core/vm: support for multiple interpreters (#17093)

- Define an Interpreter interface
- One contract can call contracts from other interpreter types.
- Pass the interpreter to the operands instead of the evm.
  This is meant to prevent type assertions in operands.

1 files changed, 46 insertions, 7 deletions

diff --git a/core/vm/interpreter.go b/core/vm/interpreter.go
index 0d6038cbb..1e9202424 100644
--- a/core/vm/interpreter.go
+++ b/core/vm/interpreter.go
@@ -45,7 +45,30 @@ type Config struct {
 // passed environment to query external sources for state information.
 // The Interpreter will run the byte code VM based on the passed
 // configuration.
-type Interpreter struct {
+type Interpreter interface {
+	// Run loops and evaluates the contract's code with the given input data and returns
+	// the return byte-slice and an error if one occurred.
+	Run(contract *Contract, input []byte) ([]byte, error)
+	// CanRun tells if the contract, passed as an argument, can be
+	// run by the current interpreter. This is meant so that the
+	// caller can do something like:
+	//
+	// ```golang
+	// for _, interpreter := range interpreters {
+	//   if interpreter.CanRun(contract.code) {
+	//     interpreter.Run(contract.code, input)
+	//   }
+	// }
+	// ```
+	CanRun([]byte) bool
+	// IsReadOnly reports if the interpreter is in read only mode.
+	IsReadOnly() bool
+	// SetReadOnly sets (or unsets) read only mode in the interpreter.
+	SetReadOnly(bool)
+}
+
+// EVMInterpreter represents an EVM interpreter
+type EVMInterpreter struct {
 	evm      *EVM
 	cfg      Config
 	gasTable params.GasTable
@@ -55,8 +78,8 @@ type Interpreter struct {
 	returnData []byte // Last CALL's return data for subsequent reuse
 }
 
-// NewInterpreter returns a new instance of the Interpreter.
-func NewInterpreter(evm *EVM, cfg Config) *Interpreter {
+// NewEVMInterpreter returns a new instance of the Interpreter.
+func NewEVMInterpreter(evm *EVM, cfg Config) *EVMInterpreter {
 	// We use the STOP instruction whether to see
 	// the jump table was initialised. If it was not
 	// we'll set the default jump table.
@@ -73,14 +96,14 @@ func NewInterpreter(evm *EVM, cfg Config) *Interpreter {
 		}
 	}
 
-	return &Interpreter{
+	return &EVMInterpreter{
 		evm:      evm,
 		cfg:      cfg,
 		gasTable: evm.ChainConfig().GasTable(evm.BlockNumber),
 	}
 }
 
-func (in *Interpreter) enforceRestrictions(op OpCode, operation operation, stack *Stack) error {
+func (in *EVMInterpreter) enforceRestrictions(op OpCode, operation operation, stack *Stack) error {
 	if in.evm.chainRules.IsByzantium {
 		if in.readOnly {
 			// If the interpreter is operating in readonly mode, make sure no
@@ -102,7 +125,7 @@ func (in *Interpreter) enforceRestrictions(op OpCode, operation operation, stack
 // It's important to note that any errors returned by the interpreter should be
 // considered a revert-and-consume-all-gas operation except for
 // errExecutionReverted which means revert-and-keep-gas-left.
-func (in *Interpreter) Run(contract *Contract, input []byte) (ret []byte, err error) {
+func (in *EVMInterpreter) Run(contract *Contract, input []byte) (ret []byte, err error) {
 	if in.intPool == nil {
 		in.intPool = poolOfIntPools.get()
 		defer func() {
@@ -209,7 +232,7 @@ func (in *Interpreter) Run(contract *Contract, input []byte) (ret []byte, err er
 		}
 
 		// execute the operation
-		res, err := operation.execute(&pc, in.evm, contract, mem, stack)
+		res, err := operation.execute(&pc, in, contract, mem, stack)
 		// verifyPool is a build flag. Pool verification makes sure the integrity
 		// of the integer pool by comparing values to a default value.
 		if verifyPool {
@@ -234,3 +257,19 @@ func (in *Interpreter) Run(contract *Contract, input []byte) (ret []byte, err er
 	}
 	return nil, nil
 }
+
+// CanRun tells if the contract, passed as an argument, can be
+// run by the current interpreter.
+func (in *EVMInterpreter) CanRun(code []byte) bool {
+	return true
+}
+
+// IsReadOnly reports if the interpreter is in read only mode.
+func (in *EVMInterpreter) IsReadOnly() bool {
+	return in.readOnly
+}
+
+// SetReadOnly sets (or unsets) read only mode in the interpreter.
+func (in *EVMInterpreter) SetReadOnly(ro bool) {
+	in.readOnly = ro
+}