83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
// Copyright 2020 The Inet.Af AUTHORS. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package netaddr
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import "math/bits"
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// uint128 represents a uint128 using two uint64s.
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//
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// When the methods below mention a bit number, bit 0 is the most
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// significant bit (in hi) and bit 127 is the lowest (lo&1).
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type uint128 struct {
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hi uint64
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lo uint64
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}
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// isZero reports whether u == 0.
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//
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// It's faster than u == (uint128{}) because the compiler (as of Go
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// 1.15/1.16b1) doesn't do this trick and instead inserts a branch in
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// its eq alg's generated code.
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func (u uint128) isZero() bool { return u.hi|u.lo == 0 }
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// and returns the bitwise AND of u and m (u&m).
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func (u uint128) and(m uint128) uint128 {
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return uint128{u.hi & m.hi, u.lo & m.lo}
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}
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// xor returns the bitwise XOR of u and m (u^m).
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func (u uint128) xor(m uint128) uint128 {
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return uint128{u.hi ^ m.hi, u.lo ^ m.lo}
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}
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// or returns the bitwise OR of u and m (u|m).
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func (u uint128) or(m uint128) uint128 {
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return uint128{u.hi | m.hi, u.lo | m.lo}
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}
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// not returns the bitwise NOT of u.
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func (u uint128) not() uint128 {
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return uint128{^u.hi, ^u.lo}
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}
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// subOne returns u - 1.
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func (u uint128) subOne() uint128 {
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lo, borrow := bits.Sub64(u.lo, 1, 0)
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return uint128{u.hi - borrow, lo}
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}
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// addOne returns u + 1.
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func (u uint128) addOne() uint128 {
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lo, carry := bits.Add64(u.lo, 1, 0)
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return uint128{u.hi + carry, lo}
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}
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func u64CommonPrefixLen(a, b uint64) uint8 {
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return uint8(bits.LeadingZeros64(a ^ b))
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}
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func (u uint128) commonPrefixLen(v uint128) (n uint8) {
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if n = u64CommonPrefixLen(u.hi, v.hi); n == 64 {
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n += u64CommonPrefixLen(u.lo, v.lo)
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}
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return
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}
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func (u *uint128) halves() [2]*uint64 {
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return [2]*uint64{&u.hi, &u.lo}
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}
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// bitsSetFrom returns a copy of u with the given bit
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// and all subsequent ones set.
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func (u uint128) bitsSetFrom(bit uint8) uint128 {
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return u.or(mask6[bit].not())
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}
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// bitsClearedFrom returns a copy of u with the given bit
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// and all subsequent ones cleared.
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func (u uint128) bitsClearedFrom(bit uint8) uint128 {
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return u.and(mask6[bit])
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}
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