feat: add GetOrCreate and GetOrCall methods

Also add Len/Clear/Trunc utility methods.

Signed-off-by: Dmitriy Matrenichev <dmitry.matrenichev@siderolabs.com>

containers/map.go

@@ -22,6 +22,49 @@ func (m *ConcurrentMap[K, V]) Get(key K) (V, bool) {
 	return val, ok
 }
 
+// GetOrCreate returns the existing value for the key if present. Otherwise, it stores and returns the given value.
+// The loaded result is true if the value was loaded, false if stored.
+func (m *ConcurrentMap[K, V]) GetOrCreate(key K, val V) (V, bool) {
+	m.mx.Lock()
+	defer m.mx.Unlock()
+
+	if res, ok := m.m[key]; ok {
+		return res, true
+	}
+
+	if m.m == nil {
+		m.m = map[K]V{}
+	}
+
+	m.m[key] = val
+
+	return val, false
+}
+
+// GetOrCall returns the existing value for the key if present. Otherwise, it calls fn, stores the result and returns it.
+// The loaded result is true if the value was loaded, false if it was created using fn.
+//
+// The main reason for this function is to avoid unnecessary allocations if you use pointer types as values, since
+// compiler cannot prove that the value does not escape if it's not stored.
+func (m *ConcurrentMap[K, V]) GetOrCall(key K, fn func() V) (V, bool) {
+	m.mx.Lock()
+	defer m.mx.Unlock()
+
+	if res, ok := m.m[key]; ok {
+		return res, true
+	}
+
+	if m.m == nil {
+		m.m = map[K]V{}
+	}
+
+	val := fn()
+
+	m.m[key] = val
+
+	return val, false
+}
+
 // Set sets the value for the given key.
 func (m *ConcurrentMap[K, V]) Set(key K, val V) {
 	m.mx.Lock()
@@ -46,6 +89,21 @@ func (m *ConcurrentMap[K, V]) Remove(key K) {
 	delete(m.m, key)
 }
 
+// RemoveAndGet removes the value for the given key and returns it if it exists.
+func (m *ConcurrentMap[K, V]) RemoveAndGet(key K) (V, bool) {
+	m.mx.Lock()
+	defer m.mx.Unlock()
+
+	if m.m == nil {
+		return *new(V), false //nolint:gocritic
+	}
+
+	val, ok := m.m[key]
+	delete(m.m, key)
+
+	return val, ok
+}
+
 // ForEach calls the given function for each key-value pair.
 func (m *ConcurrentMap[K, V]) ForEach(f func(K, V)) {
 	m.mx.Lock()
@@ -56,6 +114,14 @@ func (m *ConcurrentMap[K, V]) ForEach(f func(K, V)) {
 	}
 }
 
+// Len returns the number of elements in the map.
+func (m *ConcurrentMap[K, V]) Len() int {
+	m.mx.Lock()
+	defer m.mx.Unlock()
+
+	return len(m.m)
+}
+
 // Clear removes all key-value pairs.
 func (m *ConcurrentMap[K, V]) Clear() {
 	m.mx.Lock()
@@ -65,3 +131,11 @@ func (m *ConcurrentMap[K, V]) Clear() {
 		delete(m.m, k)
 	}
 }
+
+// Reset resets the underlying map.
+func (m *ConcurrentMap[K, V]) Reset() {
+	m.mx.Lock()
+	defer m.mx.Unlock()
+
+	m.m = nil
+}

containers/map_test.go

@@ -5,26 +5,37 @@
 package containers_test
 
 import (
+	"fmt"
+	"math/rand"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/siderolabs/gen/containers"
+	"github.com/siderolabs/gen/xsync"
 )
 
 func TestConcurrentMap(t *testing.T) {
+	t.Parallel()
+
 	t.Run("should return nothing if key doesnt exist", func(t *testing.T) {
+		t.Parallel()
+
 		m := containers.ConcurrentMap[int, int]{}
 		_, ok := m.Get(0)
 		require.False(t, ok)
 	})
 
 	t.Run("should remove nothing if map is empty", func(t *testing.T) {
+		t.Parallel()
+
 		m := containers.ConcurrentMap[int, int]{}
 		m.Remove(0)
 	})
 
 	t.Run("should return setted value", func(t *testing.T) {
+		t.Parallel()
+
 		m := containers.ConcurrentMap[int, int]{}
 		m.Set(1, 1)
 		val, ok := m.Get(1)
@@ -33,14 +44,34 @@ func TestConcurrentMap(t *testing.T) {
 	})
 
