Transaction: Prepare txSetupComputation to support txCallEvm

After recent changes, there's only one call left to `setupComputation`, and
it's just a variant like `rpcSetupComputation` but for transaction processing.
The similarity to `rpcSetupComputation` is obvious.

Gather this into `call_evm`: `setupComputation` -> `txSetupComputation`.

Signed-off-by: Jamie Lokier <jamie@shareable.org>

nimbus/p2p/executor.nim

@@ -5,7 +5,8 @@ import options, sets,
   ../vm_state, ../vm_types, ../vm_state_transactions,
   ../vm_computation, ../vm_message, ../vm_precompiles,
   ../vm_types2,
-  ./dao, ../config
+  ./dao, ../config,
+  ../transaction/call_evm
 
 proc validateTransaction*(vmState: BaseVMState, tx: Transaction,
                           sender: EthAddress, fork: Fork): bool =
@@ -64,7 +65,7 @@ proc processTransaction*(tx: Transaction, sender: EthAddress, vmState: BaseVMSta
         db.accessList(c)
 
   if validateTransaction(vmState, tx, sender, fork):
-    var c = setupComputation(vmState, tx, sender, fork)
+    var c = txSetupComputation(tx, sender, vmState, fork)
     vmState.mutateStateDB:
       db.subBalance(sender, tx.gasLimit.u256 * tx.gasPrice.u256)
     execComputation(c)

nimbus/transaction/call_evm.nim

@@ -148,3 +148,27 @@ proc rpcEstimateGas*(call: RpcCallData, header: BlockHeader, chain: BaseChainDB,
   let maxRefund = (gasLimit - c.gasMeter.gasRemaining) div 2
   let refund = min(c.getGasRefund(), maxRefund)
   return gasLimit - c.gasMeter.gasRemaining - refund
+
+proc txSetupComputation*(tx: Transaction, sender: EthAddress, vmState: BaseVMState, fork: Fork): Computation =
+  var gas = tx.gasLimit - tx.intrinsicGas(fork)
+  assert gas >= 0
+
+  vmState.setupTxContext(
+    origin = sender,
+    gasPrice = tx.gasPrice,
+    forkOverride = some(fork)
+  )
+
+  let msg = Message(
+    kind: if tx.isContractCreation: evmcCreate else: evmcCall,
+    depth: 0,
+    gas: gas,
+    sender: sender,
+    contractAddress: tx.getRecipient(),
+    codeAddress: tx.to,
+    value: tx.value,
+    data: tx.payload
+    )
+
+  result = newComputation(vmState, msg)
+  doAssert result.isOriginComputation

nimbus/vm/state_transactions.nim

@@ -11,30 +11,6 @@ import
   ../transaction,
   ./computation, ./interpreter, ./state, ./types
 
-proc setupComputation*(vmState: BaseVMState, tx: Transaction, sender: EthAddress, fork: Fork) : Computation =
-  var gas = tx.gasLimit - tx.intrinsicGas(fork)
-  assert gas >= 0
-
-  vmState.setupTxContext(
-    origin = sender,
-    gasPrice = tx.gasPrice,
-    forkOverride = some(fork)
-  )
-
-  let msg = Message(
-    kind: if tx.isContractCreation: evmcCreate else: evmcCall,
-    depth: 0,
-    gas: gas,
-    sender: sender,
-    contractAddress: tx.getRecipient(),
-    codeAddress: tx.to,
-    value: tx.value,
-    data: tx.payload
-    )
-
-  result = newComputation(vmState, msg)
-  doAssert result.isOriginComputation
-
 proc execComputation*(c: Computation) =
   if not c.msg.isCreate:
     c.vmState.mutateStateDB:

nimbus/vm_state_transactions.nim

@@ -17,7 +17,6 @@ else:
 
 export
   vmx.execComputation,
-  vmx.refundGas,
+  vmx.refundGas
-  vmx.setupComputation
 
 # End