[Code Health] refactor: simplify protocol.CountHashDifficultyBits() (#656)

Co-authored-by: Daniel Olshansky <olshansky.daniel@gmail.com>

Author: bryanchriswhite

pkg/crypto/protocol/difficulty.go

@@ -0,0 +1,20 @@
+package protocol
+
+import (
+	"encoding/binary"
+	"math/bits"
+)
+
+// CountHashDifficultyBits returns the number of leading zero bits in the given byte slice.
+// TODO_MAINNET: Consider generalizing difficulty to a target hash. See:
+// - https://bitcoin.stackexchange.com/questions/107976/bitcoin-difficulty-why-leading-0s
+// - https://bitcoin.stackexchange.com/questions/121920/is-it-always-possible-to-find-a-number-whose-hash-starts-with-a-certain-number-o
+// - https://github.com/pokt-network/poktroll/pull/656/files#r1666712528
+func CountHashDifficultyBits(bz [32]byte) int {
+	// Using BigEndian for contiguous bit/byte ordering such leading zeros
+	// accumulate across adjacent bytes.
+	// E.g.: []byte{0, 0b00111111, 0x00, 0x00} has 10 leading zero bits. If
+	// LittleEndian were applied instead, it would have 18 leading zeros because it would
+	// look like []byte{0, 0, 0b00111111, 0}.
+	return bits.LeadingZeros64(binary.BigEndian.Uint64(bz[:]))
+}

pkg/crypto/protocol/difficulty_test.go

@@ -0,0 +1,51 @@
+package protocol_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/pokt-network/poktroll/pkg/crypto/protocol"
+)
+
+func TestCountDifficultyBits(t *testing.T) {
+	tests := []struct {
+		bz         []byte
+		difficulty int
+	}{
+		{
+			bz:         []byte{0b11111111},
+			difficulty: 0,
+		},
+		{
+			bz:         []byte{0b01111111},
+			difficulty: 1,
+		},
+		{
+			bz:         []byte{0, 255},
+			difficulty: 8,
+		},
+		{
+			bz:         []byte{0, 0b01111111},
+			difficulty: 9,
+		},
+		{
+			bz:         []byte{0, 0b00111111},
+			difficulty: 10,
+		},
+		{
+			bz:         []byte{0, 0, 255},
+			difficulty: 16,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("difficulty_%d_zero_bits", test.difficulty), func(t *testing.T) {
+			var bz [32]byte
+			copy(bz[:], test.bz)
+			actualDifficulty := protocol.CountHashDifficultyBits(bz)
+			require.Equal(t, test.difficulty, actualDifficulty)
+		})
+	}
+}

pkg/crypto/protocol/errors.go

@@ -0,0 +1,5 @@
+package protocol
+
+var (
+	codespace = "crypto/protocol"
+)

pkg/relayer/miner/gen/gen_fixtures.go

@@ -17,11 +17,11 @@ import (
 	"sync"
 	"time"
 
+	"github.com/pokt-network/poktroll/pkg/crypto/protocol"
 	"github.com/pokt-network/poktroll/pkg/observable"
 	"github.com/pokt-network/poktroll/pkg/observable/channel"
 	"github.com/pokt-network/poktroll/pkg/relayer"
 	"github.com/pokt-network/poktroll/pkg/relayer/miner"
-	"github.com/pokt-network/poktroll/pkg/relayer/protocol"
 	servicetypes "github.com/pokt-network/poktroll/x/service/types"
 )
 
@@ -200,13 +200,13 @@ func exitOnError(errCh <-chan error) {
 // difficultyGTE returns true if the given hash has a difficulty greater than or
 // equal to flagDifficultyBitsThreshold.
 func difficultyGTE(hash []byte) bool {
-	return protocol.MustCountDifficultyBits(hash) >= flagDifficultyBitsThreshold
+	return protocol.CountDifficultyBits(hash) >= flagDifficultyBitsThreshold
 }
 
 // difficultyLT returns true if the given hash has a difficulty less than
 // flagDifficultyBitsThreshold.
 func difficultyLT(hash []byte) bool {
-	return protocol.MustCountDifficultyBits(hash) < flagDifficultyBitsThreshold
+	return protocol.CountDifficultyBits(hash) < flagDifficultyBitsThreshold
 }
 
 // getMarshaledRelayFmtLines performs two map operations followed by a collect.

