From 74bc45116aa1c5d0e549f522dccefc58356c1410 Mon Sep 17 00:00:00 2001
From: obscuren <obscuren@obscura.com>
Date: Sun, 29 Dec 2013 23:50:43 +0100
Subject: [PATCH] Encoding helpers with tests

---
 encoding.go      | 46 ++++++++++++++++++++++++++++++++++++++++++++
 encoding_test.go | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 encoding.go
 create mode 100644 encoding_test.go

diff --git a/encoding.go b/encoding.go
new file mode 100644
index 000000000..ca30b47c9
--- /dev/null
+++ b/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
+}
diff --git a/encoding_test.go b/encoding_test.go
new file mode 100644
index 000000000..63f7878bf
--- /dev/null
+++ b/encoding_test.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+  "testing"
+  "fmt"
+)
+
+func TestCompactEncode(t *testing.T) {
+  test1 := []int{1,2,3,4,5}
+  if res := CompactEncode(test1); res != "\x11\x23\x45" {
+    t.Error(fmt.Sprintf("even compact encode failed. Got: %q", res))
+  }
+
+  test2 := []int{0, 1, 2, 3, 4, 5}
+  if res := CompactEncode(test2); res != "\x00\x01\x23\x45" {
+    t.Error(fmt.Sprintf("odd compact encode failed. Got: %q", res))
+  }
+
+  test3 := []int{0, 15, 1, 12, 11, 8, /*term*/16}
+  if res := CompactEncode(test3); res != "\x20\x0f\x1c\xb8" {
+    t.Error(fmt.Sprintf("odd terminated compact encode failed. Got: %q", res))
+  }
+
+  test4 := []int{15, 1, 12, 11, 8, /*term*/16}
+  if res := CompactEncode(test4); res != "\x3f\x1c\xb8" {
+    t.Error(fmt.Sprintf("even terminated compact encode failed. Got: %q", res))
+  }
+}
+
+// Helper function for comparing slices
+func CompareIntSlice(a, b []int) bool {
+  if len(a) != len(b) {
+    return false
+  }
+  for i, v := range a {
+    if v != b[i] {
+      return false
+    }
+  }
+  return true
+}
+
+func TestCompactHexDecode(t *testing.T) {
+  exp := []int{7, 6, 6, 5, 7, 2, 6, 2, 16}
+  res := CompactHexDecode("verb")
+
+  if !CompareIntSlice(res, exp) {
+    t.Error("Error compact hex decode. Expected", exp, "got", res)
+  }
+}