Merge pull request #277 from slingamn/bitset.3

implement #263

Makefile

@@ -1,5 +1,7 @@
 .PHONY: all build
 
+capdef_file = ./irc/caps/defs.go
+
 all: build
 
 build:
@@ -8,11 +10,16 @@ build:
 buildrelease:
 	goreleaser --skip-publish --rm-dist
 
+capdefs:
+	python3 ./gencapdefs.py > ${capdef_file}
+
 deps:
 	git submodule update --init
 
 test:
+	python3 ./gencapdefs.py | diff - ${capdef_file}
 	cd irc && go test . && go vet .
+	cd irc/caps && go test . && go vet .
 	cd irc/isupport && go test . && go vet .
 	cd irc/modes && go test . && go vet .
 	cd irc/utils && go test . && go vet .

gencapdefs.py

@@ -0,0 +1,200 @@
+#!/usr/bin/env python3
+
+"""
+Updates the capability definitions at irc/caps/defs.go
+
+To add a capability, add it to the CAPDEFS list below,
+then run `make capdefs` from the project root.
+"""
+
+import io
+import subprocess
+import sys
+from collections import namedtuple
+
+CapDef = namedtuple("CapDef", ['identifier', 'name', 'url', 'standard'])
+
+CAPDEFS = [
+    CapDef(
+        identifier="AccountNotify",
+        name="account-notify",
+        url="https://ircv3.net/specs/extensions/account-notify-3.1.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="AccountTag",
+        name="account-tag",
+        url="https://ircv3.net/specs/extensions/account-tag-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="AwayNotify",
+        name="away-notify",
+        url="https://ircv3.net/specs/extensions/away-notify-3.1.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="Batch",
+        name="batch",
+        url="https://ircv3.net/specs/extensions/batch-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="CapNotify",
+        name="cap-notify",
+        url="https://ircv3.net/specs/extensions/cap-notify-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="ChgHost",
+        name="chghost",
+        url="https://ircv3.net/specs/extensions/chghost-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="EchoMessage",
+        name="echo-message",
+        url="https://ircv3.net/specs/extensions/echo-message-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="ExtendedJoin",
+        name="extended-join",
+        url="https://ircv3.net/specs/extensions/extended-join-3.1.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="InviteNotify",
+        name="invite-notify",
+        url="https://ircv3.net/specs/extensions/invite-notify-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="LabeledResponse",
+        name="draft/labeled-response",
+        url="https://ircv3.net/specs/extensions/labeled-response.html",
+        standard="draft IRCv3",
+    ),
+    CapDef(
+        identifier="Languages",
+        name="draft/languages",
+        url="https://gist.github.com/DanielOaks/8126122f74b26012a3de37db80e4e0c6",
+        standard="proposed IRCv3",
+    ),
+    CapDef(
+        identifier="MaxLine",
+        name="oragono.io/maxline",
+        url="https://oragono.io/maxline",
+        standard="Oragono-specific",
+    ),
+    CapDef(
+        identifier="MessageTags",
+        name="draft/message-tags-0.2",
+        url="https://ircv3.net/specs/core/message-tags-3.3.html",
+        standard="draft IRCv3",
+    ),
+    CapDef(