pkg/relayer/miner/miner.go

@@ -6,13 +6,13 @@ import (
 	"cosmossdk.io/depinject"
 
 	"github.com/pokt-network/poktroll/pkg/client"
+	"github.com/pokt-network/poktroll/pkg/crypto/protocol"
 	"github.com/pokt-network/poktroll/pkg/either"
 	"github.com/pokt-network/poktroll/pkg/observable"
 	"github.com/pokt-network/poktroll/pkg/observable/channel"
 	"github.com/pokt-network/poktroll/pkg/observable/filter"
 	"github.com/pokt-network/poktroll/pkg/observable/logging"
 	"github.com/pokt-network/poktroll/pkg/relayer"
-	"github.com/pokt-network/poktroll/pkg/relayer/protocol"
 	servicetypes "github.com/pokt-network/poktroll/x/service/types"
 )
 
@@ -112,18 +112,17 @@ func (mnr *miner) mapMineRelay(
 	if err != nil {
 		return either.Error[*relayer.MinedRelay](err), false
 	}
-	relayHashArr := servicetypes.GetHashFromBytes(relayBz)
-	relayHash := relayHashArr[:]
+	relayHash := servicetypes.GetHashFromBytes(relayBz)
 
 	// The relay IS NOT volume / reward applicable
-	if uint64(protocol.MustCountDifficultyBits(relayHash)) < mnr.relayDifficultyBits {
+	if uint64(protocol.CountHashDifficultyBits(relayHash)) < mnr.relayDifficultyBits {
 		return either.Success[*relayer.MinedRelay](nil), true
 	}
 
 	// The relay IS volume / reward applicable
 	return either.Success(&relayer.MinedRelay{
 		Relay: *relay,
 		Bytes: relayBz,
-		Hash:  relayHash,
+		Hash:  relayHash[:],
 	}), false
 }

pkg/relayer/protocol/difficulty.go

@@ -18,7 +18,7 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
-	"github.com/pokt-network/poktroll/pkg/relayer/protocol"
+	"github.com/pokt-network/poktroll/pkg/crypto/protocol"
 	"github.com/pokt-network/poktroll/telemetry"
 	"github.com/pokt-network/poktroll/x/proof/types"
 	servicetypes "github.com/pokt-network/poktroll/x/service/types"
@@ -476,14 +476,7 @@ func verifyClosestProof(
 // function that can be used by both the proof and the miner packages.
 func validateMiningDifficulty(relayBz []byte, minRelayDifficultyBits uint64) error {
 	relayHash := servicetypes.GetHashFromBytes(relayBz)
-
-	relayDifficultyBits, err := protocol.CountHashDifficultyBits(relayHash[:])
-	if err != nil {
-		return types.ErrProofInvalidRelay.Wrapf(
-			"error counting difficulty bits: %s",
-			err,
-		)
-	}
+	relayDifficultyBits := protocol.CountHashDifficultyBits(relayHash)
 
 	// TODO_MAINNET: Devise a test that tries to attack the network and ensure that there
 	// is sufficient telemetry.

pkg/relayer/protocol/difficulty_test.go

@@ -16,10 +16,10 @@ import (
 	"google.golang.org/grpc/status"
 
 	"github.com/pokt-network/poktroll/pkg/crypto"
+	"github.com/pokt-network/poktroll/pkg/crypto/protocol"
 	"github.com/pokt-network/poktroll/pkg/crypto/rings"
 	"github.com/pokt-network/poktroll/pkg/polylog/polyzero"
 	"github.com/pokt-network/poktroll/pkg/relayer"
-	"github.com/pokt-network/poktroll/pkg/relayer/protocol"
 	"github.com/pokt-network/poktroll/pkg/relayer/session"
 	testutilevents "github.com/pokt-network/poktroll/testutil/events"
 	keepertest "github.com/pokt-network/poktroll/testutil/keeper"
@@ -1394,10 +1394,7 @@ func getClosestRelayDifficultyBits(
 	require.NoError(t, err)
 
 	// Count the number of leading 0s in the relay hash to determine its difficulty.
-	relayDifficultyBits, err := protocol.CountHashDifficultyBits(relayHash[:])
-	require.NoError(t, err)
-
-	return uint64(relayDifficultyBits)
+	return uint64(protocol.CountHashDifficultyBits(relayHash))
 }
 
 // resetBlockHeightFn returns a function that resets the block height of the