[release/1.4.16] core/state: implement reverts by journaling all changes

This commit replaces the deep-copy based state revert mechanism with a
linear complexity journal. This commit also hides several internal
StateDB methods to limit the number of ways in which calling code can
use the journal incorrectly.

As usual consultation and bug fixes to the initial implementation were
provided by @karalabe, @obscuren and @Arachnid. Thank you!

(cherry picked from commit 1f1ea18b5414bea22332bb4fce53cc95b5c6a07d)

1 files changed, 6 insertions, 2 deletions

diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index cbd2982df..2f4d39410 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -97,7 +97,8 @@ func (b *SimulatedBackend) ContractCall(contract common.Address, data []byte, pe
 		statedb *state.StateDB
 	)
 	if pending {
-		block, statedb = b.pendingBlock, b.pendingState.Copy()
+		block, statedb = b.pendingBlock, b.pendingState
+		defer statedb.RevertToSnapshot(statedb.Snapshot())
 	} else {
 		block = b.blockchain.CurrentBlock()
 		statedb, _ = b.blockchain.State()
@@ -119,6 +120,7 @@ func (b *SimulatedBackend) ContractCall(contract common.Address, data []byte, pe
 		value:    new(big.Int),
 		data:     data,
 	}
+
 	// Execute the call and return
 	vmenv := core.NewEnv(statedb, chainConfig, b.blockchain, msg, block.Header(), vm.Config{})
 	gaspool := new(core.GasPool).AddGas(common.MaxBig)
@@ -146,8 +148,10 @@ func (b *SimulatedBackend) EstimateGasLimit(sender common.Address, contract *com
 	// Create a copy of the currently pending state db to screw around with
 	var (
 		block   = b.pendingBlock
-		statedb = b.pendingState.Copy()
+		statedb = b.pendingState
 	)
+	defer statedb.RevertToSnapshot(statedb.Snapshot())
+
 	// If there's no code to interact with, respond with an appropriate error
 	if contract != nil {
 		if code := statedb.GetCode(*contract); len(code) == 0 {