github.com/sanprasirt/go@v0.0.0-20170607001320-a027466e4b6d/src/math/big/intmarsh.go (about)

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