrags) > 0 {
+			fil.fragIndex = possibleFrags[0]
+		} else {
+			fil.fragIndex = len(w.frags)
+			w.frags = append(w.frags, fragment{
+				w:     w,
+				files: []*fileHolder{fil},
+				sizes: []uint32{fragSize},
+			})
+		}
+	}
+}
+
+func (w *Writer) calculateFragsAndBlockSizes() {
+	for _, files := range w.structure {
+		for i := range files {
+			files[i].fragIndex = -1
+			files[i].blockSizes = make([]uint32, files[i].size/uint64(w.BlockSize))
+			for j := range files[i].blockSizes {
+				files[i].blockSizes[j] = w.BlockSize
+			}
+			fragSize := uint32(files[i].size % uint64(w.BlockSize))
+			if fragSize > 0 {
+				files[i].blockSizes = append(files[i].blockSizes, fragSize)
+				if !w.Flags.NoFragments {
+					w.addToFragments(files[i])
+				}
+			}
+		}
+	}
+}
diff --git a/writer_inodes.go b/writer_inodes.go
index 685efbe..e9a857d 100644
--- a/writer_inodes.go
+++ b/writer_inodes.go
@@ -7,17 +7,3 @@ func (w *Writer) countInodes() (out uint32) {
 	}
 	return
 }
-
-//intilialize the block sizes. These values will be overwritten with their compressed sizes later.
-func (w *Writer) calculateBlockSizes(fil *fileHolder) {
-	tmp := fil.size
-	for {
-		if tmp < uint64(w.BlockSize) {
-			fil.blockSizes = append(fil.blockSizes, uint32(tmp))
-			break
-		}
-		tmp -= uint64(w.BlockSize)
-		fil.blockSizes = append(fil.blockSizes, w.BlockSize)
-	}
-	return
-}
diff --git a/writer_write.go b/writer_write.go
index 17b56ab..03e8609 100644
--- a/writer_write.go
+++ b/writer_write.go
@@ -24,6 +24,8 @@ func (w *Writer) fixFolders() error {
 //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 {
@@ -37,6 +39,7 @@ func (w *Writer) WriteTo(write io.Writer) (int64, error) {
 	w.Flags.RemoveDuplicates = false
 	w.Flags.Exportable = false
 	w.Flags.NoXattr = true
+	w.calculateFragsAndBlockSizes()
 	w.superblock = superblock{
 		Magic:           magic,
 		InodeCount:      w.countInodes(),
@@ -49,6 +52,5 @@ func (w *Writer) WriteTo(write io.Writer) (int64, error) {
 		MajorVersion:    4,
 		MinorVersion:    0,
 	}
-	_ = super
 	return 0, errors.New("I SAID DON'T")
 }