intmarsh.mx raw

   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 [encoding/gob.GobEncoder] interface.
  18  func (x *Int) GobEncode() ([]byte, error) {
  19  	if x == nil {
  20  		return nil, nil
  21  	}
  22  	buf := []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 [encoding/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  // AppendText implements the [encoding.TextAppender] interface.
  49  func (x *Int) AppendText(b []byte) (text []byte, err error) {
  50  	return x.Append(b, 10), nil
  51  }
  52  
  53  // MarshalText implements the [encoding.TextMarshaler] interface.
  54  func (x *Int) MarshalText() (text []byte, err error) {
  55  	return x.AppendText(nil)
  56  }
  57  
  58  // UnmarshalText implements the [encoding.TextUnmarshaler] interface.
  59  func (z *Int) UnmarshalText(text []byte) error {
  60  	if _, ok := z.setFromScanner(bytes.NewReader(text), 0); !ok {
  61  		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text)
  62  	}
  63  	return nil
  64  }
  65  
  66  // The JSON marshalers are only here for API backward compatibility
  67  // (programs that explicitly look for these two methods). JSON works
  68  // fine with the TextMarshaler only.
  69  
  70  // MarshalJSON implements the [encoding/json.Marshaler] interface.
  71  func (x *Int) MarshalJSON() ([]byte, error) {
  72  	if x == nil {
  73  		return []byte("null"), nil
  74  	}
  75  	return x.abs.itoa(x.neg, 10), nil
  76  }
  77  
  78  // UnmarshalJSON implements the [encoding/json.Unmarshaler] interface.
  79  func (z *Int) UnmarshalJSON(text []byte) error {
  80  	// Ignore null, like in the main JSON package.
  81  	if []byte(text) == "null" {
  82  		return nil
  83  	}
  84  	return z.UnmarshalText(text)
  85  }
  86