1 files changed, 76 insertions, 0 deletions
diff --git a/ethtrie/encoding.go b/ethtrie/encoding.go
new file mode 100644
index 000000000..c9c391110
--- /dev/null
+++ b/ethtrie/encoding.go
@@ -0,0 +1,76 @@
+package ethtrie
+
+import (
+	"bytes"
+	"encoding/hex"
+	"strings"
+)
+
+func CompactEncode(hexSlice []int) string {
+	terminator := 0
+	if hexSlice[len(hexSlice)-1] == 16 {
+		terminator = 1
+	}
+
+	if terminator == 1 {
+		hexSlice = hexSlice[:len(hexSlice)-1]
+	}
+
+	oddlen := len(hexSlice) % 2
+	flags := 2*terminator + oddlen
+	if oddlen != 0 {
+		hexSlice = append([]int{flags}, hexSlice...)
+	} else {
+		hexSlice = append([]int{flags, 0}, hexSlice...)
+	}
+
+	var buff bytes.Buffer
+	for i := 0; i < len(hexSlice); i += 2 {
+		buff.WriteByte(byte(16*hexSlice[i] + hexSlice[i+1]))
+	}
+
+	return buff.String()
+}
+
+func CompactDecode(str string) []int {
+	base := CompactHexDecode(str)
+	base = base[:len(base)-1]
+	if base[0] >= 2 {
+		base = append(base, 16)
+	}
+	if base[0]%2 == 1 {
+		base = base[1:]
+	} else {
+		base = base[2:]
+	}
+
+	return base
+}
+
+func CompactHexDecode(str string) []int {
+	base := "0123456789abcdef"
+	hexSlice := make([]int, 0)
+
+	enc := hex.EncodeToString([]byte(str))
+	for _, v := range enc {
+		hexSlice = append(hexSlice, strings.IndexByte(base, byte(v)))
+	}
+	hexSlice = append(hexSlice, 16)
+
+	return hexSlice
+}
+
+func DecodeCompact(key []int) string {
+	base := "0123456789abcdef"
+	var str string
+
+	for _, v := range key {
+		if v < 16 {
+			str += string(base[v])
+		}
+	}
+
+	res, _ := hex.DecodeString(str)
+
+	return string(res)
+}