From a93e1e96c9e2419e298ece656578db140e1eb4ff Mon Sep 17 00:00:00 2001
From: Ivan Kuznetsov <me@jeiwan.ru>
Date: Mon, 28 Aug 2017 16:28:23 +0700
Subject: [PATCH] Store a DB connection in Blockchain

---
 blockchain.db | Bin 32768 -> 32768 bytes
 blockchain.go |  40 ++++++++++++++++++++--------------------
 main.go       |   5 +++--
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/blockchain.db b/blockchain.db
index 090c32ce8f4764e27c0298725bbf74d4e9e09ced..a4e79c3c7e308999f553d34e061ae120c9849391 100644
GIT binary patch
delta 542
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zyZOl#sB8m2Pywd^0~1(^d9$Fwd;UoV0+R&-I5tZdum~_do-FHN8nO+llZ}yqK>^5~
z0Oc=(^7labML=_aLSQuv3<(+<Rqt4DxqWWRn{&5gdn1p`hed1!nv=9E60&>tOm1`x
znB3sR&U8d-@;pWHG=|;`$qQUxRi|8CUu2)tJCSGlWufe1qj_Ae;^+PaykJxyWFX@|
zlY2nB@f!oOHNpOW6XT!F?nfjTdEHa<Qj0T-6`XSNle3wCcHq~}_?MZ}3uwvPt!_F0
zPWFZ=uXBx=viJ#;!3MqNZ+ZT!9&C#@IMocYgfkmziPYr(4l)@80)r7~Gk!A}|1$Mf
QFys(YwlVNK&!PYW0HtrlDF6Tf

literal 32768
zcmeI&KWGzC9KiAS@<-67wiKm`1s`Gu9f}4Os!&QJCW>0YA`U`1<4MytN!x@tiUmPM
za1dQ8D2ga{6f@`|mJT8)I5;?nE+UmwbZCW!#COTPQcLBQA~k*wF8AK`-Q{<mX8GOk
zCq#7%xW~f#P{HSn8-G9V{#gXw!7BG?u6vj}KNXqSu-mNThyVfzAb<b@2q1s}0tg_0
z00JvVK)RurJbrQhUwId>AY8vYHu=AqH=MdTvwgO`W5H5}2q1s}0tg_000IagfB*sr
zAh1FNOn&bZ)i(jor&IcO^7|P*IX#$;4`luntWTKyUx*!gk<$A$ckvr{o_FUr^xd4h
zD`)PXm^^!KcCHxSG=6ui|MJiLleV#`JwMhKkF?&twJ*|LzTlTK*yVh=ERPBql&gCZ
zNjsCZl0z~eWMIFQwd5Kh>yM4txyrhjmFaWN1k50KG@XjudbJQ8<xyFD9DO=1>!Wtc
z&LlFba*a=UMIuYv4hd0rKNNl4ez7}o;LGs3t-U8(?!9}ttL@eGjUS(f*AIVK?r`n-
zaGQ?XsWWP)>gtK8Y+4=6St;oqv+@d9mbRqCpw}wrAH{|M0tg_000IagfB*srAW$0u
zCVy`f)i(jA55V;K*Tz%w6bK-I00IagfB*srAb<b@2>jmyCf{GG{{Kn867Z`3o9l(>
z)R0Q=&-CtWb-LKE^wIPKJaXrzA7Dt|U7xC~5%NXz+Xv&H?<AW#TQ?W3PBz58Uuwzk
zJ@NJMm2XyPdbtbi{qqI(=1PG*tdi*wdr_6$qv$V{SJbl98>7`BK42O$mg>y-TdfWr
zKQR3}WJ3S}1Q0*~0R#|0009JQTfo%$P5r;x1)#Im+J0=F4gmxZKmY**5I_I{1Q0*~
w0R#|0009ILKmY**5I_I{1Q0*~0R#|0009ILKmY**5I_I{1Q0*~fqzQi7iwCc(f|Me

diff --git a/blockchain.go b/blockchain.go
index 0aecb89..5c6b119 100644
--- a/blockchain.go
+++ b/blockchain.go
@@ -12,33 +12,33 @@ const blocksBucket = "blocks"
 // Blockchain keeps a sequence of Blocks
 type Blockchain struct {
 	tip []byte
+	db  *bolt.DB
 }
 
