Encoding helpers with tests

encoding.go

@@ -0,0 +1,46 @@
+package main
+
+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 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
+}