93 create common folder

blockchain/block.go

@@ -2,10 +2,11 @@ package blockchain
 
 // BlockHeader contains metadata about a block
 import (
-	"encoding/binary"
 	"encoding/gob"
 	"fmt"
 	"io"
+
+	"github.com/ubclaunchpad/cumulus/common"
 )
 
 // BlockHeader contains metadata about a block
@@ -29,21 +30,11 @@ type BlockHeader struct {
 // Marshal converts a BlockHeader to a byte slice
 func (bh *BlockHeader) Marshal() []byte {
 	var buf []byte
-
-	tempBufBlockNumber := make([]byte, 4)
-	binary.LittleEndian.PutUint32(tempBufBlockNumber, bh.BlockNumber)
-
-	tempBufTime := make([]byte, 4)
-	binary.LittleEndian.PutUint32(tempBufTime, bh.Time)
-
-	tempBufNonce := make([]byte, 8)
-	binary.LittleEndian.PutUint64(tempBufNonce, bh.Nonce)
-
-	buf = append(buf, tempBufBlockNumber...)
+	buf = common.AppendUint32(buf, bh.BlockNumber)
 	buf = append(buf, bh.LastBlock.Marshal()...)
 	buf = append(buf, bh.Target.Marshal()...)
-	buf = append(buf, tempBufTime...)
-	buf = append(buf, tempBufNonce...)
+	buf = common.AppendUint32(buf, bh.Time)
+	buf = common.AppendUint64(buf, bh.Nonce)
 	buf = append(buf, bh.ExtraData...)
 
 	return buf

blockchain/block_test.go

@@ -3,7 +3,8 @@ package blockchain
 import (
 	"bytes"
 	"testing"
-	"time"
+
+	"github.com/ubclaunchpad/cumulus/common"
 )
 
 func TestEncodeDecodeBlock(t *testing.T) {
@@ -32,7 +33,7 @@ func TestBlockHeaderLen(t *testing.T) {
 		0,
 		NewTestHash(),
 		NewValidTestTarget(),
-		uint32(time.Now().Unix()),
+		common.UnixNow(),
 		0,
 		[]byte{0x00, 0x01, 0x02},
 	}
@@ -47,7 +48,7 @@ func TestBlockHeaderLen(t *testing.T) {
 		0,
 		NewTestHash(),
 		NewValidTestTarget(),
-		uint32(time.Now().Unix()),
+		common.UnixNow(),
 		0,
 		[]byte{},
 	}

blockchain/genesis.go

@@ -1,8 +1,6 @@
 package blockchain
 
-import (
-	"time"
-)
+import "github.com/ubclaunchpad/cumulus/common"
 
 // Genesis creates the Genesis block and returns is.
 //
@@ -36,7 +34,7 @@ func Genesis(miner Address, target Hash, blockReward uint64, extraData []byte) *
 			BlockNumber: 0,
 			LastBlock:   NilHash,
 			Target:      target,
-			Time:        uint32(time.Now().Unix()),
+			Time:        common.UnixNow(),
 			Nonce:       0,
 			ExtraData:   extraData,
 		},

blockchain/genesis_test.go

@@ -1,8 +1,9 @@
 package blockchain
 
 import (
-	"math/big"
 	"testing"
+
+	c "github.com/ubclaunchpad/cumulus/common/constants"
 )
 
 func TestGenesis(t *testing.T) {
@@ -22,7 +23,7 @@ func TestGenesis(t *testing.T) {
 	}
 
 	// Check if the genesis block's last block hash is equal to 0
-	if HashToBigInt(gb.BlockHeader.LastBlock).Cmp(big.NewInt(0)) != 0 {
+	if HashToBigInt(gb.BlockHeader.LastBlock).Cmp(c.Big0) != 0 {
 		t.Fail()
 	}
 

blockchain/hash.go

@@ -3,6 +3,8 @@ package blockchain
 import (
 	"crypto/sha256"
 	"math/big"
+
+	c "github.com/ubclaunchpad/cumulus/common/constants"
 )
 
 const (
@@ -12,7 +14,7 @@ const (
 
 var (
 	// NilHash represents a nil hash
-	NilHash = BigIntToHash(big.NewInt(0))
+	NilHash = BigIntToHash(c.Big0)
 )
 
 // Hash represents a 256-bit hash of a block or transaction
@@ -58,7 +60,8 @@ func HashToBigInt(h Hash) *big.Int {
 	return new(big.Int).SetBytes(h[:])
 }
 
