Add ethash.VerifyWithTarget to get target along with share validation…

ethash.go

@@ -116,12 +116,17 @@ type Light struct {
 
 // Verify checks whether the block's nonce is valid.
 func (l *Light) Verify(block pow.Block) bool {
+	result, _ := l.VerifyWithTarget(block)
+	return result
+}
+
+func (l *Light) VerifyWithTarget(block pow.Block) (bool, *big.Int) {
 	// TODO: do ethash_quick_verify before getCache in order
 	// to prevent DOS attacks.
 	blockNum := block.NumberU64()
 	if blockNum >= epochLength*2048 {
 		glog.V(logger.Debug).Infof("block number %d too high, limit is %d", epochLength*2048)
-		return false
+		return false, nil
 	}
 
 	difficulty := block.Difficulty()
@@ -132,7 +137,7 @@ func (l *Light) Verify(block pow.Block) bool {
 	*/
 	if difficulty.Cmp(common.Big0) == 0 {
 		glog.V(logger.Debug).Infof("invalid block difficulty")
-		return false
+		return false, nil
 	}
 
 	cache := l.getCache(blockNum)
@@ -145,12 +150,12 @@ func (l *Light) Verify(block pow.Block) bool {
 	hash := hashToH256(block.HashNoNonce())
 	ret := C.ethash_light_compute_internal(cache.ptr, dagSize, hash, C.uint64_t(block.Nonce()))
 	if !ret.success {
-		return false
+		return false, nil
 	}
 
 	// avoid mixdigest malleability as it's not included in a block's "hashNononce"
 	if block.MixDigest() != h256ToHash(ret.mix_hash) {
-		return false
+		return false, nil
 	}
 
 	// Make sure cache is live until after the C call.
@@ -159,7 +164,8 @@ func (l *Light) Verify(block pow.Block) bool {
 	_ = cache
 	// The actual check.
 	target := new(big.Int).Div(maxUint256, difficulty)
-	return h256ToHash(ret.result).Big().Cmp(target) <= 0
+	blockTarget := h256ToHash(ret.result).Big()
+	return blockTarget.Cmp(target) <= 0, blockTarget
 }
 
 func h256ToHash(in C.ethash_h256_t) common.Hash {

ethash_test.go

@@ -85,6 +85,20 @@ var invalidZeroDiffBlock = testBlock{
 	mixDigest:   crypto.Sha3Hash([]byte("bar")),
 }
 
+func TestEthashVerifyValidWithTarget(t *testing.T) {
+	eth := New()
+	for i, block := range validBlocks {
+		isValid, target := eth.VerifyWithTarget(block)
+		if !isValid {
+			t.Errorf("block %d (%x) did not validate.", i, block.hashNoNonce[:6])
+		}
+		blockTarget := new(big.Int).Div(maxUint256, block.Difficulty())
+		if target.Cmp(blockTarget) >= 0 {
+			t.Errorf("target should be greater than or equal to")
+		}
+	}
+}
+
 func TestEthashVerifyValid(t *testing.T) {
 	eth := New()
 	for i, block := range validBlocks {
@@ -94,6 +108,17 @@ func TestEthashVerifyValid(t *testing.T) {
 	}
 }
 
+func TestEthashVerifyWithTargetInvalid(t *testing.T) {
+	eth := New()
+	isValid, diff := eth.VerifyWithTarget(&invalidZeroDiffBlock)
+	if isValid {
+		t.Errorf("should not validate - we just ensure it does not panic on this block")
+	}
+	if diff != nil {
+		t.Errorf("target should be nil for invalid block")
+	}
+}
+
 func TestEthashVerifyInvalid(t *testing.T) {
 	eth := New()
 	if eth.Verify(&invalidZeroDiffBlock) {