Re-wrote a bunch to try to figure out why things weren't working.

Turned out I was reading if a block was compressed exactly opposite.
Started to work more on looking up dirs.

compression.go

@@ -0,0 +1,39 @@
+package squashfs
+
+import (
+	"bytes"
+	"compress/zlib"
+	"io"
+)
+
+type Decompressor interface {
+	Decompress(io.Reader) ([]byte, error)
+	DecompressCopy(*io.Writer, *io.SectionReader) error
+}
+
+type ZlibDecompressor struct{}
+
+func (z *ZlibDecompressor) Decompress(r io.Reader) ([]byte, error) {
+	rdr, err := zlib.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	var data bytes.Buffer
+	_, err = io.Copy(&data, rdr)
+	if err != nil {
+		return nil, err
+	}
+	return data.Bytes(), nil
+}
+
+func (z *ZlibDecompressor) DecompressCopy(w *io.Writer, r *io.SectionReader) error {
+	rdr, err := zlib.NewReader(r)
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(*w, rdr)
+	if err != nil {
+		return err
+	}
+	return err
+}