p2p: remove unused MakePoWTarget() (#5684)

CHANGELOG_PENDING.md

@@ -16,6 +16,7 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - P2P Protocol
 
 - Go API
+  - [p2p] Removed unused function `MakePoWTarget`. (@erikgrinaker)
 
 - [libs/os] Kill() and {Must,}{Read,Write}File() functions have been removed. (@alessio)
 

p2p/key.go

@@ -1,9 +1,7 @@
 package p2p
 
 import (
-	"bytes"
 	"encoding/hex"
-	"fmt"
 	"io/ioutil"
 
 	"github.com/tendermint/tendermint/crypto"
@@ -94,27 +92,3 @@ func (nodeKey *NodeKey) SaveAs(filePath string) error {
 	}
 	return nil
 }
-
-//------------------------------------------------------------------------------
-
-// MakePoWTarget returns the big-endian encoding of 2^(targetBits - difficulty) - 1.
-// It can be used as a Proof of Work target.
-// NOTE: targetBits must be a multiple of 8 and difficulty must be less than targetBits.
-func MakePoWTarget(difficulty, targetBits uint) []byte {
-	if targetBits%8 != 0 {
-		panic(fmt.Sprintf("targetBits (%d) not a multiple of 8", targetBits))
-	}
-	if difficulty >= targetBits {
-		panic(fmt.Sprintf("difficulty (%d) >= targetBits (%d)", difficulty, targetBits))
-	}
-	targetBytes := targetBits / 8
-	zeroPrefixLen := (int(difficulty) / 8)
-	prefix := bytes.Repeat([]byte{0}, zeroPrefixLen)
-	mod := (difficulty % 8)
-	if mod > 0 {
-		nonZeroPrefix := byte(1<<(8-mod) - 1)
-		prefix = append(prefix, nonZeroPrefix)
-	}
-	tailLen := int(targetBytes) - len(prefix)
-	return append(prefix, bytes.Repeat([]byte{0xFF}, tailLen)...)
-}

p2p/key_test.go

@@ -1,7 +1,6 @@
 package p2p
 
 import (
-	"bytes"
 	"os"
 	"path/filepath"
 	"testing"
@@ -52,30 +51,3 @@ func TestNodeKeySaveAs(t *testing.T) {
 	assert.NoError(t, err)
 	assert.FileExists(t, filePath)
 }
-
-//----------------------------------------------------------
-
-func padBytes(bz []byte, targetBytes int) []byte {
-	return append(bz, bytes.Repeat([]byte{0xFF}, targetBytes-len(bz))...)
-}
-
-func TestPoWTarget(t *testing.T) {
-
-	targetBytes := 20
-	cases := []struct {
-		difficulty uint
-		target     []byte
-	}{
-		{0, padBytes([]byte{}, targetBytes)},
-		{1, padBytes([]byte{127}, targetBytes)},
-		{8, padBytes([]byte{0}, targetBytes)},
-		{9, padBytes([]byte{0, 127}, targetBytes)},
-		{10, padBytes([]byte{0, 63}, targetBytes)},
-		{16, padBytes([]byte{0, 0}, targetBytes)},
-		{17, padBytes([]byte{0, 0, 127}, targetBytes)},
-	}
-
-	for _, c := range cases {
-		assert.Equal(t, MakePoWTarget(c.difficulty, 20*8), c.target)
-	}
-}