+        identifier="MultiPrefix",
+        name="multi-prefix",
+        url="https://ircv3.net/specs/extensions/multi-prefix-3.1.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="Rename",
+        name="draft/rename",
+        url="https://github.com/SaberUK/ircv3-specifications/blob/rename/extensions/rename.md",
+        standard="proposed IRCv3",
+    ),
+    CapDef(
+        identifier="Resume",
+        name="draft/resume",
+        url="https://github.com/DanielOaks/ircv3-specifications/blob/master+resume/extensions/resume.md",
+        standard="proposed IRCv3",
+    ),
+    CapDef(
+        identifier="SASL",
+        name="sasl",
+        url="https://ircv3.net/specs/extensions/sasl-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="ServerTime",
+        name="server-time",
+        url="https://ircv3.net/specs/extensions/server-time-3.2.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="STS",
+        name="sts",
+        url="https://ircv3.net/specs/extensions/sts.html",
+        standard="IRCv3",
+    ),
+    CapDef(
+        identifier="UserhostInNames",
+        name="userhost-in-names",
+        url="https://ircv3.net/specs/extensions/userhost-in-names-3.2.html",
+        standard="IRCv3",
+    ),
+]
+
+def validate_defs():
+    numCaps = len(CAPDEFS)
+    numNames = len(set(capdef.name for capdef in CAPDEFS))
+    if numCaps != numNames:
+        raise Exception("defs must have unique names, but found duplicates")
+    numIdentifiers = len(set(capdef.identifier for capdef in CAPDEFS))
+    if numCaps != numIdentifiers:
+        raise Exception("defs must have unique identifiers, but found duplicates")
+
+def main():
+    validate_defs()
+    output = io.StringIO()
+    print("""
+package caps
+
+/*
+	WARNING: this file is autogenerated by `make capdefs`
+	DO NOT EDIT MANUALLY.
+*/
+
+
+    """, file=output)
+
+
+    numCapabs = len(CAPDEFS)
+    bitsetLen = numCapabs // 64
+    if numCapabs % 64 > 0:
+        bitsetLen += 1
+    print ("""
+const (
+	// number of recognized capabilities:
+	numCapabs = %d
+	// length of the uint64 array that represents the bitset:
+	bitsetLen = %d
+)
+    """ % (numCapabs, bitsetLen), file=output)
+
+    print("const (", file=output)
+    for capdef in CAPDEFS:
+        print("// %s is the %s capability named \"%s\":" % (capdef.identifier, capdef.standard, capdef.name), file=output)
+        print("// %s" % (capdef.url,), file=output)
+        print("%s Capability = iota" % (capdef.identifier,), file=output)
+        print(file=output)
+    print(")", file=output)
+
+    print("// `capabilityNames[capab]` is the string name of the capability `capab`", file=output)
+    print("""var ( capabilityNames = [numCapabs]string{""", file=output)
+    for capdef in CAPDEFS:
+        print("\"%s\"," % (capdef.name,), file=output)
+    print("})", file=output)
+
+    # run the generated code through `gofmt -s`, which will print it to stdout
+    gofmt = subprocess.Popen(['gofmt', '-s'], stdin=subprocess.PIPE)
+    gofmt.communicate(input=output.getvalue().encode('utf-8'))
+    if gofmt.poll() != 0:
+        print(output.getvalue())
+        raise Exception("gofmt failed")
+    return 0
+
+if __name__ == '__main__':
+    sys.exit(main())

