From ca5e14da6a376e706ac25aefb2f2144d9fa992e8 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Sat, 12 Nov 2016 19:41:08 -0800
Subject: [PATCH] rpctest: publicly export the CreateBlock funciton

This commit publicly exports the CreateBlock function as it can be very
useful for generating blocks for tests. Additionally, the behavior of
the function has been modified slightly to build off of the genesis
block for the specified chain if the `prevBlock` paramter is nil.
---
 rpctest/blockgen.go    | 29 ++++++++++++++++++++++++-----
 rpctest/rpc_harness.go |  2 +-
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/rpctest/blockgen.go b/rpctest/blockgen.go
index 9f50dc84..fd3bfb8b 100644
--- a/rpctest/blockgen.go
+++ b/rpctest/blockgen.go
@@ -112,13 +112,32 @@ func createCoinbaseTx(coinbaseScript []byte, nextBlockHeight int32,
 	return btcutil.NewTx(tx), nil
 }
 
-// createBlock creates a new block building from the previous block.
-func createBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
+// CreateBlock creates a new block building from the previous block with a
+// specified blockversion and timestamp. If the timestamp passed is zero (not
+// initialized), then the timestamp of the previous block will be used plus 1
+// second is used. Passing nil for the previous block results in a block that
+// builds off of the genesis block for the specified chain.
+func CreateBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
 	blockVersion int32, blockTime time.Time,
 	miningAddr btcutil.Address, net *chaincfg.Params) (*btcutil.Block, error) {
 
-	prevHash := prevBlock.Hash()
-	blockHeight := prevBlock.Height() + 1
+	var (
+		prevHash      *chainhash.Hash
+		blockHeight   int32
+		prevBlockTime time.Time
+	)
+
+	// If the previous block isn't specified, then we'll construct a block
+	// that builds off of the genesis block for the chain.
+	if prevBlock == nil {
+		prevHash = net.GenesisHash
+		blockHeight = 1
+		prevBlockTime = net.GenesisBlock.Header.Timestamp.Add(time.Minute)
+	} else {
+		prevHash = prevBlock.Hash()
+		blockHeight = prevBlock.Height() + 1
+		prevBlockTime = prevBlock.MsgBlock().Header.Timestamp
+	}
 
 	// If a target block time was specified, then use that as the header's
 	// timestamp. Otherwise, add one second to the previous block unless
@@ -128,7 +147,7 @@ func createBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
 	case !blockTime.IsZero():
 		ts = blockTime
 	default:
-		ts = prevBlock.MsgBlock().Header.Timestamp.Add(time.Second)
+		ts = prevBlockTime.Add(time.Second)
 	}
 
 	extraNonce := uint64(0)
diff --git a/rpctest/rpc_harness.go b/rpctest/rpc_harness.go
index 16ba96d4..16789731 100644
--- a/rpctest/rpc_harness.go
+++ b/rpctest/rpc_harness.go
@@ -421,7 +421,7 @@ func (h *Harness) GenerateAndSubmitBlock(txns []*btcutil.Tx, blockVersion int32,
 	prevBlock.SetHeight(prevBlockHeight)
 
 	// Create a new block including the specified transactions
-	newBlock, err := createBlock(prevBlock, txns, blockVersion,
+	newBlock, err := CreateBlock(prevBlock, txns, blockVersion,
 		blockTime, h.wallet.coinbaseAddr, h.ActiveNet)
 	if err != nil {
 		return nil, err