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net: fix IPMask.String not to crash on all-0xff mask

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R=r
CC=golang-dev
https://golang.org/cl/438042
This commit is contained in:
Russ Cox 2010-03-16 14:16:33 -07:00
parent 7f4c2caea5
commit 0b986316b8
1 changed files with 38 additions and 21 deletions
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59
src/pkg/net/ip.go
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@ -51,6 +51,20 @@ func IPv4(a, b, c, d byte) IP {
return p
}
// IPv4Mask returns the IP mask (in 16-byte form) of the
// IPv4 mask a.b.c.d.
func IPv4Mask(a, b, c, d byte) IPMask {
p := make(IPMask, IPv6len)
for i := 0; i < 12; i++ {
p[i] = 0xff
}
p[12] = a
p[13] = b
p[14] = c
p[15] = d
return p
}
// Well-known IPv4 addresses
var (
IPv4bcast = IPv4(255, 255, 255, 255) // broadcast
@ -103,9 +117,9 @@ func (ip IP) To16() IP {
// Default route masks for IPv4.
var (
classAMask = IPMask(IPv4(0xff, 0, 0, 0))
classBMask = IPMask(IPv4(0xff, 0xff, 0, 0))
classCMask = IPMask(IPv4(0xff, 0xff, 0xff, 0))
classAMask = IPv4Mask(0xff, 0, 0, 0)
classBMask = IPv4Mask(0xff, 0xff, 0, 0)
classCMask = IPv4Mask(0xff, 0xff, 0xff, 0)
)
// DefaultMask returns the default IP mask for the IP address ip.
@ -229,25 +243,28 @@ func (ip IP) String() string {
// If mask is a sequence of 1 bits followed by 0 bits,
// return the number of 1 bits.
func simpleMaskLength(mask IPMask) int {
var i int
for i = 0; i < len(mask); i++ {
if mask[i] != 0xFF {
break
var n int
for i, v := range mask {
if v == 0xff {
n += 8
continue
}
}
n := 8 * i
v := mask[i]
for v&0x80 != 0 {
n++
v <<= 1
}
if v != 0 {
return -1
}
for i++; i < len(mask); i++ {
if mask[i] != 0 {
// found non-ff byte
// count 1 bits
for v&0x80 != 0 {
n++
v <<= 1
}
// rest must be 0 bits
if v != 0 {
return -1
}
for i++; i < len(mask); i++ {
if mask[i] != 0 {
return -1
}
}
break
}
return n
}
@ -266,8 +283,8 @@ func (mask IPMask) String() string {
}
case 16:
n := simpleMaskLength(mask)
if n >= 0 {
return itod(uint(n))
if n >= 12*8 {
return itod(uint(n - 12*8))
}
}
return IP(mask).String()