irc/caps/constants.go

@@ -3,58 +3,30 @@
 
 package caps
 
+import "errors"
+
 // Capability represents an optional feature that a client may request from the server.
-type Capability string
+type Capability uint
 
-const (
+// actual capability definitions appear in defs.go
-	// LabelTagName is the tag name used for the labeled-response spec.
-	LabelTagName = "draft/label"
 
-	// AccountNotify is this IRCv3 capability: http://ircv3.net/specs/extensions/account-notify-3.1.html
+var (
-	AccountNotify Capability = "account-notify"
+	nameToCapability map[string]Capability
-	// AccountTag is this IRCv3 capability: http://ircv3.net/specs/extensions/account-tag-3.2.html
+
-	AccountTag Capability = "account-tag"
+	NoSuchCap = errors.New("Unsupported capability name")
-	// AwayNotify is this IRCv3 capability: http://ircv3.net/specs/extensions/away-notify-3.1.html
-	AwayNotify Capability = "away-notify"
-	// Batch is this IRCv3 capability: http://ircv3.net/specs/extensions/batch-3.2.html
-	Batch Capability = "batch"
-	// CapNotify is this IRCv3 capability: http://ircv3.net/specs/extensions/cap-notify-3.2.html
-	CapNotify Capability = "cap-notify"
-	// ChgHost is this IRCv3 capability: http://ircv3.net/specs/extensions/chghost-3.2.html
-	ChgHost Capability = "chghost"
-	// EchoMessage is this IRCv3 capability: http://ircv3.net/specs/extensions/echo-message-3.2.html
-	EchoMessage Capability = "echo-message"
-	// ExtendedJoin is this IRCv3 capability: http://ircv3.net/specs/extensions/extended-join-3.1.html
-	ExtendedJoin Capability = "extended-join"
-	// InviteNotify is this IRCv3 capability: http://ircv3.net/specs/extensions/invite-notify-3.2.html
-	InviteNotify Capability = "invite-notify"
-	// LabeledResponse is this draft IRCv3 capability: http://ircv3.net/specs/extensions/labeled-response.html
-	LabeledResponse Capability = "draft/labeled-response"
-	// Languages is this proposed IRCv3 capability: https://gist.github.com/DanielOaks/8126122f74b26012a3de37db80e4e0c6
-	Languages Capability = "draft/languages"
-	// MaxLine is this capability: https://oragono.io/maxline
-	MaxLine Capability = "oragono.io/maxline"
-	// MessageTags is this draft IRCv3 capability: http://ircv3.net/specs/core/message-tags-3.3.html
-	MessageTags Capability = "draft/message-tags-0.2"
-	// MultiPrefix is this IRCv3 capability: http://ircv3.net/specs/extensions/multi-prefix-3.1.html
-	MultiPrefix Capability = "multi-prefix"
-	// Rename is this proposed capability: https://github.com/SaberUK/ircv3-specifications/blob/rename/extensions/rename.md
-	Rename Capability = "draft/rename"
-	// Resume is this proposed capability: https://github.com/DanielOaks/ircv3-specifications/blob/master+resume/extensions/resume.md
-	Resume Capability = "draft/resume"
-	// SASL is this IRCv3 capability: http://ircv3.net/specs/extensions/sasl-3.2.html
-	SASL Capability = "sasl"
-	// ServerTime is this IRCv3 capability: http://ircv3.net/specs/extensions/server-time-3.2.html
-	ServerTime Capability = "server-time"
-	// STS is this IRCv3 capability: http://ircv3.net/specs/extensions/sts.html
-	STS Capability = "sts"
-	// UserhostInNames is this IRCv3 capability: http://ircv3.net/specs/extensions/userhost-in-names-3.2.html
-	UserhostInNames Capability = "userhost-in-names"
 )
 
 // Name returns the name of the given capability.
 func (capability Capability) Name() string {
-	return string(capability)
+	return capabilityNames[capability]
+}
+
+func NameToCapability(name string) (result Capability, err error) {
+	result, found := nameToCapability[name]
+	if !found {
+		err = NoSuchCap
+	}
+	return
 }
 
 // Version is used to select which max version of CAP the client supports.
@@ -78,3 +50,16 @@ const (
 	// NegotiatedState means CAP negotiation has been successfully ended and reg should complete.
 	NegotiatedState State = iota
 )
+
+const (
+	// LabelTagName is the tag name used for the labeled-response spec.
+	// https://ircv3.net/specs/extensions/labeled-response.html
+	LabelTagName = "draft/label"
+)
+
+func init() {
+	nameToCapability = make(map[string]Capability)
+	for capab, name := range capabilityNames {
+		nameToCapability[name] = Capability(capab)
+	}
+}

