read and write into the SequenceFee by Sequence value.

x/ibctransfermiddleware/keeper/keeper.go

@@ -65,6 +65,22 @@ func (k Keeper) GetParams(ctx sdk.Context) (p types.Params) {
 	return p
 }
 
+func (k Keeper) GetSequenceFee(ctx sdk.Context, sequence uint64) (coin sdk.Coin, found bool) {
+	store := ctx.KVStore(k.storeKey)
+
+	value := store.Get(types.GetSequenceKey(sequence))
+	if value == nil {
+		return sdk.Coin{}, false
+	}
+
+	fee := types.MustUnmarshalCoin(k.cdc, value)
+	return fee, true
+}
+func (k Keeper) SetSequenceFee(ctx sdk.Context, sequence uint64, coin sdk.Coin) {
+	store := ctx.KVStore(k.storeKey)
+	store.Set(types.GetSequenceKey(sequence), types.MustMarshalCoin(k.cdc, &coin))
+}
+
 func (k Keeper) GetCoin(ctx sdk.Context, targetChannelID, denom string) *types.CoinItem {
 	params := k.GetParams(ctx)
 	channelFee := findChannelParams(params.ChannelFees, targetChannelID)

x/ibctransfermiddleware/types/keys.go

@@ -1,8 +1,17 @@
 package types
 
+import (
+	"strconv"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	types "github.com/cosmos/cosmos-sdk/types"
+)
+
 // ParamsKey is the key to use for the keeper store.
 var (
 	ParamsKey = []byte{0x01} // key for global staking middleware params in the keeper store
+
+	SequenceFeeKey = []byte{0x21} // prefix for sequence fee
 )
 
 const (
@@ -15,3 +24,28 @@ const (
 
 	RouterKey = ModuleName
 )
+
+// GetSequenceKey returns a key prefix for indexing HistoricalInfo objects.
+func GetSequenceKey(sequence uint64) []byte {
+	return append(SequenceFeeKey, []byte(strconv.FormatUint(sequence, 10))...)
+}
+
+func MustMarshalCoin(cdc codec.BinaryCodec, validator *types.Coin) []byte {
+	return cdc.MustMarshal(validator)
+}
+
+// unmarshal a redelegation from a store value
+func MustUnmarshalCoin(cdc codec.BinaryCodec, value []byte) types.Coin {
+	validator, err := UnmarshalCoin(cdc, value)
+	if err != nil {
+		panic(err)
+	}
+
+	return validator
+}
+
+// unmarshal a redelegation from a store value
+func UnmarshalCoin(cdc codec.BinaryCodec, value []byte) (v types.Coin, err error) {
+	err = cdc.Unmarshal(value, &v)
+	return v, err
+}