From 95cd5c85f09e79b1d6cecdac7d5180c3483a05f0 Mon Sep 17 00:00:00 2001
From: mappu <mappu04@gmail.com>
Date: Sat, 25 Nov 2017 14:25:17 +1300
Subject: [PATCH] tth: working

--HG--
branch : adc
---
 tth.go      | 36 +++++++++++++-----------------------
 tth_test.go |  2 +-
 2 files changed, 14 insertions(+), 24 deletions(-)

diff --git a/tth.go b/tth.go
index b7c3892..8a245ec 100644
--- a/tth.go
+++ b/tth.go
@@ -3,38 +3,28 @@ package libnmdc
 import (
 	"encoding/base32"
 	"errors"
+	"strings"
 
 	"github.com/cxmcc/tiger"
 )
 
-func tth(input []byte) (string, error) {
+// TTH returns the TTH hash of a string. This is a rudimentary implementation
+// that only supports content up to 1024 bytes in length.
+func TTH(input string) (string, error) {
+
+	// Short segments do not need to be padded.
+	// Content above 1024 bytes needs tree handling (0x00 prefix for leaf nodes,
+	// 0x01 prefix for hash nodes) but for content less than 1024 bytes, just
+	// return the leaf hash
+	// @ref http://adc.sourceforge.net/draft-jchapweske-thex-02.html
 	if len(input) > 1024 {
 		return "", errors.New("TTH content exceeded 1024 bytes")
 	}
 
+	// Single leaf hash only
 	leafHash := tiger.New()
-
-	//buff := make([]byte, 1024)
-	//leafHash.Write([]byte("\x00"))
-	//copy(buff[1:], []byte(input))
-	//leafHash.Write(buff)
-	//fmt.Printf("%#v\n", buff)
-
-	leafHash.Write([]byte("\x00" + string(input)))
+	leafHash.Write([]byte("\x00" + input))
 	leafHashBytes := leafHash.Sum(nil)
 
-	rootHash := tiger.New()
-	//rootHash.Write([]byte("\x01"))
-	//rootHash.Write(leafHashBytes)
-	rootHash.Write([]byte("\x01" + string(leafHashBytes)))
-	rootHashBytes := rootHash.Sum(nil)
-
-	/*
-	   * The Tiger Hash function, modified to prepend the specified byte to the input
-	    * data. This is useful for the THEX algorithm which prepends a 0x00 to leaf
-	    * nodes and 0x01 to the hash nodes.
-	    **/
-
-	// Definitely StdEncoding
-	return base32.StdEncoding.EncodeToString(rootHashBytes), nil
+	return strings.TrimRight(base32.StdEncoding.EncodeToString(leafHashBytes), "="), nil
 }
diff --git a/tth_test.go b/tth_test.go
index 1756872..ca41ad3 100644
--- a/tth_test.go
+++ b/tth_test.go
@@ -24,7 +24,7 @@ func TestTTH(t *testing.T) {
 
 	for _, testCase := range testCases {
 		input, expected := testCase[0], testCase[1]
-		result, err := tth([]byte(input))
+		result, err := TTH(input)
 		if err != nil {
 			t.Fatalf("Error getting TTH for '%s': %s", short(input), err.Error())
 		}