1 files changed, 184 insertions, 0 deletions
diff --git a/core/vm/contract.go b/core/vm/contract.go
new file mode 100644
index 0000000..ed17402
--- /dev/null
+++ b/core/vm/contract.go
@@ -0,0 +1,184 @@
+// 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/ava-labs/go-ethereum/common"
+)
+
+// 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
+
+// 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
+}
+
+func (c *Contract) validJumpdest(dest *big.Int) bool {
+	udest := dest.Uint64()
+	// PC cannot go beyond len(code) and certainly can't be bigger than 63bits.
+	// Don't bother checking for JUMPDEST in that case.
+	if dest.BitLen() >= 63 || udest >= uint64(len(c.Code)) {
+		return false
+	}
+	// Only JUMPDESTs allowed for destinations
+	if OpCode(c.Code[udest]) != JUMPDEST {
+		return false
+	}
+	// Do we have a contract hash already?
+	if c.CodeHash != (common.Hash{}) {
+		// Does parent context have the analysis?
+		analysis, exist := c.jumpdests[c.CodeHash]
+		if !exist {
+			// Do the analysis and save in parent context
+			// We do not need to store it in c.analysis
+			analysis = codeBitmap(c.Code)
+			c.jumpdests[c.CodeHash] = analysis
+		}
+		return analysis.codeSegment(udest)
+	}
+	// We don't have the code hash, most likely a piece of initcode not already
+	// in state trie. In that case, we do an analysis, and save it locally, so
+	// we don't have to recalculate it for every JUMP instruction in the execution
+	// However, we don't save it within the parent context
+	if c.analysis == nil {
+		c.analysis = codeBitmap(c.Code)
+	}
+	return c.analysis.codeSegment(udest)
+}
+
+// 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
+}
+
+// GetOp returns the n'th element in the contract's byte array
+func (c *Contract) GetOp(n uint64) OpCode {
+	return OpCode(c.GetByte(n))
+}
+
+// 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()
+}
+
+// Value returns the contract's value (sent to it from it's caller)
+func (c *Contract) Value() *big.Int {
+	return c.value
+}
+
+// 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
+}