From 756ca99f6d1fca9eff7667fb5aa61072dd762ca2 Mon Sep 17 00:00:00 2001
From: Gav Wood <i@gavwood.com>
Date: Tue, 28 Jul 2015 21:54:53 +0200
Subject: [PATCH] Minor updates to gas limit floor machanism.

---
 eth/main.cpp             |  5 +++++
 libethcore/BlockInfo.cpp | 14 +++++++-------
 libethcore/BlockInfo.h   |  3 ++-
 libethcore/Params.cpp    |  3 ++-
 libethcore/Params.h      |  1 +
 5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/eth/main.cpp b/eth/main.cpp
index 8528b0526..e17a6ebaf 100644
--- a/eth/main.cpp
+++ b/eth/main.cpp
@@ -1105,6 +1105,7 @@ int main(int argc, char** argv)
 	string jsonAdmin;
 	string genesisJSON;
 	dev::eth::Network releaseNetwork = c_network;
+	u256 gasFloor = UndefinedU256;
 	string privateChain;
 
 	bool upnp = true;
@@ -1347,6 +1348,8 @@ int main(int argc, char** argv)
 		}
 		else if (arg == "--frontier")
 			releaseNetwork = eth::Network::Frontier;
+		else if (arg == "--gas-floor" && i + 1 < argc)
+			gasFloor = u256(argv[++i]);
 		else if (arg == "--olympic")
 			releaseNetwork = eth::Network::Olympic;
 /*		else if ((arg == "-B" || arg == "--block-fees") && i + 1 < argc)
@@ -1514,6 +1517,8 @@ int main(int argc, char** argv)
 		CanonBlockChain<Ethash>::forceGenesisExtraData(sha3(privateChain).asBytes());
 	if (!genesisJSON.empty())
 		CanonBlockChain<Ethash>::setGenesis(genesisJSON);
+	if (gasFloor != UndefinedU256)
+		c_gasFloorTarget = gasFloor;
 
 	if (g_logVerbosity > 0)
 	{
diff --git a/libethcore/BlockInfo.cpp b/libethcore/BlockInfo.cpp
index 4729ff25e..0b1cdd622 100644
--- a/libethcore/BlockInfo.cpp
+++ b/libethcore/BlockInfo.cpp
@@ -184,23 +184,23 @@ void BlockInfo::populateFromParent(BlockInfo const& _parent)
 	m_stateRoot = _parent.stateRoot();
 	m_number = _parent.m_number + 1;
 	m_parentHash = _parent.m_hash;
-	m_gasLimit = selectGasLimit(_parent);
+	m_gasLimit = _parent.childGasLimit();
 	m_gasUsed = 0;
 	m_difficulty = calculateDifficulty(_parent);
 }
 
-u256 BlockInfo::selectGasLimit(BlockInfo const& _parent) const
+u256 BlockInfo::childGasLimit(u256 const& _gasFloorTarget) const
 {
-	u256 const c_gasFloorTarget = c_network == Network::Frontier ? 5000 : 3141592;
+	u256 gasFloorTarget =
+		_gasFloorTarget == UndefinedU256 ? c_gasFloorTarget : _gasFloorTarget;
 
 	if (!m_number)
 		throw GenesisBlockCannotBeCalculated();
 	else
-		// target minimum of 3141592
-		if (_parent.m_gasLimit < c_gasFloorTarget)
-			return min<u256>(c_gasFloorTarget, _parent.m_gasLimit + _parent.m_gasLimit / c_gasLimitBoundDivisor - 1);
+		if (m_gasLimit < gasFloorTarget)
+			return min<u256>(gasFloorTarget, m_gasLimit + m_gasLimit / c_gasLimitBoundDivisor - 1);
 		else
-			return max<u256>(c_gasFloorTarget, _parent.m_gasLimit - _parent.m_gasLimit / c_gasLimitBoundDivisor + 1 + (_parent.m_gasUsed * 6 / 5) / c_gasLimitBoundDivisor);
+			return max<u256>(gasFloorTarget, m_gasLimit - m_gasLimit / c_gasLimitBoundDivisor + 1 + (m_gasUsed * 6 / 5) / c_gasLimitBoundDivisor);
 }
 
 u256 BlockInfo::calculateDifficulty(BlockInfo const& _parent) const
diff --git a/libethcore/BlockInfo.h b/libethcore/BlockInfo.h
index 8474284a3..c6812a112 100644
--- a/libethcore/BlockInfo.h
+++ b/libethcore/BlockInfo.h
@@ -115,7 +115,7 @@ public:
 	void populateFromParent(BlockInfo const& parent);
 
 	u256 calculateDifficulty(BlockInfo const& _parent) const;
-	u256 selectGasLimit(BlockInfo const& _parent) const;
+	u256 childGasLimit(u256 const& _gasFloorTarget = UndefinedU256) const;
 	h256 const& boundary() const;
 
 	h256 const& parentHash() const { return m_parentHash; }
@@ -127,6 +127,7 @@ public:
 	void setCoinbaseAddress(Address const& _v) { m_coinbaseAddress = _v; noteDirty(); }
 	void setRoots(h256 const& _t, h256 const& _r, h256 const& _u, h256 const& _s) { m_transactionsRoot = _t; m_receiptsRoot = _r; m_stateRoot = _s; m_sha3Uncles = _u; noteDirty(); }
 	void setGasUsed(u256 const& _v) { m_gasUsed = _v; noteDirty(); }
+	void setGasLimit(u256 const& _v) { m_gasLimit = _v; noteDirty(); }
 	void setExtraData(bytes const& _v) { m_extraData = _v; noteDirty(); }
 	void setLogBloom(LogBloom const& _v) { m_logBloom = _v; noteDirty(); }
 	void setDifficulty(u256 const& _v) { m_difficulty = _v; noteDirty(); }
diff --git a/libethcore/Params.cpp b/libethcore/Params.cpp
index 0612db84e..fbf0f6d9e 100644
--- a/libethcore/Params.cpp
+++ b/libethcore/Params.cpp
@@ -36,6 +36,7 @@ u256 c_minimumDifficulty;
 u256 c_difficultyBoundDivisor;
 u256 c_durationLimit;
 u256 c_blockReward;
+u256 c_gasFloorTarget;
 //--- END: AUTOGENERATED FROM /feeStructure.json
 
 #if ETH_FRONTIER
@@ -60,7 +61,7 @@ Network resetNetwork(Network _n)
 		c_minGasLimit = 5000;
 		break;
 	}
-
+	c_gasFloorTarget = c_network == Network::Frontier ? 5000 : 3141592;
 	c_gasLimitBoundDivisor = 1024;
 	c_minimumDifficulty = 131072;
 	c_difficultyBoundDivisor = 2048;
diff --git a/libethcore/Params.h b/libethcore/Params.h
index 6736d4f86..69469612b 100644
--- a/libethcore/Params.h
+++ b/libethcore/Params.h
@@ -36,6 +36,7 @@ extern u256 c_difficultyBoundDivisor;
 extern u256 c_durationLimit;
 extern u256 c_maximumExtraDataSize;
 extern u256 c_blockReward;
+extern u256 c_gasFloorTarget;
 //--- END: AUTOGENERATED FROM /feeStructure.json
 
 }