From 3939fa832f5131b8fbdae7f13f2df81476bbf253 Mon Sep 17 00:00:00 2001
From: Ivan Voras <ivoras@gmail.com>
Date: Fri, 1 Feb 2019 23:35:18 +0100
Subject: [PATCH] Initial work on PoW

---
 blockchain.go            |  2 +-
 chainparams.example.json |  1 +
 chainparams.go           |  9 +++++++++
 util.go                  | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/blockchain.go b/blockchain.go
index f4c45b5..a793573 100644
--- a/blockchain.go
+++ b/blockchain.go
@@ -22,10 +22,10 @@ const GenesisBlockPreviousBlockHash = "10000000000000000000000000000000000000000
 
 // ChainParams describe the genesis block and other blockchain properties
 var defaultChainParams = ChainParams{
+	ConsensusType:             ChainConsensusPoA,
 	GenesisBlockHash:          "9a0ff19183d1525a36de803047de4b73eb72506be8c81296eb463476a5c2d9e2",
 	GenesisBlockHashSignature: "30460221008b8b3b3cfee2493ef58f2f6a1f1768b564f4c9e9a341ad42912cbbcf5c3ec82f022100fbcdfd0258fa1a5b073d18f688c2fb3d8f9a7c59204c6777f2bbf1faeb1eb1ed",
 	GenesisBlockTimestamp:     "2017-05-06T10:38:50Z02:00",
-	//GenesisBlockTimestamp:     "Sat, 06 May 2017 10:38:50 +0200",
 }
 
 var chainParams = defaultChainParams
diff --git a/chainparams.example.json b/chainparams.example.json
index 7ebb507..e653225 100644
--- a/chainparams.example.json
+++ b/chainparams.example.json
@@ -1,4 +1,5 @@
 {
+    "consensus_type": "PoA",
     "creator": "Ivan Voras <ivoras@gmail.com>",
     "genesis_block_timestamp": "2018-08-16T12:49:32+02:00",
     "bootstrap_peers": [ "cosmos.ivoras.net:2017" ]
diff --git a/chainparams.go b/chainparams.go
index 0199ba0..c616c27 100644
--- a/chainparams.go
+++ b/chainparams.go
@@ -1,5 +1,10 @@
 package main
 
+const (
+	ChainConsensusPoA = 0
+	ChainConsensusPoW = 1
+)
+
 // ChainParams holds blockchain configuration
 type ChainParams struct {
 	// GenesisBlockHash is the SHA256 hash of the genesis block payload
@@ -16,4 +21,8 @@ type ChainParams struct {
 
 	// List of host:port string specifying default peers for this blockchain. If empty, the defaults are used.
 	BootstrapPeers []string `json:"bootstrap_peers"`
+
+	// Consensus algorithm used: "PoA", "PoW"
+	ConsensusTypeString string `json:"consensus_type"`
+	ConsensusType       int
 }
diff --git a/util.go b/util.go
index 04d6b4e..641c784 100644
--- a/util.go
+++ b/util.go
@@ -72,6 +72,25 @@ func hashFileToHexString(fileName string) (string, error) {
 	return hex.EncodeToString(hash.Sum(nil)), nil
 }
 
+func hashFileToBytes(fileName string) ([]byte, error) {
+	file, err := os.Open(fileName)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		err = file.Close()
+		if err != nil {
+			log.Printf("hashFileToHexString file.Close: %v", err)
+		}
+	}()
+	hash := sha256.New()
+	_, err = io.Copy(hash, file)
+	if err != nil {
+		return nil, err
+	}
+	return hash.Sum(nil), nil
+}
+
 func mustDecodeHex(hexs string) []byte {
 	b, err := hex.DecodeString(hexs)
 	if err != nil {
@@ -356,3 +375,21 @@ func copyFile(src, dst string) error {
 	}
 	return out.Close()
 }
+
+func countStartZeroBits(b []byte) int {
+	nBits := 0
+	for i := 0; i < len(b); i++ {
+		if b[i] == 0 {
+			nBits += 8
+		} else {
+			for z := uint(7); z >= 0; z-- {
+				if b[i]&(1<<z) == 0 {
+					nBits++
+				} else {
+					break
+				}
+			}
+		}
+	}
+	return nBits
+}