1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // This file implements encoding/decoding of Ints. 6 7 package big 8 9 import ( 10 "bytes" 11 "fmt" 12 ) 13 14 // Gob codec version. Permits backward-compatible changes to the encoding. 15 const intGobVersion byte = 1 16 17 // GobEncode implements the gob.GobEncoder interface. 18 func (x *Int) GobEncode() ([]byte, error) { 19 if x == nil { 20 return nil, nil 21 } 22 buf := make([]byte, 1+len(x.abs)*_S) // extra byte for version and sign bit 23 i := x.abs.bytes(buf) - 1 // i >= 0 24 b := intGobVersion << 1 // make space for sign bit 25 if x.neg { 26 b |= 1 27 } 28 buf[i] = b 29 return buf[i:], nil 30 } 31 32 // GobDecode implements the gob.GobDecoder interface. 33 func (z *Int) GobDecode(buf []byte) error { 34 if len(buf) == 0 { 35 // Other side sent a nil or default value. 36 *z = Int{} 37 return nil 38 } 39 b := buf[0] 40 if b>>1 != intGobVersion { 41 return fmt.Errorf("Int.GobDecode: encoding version %d not supported", b>>1) 42 } 43 z.neg = b&1 != 0 44 z.abs = z.abs.setBytes(buf[1:]) 45 return nil 46 } 47 48 // MarshalText implements the encoding.TextMarshaler interface. 49 func (x *Int) MarshalText() (text []byte, err error) { 50 if x == nil { 51 return []byte("<nil>"), nil 52 } 53 return x.abs.itoa(x.neg, 10), nil 54 } 55 56 // UnmarshalText implements the encoding.TextUnmarshaler interface. 57 func (z *Int) UnmarshalText(text []byte) error { 58 if _, ok := z.setFromScanner(bytes.NewReader(text), 0); !ok { 59 return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text) 60 } 61 return nil 62 } 63 64 // The JSON marshalers are only here for API backward compatibility 65 // (programs that explicitly look for these two methods). JSON works 66 // fine with the TextMarshaler only. 67 68 // MarshalJSON implements the json.Marshaler interface. 69 func (x *Int) MarshalJSON() ([]byte, error) { 70 return x.MarshalText() 71 } 72 73 // UnmarshalJSON implements the json.Unmarshaler interface. 74 func (z *Int) UnmarshalJSON(text []byte) error { 75 // Ignore null, like in the main JSON package. 76 if string(text) == "null" { 77 return nil 78 } 79 return z.UnmarshalText(text) 80 } 81
