refactor(misc): enhance performance on bytes pool, entrypoint, access log and route context handling

- Introduced benchmark tests for Entrypoint and ReverseProxy to evaluate performance.
- Updated Entrypoint's ServeHTTP method to improve route context management.
- Added new test file for entrypoint benchmarks and refined existing tests for route handling.

internal/entrypoint/entrypoint.go

@@ -13,7 +13,6 @@ import (
 	"github.com/yusing/go-proxy/internal/route/routes"
 	"github.com/yusing/go-proxy/internal/task"
 	"github.com/yusing/go-proxy/internal/types"
-	"github.com/yusing/go-proxy/internal/utils/strutils"
 )
 
 type Entrypoint struct {
@@ -73,12 +72,13 @@ func (ep *Entrypoint) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		w = accesslog.NewResponseRecorder(w)
 		defer ep.accessLogger.Log(r, w.(*accesslog.ResponseRecorder).Response())
 	}
-	mux, err := ep.findRouteFunc(r.Host)
+	route, err := ep.findRouteFunc(r.Host)
 	if err == nil {
+		r = routes.WithRouteContext(r, route)
 		if ep.middleware != nil {
-			ep.middleware.ServeHTTP(mux.ServeHTTP, w, routes.WithRouteContext(r, mux))
+			ep.middleware.ServeHTTP(route.ServeHTTP, w, r)
 		} else {
-			mux.ServeHTTP(w, r)
+			route.ServeHTTP(w, r)
 		}
 		return
 	}
@@ -106,20 +106,23 @@ func (ep *Entrypoint) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 func findRouteAnyDomain(host string) (types.HTTPRoute, error) {
-	hostSplit := strutils.SplitRune(host, '.')
-	target := hostSplit[0]
-
-	if r, ok := routes.GetHTTPRouteOrExact(target, host); ok {
+	idx := strings.IndexByte(host, '.')
+	if idx != -1 {
+		target := host[:idx]
+		if r, ok := routes.HTTP.Get(target); ok {
+			return r, nil
+		}
+	}
+	if r, ok := routes.HTTP.Get(host); ok {
 		return r, nil
 	}
-	return nil, fmt.Errorf("%w: %s", ErrNoSuchRoute, target)
+	return nil, fmt.Errorf("%w: %s", ErrNoSuchRoute, host)
 }
 
 func findRouteByDomains(domains []string) func(host string) (types.HTTPRoute, error) {
 	return func(host string) (types.HTTPRoute, error) {
 		for _, domain := range domains {
-			if strings.HasSuffix(host, domain) {
-				target := strings.TrimSuffix(host, domain)
+			if target, ok := strings.CutSuffix(host, domain); ok {
 				if r, ok := routes.HTTP.Get(target); ok {
 					return r, nil
 				}

