lotus/chain/types/bigint.go
2019-11-13 15:48:57 +01:00

215 lines
3.9 KiB
Go

package types
import (
"encoding/json"
"fmt"
"io"
"math/big"
"github.com/filecoin-project/lotus/build"
cbor "github.com/ipfs/go-ipld-cbor"
"github.com/polydawn/refmt/obj/atlas"
cbg "github.com/whyrusleeping/cbor-gen"
"golang.org/x/xerrors"
)
const BigIntMaxSerializedLen = 128 // is this big enough? or too big?
var TotalFilecoinInt = FromFil(build.TotalFilecoin)
func init() {
cbor.RegisterCborType(atlas.BuildEntry(BigInt{}).Transform().
TransformMarshal(atlas.MakeMarshalTransformFunc(
func(i BigInt) ([]byte, error) {
return i.cborBytes(), nil
})).
TransformUnmarshal(atlas.MakeUnmarshalTransformFunc(
func(x []byte) (BigInt, error) {
return fromCborBytes(x)
})).
Complete())
}
var EmptyInt = BigInt{}
type BigInt struct {
*big.Int
}
func NewInt(i uint64) BigInt {
return BigInt{big.NewInt(0).SetUint64(i)}
}
func FromFil(i uint64) BigInt {
return BigMul(NewInt(i), NewInt(build.FilecoinPrecision))
}
func BigFromBytes(b []byte) BigInt {
i := big.NewInt(0).SetBytes(b)
return BigInt{i}
}
func BigFromString(s string) (BigInt, error) {
v, ok := big.NewInt(0).SetString(s, 10)
if !ok {
return BigInt{}, fmt.Errorf("failed to parse string as a big int")
}
return BigInt{v}, nil
}
func BigMul(a, b BigInt) BigInt {
return BigInt{big.NewInt(0).Mul(a.Int, b.Int)}
}
func BigDiv(a, b BigInt) BigInt {
return BigInt{big.NewInt(0).Div(a.Int, b.Int)}
}
func BigMod(a, b BigInt) BigInt {
return BigInt{big.NewInt(0).Mod(a.Int, b.Int)}
}
func BigAdd(a, b BigInt) BigInt {
return BigInt{big.NewInt(0).Add(a.Int, b.Int)}
}
func BigSub(a, b BigInt) BigInt {
return BigInt{big.NewInt(0).Sub(a.Int, b.Int)}
}
func BigCmp(a, b BigInt) int {
return a.Int.Cmp(b.Int)
}
func (bi BigInt) Nil() bool {
return bi.Int == nil
}
// LessThan returns true if bi < o
func (bi BigInt) LessThan(o BigInt) bool {
return BigCmp(bi, o) < 0
}
// LessThan returns true if bi > o
func (bi BigInt) GreaterThan(o BigInt) bool {
return BigCmp(bi, o) > 0
}
func (bi *BigInt) MarshalJSON() ([]byte, error) {
return json.Marshal(bi.String())
}
func (bi *BigInt) UnmarshalJSON(b []byte) error {
var s string
if err := json.Unmarshal(b, &s); err != nil {
return err
}
i, ok := big.NewInt(0).SetString(s, 10)
if !ok {
if string(s) == "<nil>" {
return nil
}
return xerrors.Errorf("failed to parse bigint string: '%s'", string(b))
}
bi.Int = i
return nil
}
func (bi *BigInt) cborBytes() []byte {
if bi.Int == nil {
return []byte{}
}
switch {
case bi.Sign() == 0:
return []byte{}
case bi.Sign() > 0:
return append([]byte{0}, bi.Bytes()...)
case bi.Sign() < 0:
return append([]byte{1}, bi.Bytes()...)
}
panic("unreachable")
}
func fromCborBytes(buf []byte) (BigInt, error) {
if len(buf) == 0 {
return NewInt(0), nil
}
var negative bool
switch buf[0] {
case 0:
negative = false
case 1:
negative = true
default:
return EmptyInt, fmt.Errorf("big int prefix should be either 0 or 1, got %d", buf[0])
}
i := big.NewInt(0).SetBytes(buf[1:])
if negative {
i.Neg(i)
}
return BigInt{i}, nil
}
func (bi *BigInt) MarshalCBOR(w io.Writer) error {
if bi.Int == nil {
zero := NewInt(0)
return zero.MarshalCBOR(w)
}
enc := bi.cborBytes()
header := cbg.CborEncodeMajorType(cbg.MajByteString, uint64(len(enc)))
if _, err := w.Write(header); err != nil {
return err
}
if _, err := w.Write(enc); err != nil {
return err
}
return nil
}
func (bi *BigInt) UnmarshalCBOR(br io.Reader) error {
maj, extra, err := cbg.CborReadHeader(br)
if err != nil {
return err
}
if maj != cbg.MajByteString {
return fmt.Errorf("cbor input for fil big int was not a byte string")
}
if extra == 0 {
bi.Int = big.NewInt(0)
return nil
}
if extra > BigIntMaxSerializedLen {
return fmt.Errorf("big integer byte array too long")
}
buf := make([]byte, extra)
if _, err := io.ReadFull(br, buf); err != nil {
return err
}
i, err := fromCborBytes(buf)
if err != nil {
return err
}
*bi = i
return nil
}