From 461aafcfc962dc0a0253a506dd4dca79a45a493d Mon Sep 17 00:00:00 2001
From: arnaucube <arnaucube@gmail.com>
Date: Sat, 6 Apr 2019 19:59:14 +0200
Subject: [PATCH] first commit

---
 README.md           |  5 +++++
 core/common.go      | 51 ++++++++++++++++++++++++++++++++++++++++++
 core/common_test.go | 54 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 README.md
 create mode 100644 core/common.go
 create mode 100644 core/common_test.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..26836c9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,5 @@
+# slowlorisdb
+
+Slow and decentralized cryptographically consistent database
+
+![slowloris](https://04019a5a-a-62cb3a1a-s-sites.googlegroups.com/site/jchristensensdigitalportfolio/slow-loris/IO-moth-eating-frozen-apple-sauce.jpg "slowloris")
diff --git a/core/common.go b/core/common.go
new file mode 100644
index 0000000..183b5f6
--- /dev/null
+++ b/core/common.go
@@ -0,0 +1,51 @@
+package core
+
+import (
+	"bytes"
+	"crypto/sha256"
+)
+
+// Hash is the type for a hash data packet
+type Hash [32]byte
+
+// IsZero returns true if the Hash is empty (all zeroes)
+func (h *Hash) IsZero() bool {
+	z := Hash{}
+	if bytes.Equal(z[:], h[:]) {
+		return true
+	}
+	return false
+}
+
+// HashBytes performs a hash over a given byte array
+func HashBytes(b []byte) Hash {
+	h := sha256.Sum256(b)
+	return h
+}
+
+// PoWData is the interface for the data that have the Nonce parameter to calculate the Proof-of-Work
+type PoWData interface {
+	Bytes() []byte
+	GetNonce() uint64
+	IncrementNonce()
+}
+
+// CheckPoW verifies the PoW difficulty of a Hash
+func CheckPoW(hash Hash, difficulty int) bool {
+	var empty [32]byte
+	if !bytes.Equal(hash[:][0:difficulty], empty[0:difficulty]) {
+		return false
+	}
+	return true
+}
+
+// CalculatePoW calculates the nonce for the given data in order to fit in the current Proof of Work difficulty
+func CalculatePoW(data PoWData, difficulty int) (uint64, error) {
+	hash := HashBytes(data.Bytes())
+	for !CheckPoW(hash, difficulty) {
+		data.IncrementNonce()
+
+		hash = HashBytes(data.Bytes())
+	}
+	return data.GetNonce(), nil
+}
diff --git a/core/common_test.go b/core/common_test.go
new file mode 100644
index 0000000..f47f808
--- /dev/null
+++ b/core/common_test.go
@@ -0,0 +1,54 @@
+package core
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHashBytes(t *testing.T) {
+	m := []byte("test")
+	h := HashBytes(m)
+	assert.Equal(t, hex.EncodeToString(h[:]), "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08")
+	assert.True(t, !h.IsZero())
+
+	z := Hash{}
+	assert.True(t, z.IsZero())
+}
+
+type testData struct {
+	Data  []byte
+	Nonce uint64
+}
+
+func (d *testData) Bytes() []byte {
+	b, _ := json.Marshal(d)
+	return b
+}
+
+func (d *testData) GetNonce() uint64 {
+	return d.Nonce
+}
+func (d *testData) IncrementNonce() {
+	d.Nonce++
+}
+
+func TestPoW(t *testing.T) {
+	difficulty := 2
+	data := &testData{
+		Data:  []byte("test"),
+		Nonce: 0,
+	}
+	nonce, err := CalculatePoW(data, difficulty)
+	assert.Nil(t, err)
+	data.Nonce = nonce
+
+	h := HashBytes(data.Bytes())
+
+	assert.Equal(t, hex.EncodeToString(h[:]), "0000020881c02f5171b978e74bb710242e95cc67b36416e382118a7ab2a69321")
+
+	// CheckPoW
+	assert.True(t, CheckPoW(h, difficulty))
+}