internal/entrypoint/entrypoint_benchmark_test.go

@@ -0,0 +1,154 @@
+package entrypoint
+
+import (
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/yusing/go-proxy/internal/route"
+	"github.com/yusing/go-proxy/internal/route/routes"
+	"github.com/yusing/go-proxy/internal/task"
+	"github.com/yusing/go-proxy/internal/types"
+)
+
+type noopResponseWriter struct {
+	statusCode int
+	written    []byte
+}
+
+func (w *noopResponseWriter) Header() http.Header {
+	return http.Header{}
+}
+func (w *noopResponseWriter) Write(b []byte) (int, error) {
+	w.written = b
+	return len(b), nil
+}
+func (w *noopResponseWriter) WriteHeader(statusCode int) {
+	w.statusCode = statusCode
+}
+
+type noopTransport struct{}
+
+func (t noopTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       io.NopCloser(strings.NewReader("1")),
+		Request:    req,
+		Header:     http.Header{},
+	}, nil
+}
+
+func BenchmarkEntrypointReal(b *testing.B) {
+	var ep Entrypoint
+	var req = http.Request{
+		Method: "GET",
+		URL:    &url.URL{Path: "/", RawPath: "/"},
+		Host:   "test.domain.tld",
+	}
+	ep.SetFindRouteDomains([]string{})
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Length", "1")
+		w.Write([]byte("1"))
+	}))
+	defer srv.Close()
+
+	url, err := url.Parse(srv.URL)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	host, port, err := net.SplitHostPort(url.Host)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	portInt, err := strconv.Atoi(port)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	r := &route.Route{
+		Alias:       "test",
+		Scheme:      "http",
+		Host:        host,
+		Port:        route.Port{Proxy: portInt},
+		HealthCheck: &types.HealthCheckConfig{Disable: true},
+	}
+
+	err = r.Validate()
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	err = r.Start(task.RootTask("test", false))
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	var w noopResponseWriter
+
+	b.ResetTimer()
+	for b.Loop() {
+		ep.ServeHTTP(&w, &req)
+		// if w.statusCode != http.StatusOK {
+		// 	b.Fatalf("status code is not 200: %d", w.statusCode)
+		// }
+		// if string(w.written) != "1" {
+		// 	b.Fatalf("written is not 1: %s", string(w.written))
+		// }
+	}
+}
+
+func BenchmarkEntrypoint(b *testing.B) {
+	var ep Entrypoint
+	var req = http.Request{
+		Method: "GET",
+		URL:    &url.URL{Path: "/", RawPath: "/"},
+		Host:   "test.domain.tld",
+	}
+	ep.SetFindRouteDomains([]string{})
+
+	r := &route.Route{
+		Alias:  "test",
+		Scheme: "http",
+		Host:   "localhost",
+		Port: route.Port{
+			Proxy: 8080,
+		},
+		HealthCheck: &types.HealthCheckConfig{
+			Disable: true,
+		},
+	}
+
+	err := r.Validate()
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	err = r.Start(task.RootTask("test", false))
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	rev, ok := routes.HTTP.Get("test")
+	if !ok {
+		b.Fatal("route not found")
+	}
+	rev.(types.ReverseProxyRoute).ReverseProxy().Transport = noopTransport{}
+
+	var w noopResponseWriter
+
+	b.ResetTimer()
+	for b.Loop() {
+		ep.ServeHTTP(&w, &req)
+		if w.statusCode != http.StatusOK {
+			b.Fatalf("status code is not 200: %d", w.statusCode)
+		}
+	}
+}

internal/entrypoint/entrypoint_test.go

@@ -15,6 +15,9 @@ func addRoute(alias string) {
 	routes.HTTP.Add(&route.ReveseProxyRoute{
 		Route: &route.Route{
 			Alias: alias,
+			Port: route.Port{
+				Proxy: 80,
+			},
 		},
 	})
 }

internal/logging/accesslog/access_logger.go

@@ -76,7 +76,7 @@ const (
 	errBurst     = 5
 )
 
-var lineBufPool = synk.GetBytesPool()
+var lineBufPool = synk.GetBytesPoolWithUniqueMemory()
 
 func NewAccessLogger(parent task.Parent, cfg AnyConfig) (*AccessLogger, error) {
 	io, err := cfg.IO()

internal/logging/accesslog/rotate.go

@@ -66,7 +66,7 @@ type lineInfo struct {
 	Size int64 // Size of this line
 }
 
-var rotateBytePool = synk.GetBytesPool()
+var rotateBytePool = synk.GetBytesPoolWithUniqueMemory()
 
 // rotateLogFile rotates the log file based on the retention policy.
 // It returns the result of the rotation and an error if any.

