diff --git a/chunk/in_memory.go b/chunk/in_memory.go
index cd95427..ca7259c 100644
--- a/chunk/in_memory.go
+++ b/chunk/in_memory.go
@@ -2,28 +2,67 @@
 
 import (
 	"bytes"
+	"errors"
 	"io"
+
+	"pcloud/api"
 )
 
 type InMemoryChunk struct {
-	payload bytes.Buffer
+	status    api.ChunkStatus
+	payload   []byte
+	committed int
 }
 
-func (c *InMemoryChunk) SizeBytes() int {
-	return len(c.payload.Bytes())
+func (c *InMemoryChunk) Stats() (ChunkInfo, error) {
+	return ChunkInfo{c.status, len(c.payload), c.committed}, nil
 }
 
-func (c *InMemoryChunk) ReadSeeker() io.ReadSeeker {
-	return bytes.NewReader(c.payload.Bytes())
+func (c *InMemoryChunk) ReaderAt() io.ReaderAt {
+	return bytes.NewReader(c.payload[:c.committed])
 }
 
-func (c *InMemoryChunk) Writer() io.Writer {
-	return &c.payload
+func (c *InMemoryChunk) WriterAt() io.WriterAt {
+	return &byteWriter{c}
+}
+
+type byteWriter struct {
+	c *InMemoryChunk
+}
+
+func (w *byteWriter) WriteAt(p []byte, offset int64) (n int, err error) {
+	if int(offset) > w.c.committed {
+		panic(1)
+		return 0, errors.New("Gaps are not allowed when writing in chunks")
+	}
+	if int(offset) < w.c.committed {
+		if int(offset)+len(p) <= w.c.committed {
+			if bytes.Compare(w.c.payload[int(offset):int(offset)+len(p)], p) != 0 {
+				panic(2)
+				return 0, errors.New("Can not change contents of allready committed chunk bytes")
+			}
+			panic(3)
+			return len(p), nil
+		}
+		n = w.c.committed - int(offset)
+		p = p[n:]
+		offset = int64(w.c.committed)
+	}
+	if w.c.committed+len(p) > len(w.c.payload) {
+		panic(4)
+		return 0, errors.New("In memory chunk does not have enough space available")
+	}
+	n += copy(w.c.payload[w.c.committed:], p)
+	w.c.committed += n
+	return
 }
 
 type InMemoryChunkFactory struct {
 }
 
-func (f InMemoryChunkFactory) New() Chunk {
-	return &InMemoryChunk{}
+func (f InMemoryChunkFactory) New(size int) Chunk {
+	return &InMemoryChunk{
+		status:    api.ChunkStatus_CREATED,
+		payload:   make([]byte, size),
+		committed: 0}
 }