params: core, core/vm, miner: 64bit gas instructions

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

1 files changed, 9 insertions, 24 deletions

diff --git a/core/vm/contract.go b/core/vm/contract.go
index dfa93ab18..091106d84 100644
--- a/core/vm/contract.go
+++ b/core/vm/contract.go
@@ -24,7 +24,6 @@ import (
 
 // ContractRef is a reference to the contract's backing object
 type ContractRef interface {
-	ReturnGas(*big.Int)
 	Address() common.Address
 	Value() *big.Int
 	SetCode(common.Hash, []byte)
@@ -48,7 +47,8 @@ type Contract struct {
 	CodeAddr *common.Address
 	Input    []byte
 
-	value, Gas, UsedGas *big.Int
+	Gas   uint64
+	value *big.Int
 
 	Args []byte
 
@@ -56,7 +56,7 @@ type Contract struct {
 }
 
 // NewContract returns a new contract environment for the execution of EVM.
-func NewContract(caller ContractRef, object ContractRef, value, gas *big.Int) *Contract {
+func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uint64) *Contract {
 	c := &Contract{CallerAddress: caller.Address(), caller: caller, self: object, Args: nil}
 
 	if parent, ok := caller.(*Contract); ok {
@@ -68,9 +68,8 @@ func NewContract(caller ContractRef, object ContractRef, value, gas *big.Int) *C
 
 	// Gas should be a pointer so it can safely be reduced through the run
 	// This pointer will be off the state transition
-	c.Gas = gas //new(big.Int).Set(gas)
+	c.Gas = gas
 	c.value = new(big.Int).Set(value)
-	c.UsedGas = new(big.Int)
 
 	return c
 }
@@ -107,27 +106,13 @@ func (c *Contract) Caller() common.Address {
 	return c.CallerAddress
 }
 
-// Finalise finalises the contract and returning any remaining gas to the original
-// caller.
-func (c *Contract) Finalise() {
-	// Return the remaining gas to the caller
-	c.caller.ReturnGas(c.Gas)
-}
-
 // UseGas attempts the use gas and subtracts it and returns true on success
-func (c *Contract) UseGas(gas *big.Int) (ok bool) {
-	ok = useGas(c.Gas, gas)
-	if ok {
-		c.UsedGas.Add(c.UsedGas, gas)
+func (c *Contract) UseGas(gas uint64) (ok bool) {
+	if c.Gas < gas {
+		return false
 	}
-	return
-}
-
-// ReturnGas adds the given gas back to itself.
-func (c *Contract) ReturnGas(gas *big.Int) {
-	// Return the gas to the context
-	c.Gas.Add(c.Gas, gas)
-	c.UsedGas.Sub(c.UsedGas, gas)
+	c.Gas -= gas
+	return true
 }
 
 // Address returns the contracts address