From b78d61e93a8546675d97d953bf9b24a8f44e29b3 Mon Sep 17 00:00:00 2001
From: arjunshajitech <arjunforpc@gmail.com>
Date: Fri, 26 Dec 2025 22:30:57 +0530
Subject: [PATCH] Avoid RTPBuffer allocation

Previously, NewInterceptor validated the RTP
buffer size by calling rtpbuffer.NewRTPBuffer
this resulted in unnecessary memory allocations
during interceptor construction, even though
the buffer itself was not used at that stage.
---
 internal/rtpbuffer/rtpbuffer.go   | 33 +++++++++++++++++--------------
 pkg/nack/generator_interceptor.go |  3 ++-
 pkg/nack/receive_log.go           | 16 ++-------------
 pkg/nack/responder_interceptor.go |  2 +-
 4 files changed, 23 insertions(+), 31 deletions(-)

diff --git a/internal/rtpbuffer/rtpbuffer.go b/internal/rtpbuffer/rtpbuffer.go
index 94c7adfe..a2f8eb29 100644
--- a/internal/rtpbuffer/rtpbuffer.go
+++ b/internal/rtpbuffer/rtpbuffer.go
@@ -4,9 +4,7 @@
 // Package rtpbuffer provides a buffer for storing RTP packets
 package rtpbuffer
 
-import (
-	"fmt"
-)
+import "fmt"
 
 const (
 	// Uint16SizeHalf is half of a math.Uint16.
@@ -26,25 +24,30 @@ type RTPBuffer struct {
 
 // NewRTPBuffer constructs a new RTPBuffer.
 func NewRTPBuffer(size uint16) (*RTPBuffer, error) {
-	allowedSizes := make([]uint16, 0)
-	correctSize := false
+	if err := IsBufferSizeValid(size); err != nil {
+		return nil, err
+	}
+
+	return &RTPBuffer{
+		packets: make([]*RetainablePacket, size),
+		size:    size,
+	}, nil
+}
+
+func IsBufferSizeValid(size uint16) error {
 	for i := 0; i < 16; i++ {
 		if size == 1<<i {
-			correctSize = true
-
-			break
+			return nil
 		}
-		allowedSizes = append(allowedSizes, 1<<i)
 	}
 
-	if !correctSize {
-		return nil, fmt.Errorf("%w: %d is not a valid size, allowed sizes: %v", ErrInvalidSize, size, allowedSizes)
+	// Only build allowedSizes if we actually need the error
+	allowedSizes := make([]uint16, 0)
+	for i := 0; i < 16; i++ {
+		allowedSizes = append(allowedSizes, 1<<i)
 	}
 
-	return &RTPBuffer{
-		packets: make([]*RetainablePacket, size),
-		size:    size,
-	}, nil
+	return fmt.Errorf("%w: %d is not a valid size, allowed sizes: %v", ErrInvalidSize, size, allowedSizes)
 }
 
 // Add places the RetainablePacket in the RTPBuffer.
diff --git a/pkg/nack/generator_interceptor.go b/pkg/nack/generator_interceptor.go
index 58ff3b32..6767ea00 100644
--- a/pkg/nack/generator_interceptor.go
+++ b/pkg/nack/generator_interceptor.go
@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/pion/interceptor"
+	"github.com/pion/interceptor/internal/rtpbuffer"
 	"github.com/pion/logging"
 	"github.com/pion/rtcp"
 )
@@ -39,7 +40,7 @@ func (g *GeneratorInterceptorFactory) NewInterceptor(_ string) (interceptor.Inte
 		}
 	}
 
-	if _, err := newReceiveLog(generatorInterceptor.size); err != nil {
+	if err := rtpbuffer.IsBufferSizeValid(generatorInterceptor.size); err != nil {
 		return nil, err
 	}
 
diff --git a/pkg/nack/receive_log.go b/pkg/nack/receive_log.go
index c37407d1..ceb46f4b 100644
--- a/pkg/nack/receive_log.go
+++ b/pkg/nack/receive_log.go
@@ -4,7 +4,6 @@
 package nack
 
 import (
-	"fmt"
 	"sync"
 
 	"github.com/pion/interceptor/internal/rtpbuffer"
@@ -20,19 +19,8 @@ type receiveLog struct {
 }
 
 func newReceiveLog(size uint16) (*receiveLog, error) {
-	allowedSizes := make([]uint16, 0)
-	correctSize := false
-	for i := 6; i < 16; i++ {
-		if size == 1<<i {
-			correctSize = true
-
-			break
-		}
-		allowedSizes = append(allowedSizes, 1<<i)
-	}
-
-	if !correctSize {
-		return nil, fmt.Errorf("%w: %d is not a valid size, allowed sizes: %v", ErrInvalidSize, size, allowedSizes)
+	if err := rtpbuffer.IsBufferSizeValid(size); err != nil {
+		return nil, err
 	}
 
 	return &receiveLog{
diff --git a/pkg/nack/responder_interceptor.go b/pkg/nack/responder_interceptor.go
index 6284f368..dfbb80ad 100644
--- a/pkg/nack/responder_interceptor.go
+++ b/pkg/nack/responder_interceptor.go
@@ -37,7 +37,7 @@ func (r *ResponderInterceptorFactory) NewInterceptor(_ string) (interceptor.Inte
 		responderInterceptor.packetFactory = rtpbuffer.NewPacketFactoryCopy()
 	}
 
-	if _, err := rtpbuffer.NewRTPBuffer(responderInterceptor.size); err != nil {
+	if err := rtpbuffer.IsBufferSizeValid(responderInterceptor.size); err != nil {
 		return nil, err
 	}