internal/net/gphttp/reverseproxy/reverse_proxy_benchmark_test.go

@@ -0,0 +1,49 @@
+package reverseproxy
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"testing"
+
+	nettypes "github.com/yusing/go-proxy/internal/net/types"
+)
+
+type noopTransport struct{}
+
+func (t noopTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	return &http.Response{
+		StatusCode:    http.StatusOK,
+		Body:          io.NopCloser(strings.NewReader("Hello, world!")),
+		Request:       req,
+		ContentLength: int64(len("Hello, world!")),
+		Header:        http.Header{},
+	}, nil
+}
+
+type noopResponseWriter struct{}
+
+func (w noopResponseWriter) Header() http.Header {
+	return http.Header{}
+}
+
+func (w noopResponseWriter) Write(b []byte) (int, error) {
+	return len(b), nil
+}
+
+func (w noopResponseWriter) WriteHeader(statusCode int) {
+}
+
+func BenchmarkReverseProxy(b *testing.B) {
+	var w noopResponseWriter
+	var req = http.Request{
+		Method: "GET",
+		URL:    &url.URL{Scheme: "http", Host: "test"},
+		Body:   io.NopCloser(strings.NewReader("Hello, world!")),
+	}
+	proxy := NewReverseProxy("test", nettypes.MustParseURL("http://localhost:8080"), noopTransport{})
+	for b.Loop() {
+		proxy.ServeHTTP(w, &req)
+	}
+}

internal/route/routes/context.go

@@ -2,18 +2,42 @@ package routes
 
 import (
 	"context"
+	"crypto/tls"
+	"fmt"
+	"io"
+	"mime/multipart"
 	"net/http"
 	"net/url"
+	"reflect"
+	"unsafe"
 
 	"github.com/yusing/go-proxy/internal/types"
 )
 
-type RouteContext struct{}
+type RouteContextKey struct{}
 
-var routeContextKey = RouteContext{}
+type RouteContext struct {
+	context.Context
+	Route types.HTTPRoute
+}
+
+var routeContextKey = RouteContextKey{}
+
+func (r *RouteContext) Value(key any) any {
+	if key == routeContextKey {
+		return r.Route
+	}
+	return r.Context.Value(key)
+}
 
 func WithRouteContext(r *http.Request, route types.HTTPRoute) *http.Request {
-	return r.WithContext(context.WithValue(r.Context(), routeContextKey, route))
+	// we don't want to copy the request object every fucking requests
+	// return r.WithContext(context.WithValue(r.Context(), routeContextKey, route))
+	(*requestInternal)(unsafe.Pointer(r)).ctx = &RouteContext{
+		Context: r.Context(),
+		Route:   route,
+	}
+	return r
 }
 
 func TryGetRoute(r *http.Request) types.HTTPRoute {
@@ -74,3 +98,44 @@ func TryGetUpstreamURL(r *http.Request) string {
 	}
 	return ""
 }
+
+type requestInternal struct {
+	Method           string
+	URL              *url.URL
+	Proto            string
+	ProtoMajor       int
+	ProtoMinor       int
+	Header           http.Header
+	Body             io.ReadCloser
+	GetBody          func() (io.ReadCloser, error)
+	ContentLength    int64
+	TransferEncoding []string
+	Close            bool
+	Host             string
+	Form             url.Values
+	PostForm         url.Values
+	MultipartForm    *multipart.Form
+	Trailer          http.Header
+	RemoteAddr       string
+	RequestURI       string
+	TLS              *tls.ConnectionState
+	Cancel           <-chan struct{}
+	Response         *http.Response
+	Pattern          string
+	ctx              context.Context
+}
+
+func init() {
+	// make sure ctx has the same offset as http.Request
+	f, ok := reflect.TypeFor[requestInternal]().FieldByName("ctx")
+	if !ok {
+		panic("ctx field not found")
+	}
+	f2, ok := reflect.TypeFor[http.Request]().FieldByName("ctx")
+	if !ok {
+		panic("ctx field not found")
+	}
+	if f.Offset != f2.Offset {
+		panic(fmt.Sprintf("ctx has different offset than http.Request: %d != %d", f.Offset, f2.Offset))
+	}
+}

internal/utils/strutils/string.go

@@ -20,8 +20,10 @@ func CommaSeperatedList(s string) []string {
 	return res
 }
 
+var caseTitle = cases.Title(language.AmericanEnglish)
+
 func Title(s string) string {
-	return cases.Title(language.AmericanEnglish).String(s)
+	return caseTitle.String(s)
 }
 
 func ContainsFold(s, substr string) bool {

internal/utils/synk/pool.go

@@ -41,6 +41,28 @@ type BytesPoolWithMemory struct {
 	pool             chan weakBuf
 }
 
