neoneo-go/pkg/core/interop/binary/itoa.go
Evgenii Stratonikov e4bf531e3e core: implement System.Binary.Atoi/Itoa syscalls
They follow C# conversion rules, but differ from our `bigint` module
conversions:
1. String must be big-endian.
2. Sign extension is 4-bit in size (single hex character)
   and not 8-byte.
2020-11-10 16:15:10 +03:00

91 lines
1.7 KiB
Go

package binary
import (
"encoding/hex"
"errors"
"math/big"
"strings"
"github.com/nspcc-dev/neo-go/pkg/core/interop"
"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
)
var (
// ErrInvalidBase is returned when base is invalid.
ErrInvalidBase = errors.New("invalid base")
// ErrInvalidFormat is returned when string is not a number.
ErrInvalidFormat = errors.New("invalid format")
)
// Itoa converts number to string.
func Itoa(ic *interop.Context) error {
num := ic.VM.Estack().Pop().BigInt()
base := ic.VM.Estack().Pop().BigInt()
if !base.IsInt64() {
return ErrInvalidBase
}
var s string
switch b := base.Int64(); b {
case 10:
s = num.Text(10)
case 16:
if num.Sign() == 0 {
s = "0"
break
}
bs := bigint.ToBytes(num)
reverse(bs)
s = hex.EncodeToString(bs)
if pad := bs[0] & 0xF8; pad == 0 || pad == 0xF8 {
s = s[1:]
}
s = strings.ToUpper(s)
default:
return ErrInvalidBase
}
ic.VM.Estack().PushVal(s)
return nil
}
// Atoi converts string to number.
func Atoi(ic *interop.Context) error {
num := ic.VM.Estack().Pop().String()
base := ic.VM.Estack().Pop().BigInt()
if !base.IsInt64() {
return ErrInvalidBase
}
var bi *big.Int
switch b := base.Int64(); b {
case 10:
var ok bool
bi, ok = new(big.Int).SetString(num, int(b))
if !ok {
return ErrInvalidFormat
}
case 16:
changed := len(num)%2 != 0
if changed {
num = "0" + num
}
bs, err := hex.DecodeString(num)
if err != nil {
return ErrInvalidFormat
}
if changed && bs[0]&0x8 != 0 {
bs[0] |= 0xF0
}
reverse(bs)
bi = bigint.FromBytes(bs)
default:
return ErrInvalidBase
}
ic.VM.Estack().PushVal(bi)
return nil
}
func reverse(b []byte) {
l := len(b)
for i := 0; i < l/2; i++ {
b[i], b[l-i-1] = b[l-i-1], b[i]
}
}