Pull request 1906: 5896-safe-browsing-cpu-ram

Updates #5896.

Squashed commit of the following:

commit 81ac59e2f95ef3ad6ac5c4668c07c35d69570454
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Jul 4 16:07:33 2023 +0300

    hashprefix: fix cache coding

CHANGELOG.md

@@ -23,6 +23,13 @@ See also the [v0.107.34 GitHub milestone][ms-v0.107.34].
 NOTE: Add new changes BELOW THIS COMMENT.
 -->
 
+### Fixed
+
+- Excessive RAM and CPU consumption by Safe Browsing and Parental Control
+  filters ([#5896]).
+
+[#5896]: https://github.com/AdguardTeam/AdGuardHome/issues/5896
+
 <!--
 NOTE: Add new changes ABOVE THIS COMMENT.
 -->

internal/filtering/hashprefix/cache.go

@@ -25,7 +25,7 @@ func toCacheItem(data []byte) *cacheItem {
 	t := time.Unix(int64(binary.BigEndian.Uint64(data)), 0)
 
 	data = data[expirySize:]
-	hashes := make([]hostnameHash, len(data)/hashSize)
+	hashes := make([]hostnameHash, 0, len(data)/hashSize)
 
 	for i := 0; i < len(data); i += hashSize {
 		var hash hostnameHash
@@ -41,9 +41,10 @@ func toCacheItem(data []byte) *cacheItem {
 
 // fromCacheItem encodes cacheItem into data.
 func fromCacheItem(item *cacheItem) (data []byte) {
-	data = make([]byte, len(item.hashes)*hashSize+expirySize)
+	data = make([]byte, 0, len(item.hashes)*hashSize+expirySize)
+
 	expiry := item.expiry.Unix()
-	binary.BigEndian.PutUint64(data[:expirySize], uint64(expiry))
+	data = binary.BigEndian.AppendUint64(data, uint64(expiry))
 
 	for _, v := range item.hashes {
 		// nolint:looppointer // The subsilce is used for a copy.

internal/filtering/hashprefix/cache_internal_test.go

@@ -0,0 +1,44 @@
+package hashprefix
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCacheItem(t *testing.T) {
+	item := &cacheItem{
+		expiry: time.Unix(0x01_23_45_67_89_AB_CD_EF, 0),
+		hashes: []hostnameHash{{
+			0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+			0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+			0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+			0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		}, {
+			0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+			0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+			0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+			0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+		}},
+	}
+
+	wantData := []byte{
+		0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF,
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+		0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+		0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+		0x01, 0x03, 0x05, 0x07, 0x02, 0x04, 0x06, 0x08,
+	}
+
+	gotData := fromCacheItem(item)
+	assert.Equal(t, wantData, gotData)
+
+	newItem := toCacheItem(gotData)
+	gotData = fromCacheItem(newItem)
+	assert.Equal(t, wantData, gotData)
+}