refactor: count difficulty; bit resolution

pkg/relayer/miner/miner.go

@@ -21,7 +21,7 @@ var (
 	// TODO_BLOCKER: query on-chain governance params once available.
 	// Setting this to 0 to effectively disables mining for now.
 	// I.e., all relays are added to the tree.
-	defaultRelayDifficulty = 0
+	defaultRelayDifficultyBits = 0
 )
 
 // Miner is responsible for observing servedRelayObs, hashing and checking the
@@ -102,7 +102,7 @@ func (mnr *miner) mapMineRelay(
 	relayHash := mnr.hash(relayBz)
 
 	// The relay IS NOT volume / reward applicable
-	if !protocol.BytesDifficultyGreaterThan(relayHash, defaultRelayDifficulty) {
+	if protocol.MustCountDifficultyBits(relayHash) >= defaultRelayDifficultyBits {
 		return either.Success[*relayer.MinedRelay](nil), true
 	}
 

pkg/relayer/protocol/difficulty.go

@@ -1,17 +1,40 @@
 package protocol
 
 import (
-	"encoding/hex"
-	"strings"
+	"math/bits"
 )
 
 // TODO_BLOCKER: Revisit this part of the algorithm after initial TestNet Launch.
 // TODO_TEST: Add extensive tests for the core relay mining business logic.
-// BytesDifficultyGreaterThan determines if the bytes exceed a certain difficulty, and it
-// is used to determine if a relay is volume applicable. See the spec for more details: https://github.com/pokt-network/pocket-network-protocol
-func BytesDifficultyGreaterThan(bz []byte, compDifficultyBytes int) bool {
-	hexZerosPrefix := strings.Repeat("0", compDifficultyBytes*2) // 2 hex chars per byte.
-	hexBz := hex.EncodeToString(bz)
 
-	return strings.HasPrefix(hexBz, hexZerosPrefix)
+// MustCountDifficultyBits returns the number of leading zero bits in the given
+// byte slice. It panics if an error is encountered.
+func MustCountDifficultyBits(bz []byte) int {
+	diff, err := CountDifficultyBits(bz)
+	if err != nil {
+		panic(err)
+	}
+
+	return diff
+}
+
+// CountDifficultyBits returns the number of leading zero bits in the given byte
+// slice. It returns an error if the byte slice is all zero bits.
+func CountDifficultyBits(bz []byte) (int, error) {
+	bzLen := len(bz)
+
+	var zeroBits int
+	for i, b := range bz {
+		if b != 0 {
+			zeroBits = bits.LeadingZeros8(b)
+			if zeroBits == 8 {
+				// we already checked that b != 0.
+				return 0, ErrDifficulty.Wrap("impossible code path")
+			}
+
+			return (i)*8 + zeroBits, nil
+		}
+	}
+
+	return 0, ErrDifficulty.Wrapf("difficulty matches bytes length: %d; bytes (hex): % x", bzLen, bz)
 }

pkg/relayer/protocol/errors.go

@@ -0,0 +1,8 @@
+package protocol
+
+import errorsmod "cosmossdk.io/errors"
+
+var (
+	ErrDifficulty = errorsmod.New(codespace, 1, "difficulty error")
+	codespace     = "relayer/protocol"
+)