 // BlockchainIterator is used to iterate over blockchain blocks
 type BlockchainIterator struct {
 	currentHash []byte
+	db          *bolt.DB
 }
 
 // AddBlock saves provided data as a block in the blockchain
 func (bc *Blockchain) AddBlock(data string) {
 	var lastHash []byte
 
-	db, err := bolt.Open(dbFile, 0600, nil)
-	if err != nil {
-		log.Panic(err)
-	}
-	defer db.Close()
-
-	err = db.View(func(tx *bolt.Tx) error {
+	err := bc.db.View(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(blocksBucket))
 		lastHash = b.Get([]byte("l"))
 
 		return nil
 	})
 
+	if err != nil {
+		log.Panic(err)
+	}
+
 	newBlock := NewBlock(data, lastHash)
 
-	err = db.Update(func(tx *bolt.Tx) error {
+	err = bc.db.Update(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(blocksBucket))
 		err := b.Put(newBlock.Hash, newBlock.Serialize())
 		if err != nil {
@@ -58,7 +58,7 @@ func (bc *Blockchain) AddBlock(data string) {
 
 // Iterator ...
 func (bc *Blockchain) Iterator() *BlockchainIterator {
-	bci := &BlockchainIterator{bc.tip}
+	bci := &BlockchainIterator{bc.tip, bc.db}
 
 	return bci
 }
@@ -66,13 +66,8 @@ func (bc *Blockchain) Iterator() *BlockchainIterator {
 // Next returns next block starting from the tip
 func (i *BlockchainIterator) Next() *Block {
 	var block *Block
-	db, err := bolt.Open(dbFile, 0600, nil)
-	if err != nil {
-		log.Panic(err)
-	}
-	defer db.Close()
 
-	err = db.View(func(tx *bolt.Tx) error {
+	err := i.db.View(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(blocksBucket))
 		encodedBlock := b.Get(i.currentHash)
 		block = DeserializeBlock(encodedBlock)
@@ -80,6 +75,10 @@ func (i *BlockchainIterator) Next() *Block {
 		return nil
 	})
 
+	if err != nil {
+		log.Panic(err)
+	}
+
 	i.currentHash = block.PrevBlockHash
 
 	return block
@@ -87,12 +86,11 @@ func (i *BlockchainIterator) Next() *Block {
 
 // NewBlockchain creates a new Blockchain with genesis Block
 func NewBlockchain() *Blockchain {
-	bc := Blockchain{}
+	var tip []byte
 	db, err := bolt.Open(dbFile, 0600, nil)
 	if err != nil {
 		log.Panic(err)
 	}
-	defer db.Close()
 
 	err = db.Update(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(blocksBucket))
@@ -114,17 +112,19 @@ func NewBlockchain() *Blockchain {
 			if err != nil {
 				log.Panic(err)
 			}
-			bc.tip = genesis.Hash
+			tip = genesis.Hash
 		} else {
-			tip := b.Get([]byte("l"))
-			bc.tip = tip
+			tip = b.Get([]byte("l"))
 		}
 
 		return nil
 	})
+
 	if err != nil {
 		log.Panic(err)
 	}
 
+	bc := Blockchain{tip, db}
+
 	return &bc
 }
diff --git a/main.go b/main.go
index 58fcacd..57cc9bc 100644
--- a/main.go
+++ b/main.go
@@ -7,9 +7,10 @@ import (
 
 func main() {
 	bc := NewBlockchain()
+	defer bc.db.Close()
 
-	bc.AddBlock("Send 1 BTC to Ivan")
-	bc.AddBlock("Send 2 more BTC to Ivan")
+	// bc.AddBlock("Send 1 BTC to Ivan")
+	// bc.AddBlock("Send 2 more BTC to Ivan")
 
 	bci := bc.Iterator()