support java data structrue

math/big/integer.go

@@ -18,6 +18,7 @@
 package gxbig
 
 import (
+	"encoding/binary"
 	"fmt"
 	"math/big"
 )
@@ -27,7 +28,13 @@ type Integer struct {
 	bigInt big.Int
 
 	// for hessian
-	Value string
+	Signum int32
+	Mag    []int
+
+	FirstNonzeroIntNum int
+	LowestSetBit       int
+	BitLength          int
+	BitCount           int
 }
 
 func (Integer) JavaClassName() string {
@@ -45,10 +52,45 @@ func (i *Integer) FromString(s string) error {
 	return nil
 }
 
-// FromBytes set data from a 10-bases number bytes
-func (i *Integer) FromBytes(bytes []byte) error {
+// FromMag set data from a array of big-endian unsigned uint32
+// @see https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#BigInteger-int-byte:A-
+func (i *Integer) FromSignAndMag(signum int32, mag []int) {
+	if signum == 0 && len(mag) == 0 {
+		return
+	}
+
+	i.Signum = signum
+	i.Mag = mag
+
+	bytes := make([]byte, 4*len(i.Mag))
+	for j := 0; j < len(i.Mag); j++ {
+		binary.BigEndian.PutUint32(bytes[j*4:(j+1)*4], uint32(i.Mag[j]))
+	}
 	i.bigInt = *i.bigInt.SetBytes(bytes)
-	return nil
+
+	if i.Signum == -1 {
+		i.bigInt.Neg(&i.bigInt)
+	}
+}
+
+func (i *Integer) GetSignAndMag() (signum int32, mag []int) {
+	signum = int32(i.bigInt.Sign())
+
+	bytes := i.bigInt.Bytes()
+	outOf4 := len(bytes) % 4
+	if outOf4 > 0 {
+		bytes = append(make([]byte, 4-outOf4), bytes...)
+	}
+
+	size := len(bytes) / 4
+
+	mag = make([]int, size)
+
+	for i := 0; i < size; i++ {
+		mag[i] = int(binary.BigEndian.Uint32(bytes[i*4 : (i+1)*4]))
+	}
+
+	return
 }
 
 // GetBigInt getter
@@ -64,3 +106,7 @@ func (i *Integer) SetBigInt(bigInt big.Int) {
 func (i *Integer) String() string {
 	return i.bigInt.String()
 }
+
+func (i *Integer) Bytes() []byte {
+	return i.bigInt.Bytes()
+}

math/big/integer_test.go

@@ -18,6 +18,7 @@
 package gxbig
 
 import (
+	"reflect"
 	"testing"
 )
 
@@ -52,3 +53,48 @@ func TestInteger(t *testing.T) {
 		})
 	}
 }
+
+func TestInteger_FromSignAndMag(t *testing.T) {
+	type args struct {
+		signum int32
+		mag    []int
+	}
+	tests := []struct {
+		name  string
+		digit string
+		args  args
+	}{
+		{`0`, `0`, args{0, []int{}}},
+		{`1`, `1`, args{1, []int{1}}},
+		{`2147483647`, `2147483647`, args{1, []int{2147483647}}},
+		{`4294967295`, `4294967295`, args{1, []int{4294967295}}},
+		{`4294967296`, `4294967296`, args{1, []int{1, 0}}},
+		{`4294967298`, `4294967298`, args{1, []int{1, 2}}},
+		{`1x2x3`, `18446744082299486211`, args{1, []int{1, 2, 3}}},
+		{`-1`, `-1`, args{-1, []int{1}}},
+		{`-4294967296`, `-4294967296`, args{-1, []int{1, 0}}},
+		{`-4294967298`, `-4294967298`, args{-1, []int{1, 2}}},
+		{`-1x2x3`, `-18446744082299486211`, args{-1, []int{1, 2, 3}}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &Integer{}
+			i.FromSignAndMag(tt.args.signum, tt.args.mag)
+			if i.String() != tt.digit {
+				t.Errorf("digit %s got = %s", tt.digit, i.String())
+			}
+
+			s := &Integer{}
+			err := s.FromString(tt.digit)
+			if err != nil {
+				t.Error("FromString error = ", err)
+			}
+
+			sign, mag := s.GetSignAndMag()
+			if !(sign == tt.args.signum && reflect.DeepEqual(mag, tt.args.mag)) {
+				t.Error("want ", tt.args.signum, tt.args.mag,
+					"got", sign, mag)
+			}
+		})
+	}
+}