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// 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 [encoding/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 [encoding/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 [encoding/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 [encoding/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)
}
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