1 files changed, 84 insertions, 0 deletions
diff --git a/compression/rle/read_write.go b/compression/rle/read_write.go
new file mode 100644
index 000000000..dde0e41ab
--- /dev/null
+++ b/compression/rle/read_write.go
@@ -0,0 +1,84 @@
+package rle
+
+import (
+	"bytes"
+	"errors"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+const (
+	token             byte = 0xfe
+	emptyShaToken          = 0xfd
+	emptyListShaToken      = 0xfe
+	tokenToken             = 0xff
+)
+
+var empty = crypto.Sha3([]byte(""))
+var emptyList = crypto.Sha3([]byte{0x80})
+
+func Decompress(dat []byte) ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	for i := 0; i < len(dat); i++ {
+		if dat[i] == token {
+			if i+1 < len(dat) {
+				switch dat[i+1] {
+				case emptyShaToken:
+					buf.Write(empty)
+				case emptyListShaToken:
+					buf.Write(emptyList)
+				case tokenToken:
+					buf.WriteByte(token)
+				default:
+					buf.Write(make([]byte, int(dat[i+1]-2)))
+				}
+				i++
+			} else {
+				return nil, errors.New("error reading bytes. token encountered without proceeding bytes")
+			}
+		} else {
+			buf.WriteByte(dat[i])
+		}
+	}
+
+	return buf.Bytes(), nil
+}
+
+func compressChunk(dat []byte) (ret []byte, n int) {
+	switch {
+	case dat[0] == token:
+		return []byte{token, tokenToken}, 1
+	case len(dat) > 1 && dat[0] == 0x0 && dat[1] == 0x0:
+		j := 0
+		for j <= 254 && j < len(dat) {
+			if dat[j] != 0 {
+				break
+			}
+			j++
+		}
+		return []byte{token, byte(j + 2)}, j
+	case len(dat) >= 32:
+		if dat[0] == empty[0] && bytes.Compare(dat[:32], empty) == 0 {
+			return []byte{token, emptyShaToken}, 32
+		} else if dat[0] == emptyList[0] && bytes.Compare(dat[:32], emptyList) == 0 {
+			return []byte{token, emptyListShaToken}, 32
+		}
+		fallthrough
+	default:
+		return dat[:1], 1
+	}
+}
+
+func Compress(dat []byte) []byte {
+	buf := new(bytes.Buffer)
+
+	i := 0
+	for i < len(dat) {
+		b, n := compressChunk(dat[i:])
+		buf.Write(b)
+		i += n
+	}
+
+	return buf.Bytes()
+}