device: remove code using unsafe

There is no performance impact.

name                             old time/op  new time/op  delta
TrieIPv4Peers100Addresses1000-8  78.6ns ± 1%  79.4ns ± 3%    ~     (p=0.604 n=10+9)
TrieIPv4Peers10Addresses10-8     29.1ns ± 2%  28.8ns ± 1%  -1.12%  (p=0.014 n=10+9)
TrieIPv6Peers100Addresses1000-8  78.9ns ± 1%  78.6ns ± 1%    ~     (p=0.492 n=10+10)
TrieIPv6Peers10Addresses10-8     29.3ns ± 2%  28.6ns ± 2%  -2.16%  (p=0.000 n=10+10)

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/device/allowedips.go b/device/allowedips.go
index 7a0b2756037ad2b40cc9257577dc8f0e59bcddfb..06c54656f61457aa6cad2de5db26ed2a20c61429 100644 (file)
--- a/device/allowedips.go
+++ b/device/allowedips.go
@@ -7,6 +7,7 @@ package device
 
 import (
        "container/list"
+       "encoding/binary"
        "errors"
        "math/bits"
        "net"
@@ -32,45 +33,24 @@ type trieEntry struct {
        perPeerElem *list.Element
 }
 
-func isLittleEndian() bool {
-       one := uint32(1)
-       return *(*byte)(unsafe.Pointer(&one)) != 0
-}
-
-func swapU32(i uint32) uint32 {
-       if !isLittleEndian() {
-               return i
-       }
-
-       return bits.ReverseBytes32(i)
-}
-
-func swapU64(i uint64) uint64 {
-       if !isLittleEndian() {
-               return i
-       }
-
-       return bits.ReverseBytes64(i)
-}
-
 func commonBits(ip1, ip2 []byte) uint8 {
        size := len(ip1)
        if size == net.IPv4len {
-               a := (*uint32)(unsafe.Pointer(&ip1[0]))
-               b := (*uint32)(unsafe.Pointer(&ip2[0]))
-               x := *a ^ *b
-               return uint8(bits.LeadingZeros32(swapU32(x)))
+               a := binary.BigEndian.Uint32(ip1)
+               b := binary.BigEndian.Uint32(ip2)
+               x := a ^ b
+               return uint8(bits.LeadingZeros32(x))
        } else if size == net.IPv6len {
-               a := (*uint64)(unsafe.Pointer(&ip1[0]))
-               b := (*uint64)(unsafe.Pointer(&ip2[0]))
-               x := *a ^ *b
+               a := binary.BigEndian.Uint64(ip1)
+               b := binary.BigEndian.Uint64(ip2)
+               x := a ^ b
                if x != 0 {
-                       return uint8(bits.LeadingZeros64(swapU64(x)))
+                       return uint8(bits.LeadingZeros64(x))
                }
-               a = (*uint64)(unsafe.Pointer(&ip1[8]))
-               b = (*uint64)(unsafe.Pointer(&ip2[8]))
-               x = *a ^ *b
-               return 64 + uint8(bits.LeadingZeros64(swapU64(x)))
+               a = binary.BigEndian.Uint64(ip1[8:])
+               b = binary.BigEndian.Uint64(ip2[8:])
+               x = a ^ b
+               return 64 + uint8(bits.LeadingZeros64(x))
        } else {
                panic("Wrong size bit string")
        }