From 7d3f06b9820b40eda53cf81434c97b2d9942a3a7 Mon Sep 17 00:00:00 2001
From: Dan Turner <dan.turner@cba.com.au>
Date: Sun, 15 May 2016 17:05:28 +1000
Subject: [PATCH] Implement fixed difficulty flag

---
 cmd/geth/main.go        |  1 +
 cmd/utils/flags.go      |  9 ++++++++-
 core/block_validator.go |  5 ++++-
 core/chain_makers.go    |  2 +-
 core/config.go          |  2 ++
 eth/backend.go          |  4 ++++
 miner/miner.go          |  4 +++-
 wercker.yml             | 19 +++++++++++++++++++
 8 files changed, 42 insertions(+), 4 deletions(-)
 create mode 100644 wercker.yml

diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index 5a2fc62873..f42b030ead 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -233,6 +233,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 		utils.GpobaseStepUpFlag,
 		utils.GpobaseCorrectionFactorFlag,
 		utils.ExtraDataFlag,
+        utils.FixedDifficultyFlag,
 	}
 	app.Flags = append(app.Flags, debug.Flags...)
 
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 43dbc37f74..b00076904d 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -392,6 +392,11 @@ var (
 		Usage: "Suggested gas price base correction factor (%)",
 		Value: 110,
 	}
+    FixedDifficultyFlag = cli.IntFlag{
+        Name:  "difficulty",
+        Usage: "Specify a fixed difficulty.",
+        Value: -1,
+    }
 )
 
 // MustMakeDataDir retrieves the currently requested data directory, terminating
@@ -801,7 +806,9 @@ func MustMakeChainConfig(ctx *cli.Context) *core.ChainConfig {
 	db := MakeChainDatabase(ctx)
 	defer db.Close()
 
-	return MustMakeChainConfigFromDb(ctx, db)
+	config := MustMakeChainConfigFromDb(ctx, db)
+    config.FixedDifficulty = ctx.GlobalInt(FixedDifficultyFlag.Name)
+    return config
 }
 
 // MustMakeChainConfigFromDb reads the chain configuration from the given database.
diff --git a/core/block_validator.go b/core/block_validator.go
index 801d2572b6..0e58bf54e0 100644
--- a/core/block_validator.go
+++ b/core/block_validator.go
@@ -254,7 +254,10 @@ func ValidateHeader(config *ChainConfig, pow pow.PoW, header *types.Header, pare
 // the difficulty that a new block should have when created at time
 // given the parent block's time and difficulty.
 func CalcDifficulty(config *ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
+	if config.FixedDifficulty != -1 {
+        return big.NewInt(int64(config.FixedDifficulty))
+    }
+    if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
 		return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
 	} else {
 		return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
diff --git a/core/chain_makers.go b/core/chain_makers.go
index ef0ac66d1b..42328ee745 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -35,7 +35,7 @@ import (
 
 // MakeChainConfig returns a new ChainConfig with the ethereum default chain settings.
 func MakeChainConfig() *ChainConfig {
-	return &ChainConfig{HomesteadBlock: big.NewInt(0)}
+   return &ChainConfig{HomesteadBlock: big.NewInt(0), FixedDifficulty: -1}
 }
 
 // FakePow is a non-validating proof of work implementation.
diff --git a/core/config.go b/core/config.go
index 81ca76aa31..506ba7ccc1 100644
--- a/core/config.go
+++ b/core/config.go
@@ -34,6 +34,8 @@ type ChainConfig struct {
 	HomesteadBlock *big.Int // homestead switch block
 
 	VmConfig vm.Config `json:"-"`
+
+    FixedDifficulty int
 }
 
 // IsHomestead returns whether num is either equal to the homestead block or greater.
diff --git a/eth/backend.go b/eth/backend.go
index f43dea7775..96d22cd01e 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -100,6 +100,8 @@ type Config struct {
 
 	TestGenesisBlock *types.Block   // Genesis block to seed the chain database with (testing only!)
 	TestGenesisState ethdb.Database // Genesis state to seed the database with (testing only!)
+
+    FixedDifficulty int
 }
 
 type Ethereum struct {
@@ -142,6 +144,8 @@ type Ethereum struct {
 	etherbase     common.Address
 	netVersionId  int
 	netRPCService *PublicNetAPI
+
+    fixedDifficulty int
 }
 
 func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
diff --git a/miner/miner.go b/miner/miner.go
index b4a7657d50..68b90956ae 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -149,7 +149,9 @@ func (self *Miner) actuallyStart(coinbase common.Address, threads int) {
 }
 
 func (self *Miner) Stop() {
-	self.sub.Unsubscribe();
+	if(self.sub != nil) {
+        self.sub.Unsubscribe();
+    }
     self.worker.stop()
 	atomic.StoreInt32(&self.mining, 0)
 	atomic.StoreInt32(&self.shouldStart, 0)
diff --git a/wercker.yml b/wercker.yml
new file mode 100644
index 0000000000..8e265f92e9
--- /dev/null
+++ b/wercker.yml
@@ -0,0 +1,19 @@
+box: golang
+build:
+  steps:
+    - setup-go-workspace
+    - script:
+        name: go build
+        code: |
+          make geth
+          BIN=/pipeline/source/build/bin/$WERCKER_GIT_BRANCH/`cat VERSION`
+          mkdir -p $BIN
+          cp build/bin/geth $BIN/geth
+deploy:
+  steps:
+  - s3sync:
+      source_dir:     build/bin 
+      delete-removed: false
+      bucket-url:     $AWS_BUCKET_URL
+      key-id:         $AWS_ACCESS_KEY_ID
+      key-secret:     $AWS_SECRET_ACCESS_KEY