+type sliceInternal struct {
+	ptr unsafe.Pointer
+	len int
+	cap int
+}
+
+func sliceStruct(b *[]byte) *sliceInternal {
+	return (*sliceInternal)(unsafe.Pointer(b))
+}
+
+func underlyingPtr(b []byte) unsafe.Pointer {
+	return sliceStruct(&b).ptr
+}
+
+func setCap(b *[]byte, cap int) {
+	sliceStruct(b).cap = cap
+}
+
+func setLen(b *[]byte, len int) {
+	sliceStruct(b).len = len
+}
+
 const (
 	kb = 1024
 	mb = 1024 * kb
@@ -88,7 +110,7 @@ func (p *BytesPool) Get() []byte {
 			addReused(cap(bPtr))
 			return bPtr
 		default:
-			return make([]byte, 0)
+			return make([]byte, 0, p.initSize)
 		}
 	}
 }
@@ -113,10 +135,6 @@ func (p *BytesPoolWithMemory) Get() []byte {
 }
 
 func (p *BytesPool) GetSized(size int) []byte {
-	if size <= SizedPoolThreshold {
-		addNonPooled(size)
-		return make([]byte, size)
-	}
 	for {
 		select {
 		case bWeak := <-p.sizedPool:
@@ -125,10 +143,26 @@ func (p *BytesPool) GetSized(size int) []byte {
 				continue
 			}
 			capB := cap(bPtr)
-			if capB >= size {
+
+			remainingSize := capB - size
+			if remainingSize == 0 {
 				addReused(capB)
-				return (bPtr)[:size]
+				return bPtr[:size]
 			}
+
+			if remainingSize > 0 { // capB > size (buffer larger than requested)
+				addReused(size)
+
+				p.Put(bPtr[size:capB])
+
+				// return the first part and limit the capacity to the requested size
+				ret := bPtr[:size]
+				setLen(&ret, size)
+				setCap(&ret, size)
+				return ret
+			}
+
+			// size is not enough
 			select {
 			case p.sizedPool <- bWeak:
 			default:
@@ -147,11 +181,10 @@ func (p *BytesPool) Put(b []byte) {
 		return
 	}
 	b = b[:0]
-	w := makeWeak(&b)
-	if size <= SizedPoolThreshold {
-		p.put(w, p.unsizedPool)
+	if size >= SizedPoolThreshold {
+		p.put(makeWeak(&b), p.sizedPool)
 	} else {
-		p.put(w, p.sizedPool)
+		p.put(makeWeak(&b), p.unsizedPool)
 	}
 }
 

internal/utils/synk/pool_bench_test.go

@@ -21,13 +21,25 @@ func BenchmarkBytesPool_MakeSmall(b *testing.B) {
 
 func BenchmarkBytesPool_GetLarge(b *testing.B) {
 	for b.Loop() {
-		bytesPool.Put(bytesPool.GetSized(1024 * 1024))
+		buf := bytesPool.GetSized(DropThreshold / 2)
+		buf[0] = 1
+		bytesPool.Put(buf)
+	}
+}
+
+func BenchmarkBytesPool_GetLargeUnsized(b *testing.B) {
+	for b.Loop() {
+		buf := slices.Grow(bytesPool.Get(), DropThreshold/2)
+		buf = append(buf, 1)
+		bytesPool.Put(buf)
 	}
 }
 
 func BenchmarkBytesPool_MakeLarge(b *testing.B) {
 	for b.Loop() {
-		_ = make([]byte, 1024*1024)
+		buf := make([]byte, DropThreshold/2)
+		buf[0] = 1
+		_ = buf
 	}
 }
 