-// BigIntToHash converts a big integer to a hash
+// BigIntToHash converts a big integer to a hash. If the size of the big int
+// is larger than the size of hash, the function will return a hash set to 0.
 func BigIntToHash(x *big.Int) Hash {
 	bytes := x.Bytes()
 

blockchain/hash_test.go

@@ -3,11 +3,41 @@ package blockchain
 import (
 	"math/big"
 	"testing"
+
+	c "github.com/ubclaunchpad/cumulus/common/constants"
+	"github.com/ubclaunchpad/cumulus/common/math"
 )
 
+func TestBigIntToHash(t *testing.T) {
+	x := math.BigAdd(math.BigExp(2, 256), c.Big1)
+	h := BigIntToHash(x)
+
+	for i := 0; i < HashLen; i++ {
+		if h[i] != 0 {
+			t.Fail()
+		}
+	}
+
+	h = BigIntToHash(c.Big0)
+
+	for i := 0; i < HashLen; i++ {
+		if h[i] != 0 {
+			t.Fail()
+		}
+	}
+
+	h = BigIntToHash(c.MaxUint256)
+
+	for i := 0; i < HashLen; i++ {
+		if h[i] != 255 {
+			t.Fail()
+		}
+	}
+}
+
 func TestHashToBigInt(t *testing.T) {
 	// Max hash value
-	x := new(big.Int).Sub(new(big.Int).Exp(big.NewInt(int64(2)), big.NewInt(int64(256)), big.NewInt(0)), big.NewInt(1))
+	x := c.MaxUint256
 	h := BigIntToHash(x)
 
 	if HashToBigInt(h).Cmp(x) != 0 {

blockchain/test_utils.go

@@ -6,6 +6,10 @@ import (
 	"math/big"
 	mrand "math/rand"
 	"time"
+
+	"github.com/ubclaunchpad/cumulus/common"
+	c "github.com/ubclaunchpad/cumulus/common/constants"
+	"github.com/ubclaunchpad/cumulus/common/math"
 )
 
 // NewTestHash produces a hash.
@@ -99,7 +103,7 @@ func NewTestInputBlock(t []*Transaction) *Block {
 			BlockNumber: 0,
 			LastBlock:   NewTestHash(),
 			Target:      NewValidTestTarget(),
-			Time:        uint32(time.Now().Unix()),
+			Time:        common.UnixNow(),
 			Nonce:       0,
 		},
 		Transactions: t,
@@ -114,7 +118,7 @@ func NewTestOutputBlock(t []*Transaction, input *Block) *Block {
 			BlockNumber: input.BlockNumber + 1,
 			LastBlock:   HashSum(input),
 			Target:      NewValidTestTarget(),
-			Time:        uint32(time.Now().Unix()),
+			Time:        common.UnixNow(),
 			Nonce:       0,
 		},
 		Transactions: t,
@@ -204,9 +208,9 @@ func NewValidTestChainAndBlock() (*BlockChain, *Block) {
 func NewValidTestTarget() Hash {
 	r := new(big.Int).Rand(
 		mrand.New(mrand.NewSource(time.Now().Unix())),
-		new(big.Int).Add(MaxTarget, big.NewInt(1)),
+		math.BigAdd(MaxTarget, c.Big1),
 	)
-	r.Add(r, big.NewInt(1))
+	r.Add(r, c.Big1)
 	return BigIntToHash(r)
 }
 

blockchain/transaction.go

@@ -3,6 +3,8 @@ package blockchain
 import (
 	"encoding/binary"
 	"io"
+
+	"github.com/ubclaunchpad/cumulus/common"
 )
 
 // TxHashPointer is a reference to a transaction on the blockchain.
@@ -14,12 +16,10 @@ type TxHashPointer struct {
 
 // Marshal converts a TxHashPointer to a byte slice
 func (thp TxHashPointer) Marshal() []byte {
-	buf := make([]byte, 4)
-	binary.LittleEndian.PutUint32(buf, thp.BlockNumber)
+	var buf []byte
+	buf = common.AppendUint32(buf, thp.BlockNumber)
 	buf = append(buf, thp.Hash.Marshal()...)
-	tempBufIndex := make([]byte, 4)
-	binary.LittleEndian.PutUint32(tempBufIndex, thp.Index)
-	buf = append(buf, tempBufIndex...)
+	buf = common.AppendUint32(buf, thp.Index)
 	return buf
 }
 

blockchain/validation.go

@@ -3,9 +3,10 @@ package blockchain
 // ValidTransaction checks whether a transaction is valid, assuming the
 import (
 	"crypto/ecdsa"
-	"math/big"
 
 	log "github.com/Sirupsen/logrus"
+	c "github.com/ubclaunchpad/cumulus/common/constants"
+	"github.com/ubclaunchpad/cumulus/common/math"
 )
 
