1 files changed, 104 insertions, 0 deletions
diff --git a/vm/context.go b/vm/context.go
new file mode 100644
index 000000000..ccbadabda
--- /dev/null
+++ b/vm/context.go
@@ -0,0 +1,104 @@
+package vm
+
+import (
+	"math"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/ethereum/go-ethereum/state"
+)
+
+type ContextRef interface {
+	ReturnGas(*big.Int, *big.Int)
+	Address() []byte
+	SetCode([]byte)
+}
+
+type Context struct {
+	caller  ContextRef
+	object  ContextRef
+	Code    []byte
+	message *state.Message
+
+	Gas, UsedGas, Price *big.Int
+
+	Args []byte
+}
+
+// Create a new context for the given data items
+func NewContext(msg *state.Message, caller ContextRef, object ContextRef, code []byte, gas, price *big.Int) *Context {
+	c := &Context{message: msg, caller: caller, object: object, Code: code, Args: nil}
+
+	// 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)
+	// In most cases price and value are pointers to transaction objects
+	// and we don't want the transaction's values to change.
+	c.Price = new(big.Int).Set(price)
+	c.UsedGas = new(big.Int)
+
+	return c
+}
+
+func (c *Context) GetOp(x uint64) OpCode {
+	return OpCode(c.GetByte(x))
+}
+
+func (c *Context) GetByte(x uint64) byte {
+	if x < uint64(len(c.Code)) {
+		return c.Code[x]
+	}
+
+	return 0
+}
+
+func (c *Context) GetBytes(x, y int) []byte {
+	return c.GetRangeValue(uint64(x), uint64(y))
+}
+
+func (c *Context) GetRangeValue(x, size uint64) []byte {
+	x = uint64(math.Min(float64(x), float64(len(c.Code))))
+	y := uint64(math.Min(float64(x+size), float64(len(c.Code))))
+
+	return ethutil.LeftPadBytes(c.Code[x:y], int(size))
+}
+
+func (c *Context) Return(ret []byte) []byte {
+	// Return the remaining gas to the caller
+	c.caller.ReturnGas(c.Gas, c.Price)
+
+	return ret
+}
+
+/*
+ * Gas functions
+ */
+func (c *Context) UseGas(gas *big.Int) bool {
+	if c.Gas.Cmp(gas) < 0 {
+		return false
+	}
+
+	// Sub the amount of gas from the remaining
+	c.Gas.Sub(c.Gas, gas)
+	c.UsedGas.Add(c.UsedGas, gas)
+
+	return true
+}
+
+// Implement the caller interface
+func (c *Context) ReturnGas(gas, price *big.Int) {
+	// Return the gas to the context
+	c.Gas.Add(c.Gas, gas)
+	c.UsedGas.Sub(c.UsedGas, gas)
+}
+
+/*
+ * Set / Get
+ */
+func (c *Context) Address() []byte {
+	return c.object.Address()
+}
+
+func (self *Context) SetCode(code []byte) {
+	self.Code = code
+}