*: support invoking methods by offset

Allow to invoke methods by offset:
1. Every invoked contract must have manifest.
2. Check arguments count on invocation.
3. Change AppCall to a regular syscall.
4. Add test suite for `System.Contract.Call`.

pkg/rpc/server/testdata/test_contract.go

@@ -11,83 +11,91 @@ const (
 )
 
 func Main(operation string, args []interface{}) interface{} {
-	runtime.Notify("contract call", operation, args)
-	switch operation {
-	case "Put":
-		ctx := storage.GetContext()
-		storage.Put(ctx, args[0].([]byte), args[1].([]byte))
-		return true
-	case "totalSupply":
-		return totalSupply
-	case "decimals":
-		return decimals
-	case "name":
-		return "Rubl"
-	case "symbol":
-		return "RUB"
-	case "balanceOf":
-		ctx := storage.GetContext()
-		addr := args[0].([]byte)
-		if len(addr) != 20 {
-			runtime.Log("invalid address")
-			return false
-		}
-		var amount int
-		val := storage.Get(ctx, addr)
-		if val != nil {
-			amount = val.(int)
-		}
-		runtime.Notify("balanceOf", addr, amount)
-		return amount
-	case "transfer":
-		ctx := storage.GetContext()
-		from := args[0].([]byte)
-		if len(from) != 20 {
-			runtime.Log("invalid 'from' address")
-			return false
-		}
-		to := args[1].([]byte)
-		if len(to) != 20 {
-			runtime.Log("invalid 'to' address")
-			return false
-		}
-		amount := args[2].(int)
-		if amount < 0 {
-			runtime.Log("invalid amount")
-			return false
-		}
-
-		var fromBalance int
-		val := storage.Get(ctx, from)
-		if val != nil {
-			fromBalance = val.(int)
-		}
-		if fromBalance < amount {
-			runtime.Log("insufficient funds")
-			return false
-		}
-		fromBalance -= amount
-		storage.Put(ctx, from, fromBalance)
-
-		var toBalance int
-		val = storage.Get(ctx, to)
-		if val != nil {
-			toBalance = val.(int)
-		}
-		toBalance += amount
-		storage.Put(ctx, to, toBalance)
-
-		runtime.Notify("transfer", from, to, amount)
-
-		return true
-	case "init":
-		ctx := storage.GetContext()
-		h := runtime.GetExecutingScriptHash()
-		amount := totalSupply
-		storage.Put(ctx, h, amount)
-		runtime.Notify("transfer", []byte{}, h, amount)
-		return true
-	default:
-		panic("invalid operation")
-	}
+	panic("invoking via Main is no longer supported") // catch possible bugs
+}
+
+func Init() bool {
+	ctx := storage.GetContext()
+	h := runtime.GetExecutingScriptHash()
+	amount := totalSupply
+	storage.Put(ctx, h, amount)
+	runtime.Notify("transfer", []byte{}, h, amount)
+	return true
+}
+
+func Transfer(from, to []byte, amount int) bool {
+	ctx := storage.GetContext()
+	if len(from) != 20 {
+		runtime.Log("invalid 'from' address")
+		return false
+	}
+	if len(to) != 20 {
+		runtime.Log("invalid 'to' address")
+		return false
+	}
+	if amount < 0 {
+		runtime.Log("invalid amount")
+		return false
+	}
+
+	var fromBalance int
+	val := storage.Get(ctx, from)
+	if val != nil {
+		fromBalance = val.(int)
+	}
+	if fromBalance < amount {
+		runtime.Log("insufficient funds")
+		return false
+	}
+	fromBalance -= amount
+	storage.Put(ctx, from, fromBalance)
+
+	var toBalance int
+	val = storage.Get(ctx, to)
+	if val != nil {
+		toBalance = val.(int)
+	}
+	toBalance += amount
+	storage.Put(ctx, to, toBalance)
+
+	runtime.Notify("transfer", from, to, amount)
+
+	return true
+}
+
+func BalanceOf(addr []byte) int {
+	ctx := storage.GetContext()
+	if len(addr) != 20 {
+		runtime.Log("invalid address")
+		return 0
+	}
+	var amount int
+	val := storage.Get(ctx, addr)
+	if val != nil {
+		amount = val.(int)
+	}
+	runtime.Notify("balanceOf", addr, amount)
+	return amount
+}
+
+func Name() string {
+	return "Rubl"
+}
+
+func Symbol() string {
+	return "RUB"
+}
+
+func Decimals() int {
+	return decimals
+}
+
+func TotalSupply() int {
+	return totalSupply
+}
+
+func PutValue(key []byte, value []byte) bool {
+	ctx := storage.GetContext()
+	storage.Put(ctx, key, value)
+	return true
 }