@@ -37,10 +49,9 @@ func BenchmarkBytesPool_GetAll(b *testing.B) {
 	}
 }
 
-func BenchmarkBytesPoolWithMemory(b *testing.B) {
-	pool := GetBytesPoolWithUniqueMemory()
+func BenchmarkBytesPool_GetAllUnsized(b *testing.B) {
 	for i := range b.N {
-		pool.Put(slices.Grow(pool.Get(), sizes[i%len(sizes)]))
+		bytesPool.Put(slices.Grow(bytesPool.Get(), sizes[i%len(sizes)]))
 	}
 }
 
@@ -49,3 +60,10 @@ func BenchmarkBytesPool_MakeAll(b *testing.B) {
 		_ = make([]byte, sizes[i%len(sizes)])
 	}
 }
+
+func BenchmarkBytesPoolWithMemory(b *testing.B) {
+	pool := GetBytesPoolWithUniqueMemory()
+	for i := range b.N {
+		pool.Put(slices.Grow(pool.Get(), sizes[i%len(sizes)]))
+	}
+}

internal/utils/synk/pool_test.go

@@ -0,0 +1,263 @@
+package synk
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSized(t *testing.T) {
+	b := bytesPool.GetSized(2 * SizedPoolThreshold)
+	assert.Equal(t, cap(b), 2*SizedPoolThreshold)
+	bytesPool.Put(b)
+	assert.Equal(t, underlyingPtr(b), underlyingPtr(bytesPool.GetSized(SizedPoolThreshold)))
+}
+
+func TestUnsized(t *testing.T) {
+	b := bytesPool.Get()
+	assert.Equal(t, cap(b), UnsizedAvg)
+	bytesPool.Put(b)
+	assert.Equal(t, underlyingPtr(b), underlyingPtr(bytesPool.Get()))
+}
+
+func TestGetSizedExactMatch(t *testing.T) {
+	// Test exact size match reuse
+	size := SizedPoolThreshold
+	b1 := bytesPool.GetSized(size)
+	assert.Equal(t, size, len(b1))
+	assert.Equal(t, size, cap(b1))
+
+	// Put back into pool
+	bytesPool.Put(b1)
+
+	// Get same size - should reuse the same buffer
+	b2 := bytesPool.GetSized(size)
+	assert.Equal(t, size, len(b2))
+	assert.Equal(t, size, cap(b2))
+	assert.Equal(t, underlyingPtr(b1), underlyingPtr(b2))
+}
+
+func TestGetSizedBufferSplit(t *testing.T) {
+	// Test buffer splitting when capacity > requested size
+	largeSize := 2 * SizedPoolThreshold
+	requestedSize := SizedPoolThreshold
+
+	// Create a large buffer and put it in pool
+	b1 := bytesPool.GetSized(largeSize)
+	assert.Equal(t, largeSize, len(b1))
+	assert.Equal(t, largeSize, cap(b1))
+
+	bytesPool.Put(b1)
+
+	// Request smaller size - should split the buffer
+	b2 := bytesPool.GetSized(requestedSize)
+	assert.Equal(t, requestedSize, len(b2))
+	assert.Equal(t, requestedSize, cap(b2)) // capacity should remain the original
+	assert.Equal(t, underlyingPtr(b1), underlyingPtr(b2))
+
+	// The remaining part should be put back in pool
+	// Request the remaining size to verify
+	remainingSize := largeSize - requestedSize
+	b3 := bytesPool.GetSized(remainingSize)
+	assert.Equal(t, remainingSize, len(b3))
+	assert.Equal(t, remainingSize, cap(b3))
+
+	// Verify the remaining buffer points to the correct memory location
+	originalPtr := underlyingPtr(b1)
+	remainingPtr := underlyingPtr(b3)
+
+	// The remaining buffer should start at original + requestedSize
+	expectedOffset := uintptr(originalPtr) + uintptr(requestedSize)
+	actualOffset := uintptr(remainingPtr)
+	assert.Equal(t, expectedOffset, actualOffset, "Remaining buffer should point to correct offset")
+}
+
+func TestGetSizedSmallRemainder(t *testing.T) {
+	// Test when remaining size is smaller than SizedPoolThreshold
