Snapshotable binary tree

build/go.mod

@@ -4,7 +4,7 @@ go 1.22
 
 require (
 	github.com/outofforest/build/v2 v2.2.0
-	github.com/outofforest/tools v1.0.2
+	github.com/outofforest/tools v1.0.4
 )
 
 require (
@@ -19,5 +19,5 @@ require (
 	github.com/spf13/pflag v1.0.5 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.uber.org/zap v1.27.0 // indirect
-	golang.org/x/text v0.17.0 // indirect
+	golang.org/x/text v0.18.0 // indirect
 )

build/go.sum

@@ -19,8 +19,8 @@ github.com/outofforest/parallel v0.2.3 h1:DRIgHr7XTL4LLgsTqrj041kulv4ajtbCkRbkOG
 github.com/outofforest/parallel v0.2.3/go.mod h1:cu210xIjJtOMXR2ERzEcNA2kr0Z0xfZjSKw2jTxAQ2E=
 github.com/outofforest/run v0.6.0 h1:t/3vAodvU5L5vJ3BB0qRgfviX+T3JJmLgPN6G2WQs3U=
 github.com/outofforest/run v0.6.0/go.mod h1:l7TAtA/zG+7JEH017Qrfm7gzmMyM0gjd+CereJdJSpI=
-github.com/outofforest/tools v1.0.2 h1:EE+rasbu44NEX0ML7HtyNaeKdBT3CwEEURKMxGgJgoM=
-github.com/outofforest/tools v1.0.2/go.mod h1:fn8F7Z4F4SdyWCSIQIf2NvHbN08fDCum+aDVEbxSPUs=
+github.com/outofforest/tools v1.0.4 h1:PdZVOeEbHDwQoVMifrOFz0CzTGDxDNBvv295Z2A5mps=
+github.com/outofforest/tools v1.0.4/go.mod h1:fn8F7Z4F4SdyWCSIQIf2NvHbN08fDCum+aDVEbxSPUs=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
@@ -73,8 +73,8 @@ golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.17.0 h1:XtiM5bkSOt+ewxlOE/aE/AKEHibwj/6gvWMl9Rsh0Qc=
-golang.org/x/text v0.17.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+golang.org/x/text v0.18.0 h1:XvMDiNzPAl0jr17s6W9lcaIhGUfUORdGCNsuLmPG224=
+golang.org/x/text v0.18.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=

go.mod

@@ -1,3 +1,16 @@
 module github.com/outofforest/quantum
 
 go 1.22
+
+require (
+	github.com/cespare/xxhash v1.1.0
+	github.com/outofforest/photon v0.5.0
+	github.com/stretchr/testify v1.8.4
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,20 @@
+github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/outofforest/photon v0.5.0 h1:7Mq92+Dwj7TPOIZzbwOYBe05OLOP0d7GtRFvOGaU000=
+github.com/outofforest/photon v0.5.0/go.mod h1:4qOhLdJ3jiXj7umpt57hCGs5T+p3LX9QdpkipX4YDy4=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

