1 files changed, 170 insertions, 0 deletions
diff --git a/core/vm/contract.go b/core/vm/contract.go
new file mode 100644
index 000000000..37ec41cae
--- /dev/null
+++ b/core/vm/contract.go
@@ -0,0 +1,170 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+import (
+	"math/big"
+
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/crypto"
+)
+
+// ContractRef is a reference to the contract's backing object
+type ContractRef interface {
+	Address() common.Address
+}
+
+// AccountRef implements ContractRef.
+//
+// Account references are used during EVM initialisation and
+// it's primary use is to fetch addresses. Removing this object
+// proves difficult because of the cached jump destinations which
+// are fetched from the parent contract (i.e. the caller), which
+// is a ContractRef.
+type (
+	AccountRef common.Address
+	Bitvec     []byte
+)
+
+func (bits *Bitvec) Set(pos uint64) {
+	(*bits)[pos/8] |= 0x80 >> (pos % 8)
+}
+func (bits *Bitvec) Set8(pos uint64) {
+	(*bits)[pos/8] |= 0xFF >> (pos % 8)
+	(*bits)[pos/8+1] |= ^(0xFF >> (pos % 8))
+}
+
+// codeSegment checks if the position is in a code segment.
+func (bits *Bitvec) CodeSegment(pos uint64) bool {
+	return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
+}
+
+// Address casts AccountRef to a Address
+func (ar AccountRef) Address() common.Address { return (common.Address)(ar) }
+
+// Contract represents an ethereum contract in the state database. It contains
+// the contract code, calling arguments. Contract implements ContractRef
+type Contract struct {
+	// CallerAddress is the result of the caller which initialised this
+	// contract. However when the "call method" is delegated this value
+	// needs to be initialised to that of the caller's caller.
+	CallerAddress common.Address
+	caller        ContractRef
+	self          ContractRef
+
+	Jumpdests map[common.Hash]Bitvec // Aggregated result of JUMPDEST analysis.
+	Analysis  Bitvec                 // Locally cached result of JUMPDEST analysis
+
+	Code     []byte
+	CodeHash common.Hash
+	CodeAddr *common.Address
+	Input    []byte
+
+	Gas   uint64
+	Value *big.Int
+}
+
+// NewContract returns a new contract environment for the execution of EVM.
+func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uint64) *Contract {
+	c := &Contract{CallerAddress: caller.Address(), caller: caller, self: object}
+
+	if parent, ok := caller.(*Contract); ok {
+		// Reuse JUMPDEST analysis from parent context if available.
+		c.Jumpdests = parent.Jumpdests
+	} else {
+		c.Jumpdests = make(map[common.Hash]Bitvec)
+	}
+
+	// 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
+	// ensures a value is set
+	c.Value = value
+
+	return c
+}
+
+// AsDelegate sets the contract to be a delegate call and returns the current
+// contract (for chaining calls)
+func (c *Contract) AsDelegate() *Contract {
+	// NOTE: caller must, at all times be a contract. It should never happen
+	// that caller is something other than a Contract.
+	parent := c.caller.(*Contract)
+	c.CallerAddress = parent.CallerAddress
+	c.Value = parent.Value
+
+	return c
+}
+
+// GetByte returns the n'th byte in the contract's byte array
+func (c *Contract) GetByte(n uint64) byte {
+	if n < uint64(len(c.Code)) {
+		return c.Code[n]
+	}
+
+	return 0
+}
+
+// Caller returns the caller of the contract.
+//
+// Caller will recursively call caller when the contract is a delegate
+// call, including that of caller's caller.
+func (c *Contract) Caller() common.Address {
+	return c.CallerAddress
+}
+
+// UseGas attempts the use gas and subtracts it and returns true on success
+func (c *Contract) UseGas(gas uint64) (ok bool) {
+	if c.Gas < gas {
+		return false
+	}
+	c.Gas -= gas
+	return true
+}
+
+// Address returns the contracts address
+func (c *Contract) Address() common.Address {
+	return c.self.Address()
+}
+
+// SetCallCode sets the code of the contract and address of the backing data
+// object
+func (c *Contract) SetCallCode(addr *common.Address, hash common.Hash, code []byte) {
+	c.Code = code
+	c.CodeHash = hash
+	c.CodeAddr = addr
+}
+
+// SetCodeOptionalHash can be used to provide code, but it's optional to provide hash.
+// In case hash is not provided, the jumpdest analysis will not be saved to the parent context
+func (c *Contract) SetCodeOptionalHash(addr *common.Address, CodeAndHash *CodeAndHash) {
+	c.Code = CodeAndHash.Code
+	c.CodeHash = CodeAndHash.Hash()
+	c.CodeAddr = addr
+}
+
+type CodeAndHash struct {
+	Code []byte
+	hash common.Hash
+}
+
+func (c *CodeAndHash) Hash() common.Hash {
+	if c.hash == (common.Hash{}) {
+		c.hash = crypto.Keccak256Hash(c.Code)
+	}
+	return c.hash
+}