+	poolSize := SizedPoolThreshold + 100 // Just slightly larger than threshold
+	requestedSize := SizedPoolThreshold
+
+	// Create buffer and put in pool
+	b1 := bytesPool.GetSized(poolSize)
+	bytesPool.Put(b1)
+
+	// Request size that leaves small remainder
+	b2 := bytesPool.GetSized(requestedSize)
+	assert.Equal(t, requestedSize, len(b2))
+	assert.Equal(t, requestedSize, cap(b2))
+
+	// The small remainder (100 bytes) should NOT be put back in sized pool
+	// Try to get the remainder size - should create new buffer
+	b3 := bytesPool.GetSized(100)
+	assert.Equal(t, 100, len(b3))
+	assert.Equal(t, 100, cap(b3))
+	assert.NotEqual(t, underlyingPtr(b2), underlyingPtr(b3))
+}
+
+func TestGetSizedSmallBufferBypass(t *testing.T) {
+	// Test that small buffers (< SizedPoolThreshold) don't use sized pool
+	smallSize := SizedPoolThreshold - 1
+
+	b1 := bytesPool.GetSized(smallSize)
+	assert.Equal(t, smallSize, len(b1))
+	assert.Equal(t, smallSize, cap(b1))
+
+	b2 := bytesPool.GetSized(smallSize)
+	assert.Equal(t, smallSize, len(b2))
+	assert.Equal(t, smallSize, cap(b2))
+
+	// Should be different buffers (not pooled)
+	assert.NotEqual(t, underlyingPtr(b1), underlyingPtr(b2))
+}
+
+func TestGetSizedBufferTooSmall(t *testing.T) {
+	// Test when pool buffer is smaller than requested size
+	smallSize := SizedPoolThreshold
+	largeSize := 2 * SizedPoolThreshold
+
+	// Put small buffer in pool
+	b1 := bytesPool.GetSized(smallSize)
+	bytesPool.Put(b1)
+
+	// Request larger size - should create new buffer, not reuse small one
+	b2 := bytesPool.GetSized(largeSize)
+	assert.Equal(t, largeSize, len(b2))
+	assert.Equal(t, largeSize, cap(b2))
+	assert.NotEqual(t, underlyingPtr(b1), underlyingPtr(b2))
+
+	// The small buffer should still be in pool
+	b3 := bytesPool.GetSized(smallSize)
+	assert.Equal(t, underlyingPtr(b1), underlyingPtr(b3))
+}
+
+func TestGetSizedMultipleSplits(t *testing.T) {
+	// Test multiple sequential splits of the same buffer
+	hugeSize := 4 * SizedPoolThreshold
+	splitSize := SizedPoolThreshold
+
+	// Create huge buffer
+	b1 := bytesPool.GetSized(hugeSize)
+	originalPtr := underlyingPtr(b1)
+	bytesPool.Put(b1)
+
+	// Split it into smaller pieces
+	pieces := make([][]byte, 0, 4)
+	for i := range 4 {
+		piece := bytesPool.GetSized(splitSize)
+		pieces = append(pieces, piece)
+
+		// Each piece should point to the correct offset
+		expectedOffset := uintptr(originalPtr) + uintptr(i*splitSize)
+		actualOffset := uintptr(underlyingPtr(piece))
+		assert.Equal(t, expectedOffset, actualOffset, "Piece %d should point to correct offset", i)
+		assert.Equal(t, splitSize, len(piece))
+		assert.Equal(t, splitSize, cap(piece))
+	}
+
+	// All pieces should have the same underlying capacity
+	for i, piece := range pieces {
+		assert.Equal(t, splitSize, cap(piece), "Piece %d should have correct capacity", i)
+	}
+}
+
+func TestGetSizedMemorySafety(t *testing.T) {
+	// Test that split buffers don't interfere with each other
+	totalSize := 3 * SizedPoolThreshold
+	firstSize := SizedPoolThreshold
+
+	// Create buffer and split it
