use string instead of bytes, fix off by 1

main.go

@@ -4,17 +4,18 @@ import (
 	"context"
 	"crypto"
 	_ "crypto/sha1"
-	"encoding/hex"
+	"encoding/base64"
 	"fmt"
 	"math/rand"
 	"os"
 	"runtime"
+	"strings"
 	"time"
 )
 
 func main() {
 	g := Generator{
-		Difficulty: 25,
+		Difficulty: 20,
 		Timeout:    10 * time.Second,
 	}
 	c := g.RandomChallenge()
@@ -28,7 +29,6 @@ type Challenge struct {
 	Input    [48]byte
 	Date     [20]byte
 	Solution int64
-	bytes    []byte
 	Generator
 }
 type Generator struct {
@@ -72,9 +72,6 @@ var prefixLookup = []int{
 }
 
 func (c *Challenge) Solve() {
-	c.bytes = make([]byte, 76)
-	c.bytes = append(c.bytes, c.Input[:]...)
-	c.bytes = append(c.bytes, c.Date[:]...)
 	timer := time.Now()
 	solution := make(chan int64)
 	ctx, cancel := context.WithCancel(context.Background())
@@ -95,7 +92,7 @@ func (c *Challenge) Solve() {
 						cancel()
 						break
 					}
-					if c.Solution > 0xffffffffffffff {
+					if c.Solution > 0xfffffff {
 						fmt.Fprintf(os.Stderr, "%s (thread %d): could not find solution!\n", c.String(), id)
 						cancel()
 						break
@@ -121,14 +118,12 @@ func (c *Challenge) Solve() {
 	}
 }
 func (c *Challenge) CheckValue(v int64) bool {
-	bytes := make([]byte, len(c.bytes))
-	copy(bytes, c.bytes)
-	for i := range 8 {
-		bytes[75-i] = byte(v >> (i * 8))
-	}
+	var sb strings.Builder
+	sb.WriteString(c.StringNoSolution())
+	sb.WriteString(StringSolution(v))
 	sum := make([]byte, 20)
 	hash := crypto.SHA1.New()
-	hash.Write(bytes)
+	hash.Write([]byte(sb.String()))
 	sum = hash.Sum(nil)
 	count := 0
 	for _, c := range sum {
@@ -144,13 +139,26 @@ func (c *Challenge) Validate() bool {
 	return c.CheckValue(c.Solution)
 }
 func (c *Challenge) String() string {
+	var sb strings.Builder
+	sb.WriteString(c.StringNoSolution())
+	sb.WriteString(c.StringThisSolution())
+	return sb.String()
+}
+func (c *Challenge) StringNoSolution() string {
+	var sb strings.Builder
 	bytes := make([]byte, 0)
 	bytes = append(bytes, c.Input[:]...)
 	bytes = append(bytes, c.Date[:]...)
-	bytes = append(bytes, make([]byte, 8)...)
-	bytes[68] = c.Difficulty
-	for i := range 7 {
-		bytes[75-i] = byte(c.Solution >> (i * 8))
-	}
-	return hex.EncodeToString(bytes)
+	bytes = append(bytes, c.Difficulty)
+	sb.WriteString(base64.URLEncoding.EncodeToString(bytes))
+	return sb.String()
+}
+func (c *Challenge) StringThisSolution() string {
+	return StringSolution(c.Solution)
+}
+func StringSolution(v int64) string {
+	var sb strings.Builder
+	sb.WriteRune(';')
+	sb.WriteString(fmt.Sprintf("%07x", v))
+	return sb.String()
 }