 // TransactionCode is returned from ValidTransaction.
@@ -110,9 +111,9 @@ const (
 
 var (
 	// MaxTarget is the minimum difficulty
-	MaxTarget = new(big.Int).Sub(BigExp(2, 232), big.NewInt(1))
+	MaxTarget = math.BigSub(math.BigExp(2, 232), c.Big1)
 	// MinTarget is the maximum difficulty value
-	MinTarget = big.NewInt(1)
+	MinTarget = c.Big1
 )
 
 // ValidTransaction tests whether a transaction valid.
@@ -203,7 +204,7 @@ func (bc *BlockChain) ValidGenesisBlock(gb *Block) (bool, GenesisBlockCode) {
 	}
 
 	// Check if the genesis block's last block hash is equal to 0.
-	if HashToBigInt(gb.BlockHeader.LastBlock).Cmp(big.NewInt(0)) != 0 {
+	if HashToBigInt(gb.BlockHeader.LastBlock).Cmp(c.Big0) != 0 {
 		return false, BadGenesisLastBlock
 	}
 
@@ -304,9 +305,3 @@ func (bc *BlockChain) ValidBlock(b *Block) (bool, BlockCode) {
 
 	return true, ValidBlock
 }
-
-// BigExp returns an big int pointer with the result set to base**exp,
-// if exp <= 0, the result is 1
-func BigExp(base, exp int) *big.Int {
-	return new(big.Int).Exp(big.NewInt(int64(base)), big.NewInt(int64(exp)), nil)
-}

blockchain/validation_test.go

@@ -3,8 +3,10 @@ package blockchain
 import (
 	"crypto/rand"
 	"fmt"
-	"math/big"
 	"testing"
+
+	c "github.com/ubclaunchpad/cumulus/common/constants"
+	"github.com/ubclaunchpad/cumulus/common/math"
 )
 
 func TestValidTransactionNilTransaction(t *testing.T) {
@@ -116,7 +118,7 @@ func TestValidBlockBadGenesisBlock(t *testing.T) {
 	currentTarget := BigIntToHash(MaxTarget)
 	currentBlockReward := uint64(25)
 	gb := Genesis(miner.Public(), currentTarget, currentBlockReward, []byte{})
-	gb.Target = BigIntToHash(BigExp(2, 255))
+	gb.Target = BigIntToHash(math.BigExp(2, 255))
 	bc := &BlockChain{
 		Blocks: []*Block{gb},
 		Head:   HashSum(gb),
@@ -191,7 +193,7 @@ func TestValidBlockBadTime(t *testing.T) {
 
 func TestValidBlockBadTarget(t *testing.T) {
 	bc, b := NewValidTestChainAndBlock()
-	b.Target = BigIntToHash(new(big.Int).Add(MaxTarget, big.NewInt(1)))
+	b.Target = BigIntToHash(math.BigAdd(MaxTarget, c.Big1))
 	valid, code := bc.ValidBlock(b)
 
 	if valid {
@@ -201,7 +203,7 @@ func TestValidBlockBadTarget(t *testing.T) {
 		t.Fail()
 	}
 
-	b.Target = BigIntToHash(new(big.Int).Sub(MinTarget, big.NewInt(1)))
+	b.Target = BigIntToHash(math.BigSub(MinTarget, c.Big1))
 	valid, code = bc.ValidBlock(b)
 
 	if valid {
@@ -552,7 +554,7 @@ func TestValidGenesisBlockBadGenesisTarget(t *testing.T) {
 	currentTarget := BigIntToHash(MaxTarget)
 	currentBlockReward := uint64(25)
 	gb := Genesis(miner.Public(), currentTarget, currentBlockReward, []byte{})
-	gb.Target = BigIntToHash(BigExp(2, 255))
+	gb.Target = BigIntToHash(math.BigExp(2, 255))
 	bc := &BlockChain{
 		Blocks: []*Block{gb},
 		Head:   HashSum(gb),
@@ -590,30 +592,3 @@ func TestValidGenesisBlockBadGenesisTime(t *testing.T) {
 		t.Fail()
 	}
 }
-
-func TestBigExp(t *testing.T) {
-	a := big.NewInt(1)
-	b := BigExp(0, 0)
-
-	if a.Cmp(b) != 0 {
-		t.Fail()
-	}
-
-	a = big.NewInt(1)
-	b = BigExp(10, -2)
-
-	if a.Cmp(b) != 0 {
-		t.Fail()
-	}
-
-	a = new(big.Int).Exp(
-		big.NewInt(int64(2)),
-		big.NewInt(int64(256)),
-		big.NewInt(0),
-	)
-	b = BigExp(2, 256)
-
-	if a.Cmp(b) != 0 {
-		t.Fail()
-	}
-}