irc/caps/defs.go

@@ -0,0 +1,121 @@
+package caps
+
+/*
+	WARNING: this file is autogenerated by `make capdefs`
+	DO NOT EDIT MANUALLY.
+*/
+
+const (
+	// number of recognized capabilities:
+	numCapabs = 20
+	// length of the uint64 array that represents the bitset:
+	bitsetLen = 1
+)
+
+const (
+	// AccountNotify is the IRCv3 capability named "account-notify":
+	// https://ircv3.net/specs/extensions/account-notify-3.1.html
+	AccountNotify Capability = iota
+
+	// AccountTag is the IRCv3 capability named "account-tag":
+	// https://ircv3.net/specs/extensions/account-tag-3.2.html
+	AccountTag Capability = iota
+
+	// AwayNotify is the IRCv3 capability named "away-notify":
+	// https://ircv3.net/specs/extensions/away-notify-3.1.html
+	AwayNotify Capability = iota
+
+	// Batch is the IRCv3 capability named "batch":
+	// https://ircv3.net/specs/extensions/batch-3.2.html
+	Batch Capability = iota
+
+	// CapNotify is the IRCv3 capability named "cap-notify":
+	// https://ircv3.net/specs/extensions/cap-notify-3.2.html
+	CapNotify Capability = iota
+
+	// ChgHost is the IRCv3 capability named "chghost":
+	// https://ircv3.net/specs/extensions/chghost-3.2.html
+	ChgHost Capability = iota
+
+	// EchoMessage is the IRCv3 capability named "echo-message":
+	// https://ircv3.net/specs/extensions/echo-message-3.2.html
+	EchoMessage Capability = iota
+
+	// ExtendedJoin is the IRCv3 capability named "extended-join":
+	// https://ircv3.net/specs/extensions/extended-join-3.1.html
+	ExtendedJoin Capability = iota
+
+	// InviteNotify is the IRCv3 capability named "invite-notify":
+	// https://ircv3.net/specs/extensions/invite-notify-3.2.html
+	InviteNotify Capability = iota
+
+	// LabeledResponse is the draft IRCv3 capability named "draft/labeled-response":
+	// https://ircv3.net/specs/extensions/labeled-response.html
+	LabeledResponse Capability = iota
+
+	// Languages is the proposed IRCv3 capability named "draft/languages":
+	// https://gist.github.com/DanielOaks/8126122f74b26012a3de37db80e4e0c6
+	Languages Capability = iota
+
+	// MaxLine is the Oragono-specific capability named "oragono.io/maxline":
+	// https://oragono.io/maxline
+	MaxLine Capability = iota
+
+	// MessageTags is the draft IRCv3 capability named "draft/message-tags-0.2":
+	// https://ircv3.net/specs/core/message-tags-3.3.html
+	MessageTags Capability = iota
+
+	// MultiPrefix is the IRCv3 capability named "multi-prefix":
+	// https://ircv3.net/specs/extensions/multi-prefix-3.1.html
+	MultiPrefix Capability = iota
+
+	// Rename is the proposed IRCv3 capability named "draft/rename":
+	// https://github.com/SaberUK/ircv3-specifications/blob/rename/extensions/rename.md
+	Rename Capability = iota
+
+	// Resume is the proposed IRCv3 capability named "draft/resume":
+	// https://github.com/DanielOaks/ircv3-specifications/blob/master+resume/extensions/resume.md
+	Resume Capability = iota
+
+	// SASL is the IRCv3 capability named "sasl":
+	// https://ircv3.net/specs/extensions/sasl-3.2.html
+	SASL Capability = iota
+
+	// ServerTime is the IRCv3 capability named "server-time":
+	// https://ircv3.net/specs/extensions/server-time-3.2.html
+	ServerTime Capability = iota
+
+	// STS is the IRCv3 capability named "sts":
+	// https://ircv3.net/specs/extensions/sts.html
+	STS Capability = iota
+
+	// UserhostInNames is the IRCv3 capability named "userhost-in-names":
+	// https://ircv3.net/specs/extensions/userhost-in-names-3.2.html
+	UserhostInNames Capability = iota
+)
+
+// `capabilityNames[capab]` is the string name of the capability `capab`
+var (
+	capabilityNames = [numCapabs]string{
+		"account-notify",
+		"account-tag",
+		"away-notify",
+		"batch",
+		"cap-notify",
+		"chghost",
+		"echo-message",
+		"extended-join",
+		"invite-notify",
+		"draft/labeled-response",
+		"draft/languages",
+		"oragono.io/maxline",
+		"draft/message-tags-0.2",
+		"multi-prefix",
+		"draft/rename",
+		"draft/resume",
+		"sasl",
+		"server-time",
+		"sts",
+		"userhost-in-names",
+	}
+)

irc/caps/set.go

@@ -6,43 +6,34 @@ package caps
 import (
 	"sort"
 	"strings"
-	"sync"
+
+	"github.com/oragono/oragono/irc/utils"
 )
 
 // Set holds a set of enabled capabilities.
-type Set struct {
+type Set [bitsetLen]uint64
-	sync.RWMutex
-	// capabilities holds the capabilities this manager has.
-	capabilities map[Capability]bool
-}
 
 // NewSet returns a new Set, with the given capabilities enabled.
 func NewSet(capabs ...Capability) *Set {
-	newSet := Set{
+	var newSet Set
-		capabilities: make(map[Capability]bool),
+	utils.BitsetInitialize(newSet[:])
-	}
 	newSet.Enable(capabs...)
-
 	return &newSet
 }
 
 // Enable enables the given capabilities.
 func (s *Set) Enable(capabs ...Capability) {
-	s.Lock()
+	asSlice := s[:]
-	defer s.Unlock()
-
 	for _, capab := range capabs {
-		s.capabilities[capab] = true
+		utils.BitsetSet(asSlice, uint(capab), true)
 	}
 }
 