 	t.Run("should remove value", func(t *testing.T) {
+		t.Parallel()
+
 		m := containers.ConcurrentMap[int, int]{}
 		m.Set(1, 1)
 		m.Remove(1)
 		_, ok := m.Get(1)
 		require.False(t, ok)
+
+		m.Set(2, 2)
+		got, ok := m.RemoveAndGet(2)
+		require.True(t, ok)
+		require.Equal(t, 2, got)
+
+		got, ok = m.RemoveAndGet(2)
+		require.False(t, ok)
+		require.Zero(t, got)
+
+		m.Reset()
+		got, ok = m.RemoveAndGet(2)
+		require.False(t, ok)
+		require.Zero(t, got)
+
+		require.False(t, ok)
 	})
 
 	t.Run("should call fn for every key", func(t *testing.T) {
+		t.Parallel()
+
 		m := containers.ConcurrentMap[int, int]{}
 		m.Set(1, 1)
 		m.Set(2, 2)
@@ -52,4 +83,139 @@ func TestConcurrentMap(t *testing.T) {
 		})
 		require.Equal(t, 3, count)
 	})
+
+	t.Run("should clear the map", func(t *testing.T) {
+		t.Parallel()
+
+		m := containers.ConcurrentMap[int, int]{}
+		m.Set(1, 1)
+
+		require.Equal(t, 1, m.Len())
+
+		m.Clear()
+
+		require.Equal(t, 0, m.Len())
+	})
+
+	t.Run("should trunc the map", func(t *testing.T) {
+		t.Parallel()
+
+		m := containers.ConcurrentMap[int, int]{}
+		m.Set(1, 1)
+
+		require.Equal(t, 1, m.Len())
+
+		m.Reset()
+
+		require.Equal(t, 0, m.Len())
+	})
+}
+
+func TestConcurrentMap_GetOrCall(t *testing.T) {
+	var m containers.ConcurrentMap[int, int]
+
+	t.Run("group", func(t *testing.T) {
+		t.Run("try to insert value", func(t *testing.T) {
+			parallelGetOrCall(t, &m, 100, 1000)
+		})
+
+		t.Run("try to insert value #2", func(t *testing.T) {
+			parallelGetOrCall(t, &m, 1000, 100)
+		})
+	})
+}
+
+func parallelGetOrCall(t *testing.T, m *containers.ConcurrentMap[int, int], our, another int) {
+	t.Parallel()
+
+	oneAnotherGet := false
+
+	for i := 0; i < 10000; i++ {
+		key := int(rand.Int63n(10000))
+
+		res, ok := m.GetOrCall(key, func() int { return key * our })
+		if ok {
+			switch res {
+			case key * our:
+			case key * another:
+				oneAnotherGet = true
+			default:
+				t.Fatalf("unexpected value %d", res)
+			}
+		}
+	}
+
+	require.True(t, oneAnotherGet)
+}
+
+func TestConcurrentMap_GetOrCreate(t *testing.T) {
+	var m containers.ConcurrentMap[int, int]
+
+	t.Run("group", func(t *testing.T) {
+		t.Run("try to insert value", func(t *testing.T) {
+			parallelGetOrCreate(t, &m, 100, 1000)
+		})
+
+		t.Run("try to insert value #2", func(t *testing.T) {
+			parallelGetOrCreate(t, &m, 1000, 100)
+		})
+	})
+}
+
+func parallelGetOrCreate(t *testing.T, m *containers.ConcurrentMap[int, int], our, another int) {
+	t.Parallel()
+
+	oneAnotherGet := false
+
+	for i := 0; i < 10000; i++ {
+		key := int(rand.Int63n(10000))
+
+		res, ok := m.GetOrCreate(key, key*our)
+		if ok {
+			switch res {
+			case key * our:
+			case key * another:
+				oneAnotherGet = true
+			default:
+				t.Fatalf("unexpected value %d", res)
+			}
+		}
+	}
+
+	require.True(t, oneAnotherGet)
+}
+
+func Example_benchConcurrentMap() {
+	var sink int
+
+	benchResult := testing.Benchmark(func(b *testing.B) {
+		b.ReportAllocs()
+
+		var m containers.ConcurrentMap[int, *xsync.Once[int]]
+
+		for i := 0; i < b.N; i++ {
+			variable := 0
+
+			res, _ := m.GetOrCall(10, func() *xsync.Once[int] {
+				return &xsync.Once[int]{}
+			})
+
+			sink = res.Do(func() int {
+				variable++
+
+				return variable
+			})
+		}
+	})
+
+	if benchResult.AllocsPerOp() > 0 {
+		fmt.Println("this benchmark should not allocate memory")
+	}
+
+	fmt.Println("ok")
+
+	// Output:
+	// ok
+
+	_ = sink
 }

xsync/once.go

@@ -5,7 +5,9 @@
 // Package xsync contains the additions to std sync package.
 package xsync
 
-import "sync"
+import (
+	"sync"
+)
 
 // Once is small wrapper around [sync.Once]. It stores the result inside.
 type Once[T any] struct {