add lru (#9592)

cache/lru/BUILD.bazel

@@ -0,0 +1,16 @@
+load("@prysm//tools/go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["lru_wrpr.go"],
+    importpath = "github.com/prysmaticlabs/prysm/cache/lru",
+    visibility = ["//visibility:public"],
+    deps = ["@com_github_hashicorp_golang_lru//:go_default_library"],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["lru_wrpr_test.go"],
+    embed = [":go_default_library"],
+    deps = ["@com_github_stretchr_testify//assert:go_default_library"],
+)

cache/lru/lru_wrpr.go

@@ -0,0 +1,26 @@
+package lru
+
+import (
+	"fmt"
+
+	lru "github.com/hashicorp/golang-lru"
+)
+
+// New creates an LRU of the given size.
+func New(size int) *lru.Cache {
+	cache, err := lru.New(size)
+	if err != nil {
+		panic(fmt.Errorf("lru new failed: %w", err))
+	}
+	return cache
+}
+
+// NewWithEvict constructs a fixed size cache with the given eviction
+// callback.
+func NewWithEvict(size int, onEvicted func(key interface{}, value interface{})) *lru.Cache {
+	cache, err := lru.NewWithEvict(size, onEvicted)
+	if err != nil {
+		panic(fmt.Errorf("lru new with evict failed: %w", err))
+	}
+	return cache
+}

cache/lru/lru_wrpr_test.go

@@ -0,0 +1,37 @@
+package lru
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNew(t *testing.T) {
+	assert.NotPanics(t, func() {
+		New(10)
+	})
+}
+
+func TestNew_ZeroOrNegativeSize(t *testing.T) {
+	assert.Panics(t, func() {
+		New(0)
+	})
+	assert.Panics(t, func() {
+		New(-1)
+	})
+}
+
+func TestNewWithEvict(t *testing.T) {
+	assert.NotPanics(t, func() {
+		NewWithEvict(10, func(key interface{}, value interface{}) {})
+	})
+}
+
+func TestNewWithEvict_ZeroOrNegativeSize(t *testing.T) {
+	assert.Panics(t, func() {
+		NewWithEvict(0, func(key interface{}, value interface{}) {})
+	})
+	assert.Panics(t, func() {
+		NewWithEvict(-1, func(key interface{}, value interface{}) {})
+	})
+}