 // Disable disables the given capabilities.
 func (s *Set) Disable(capabs ...Capability) {
-	s.Lock()
+	asSlice := s[:]
-	defer s.Unlock()
-
 	for _, capab := range capabs {
-		delete(s.capabilities, capab)
+		utils.BitsetSet(asSlice, uint(capab), false)
 	}
 }
 
@@ -58,51 +49,35 @@ func (s *Set) Remove(capabs ...Capability) {
 	s.Disable(capabs...)
 }
 
-// Has returns true if this set has the given capabilities.
+// Has returns true if this set has the given capability.
-func (s *Set) Has(caps ...Capability) bool {
+func (s *Set) Has(capab Capability) bool {
-	s.RLock()
+	return utils.BitsetGet(s[:], uint(capab))
-	defer s.RUnlock()
-
-	for _, cap := range caps {
-		if !s.capabilities[cap] {
-			return false
-		}
-	}
-	return true
 }
 
-// List return a list of our enabled capabilities.
+// Union adds all the capabilities of another set to this set.
-func (s *Set) List() []Capability {
+func (s *Set) Union(other *Set) {
-	s.RLock()
+	utils.BitsetUnion(s[:], other[:])
-	defer s.RUnlock()
-
-	var allCaps []Capability
-	for capab := range s.capabilities {
-		allCaps = append(allCaps, capab)
-	}
-
-	return allCaps
 }
 
-// Count returns how many enabled caps this set has.
+// Empty returns whether the set is empty.
-func (s *Set) Count() int {
+func (s *Set) Empty() bool {
-	s.RLock()
+	return utils.BitsetEmpty(s[:])
-	defer s.RUnlock()
-
-	return len(s.capabilities)
 }
 
 // String returns all of our enabled capabilities as a string.
 func (s *Set) String(version Version, values *Values) string {
-	s.RLock()
-	defer s.RUnlock()
-
 	var strs sort.StringSlice
 
-	for capability := range s.capabilities {
+	var capab Capability
-		capString := capability.Name()
+	asSlice := s[:]
+	for capab = 0; capab < numCapabs; capab++ {
+		// skip any capabilities that are not enabled
+		if !utils.BitsetGet(asSlice, uint(capab)) {
+			continue
+		}
+		capString := capab.Name()
 		if version == Cap302 {
-			val, exists := values.Get(capability)
+			val, exists := values.Get(capab)
 			if exists {
 				capString += "=" + val
 			}

irc/caps/set_test.go

@@ -11,12 +11,12 @@ func TestSets(t *testing.T) {
 
 	s1.Enable(AccountTag, EchoMessage, UserhostInNames)
 
-	if !s1.Has(AccountTag, EchoMessage, UserhostInNames) {
+	if !(s1.Has(AccountTag) && s1.Has(EchoMessage) && s1.Has(UserhostInNames)) {
 		t.Error("Did not have the tags we expected")
 	}
 
-	if s1.Has(AccountTag, EchoMessage, STS, UserhostInNames) {
+	if s1.Has(STS) {
-		t.Error("Has() returned true when we don't have all the given capabilities")
+		t.Error("Has() returned true when we don't have the given capability")
 	}
 
 	s1.Disable(AccountTag)
@@ -25,14 +25,9 @@ func TestSets(t *testing.T) {
 		t.Error("Disable() did not correctly disable the given capability")
 	}
 
-	enabledCaps := make(map[Capability]bool)
+	enabledCaps := NewSet()
-	for _, capab := range s1.List() {
+	enabledCaps.Union(s1)
-		enabledCaps[capab] = true
+	expectedCaps := NewSet(EchoMessage, UserhostInNames)
-	}
-	expectedCaps := map[Capability]bool{
-		EchoMessage:     true,
-		UserhostInNames: true,
-	}
 	if !reflect.DeepEqual(enabledCaps, expectedCaps) {
 		t.Errorf("Enabled and expected capability lists do not match: %v, %v", enabledCaps, expectedCaps)
 	}
@@ -40,16 +35,12 @@ func TestSets(t *testing.T) {
 	// make sure re-enabling doesn't add to the count or something weird like that
 	s1.Enable(EchoMessage)
 
-	if s1.Count() != 2 {
-		t.Error("Count() did not match expected capability count")
-	}
-
 	// make sure add and remove work fine
 	s1.Add(InviteNotify)
 	s1.Remove(EchoMessage)
 