+	b1 := bytesPool.GetSized(totalSize)
+	// Fill with test data
+	for i := range len(b1) {
+		b1[i] = byte(i % 256)
+	}
+
+	bytesPool.Put(b1)
+
+	// Get first part
+	first := bytesPool.GetSized(firstSize)
+	assert.Equal(t, firstSize, len(first))
+
+	// Verify data integrity
+	for i := range len(first) {
+		assert.Equal(t, byte(i%256), first[i], "Data should be preserved after split")
+	}
+
+	// Get remaining part
+	remainingSize := totalSize - firstSize
+	remaining := bytesPool.GetSized(remainingSize)
+	assert.Equal(t, remainingSize, len(remaining))
+
+	// Verify remaining data
+	for i := range len(remaining) {
+		expected := byte((i + firstSize) % 256)
+		assert.Equal(t, expected, remaining[i], "Remaining data should be preserved")
+	}
+}
+
+func TestGetSizedCapacityLimiting(t *testing.T) {
+	// Test that returned buffers have limited capacity to prevent overwrites
+	largeSize := 2 * SizedPoolThreshold
+	requestedSize := SizedPoolThreshold
+
+	// Create large buffer and put in pool
+	b1 := bytesPool.GetSized(largeSize)
+	bytesPool.Put(b1)
+
+	// Get smaller buffer from the split
+	b2 := bytesPool.GetSized(requestedSize)
+	assert.Equal(t, requestedSize, len(b2))
+	assert.Equal(t, requestedSize, cap(b2), "Returned buffer should have limited capacity")
+
+	// Try to append data - should not be able to overwrite beyond capacity
+	original := make([]byte, len(b2))
+	copy(original, b2)
+
+	// This append should force a new allocation since capacity is limited
+	b2 = append(b2, 1, 2, 3, 4, 5)
+	assert.Greater(t, len(b2), requestedSize, "Buffer should have grown")
+
+	// Get the remaining buffer to verify it wasn't affected
+	remainingSize := largeSize - requestedSize
+	b3 := bytesPool.GetSized(remainingSize)
+	assert.Equal(t, remainingSize, len(b3))
+	assert.Equal(t, remainingSize, cap(b3), "Remaining buffer should have limited capacity")
+}
+
+func TestGetSizedAppendSafety(t *testing.T) {
+	// Test that appending to returned buffer doesn't affect remaining buffer
+	totalSize := 4 * SizedPoolThreshold
+	firstSize := SizedPoolThreshold
+
+	// Create buffer with specific pattern
+	b1 := bytesPool.GetSized(totalSize)
+	for i := range len(b1) {
+		b1[i] = byte(100 + i%100)
+	}
+	bytesPool.Put(b1)
+
+	// Get first part
+	first := bytesPool.GetSized(firstSize)
+	assert.Equal(t, firstSize, cap(first), "First part should have limited capacity")
+
+	// Store original first part content
+	originalFirst := make([]byte, len(first))
+	copy(originalFirst, first)
+
+	// Get remaining part to establish its state
+	remaining := bytesPool.GetSized(SizedPoolThreshold)
+
+	// Store original remaining content
+	originalRemaining := make([]byte, len(remaining))
+	copy(originalRemaining, remaining)
+
+	// Now try to append to first - this should not affect remaining buffers
+	// since capacity is limited
+	first = append(first, make([]byte, 1000)...)
+
+	// Verify remaining buffer content is unchanged
+	for i := range len(originalRemaining) {
+		assert.Equal(t, originalRemaining[i], remaining[i],
+			"Remaining buffer should be unaffected by append to first buffer")
+	}
+}