event.CheckID()

absurd performance increase benefit over a naïve id comparison!

goos: linux
goarch: amd64
pkg: github.com/nbd-wtf/go-nostr
cpu: AMD Ryzen 3 3200G with Radeon Vega Graphics
BenchmarkIDCheck/naïve-4          	 1478547	       802.9 ns/op	     488 B/op	      15 allocs/op
BenchmarkIDCheck/big_brain-4      	 1673341	       715.3 ns/op	     358 B/op	      12 allocs/op

event.go

@@ -35,6 +35,28 @@ func (evt *Event) GetID() string {
 	return hex.EncodeToString(h[:])
 }
 
+// CheckID checks if the implied ID matches the given ID
+func (evt *Event) CheckID() bool {
+	ser := evt.Serialize()
+	h := sha256.Sum256(ser)
+
+	const hextable = "0123456789abcdef"
+
+	for i := 0; i < 32; i++ {
+		b := hextable[h[i]>>4]
+		if b != evt.ID[i*2] {
+			return false
+		}
+
+		b = hextable[h[i]&0x0f]
+		if b != evt.ID[i*2+1] {
+			return false
+		}
+	}
+
+	return true
+}
+
 // Serialize outputs a byte array that can be hashed/signed to identify/authenticate.
 // JSON encoding as defined in RFC4627.
 func (evt *Event) Serialize() []byte {

event_test.go

@@ -2,9 +2,12 @@ package nostr
 
 import (
 	"encoding/json"
+	"fmt"
+	"math/rand/v2"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestEventParsingAndVerifying(t *testing.T) {
@@ -117,7 +120,6 @@ func TestEventSerializationWithExtraFields(t *testing.T) {
 
 	assert.Condition(t, func() (success bool) {
 		if evt.GetExtra("glub").(bool) != evt.GetExtraBoolean("glub") || evt.GetExtraBoolean("glub") != true {
-
 			return false
 		}
 		return true
@@ -132,3 +134,39 @@ func mustSignEvent(t *testing.T, privkey string, event *Event) {
 		t.Fatalf("event.Sign: %v", err)
 	}
 }
+
+func TestIDCheck(t *testing.T) {
+	for i := 0; i < 1000; i++ {
+		evt := Event{
+			CreatedAt: Timestamp(rand.Int64N(9999999)),
+			Content:   fmt.Sprintf("hello %d", i),
+			Tags:      Tags{},
+		}
+		evt.Sign(GeneratePrivateKey())
+		require.True(t, evt.CheckID())
+
+		evt.Content += "!"
+		require.False(t, evt.CheckID())
+	}
+}
+
+func BenchmarkIDCheck(b *testing.B) {
+	evt := Event{
+		CreatedAt: Timestamp(rand.Int64N(9999999)),
+		Content:   fmt.Sprintf("hello"),
+		Tags:      Tags{},
+	}
+	evt.Sign(GeneratePrivateKey())
+
+	b.Run("naïve", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = evt.GetID() == evt.ID
+		}
+	})
+
+	b.Run("big brain", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_ = evt.CheckID()
+		}
+	})
+}