-	if s1.Count() != 2 {
+	if !s1.Has(InviteNotify) || s1.Has(EchoMessage) {
-		t.Error("Count() did not match expected capability count")
+		t.Error("Add/Remove don't work")
 	}
 
 	// test String()
@@ -68,3 +59,24 @@ func TestSets(t *testing.T) {
 		t.Errorf("Generated Cap302 values string [%s] did not match expected values string [%s]", actualCap302ValuesString, expectedCap302ValuesString)
 	}
 }
+
+func BenchmarkSetReads(b *testing.B) {
+	set := NewSet(UserhostInNames, EchoMessage)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		set.Has(UserhostInNames)
+		set.Has(LabeledResponse)
+		set.Has(EchoMessage)
+		set.Has(Rename)
+	}
+}
+
+func BenchmarkSetWrites(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		set := NewSet(UserhostInNames, EchoMessage)
+		set.Add(Rename)
+		set.Add(ExtendedJoin)
+		set.Remove(UserhostInNames)
+		set.Remove(LabeledResponse)
+	}
+}

irc/handlers.go

@@ -442,12 +442,16 @@ func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 	capabilities := caps.NewSet()
 	var capString string
 
+	var badCaps []string
 	if len(msg.Params) > 1 {
 		capString = msg.Params[1]
-		strs := strings.Split(capString, " ")
+		strs := strings.Fields(capString)
 		for _, str := range strs {
-			if len(str) > 0 {
+			capab, err := caps.NameToCapability(str)
-				capabilities.Enable(caps.Capability(str))
+			if err != nil || !SupportedCapabilities.Has(capab) {
+				badCaps = append(badCaps, str)
+			} else {
+				capabilities.Enable(capab)
 			}
 		}
 	}
@@ -475,13 +479,11 @@ func capHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Respo
 		}
 
 		// make sure all capabilities actually exist
-		for _, capability := range capabilities.List() {
+		if len(badCaps) > 0 {
-			if !SupportedCapabilities.Has(capability) {
+			rb.Add(nil, server.name, "CAP", client.nick, "NAK", capString)
-				rb.Add(nil, server.name, "CAP", client.nick, "NAK", capString)
+			return false
-				return false
-			}
 		}
-		client.capabilities.Enable(capabilities.List()...)
+		client.capabilities.Union(capabilities)
 		rb.Add(nil, server.name, "CAP", client.nick, "ACK", capString)
 
 	case "END":

irc/modes/modes.go

@@ -7,7 +7,9 @@ package modes
 
 import (
 	"strings"
-	"sync"
+	"sync/atomic"
+
+	"github.com/oragono/oragono/irc/utils"
 )
 
 var (
@@ -322,42 +324,29 @@ func ParseChannelModeChanges(params ...string) (ModeChanges, map[rune]bool) {
 }
 
 // ModeSet holds a set of modes.
-type ModeSet struct {
+type ModeSet [1]uint64
-	sync.RWMutex // tier 0
+
-	modes        map[Mode]bool
+// valid modes go from 65 ('A') to 122 ('z'), making at most 58 possible values;
-}
+// subtract 65 from the mode value and use that bit of the uint64 to represent it
+const (
+	minMode = 65 // 'A'
+)
 
 // returns a pointer to a new ModeSet
 func NewModeSet() *ModeSet {
-	return &ModeSet{
+	var set ModeSet
-		modes: make(map[Mode]bool),
+	utils.BitsetInitialize(set[:])
-	}
+	return &set
 }
 
 // test whether `mode` is set
 func (set *ModeSet) HasMode(mode Mode) bool {
-	if set == nil {
+	return utils.BitsetGet(set[:], uint(mode)-minMode)
-		return false
-	}
-
-	set.RLock()
-	defer set.RUnlock()
-	return set.modes[mode]
 }
 
 // set `mode` to be on or off, return whether the value actually changed
 func (set *ModeSet) SetMode(mode Mode, on bool) (applied bool) {
-	set.Lock()
+	return utils.BitsetSet(set[:], uint(mode)-minMode, on)
-	defer set.Unlock()
-
-	previouslyOn := set.modes[mode]
-	needsApply := (on != previouslyOn)
-	if on && needsApply {
-		set.modes[mode] = true
-	} else if !on && needsApply {
-		delete(set.modes, mode)
-	}
-	return needsApply
 }
 
