support uint128/uint256 toString

Makefile

@@ -120,6 +120,7 @@ test/example:
 	${CELL} -d -t riscv tests/examples/if-cond.cell && ckb-debugger --bin if-cond${exe} | grep "100:0:ss"
 	${CELL} -d -t riscv tests/examples/switch.cell && ckb-debugger --bin switch${exe} | grep "five"
 	${CELL} -d -t riscv tests/examples/number-literal.cell && ckb-debugger --bin number-literal${exe}
+	${CELL} -d -t riscv tests/examples/to-string.cell && ckb-debugger --bin to-string${exe}
 	${CELL} -d -t riscv tests/examples/return.cell && ckb-debugger --bin return${exe}
 	${CELL} -d -t riscv tests/examples/named-ret-type.cell && ckb-debugger --bin named-ret-type${exe} | grep "0"
 	${CELL} -d -t riscv tests/examples/func.cell && ckb-debugger --bin func${exe} | grep "999"

pkg/builtin/builtin.cell

@@ -17,3 +17,38 @@ func (e *error) NotNone() bool {
 	return !e.none
 }
 
+type uint256 uint256
+type uint128 uint128
+
+func (x uint256) toString() string {
+	digits := []uint8{}
+	for i := x; i > 0u256; i /= 10u256 {
+		mod := byte(i % 10u256)
+		digits = append(digits, mod + '0')
+	}
+	length := uint64(len(digits))
+	digits = append(digits, byte(0))
+	str := make(string, digits[0:length])
+	for i := 0; i < length - length / 2; i++ {
+		v := str[i]
+		str[i] = str[length - 1 - i]
+		str[length - 1 - i] = v
+	}
+	return str
+}
+
+func (x uint128) toString() string {
+	digits := []uint8{}
+	for i := x; i > 0u128; i /= 10u128 {
+		mod := byte(i % 10u128)
+		digits = append(digits, mod + '0')
+	}
+	str := make(string, digits)
+	length := len(str)
+	for i := 0; i < length - length / 2; i++ {
+		v := str[i]
+		str[i] = str[length - 1 - i]
+		str[length - 1 - i] = v
+	}
+	return str
+}

tests/examples/to-string.cell

@@ -0,0 +1,12 @@
+
+func main() {
+	str := 100348u256.toString()
+	if str != "100348" {
+		return 1
+	}
+	str = 1003249u128.toString()
+	if str != "1003249" {
+		return 2
+	}
+	return 0
+}