extract BinSearch function and add unit test

ethereum/rpc/namespaces/eth/api.go

@@ -643,22 +643,11 @@ func (e *PublicAPI) EstimateGas(args evmtypes.CallArgs, blockNrOptional *rpctype
 	}
 
 	// Execute the binary search and hone in on an executable gas limit
-	for lo+1 < hi {
-		mid := (hi + lo) / 2
-		failed, _, err := executable(mid)
-
-		// If the error is not nil(consensus error), it means the provided message
-		// call or transaction will never be accepted no matter how much gas it is
-		// assigned. Return the error directly, don't struggle any more.
-		if err != nil {
-			return 0, err
-		}
-		if failed {
-			lo = mid
-		} else {
-			hi = mid
-		}
+	hi, err := evmtypes.BinSearch(lo, hi, executable)
+	if err != nil {
+		return 0, err
 	}
+
 	// Reject the transaction as invalid if it still fails at the highest allowance
 	if hi == cap {
 		failed, result, err := executable(hi)

x/evm/types/utils.go

@@ -69,3 +69,24 @@ func UnwrapEthereumMsg(tx *sdk.Tx) (*MsgEthereumTx, error) {
 
 	return msg, nil
 }
+
+// BinSearch execute the binary search and hone in on an executable gas limit
+func BinSearch(lo uint64, hi uint64, executable func(uint64) (bool, *MsgEthereumTxResponse, error)) (uint64, error) {
+	for lo+1 < hi {
+		mid := (hi + lo) / 2
+		failed, _, err := executable(mid)
+
+		// If the error is not nil(consensus error), it means the provided message
+		// call or transaction will never be accepted no matter how much gas it is
+		// assigned. Return the error directly, don't struggle any more.
+		if err != nil {
+			return 0, err
+		}
+		if failed {
+			lo = mid
+		} else {
+			hi = mid
+		}
+	}
+	return hi, nil
+}

x/evm/types/utils_test.go

@@ -1,6 +1,7 @@
 package types_test
 
 import (
+	"errors"
 	"math/big"
 	"testing"
 
@@ -79,3 +80,21 @@ func TestUnwrapEthererumMsg(t *testing.T) {
 	require.Nil(t, err)
 	require.Equal(t, msg_, msg)
 }
+
+func TestBinSearch(t *testing.T) {
+	success_executable := func(gas uint64) (bool, *evmtypes.MsgEthereumTxResponse, error) {
+		target := uint64(21000)
+		return gas < target, nil, nil
+	}
+	failed_executable := func(gas uint64) (bool, *evmtypes.MsgEthereumTxResponse, error) {
+		return true, nil, errors.New("contract failed")
+	}
+
+	gas, err := evmtypes.BinSearch(20000, 21001, success_executable)
+	require.NoError(t, err)
+	require.Equal(t, gas, uint64(21000))
+
+	gas, err = evmtypes.BinSearch(20000, 21001, failed_executable)
+	require.Error(t, err)
+	require.Equal(t, gas, uint64(0))
+}