 // return the modes in the set as a slice
@@ -366,11 +355,12 @@ func (set *ModeSet) AllModes() (result []Mode) {
 		return
 	}
 
-	set.RLock()
+	block := atomic.LoadUint64(&set[0])
-	defer set.RUnlock()
+	var i uint
-
+	for i = 0; i < 64; i++ {
-	for mode := range set.modes {
+		if block&(1<<i) != 0 {
-		result = append(result, mode)
+			result = append(result, Mode(minMode+i))
+		}
 	}
 	return
 }
@@ -381,11 +371,8 @@ func (set *ModeSet) String() (result string) {
 		return
 	}
 
-	set.RLock()
-	defer set.RUnlock()
-
 	var buf strings.Builder
-	for mode := range set.modes {
+	for _, mode := range set.AllModes() {
 		buf.WriteRune(rune(mode))
 	}
 	return buf.String()
@@ -397,12 +384,9 @@ func (set *ModeSet) Prefixes(isMultiPrefix bool) (prefixes string) {
 		return
 	}
 
-	set.RLock()
-	defer set.RUnlock()
-
 	// add prefixes in order from highest to lowest privs
 	for _, mode := range ChannelUserModes {
-		if set.modes[mode] {
+		if set.HasMode(mode) {
 			prefixes += ChannelModePrefixes[mode]
 		}
 	}

irc/server.go

@@ -898,13 +898,11 @@ func (server *Server) applyConfig(config *Config, initial bool) error {
 
 	// updated caps get DEL'd and then NEW'd
 	// so, we can just add updated ones to both removed and added lists here and they'll be correctly handled
-	server.logger.Debug("rehash", "Updated Caps", updatedCaps.String(caps.Cap301, CapValues), strconv.Itoa(updatedCaps.Count()))
+	server.logger.Debug("rehash", "Updated Caps", updatedCaps.String(caps.Cap301, CapValues))
-	for _, capab := range updatedCaps.List() {
+	addedCaps.Union(updatedCaps)
-		addedCaps.Enable(capab)
+	removedCaps.Union(updatedCaps)
-		removedCaps.Enable(capab)
-	}
 
-	if 0 < addedCaps.Count() || 0 < removedCaps.Count() {
+	if !addedCaps.Empty() || !removedCaps.Empty() {
 		capBurstClients = server.clients.AllWithCaps(caps.CapNotify)
 
 		added[caps.Cap301] = addedCaps.String(caps.Cap301, CapValues)
@@ -918,7 +916,7 @@ func (server *Server) applyConfig(config *Config, initial bool) error {
 			// remove STS policy
 			//TODO(dan): this is an ugly hack. we can write this better.
 			stsPolicy := "sts=duration=0"
-			if 0 < addedCaps.Count() {
+			if !addedCaps.Empty() {
 				added[caps.Cap302] = added[caps.Cap302] + " " + stsPolicy
 			} else {
 				addedCaps.Enable(caps.STS)
@@ -926,10 +924,10 @@ func (server *Server) applyConfig(config *Config, initial bool) error {
 			}
 		}
 		// DEL caps and then send NEW ones so that updated caps get removed/added correctly
-		if 0 < removedCaps.Count() {
+		if !removedCaps.Empty() {
 			sClient.Send(nil, server.name, "CAP", sClient.nick, "DEL", removed)
 		}
-		if 0 < addedCaps.Count() {
+		if !addedCaps.Empty() {
 			sClient.Send(nil, server.name, "CAP", sClient.nick, "NEW", added[sClient.capVersion])
 		}
 	}

