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net/netip: export Prefix.Compare, fix ordering

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Fixes #61642

Co-authored-by: David Anderson <dave@natulte.net>
Change-Id: I54795763bdc5f62da469c2ae20618c36b64396f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/700355
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
This commit is contained in:
database64128 2025-09-02 15:44:42 +08:00 • committed by Gopher Robot
parent 731e546166
commit e8f9127d1f
5 changed files with 76 additions and 11 deletions
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1
api/next/61642.txt Normal file
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@ -0,0 +1 @@
pkg net/netip, method (Prefix) Compare(Prefix) int #61642

1
doc/next/6-stdlib/99-minor/net/netip/61642.md Normal file
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@ -0,0 +1 @@
The new [Prefix.Compare] method compares two prefixes.

2
src/net/netip/export_test.go
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@ -34,5 +34,3 @@ var TestAppendToMarshal = testAppendToMarshal
func (a Addr) IsZero() bool { return a.isZero() }
func (p Prefix) IsZero() bool { return p.isZero() }
func (p Prefix) Compare(p2 Prefix) int { return p.compare(p2) }

18
src/net/netip/netip.go
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@ -1330,21 +1330,23 @@ func (p Prefix) isZero() bool { return p == Prefix{} }
// IsSingleIP reports whether p contains exactly one IP.
func (p Prefix) IsSingleIP() bool { return p.IsValid() && p.Bits() == p.ip.BitLen() }
// compare returns an integer comparing two prefixes.
// Compare returns an integer comparing two prefixes.
// The result will be 0 if p == p2, -1 if p < p2, and +1 if p > p2.
// Prefixes sort first by validity (invalid before valid), then
// address family (IPv4 before IPv6), then prefix length, then
// address.
//
// Unexported for Go 1.22 because we may want to compare by p.Addr first.
// See post-acceptance discussion on go.dev/issue/61642.
func (p Prefix) compare(p2 Prefix) int {
if c := cmp.Compare(p.Addr().BitLen(), p2.Addr().BitLen()); c != 0 {
// address family (IPv4 before IPv6), then masked prefix address, then
// prefix length, then unmasked address.
func (p Prefix) Compare(p2 Prefix) int {
// Aside from sorting based on the masked address, this use of
// Addr.Compare also enforces the valid vs. invalid and address
// family ordering for the prefix.
if c := p.Masked().Addr().Compare(p2.Masked().Addr()); c != 0 {
return c
}
if c := cmp.Compare(p.Bits(), p2.Bits()); c != 0 {
return c
}
return p.Addr().Compare(p2.Addr())
}

65
src/net/netip/netip_test.go
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@ -1123,6 +1123,9 @@ func TestPrefixCompare(t *testing.T) {
{mustPrefix("fe80::/48"), mustPrefix("fe80::/64"), -1},
{mustPrefix("1.2.3.0/24"), mustPrefix("fe80::/8"), -1},
{mustPrefix("1.2.3.0/24"), mustPrefix("1.2.3.4/24"), -1},
{mustPrefix("1.2.3.0/24"), mustPrefix("1.2.3.0/28"), -1},
}
for _, tt := range tests {
got := tt.a.Compare(tt.b)
@ -1148,10 +1151,70 @@ func TestPrefixCompare(t *testing.T) {
Prefix{},
mustPrefix("fe80::/48"),
mustPrefix("1.2.0.0/24"),
mustPrefix("1.2.3.4/24"),
mustPrefix("1.2.3.0/28"),
}
slices.SortFunc(values, Prefix.Compare)
got := fmt.Sprintf("%s", values)
want := `[invalid Prefix 1.2.0.0/16 1.2.0.0/24 1.2.3.0/24 fe80::/48 fe80::/64 fe90::/64]`
want := `[invalid Prefix 1.2.0.0/16 1.2.0.0/24 1.2.3.0/24 1.2.3.4/24 1.2.3.0/28 fe80::/48 fe80::/64 fe90::/64]`
if got != want {
t.Errorf("unexpected sort\n got: %s\nwant: %s\n", got, want)
}
// Lists from
// https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml and
// https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml,
// to verify that the sort order matches IANA's conventional
// ordering.
values = []Prefix{
mustPrefix("0.0.0.0/8"),
mustPrefix("127.0.0.0/8"),
mustPrefix("10.0.0.0/8"),
mustPrefix("203.0.113.0/24"),
mustPrefix("169.254.0.0/16"),
mustPrefix("192.0.0.0/24"),
mustPrefix("240.0.0.0/4"),
mustPrefix("192.0.2.0/24"),
mustPrefix("192.0.0.170/32"),
mustPrefix("198.18.0.0/15"),
mustPrefix("192.0.0.8/32"),
mustPrefix("0.0.0.0/32"),
mustPrefix("192.0.0.9/32"),
mustPrefix("198.51.100.0/24"),
mustPrefix("192.168.0.0/16"),
mustPrefix("192.0.0.10/32"),
mustPrefix("192.175.48.0/24"),
mustPrefix("192.52.193.0/24"),
mustPrefix("100.64.0.0/10"),
mustPrefix("255.255.255.255/32"),
mustPrefix("192.31.196.0/24"),
mustPrefix("172.16.0.0/12"),
mustPrefix("192.0.0.0/29"),
mustPrefix("192.88.99.0/24"),
mustPrefix("fec0::/10"),
mustPrefix("6000::/3"),
mustPrefix("fe00::/9"),
mustPrefix("8000::/3"),
mustPrefix("0000::/8"),
mustPrefix("0400::/6"),
mustPrefix("f800::/6"),
mustPrefix("e000::/4"),
mustPrefix("ff00::/8"),
mustPrefix("a000::/3"),
mustPrefix("fc00::/7"),
mustPrefix("1000::/4"),
mustPrefix("0800::/5"),
mustPrefix("4000::/3"),
mustPrefix("0100::/8"),
mustPrefix("c000::/3"),
mustPrefix("fe80::/10"),
mustPrefix("0200::/7"),
mustPrefix("f000::/5"),
mustPrefix("2000::/3"),
}
slices.SortFunc(values, func(a, b Prefix) int { return a.Compare(b) })
got = fmt.Sprintf("%s", values)
want = `[0.0.0.0/8 0.0.0.0/32 10.0.0.0/8 100.64.0.0/10 127.0.0.0/8 169.254.0.0/16 172.16.0.0/12 192.0.0.0/24 192.0.0.0/29 192.0.0.8/32 192.0.0.9/32 192.0.0.10/32 192.0.0.170/32 192.0.2.0/24 192.31.196.0/24 192.52.193.0/24 192.88.99.0/24 192.168.0.0/16 192.175.48.0/24 198.18.0.0/15 198.51.100.0/24 203.0.113.0/24 240.0.0.0/4 255.255.255.255/32 ::/8 100::/8 200::/7 400::/6 800::/5 1000::/4 2000::/3 4000::/3 6000::/3 8000::/3 a000::/3 c000::/3 e000::/4 f000::/5 f800::/6 fc00::/7 fe00::/9 fe80::/10 fec0::/10 ff00::/8]`
if got != want {
t.Errorf("unexpected sort\n got: %s\nwant: %s\n", got, want)
}