github.com/zxy12/golang151_with_comment@v0.0.0-20190507085033-721809559d3c/net/mac.go (about)

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