golang intmarsh 代码
文件路径：/src/math/big/intmarsh.go
/ Copyright 2015 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
/ This file implements encoding/decoding of Ints.
package big
import (
"bytes"
"fmt"
)
/ Gob codec version. Permits backward-compatible changes to the encoding.
const intGobVersion byte = 1
/ GobEncode implements the gob.GobEncoder interface.
func (x *Int) GobEncode() ([]byte, error) {
if x == nil {
return nil, nil
}
buf := make([]byte, 1+len(x.abs)*_S) / extra byte for version and sign bit
i := x.abs.bytes(buf) - 1 / i >= 0
b := intGobVersion << 1 / make space for sign bit
if x.neg {
b |= 1
}
buf[i] = b
return buf[i:], nil
}
/ GobDecode implements the gob.GobDecoder interface.
func (z *Int) GobDecode(buf []byte) error {
if len(buf) == 0 {
/ Other side sent a nil or default value.
*z = Int{}
return nil
}
b := buf[0]
if b>>1 != intGobVersion {
return fmt.Errorf("Int.GobDecode: encoding version %d not supported", b>>1)
}
z.neg = b&1 != 0
z.abs = z.abs.setBytes(buf[1:])
return nil
}
/ MarshalText implements the encoding.TextMarshaler interface.
func (x *Int) MarshalText() (text []byte, err error) {
if x == nil {
return []byte("<nil>"), nil
}
return x.abs.itoa(x.neg, 10), nil
}
/ UnmarshalText implements the encoding.TextUnmarshaler interface.
func (z *Int) UnmarshalText(text []byte) error {
if _, ok := z.setFromScanner(bytes.NewReader(text), 0); !ok {
return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text)
}
return nil
}
/ The JSON marshalers are only here for API backward compatibility
/ (programs that explicitly look for these two methods). JSON works
/ fine with the TextMarshaler only.
/ MarshalJSON implements the json.Marshaler interface.
func (x *Int) MarshalJSON() ([]byte, error) {
if x == nil {
return []byte("null"), nil
}
return x.abs.itoa(x.neg, 10), nil
}
/ UnmarshalJSON implements the json.Unmarshaler interface.
func (z *Int) UnmarshalJSON(text []byte) error {
/ Ignore null, like in the main JSON package.
if string(text) == "null" {
return nil
}
return z.UnmarshalText(text)
}