Source file src/pkg/net/mac.go

     1	// Copyright 2011 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	// MAC address manipulations
     6	
     7	package net
     8	
     9	import "errors"
    10	
    11	const hexDigit = "0123456789abcdef"
    12	
    13	// A HardwareAddr represents a physical hardware address.
    14	type HardwareAddr []byte
    15	
    16	func (a HardwareAddr) String() string {
    17		if len(a) == 0 {
    18			return ""
    19		}
    20		buf := make([]byte, 0, len(a)*3-1)
    21		for i, b := range a {
    22			if i > 0 {
    23				buf = append(buf, ':')
    24			}
    25			buf = append(buf, hexDigit[b>>4])
    26			buf = append(buf, hexDigit[b&0xF])
    27		}
    28		return string(buf)
    29	}
    30	
    31	// ParseMAC parses s as an IEEE 802 MAC-48, EUI-48, or EUI-64 using one of the
    32	// following formats:
    33	//   01:23:45:67:89:ab
    34	//   01:23:45:67:89:ab:cd:ef
    35	//   01-23-45-67-89-ab
    36	//   01-23-45-67-89-ab-cd-ef
    37	//   0123.4567.89ab
    38	//   0123.4567.89ab.cdef
    39	func ParseMAC(s string) (hw HardwareAddr, err error) {
    40		if len(s) < 14 {
    41			goto error
    42		}
    43	
    44		if s[2] == ':' || s[2] == '-' {
    45			if (len(s)+1)%3 != 0 {
    46				goto error
    47			}
    48			n := (len(s) + 1) / 3
    49			if n != 6 && n != 8 {
    50				goto error
    51			}
    52			hw = make(HardwareAddr, n)
    53			for x, i := 0, 0; i < n; i++ {
    54				var ok bool
    55				if hw[i], ok = xtoi2(s[x:], s[2]); !ok {
    56					goto error
    57				}
    58				x += 3
    59			}
    60		} else if s[4] == '.' {
    61			if (len(s)+1)%5 != 0 {
    62				goto error
    63			}
    64			n := 2 * (len(s) + 1) / 5
    65			if n != 6 && n != 8 {
    66				goto error
    67			}
    68			hw = make(HardwareAddr, n)
    69			for x, i := 0, 0; i < n; i += 2 {
    70				var ok bool
    71				if hw[i], ok = xtoi2(s[x:x+2], 0); !ok {
    72					goto error
    73				}
    74				if hw[i+1], ok = xtoi2(s[x+2:], s[4]); !ok {
    75					goto error
    76				}
    77				x += 5
    78			}
    79		} else {
    80			goto error
    81		}
    82		return hw, nil
    83	
    84	error:
    85		return nil, errors.New("invalid MAC address: " + s)
    86	}