quantum.go

@@ -0,0 +1,213 @@
+package quantum
+
+import (
+	"unsafe"
+
+	"github.com/cespare/xxhash"
+
+	"github.com/outofforest/photon"
+)
+
+// FIXME (wojciech): avoid individual heap allocations for nodes.
+
+// New creates new quantum store.
+func New[K comparable, V any]() Snapshot[K, V] {
+	return Snapshot[K, V]{
+		root:         new(node[K, V]),
+		rootSet:      new(bool),
+		defaultValue: *new(V),
+	}
+}
+
+// Snapshot represents the state at particular point in time.
+type Snapshot[K comparable, V any] struct {
+	version      uint64
+	root         *node[K, V]
+	rootSet      *bool
+	defaultValue V
+	hasher       hasher[K]
+	hashMod      uint64
+}
+
+// Next transitions to the next snapshot of the state.
+func (s Snapshot[K, V]) Next() Snapshot[K, V] {
+	s.version++
+
+	r := *s.root
+	s.root = &r
+
+	rs := *s.rootSet
+	s.rootSet = &rs
+
+	return s
+}
+
+// Get gets the value of the key.
+func (s Snapshot[K, V]) Get(key K) (value V, exists bool) {
+	h := s.hasher.Hash(key)
+	n := s.root
+	for {
+		if n == nil {
+			return s.defaultValue, false
+		}
+		if n.Hash == h {
+			if n.Key == key {
+				return n.Value, true
+			}
+
+			// conflict
+			if s.hasher.bytes == nil {
+				s.hashMod++
+				n.hasher = newHasher[K](s.hashMod)
+			}
+			h = n.hasher.Hash(key)
+		}
+
+		bit := h & 0x01
+		h >>= 1
+
+		switch bit {
+		case 0x00:
+			n = n.Left
+		default:
+			n = n.Right
+		}
+	}
+}
+
+// Set sets the value for the key.
+func (s Snapshot[K, V]) Set(key K, value V) {
+	const (
+		leftChild int = iota
+		rightChild
+	)
+
+	h := s.hasher.Hash(key)
+
+	if !*s.rootSet {
+		*s.root = node[K, V]{
+			Value:   value,
+			Key:     key,
+			Version: s.version,
+			Hash:    h,
+		}
+		*s.rootSet = true
+		return
+	}
+
+	var parentNode *node[K, V]
+	var child int
+	n := s.root
+	for {
+		if n == nil {
+			n = &node[K, V]{
+				Value:   value,
+				Key:     key,
+				Version: s.version,
+				Hash:    h,
+			}
+
+			if child == leftChild {
+				parentNode.Left = n
+			} else {
+				parentNode.Right = n
+			}
+			return
+		}
+		if n.Version < s.version {
+			n2 := *n
+			n2.Version = s.version
+
+			switch {
+			case parentNode == nil:
+				*s.root = n2
+				n = s.root
+			case child == leftChild:
+				n = &n2
+				parentNode.Left = n
+			default:
+				n = &n2
+				parentNode.Right = n
+			}
+		}
+		if n.Hash == h {
+			if n.Key == key {
+				n.Value = value
+				return
+			}
+
+			// conflict
+			if s.hasher.bytes == nil {
+				s.hashMod++
+				n.hasher = newHasher[K](s.hashMod)
+			}
+			h = n.hasher.Hash(key)
+		}
+
+		bit := h & 0x01
+		h >>= 1
+		parentNode = n
+
+		switch bit {
+		case 0x00:
+			n = n.Left
+			child = leftChild
+		case 0x01:
+			n = n.Right
+			child = rightChild
+		}
+	}
+}
+
+type node[K comparable, V any] struct {
+	Key   K
+	Value V
+
+	Version uint64
+	Hash    uint64
+	Left    *node[K, V]
+	Right   *node[K, V]
+
+	hasher hasher[K]
+}
+
+const uint64Length = 8
+
+func newHasher[K comparable](mod uint64) hasher[K] {
+	var k K
+	var bytes []byte
+	var data []byte
+	if mod > 0 {
+		bytes = make([]byte, uint64Length+unsafe.Sizeof(k))
+		copy(bytes, photon.NewFromValue(&mod).B)
+		data = bytes[uint64Length:]
+	}
+
+	return hasher[K]{
+		bytes: bytes,
+		data:  data,
+	}
+}
+
+type hasher[K comparable] struct {
+	bytes []byte
+	data  []byte
+}
+
+func (h hasher[K]) Hash(key K) uint64 {
+	var hash uint64
+	if h.bytes == nil {
+		hash = xxhash.Sum64(photon.NewFromValue[K](&key).B)
+	} else {
+		copy(h.data, photon.NewFromValue[K](&key).B)
+		hash = xxhash.Sum64(h.data)
+	}
+	if isTesting {
+		hash = testHash(hash)
+	}
+	return hash
+}
+
+func testHash(hash uint64) uint64 {
+	return hash & 0x7fffffff
+}