oid.go

Documentation: github.com/ProtonMail/go-crypto/openpgp/internal/encoding

     1  // Copyright 2017 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  package encoding
     6  
     7  import (
     8  	"io"
     9  
    10  	"github.com/ProtonMail/go-crypto/openpgp/errors"
    11  )
    12  
    13  // OID is used to store a variable-length field with a one-octet size
    14  // prefix. See https://tools.ietf.org/html/rfc6637#section-9.
    15  type OID struct {
    16  	bytes []byte
    17  }
    18  
    19  const (
    20  	// maxOID is the maximum number of bytes in a OID.
    21  	maxOID = 254
    22  	// reservedOIDLength1 and reservedOIDLength2 are OID lengths that the RFC
    23  	// specifies are reserved.
    24  	reservedOIDLength1 = 0
    25  	reservedOIDLength2 = 0xff
    26  )
    27  
    28  // NewOID returns a OID initialized with bytes.
    29  func NewOID(bytes []byte) *OID {
    30  	switch len(bytes) {
    31  	case reservedOIDLength1, reservedOIDLength2:
    32  		panic("encoding: NewOID argument length is reserved")
    33  	default:
    34  		if len(bytes) > maxOID {
    35  			panic("encoding: NewOID argument too large")
    36  		}
    37  	}
    38  
    39  	return &OID{
    40  		bytes: bytes,
    41  	}
    42  }
    43  
    44  // Bytes returns the decoded data.
    45  func (o *OID) Bytes() []byte {
    46  	return o.bytes
    47  }
    48  
    49  // BitLength is the size in bits of the decoded data.
    50  func (o *OID) BitLength() uint16 {
    51  	return uint16(len(o.bytes) * 8)
    52  }
    53  
    54  // EncodedBytes returns the encoded data.
    55  func (o *OID) EncodedBytes() []byte {
    56  	return append([]byte{byte(len(o.bytes))}, o.bytes...)
    57  }
    58  
    59  // EncodedLength is the size in bytes of the encoded data.
    60  func (o *OID) EncodedLength() uint16 {
    61  	return uint16(1 + len(o.bytes))
    62  }
    63  
    64  // ReadFrom reads into b the next OID from r.
    65  func (o *OID) ReadFrom(r io.Reader) (int64, error) {
    66  	var buf [1]byte
    67  	n, err := io.ReadFull(r, buf[:])
    68  	if err != nil {
    69  		if err == io.EOF {
    70  			err = io.ErrUnexpectedEOF
    71  		}
    72  		return int64(n), err
    73  	}
    74  
    75  	switch buf[0] {
    76  	case reservedOIDLength1, reservedOIDLength2:
    77  		return int64(n), errors.UnsupportedError("reserved for future extensions")
    78  	}
    79  
    80  	o.bytes = make([]byte, buf[0])
    81  
    82  	nn, err := io.ReadFull(r, o.bytes)
    83  	if err == io.EOF {
    84  		err = io.ErrUnexpectedEOF
    85  	}
    86  
    87  	return int64(n) + int64(nn), err
    88  }
    89
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