return false by default

README.md

@@ -4,7 +4,7 @@ HTTP Hashcash implemented in Go.
 
 Explanation at https://therootcompany.com/blog/http-hashcash/
 
-Go docs at https://godoc.org/git.rootprojects.org/root/hashcash
+Go API docs at https://pkg.go.dev/git.rootprojects.org/root/hashcash?tab=doc
 
 # CLI Usage
 
@@ -21,6 +21,7 @@ Usage:
 	hashcash new [subject *] [expires in 5m] [difficulty 10]
 	hashcash parse <hashcash>
 	hashcash solve <hashcash>
+	hashcash hash <hashcash>
 	hashcash verify <hashcash> [subject *]
 ```
 

cmd/hashcash/hashcash.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -12,16 +14,18 @@ import (
 
 func help() {
 	fmt.Println("Usage:")
-	fmt.Println("\thashcash new [subject *] [expires in 5m] [difficulty 10]")
+	fmt.Println("\thashcash new [subject *] [difficulty 10] [expires in 5m]")
 	fmt.Println("\thashcash parse <hashcash>")
 	fmt.Println("\thashcash solve <hashcash>")
+	fmt.Println("\thashcash hash <hashcash>")
 	fmt.Println("\thashcash verify <hashcash> [subject *]")
 }
 
 func main() {
 	args := os.Args[:]
+	nargs := len(args)
 
-	if len(args) < 2 {
+	if nargs < 2 {
 		help()
 		os.Exit(1)
 		return
@@ -30,27 +34,30 @@ func main() {
 	switch args[1] {
 	case "new":
 		var subject string
-		if len(args) > 3 {
+		if nargs >= 3 {
 			subject = args[2]
 		}
 
 		var difficulty int
-		if len(args) > 4 {
+		if nargs >= 4 {
 			var err error
 			difficulty, err = strconv.Atoi(args[3])
 			if nil != err {
 				help()
 				os.Exit(1)
+				return
 			}
 		}
 
 		var expIn time.Duration
-		if len(args) > 5 {
+		if nargs >= 5 {
 			var err error
 			expIn, err = time.ParseDuration(args[4])
 			if nil != err {
+				fmt.Println(err)
 				help()
 				os.Exit(1)
+				return
 			}
 		} else {
 			expIn = 5 * time.Minute
@@ -66,7 +73,7 @@ func main() {
 		return
 	case "parse":
 		var token string
-		if 3 != len(args) {
+		if 3 != nargs {
 			help()
 			os.Exit(1)
 			return
@@ -82,7 +89,7 @@ func main() {
 		return
 	case "solve":
 		var token string
-		if 3 != len(args) {
+		if 3 != nargs {
 			help()
 			os.Exit(1)
 			return
@@ -103,9 +110,20 @@ func main() {
 
 		fmt.Println(h.String())
 		return
+	case "hash":
+		var token string
+		if 3 != nargs {
+			help()
+			os.Exit(1)
+			return
+		}
+		token = args[2]
+		hash := sha256.Sum256([]byte(token))
+		fmt.Println(hex.EncodeToString(hash[:]))
+		return
 	case "verify":
 		var token string
-		if len(args) < 3 {
+		if nargs < 3 {
 			help()
 			os.Exit(1)
 			return
@@ -118,7 +136,7 @@ func main() {
 		}
 
 		subject := "*"
-		if len(args) > 3 {
+		if nargs >= 4 {
 			subject = args[3]
 		}
 

hashcash.go

@@ -216,6 +216,10 @@ func (h *Hashcash) Verify(subject string) error {
 }
 
 func verifyBits(hash []byte, bits, n int) bool {
+	if 0 == bits {
+		return true
+	}
+
 	for i := 0; i < n; i++ {
 		if bits > 8 {
 			bits -= 8
@@ -227,15 +231,12 @@ func verifyBits(hash []byte, bits, n int) bool {
 
 		// (bits % 8) == bits
 		pad := 8 - bits
-		if 0 != hash[i]>>pad {
+		if 0 == hash[i]>>pad {
+			return true
+		}
+	}
+
 	return false
-		}
-
-		return true
-	}
-
-	// 0 == bits
-	return true
 }
 
 // Solve will search for a solution, returning an error if the difficulty is