irc/utils/bitset.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2018 Shivaram Lingamneni <slingamn@cs.stanford.edu>
+// released under the MIT license
+
+package utils
+
+import "sync/atomic"
+
+// Library functions for lock-free bitsets, typically (constant-sized) arrays of uint64.
+// For examples of use, see caps.Set and modes.ModeSet; the array has to be converted to a
+// slice to use these functions.
+
+// BitsetInitialize initializes a bitset.
+func BitsetInitialize(set []uint64) {
+	// XXX re-zero the bitset using atomic stores. it's unclear whether this is required,
+	// however, golang issue #5045 suggests that you shouldn't mix atomic operations
+	// with non-atomic operations (such as the runtime's automatic zero-initialization) on
+	// the same word
+	for i := 0; i < len(set); i++ {
+		atomic.StoreUint64(&set[i], 0)
+	}
+}
+
+// BitsetGet returns whether a given bit of the bitset is set.
+func BitsetGet(set []uint64, position uint) bool {
+	idx := position / 64
+	bit := position % 64
+	block := atomic.LoadUint64(&set[idx])
+	return (block & (1 << bit)) != 0
+}
+
+// BitsetSet sets a given bit of the bitset to 0 or 1, returning whether it changed.
+func BitsetSet(set []uint64, position uint, on bool) (changed bool) {
+	idx := position / 64
+	bit := position % 64
+	addr := &set[idx]
+	var mask uint64
+	mask = 1 << bit
+	for {
+		current := atomic.LoadUint64(addr)
+		previouslyOn := (current & mask) != 0
+		if on == previouslyOn {
+			return false
+		}
+		var desired uint64
+		if on {
+			desired = current | mask
+		} else {
+			desired = current & (^mask)
+		}
+		if atomic.CompareAndSwapUint64(addr, current, desired) {
+			return true
+		}
+	}
+}
+
+// BitsetEmpty returns whether the bitset is empty.
+// Right now, this is technically free of race conditions because we don't
+// have a method that can simultaneously modify two bits separated by a word boundary
+// such that one of those modifications is an unset. If we did, there would be a race
+// that could produce false positives. It's probably better to assume that they are
+// already possible under concurrent modification (which is not how we're using this).
+func BitsetEmpty(set []uint64) (empty bool) {
+	for i := 0; i < len(set); i++ {
+		if atomic.LoadUint64(&set[i]) != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+// BitsetUnion modifies `set` to be the union of `set` and `other`.
+// This has race conditions in that we don't necessarily get a single
+// consistent view of `other` across word boundaries.
+func BitsetUnion(set []uint64, other []uint64) {
+	for i := 0; i < len(set); i++ {
+		for {
+			ourAddr := &set[i]
+			ourBlock := atomic.LoadUint64(ourAddr)
+			otherBlock := atomic.LoadUint64(&other[i])
+			newBlock := ourBlock | otherBlock
+			if atomic.CompareAndSwapUint64(ourAddr, ourBlock, newBlock) {
+				break
+			}
+		}
+	}
+}

irc/utils/bitset_test.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2018 Shivaram Lingamneni <slingamn@cs.stanford.edu>
+// released under the MIT license
+
+package utils
+
+import "testing"
+
+type testBitset [2]uint64
+
+func TestSets(t *testing.T) {
+	var t1 testBitset
+	t1s := t1[:]
+	BitsetInitialize(t1s)
+
+	if BitsetGet(t1s, 0) || BitsetGet(t1s, 63) || BitsetGet(t1s, 64) || BitsetGet(t1s, 127) {
+		t.Error("no bits should be set in a newly initialized bitset")
+	}
+
+	var i uint
+	for i = 0; i < 128; i++ {
+		if i%2 == 0 {
+			if !BitsetSet(t1s, i, true) {
+				t.Error("setting an uninitialized bit should return true")
+			}
+		}
+	}
+
+	if BitsetSet(t1s, 24, true) {
+		t.Error("setting an already-set bit should return false")
+	}
+
+	if !(BitsetGet(t1s, 0) && !BitsetGet(t1s, 1) && BitsetGet(t1s, 64) && BitsetGet(t1s, 72) && !BitsetGet(t1s, 127)) {
+		t.Error("exactly the even-numbered bits should be set")
+	}
+
+	if !BitsetSet(t1s, 72, false) {
+		t.Error("removing a set bit should return true")
+	}
+
+	if BitsetGet(t1s, 72) {
+		t.Error("remove doesn't work")
+	}
+
+	if BitsetSet(t1s, 72, false) {
+		t.Error("removing an unset bit should return false")
+	}
+
+	var t2 testBitset
+	t2s := t2[:]
+	BitsetInitialize(t2s)
+
+	for i = 0; i < 128; i++ {
+		if i%2 == 1 {
+			BitsetSet(t2s, i, true)
+		}
+	}
+
+	BitsetUnion(t1s, t2s)
+	for i = 0; i < 128; i++ {
+		expected := (i != 72)
+		if BitsetGet(t1s, i) != expected {
+			t.Error("all bits should be set except 72")
+		}
+	}
+}