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fix #527
Use []uint32 in bitset instead of []uint64, because it's harder to guarantee 64-bit alignment of []uint64 than I had realized: https://go101.org/article/memory-layout.html
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@ -204,8 +204,8 @@ package caps
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numCapabs = len(CAPDEFS)
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bitsetLen = numCapabs // 64
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if numCapabs % 64 > 0:
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bitsetLen = numCapabs // 32
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if numCapabs % 32 > 0:
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bitsetLen += 1
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print ("""
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const (
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@ -11,7 +11,7 @@ import (
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)
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// Set holds a set of enabled capabilities.
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type Set [bitsetLen]uint64
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type Set [bitsetLen]uint32
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// NewSet returns a new Set, with the given capabilities enabled.
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func NewSet(capabs ...Capability) *Set {
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@ -7,7 +7,6 @@ package modes
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import (
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"strings"
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"sync/atomic"
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"github.com/oragono/oragono/irc/utils"
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)
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@ -318,12 +317,13 @@ func ParseChannelModeChanges(params ...string) (ModeChanges, map[rune]bool) {
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}
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// ModeSet holds a set of modes.
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type ModeSet [1]uint64
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type ModeSet [2]uint32
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// valid modes go from 65 ('A') to 122 ('z'), making at most 58 possible values;
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// subtract 65 from the mode value and use that bit of the uint64 to represent it
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// subtract 65 from the mode value and use that bit of the uint32 to represent it
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const (
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minMode = 65 // 'A'
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maxMode = 122 // 'z'
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)
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// returns a pointer to a new ModeSet
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@ -357,11 +357,10 @@ func (set *ModeSet) AllModes() (result []Mode) {
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return
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}
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block := atomic.LoadUint64(&set[0])
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var i uint
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for i = 0; i < 64; i++ {
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if block&(1<<i) != 0 {
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result = append(result, Mode(minMode+i))
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var i Mode
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for i = minMode; i <= maxMode; i++ {
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if set.HasMode(i) {
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result = append(result, i)
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}
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}
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return
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@ -5,28 +5,28 @@ package utils
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import "sync/atomic"
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// Library functions for lock-free bitsets, typically (constant-sized) arrays of uint64.
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// Library functions for lock-free bitsets, typically (constant-sized) arrays of uint32.
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// For examples of use, see caps.Set and modes.ModeSet; the array has to be converted to a
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// slice to use these functions.
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// BitsetGet returns whether a given bit of the bitset is set.
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func BitsetGet(set []uint64, position uint) bool {
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idx := position / 64
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bit := position % 64
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block := atomic.LoadUint64(&set[idx])
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func BitsetGet(set []uint32, position uint) bool {
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idx := position / 32
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bit := position % 32
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block := atomic.LoadUint32(&set[idx])
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return (block & (1 << bit)) != 0
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}
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// BitsetSet sets a given bit of the bitset to 0 or 1, returning whether it changed.
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func BitsetSet(set []uint64, position uint, on bool) (changed bool) {
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idx := position / 64
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bit := position % 64
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func BitsetSet(set []uint32, position uint, on bool) (changed bool) {
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idx := position / 32
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bit := position % 32
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addr := &set[idx]
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var mask uint64
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var mask uint32
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mask = 1 << bit
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for {
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current := atomic.LoadUint64(addr)
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var desired uint64
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current := atomic.LoadUint32(addr)
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var desired uint32
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if on {
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desired = current | mask
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} else {
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@ -34,7 +34,7 @@ func BitsetSet(set []uint64, position uint, on bool) (changed bool) {
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}
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if current == desired {
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return false
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} else if atomic.CompareAndSwapUint64(addr, current, desired) {
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} else if atomic.CompareAndSwapUint32(addr, current, desired) {
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return true
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}
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}
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@ -44,9 +44,9 @@ func BitsetSet(set []uint64, position uint, on bool) (changed bool) {
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// This has false positives under concurrent modification (i.e., it can return true
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// even though w.r.t. the sequence of atomic modifications, there was no point at
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// which the bitset was completely empty), but that's not how we're using this method.
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func BitsetEmpty(set []uint64) (empty bool) {
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func BitsetEmpty(set []uint32) (empty bool) {
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for i := 0; i < len(set); i++ {
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if atomic.LoadUint64(&set[i]) != 0 {
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if atomic.LoadUint32(&set[i]) != 0 {
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return false
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}
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}
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@ -56,14 +56,14 @@ func BitsetEmpty(set []uint64) (empty bool) {
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// BitsetUnion modifies `set` to be the union of `set` and `other`.
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// This has race conditions in that we don't necessarily get a single
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// consistent view of `other` across word boundaries.
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func BitsetUnion(set []uint64, other []uint64) {
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func BitsetUnion(set []uint32, other []uint32) {
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for i := 0; i < len(set); i++ {
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for {
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ourAddr := &set[i]
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ourBlock := atomic.LoadUint64(ourAddr)
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otherBlock := atomic.LoadUint64(&other[i])
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ourBlock := atomic.LoadUint32(ourAddr)
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otherBlock := atomic.LoadUint32(&other[i])
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newBlock := ourBlock | otherBlock
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if atomic.CompareAndSwapUint64(ourAddr, ourBlock, newBlock) {
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if atomic.CompareAndSwapUint32(ourAddr, ourBlock, newBlock) {
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break
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}
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}
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@ -72,23 +72,23 @@ func BitsetUnion(set []uint64, other []uint64) {
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// BitsetCopy copies the contents of `other` over `set`.
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// Similar caveats about race conditions as with `BitsetUnion` apply.
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func BitsetCopy(set []uint64, other []uint64) {
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func BitsetCopy(set []uint32, other []uint32) {
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for i := 0; i < len(set); i++ {
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data := atomic.LoadUint64(&other[i])
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atomic.StoreUint64(&set[i], data)
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data := atomic.LoadUint32(&other[i])
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atomic.StoreUint32(&set[i], data)
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}
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}
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// BitsetSubtract modifies `set` to subtract the contents of `other`.
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// Similar caveats about race conditions as with `BitsetUnion` apply.
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func BitsetSubtract(set []uint64, other []uint64) {
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func BitsetSubtract(set []uint32, other []uint32) {
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for i := 0; i < len(set); i++ {
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for {
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ourAddr := &set[i]
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ourBlock := atomic.LoadUint64(ourAddr)
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otherBlock := atomic.LoadUint64(&other[i])
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ourBlock := atomic.LoadUint32(ourAddr)
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otherBlock := atomic.LoadUint32(&other[i])
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newBlock := ourBlock & (^otherBlock)
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if atomic.CompareAndSwapUint64(ourAddr, ourBlock, newBlock) {
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if atomic.CompareAndSwapUint32(ourAddr, ourBlock, newBlock) {
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break
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}
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}
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@ -5,7 +5,7 @@ package utils
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import "testing"
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type testBitset [2]uint64
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type testBitset [4]uint32
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func TestSets(t *testing.T) {
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var t1 testBitset
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