intmarsh.go

Documentation: math/big

		 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
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