Update submitsm encode

I mean we can't have a pool of negative size?

pdu/bufpool.go

@@ -5,17 +5,17 @@ import (
 )
 
 type BufferPoolManager struct {
-    pools map[int]*sync.Pool
+    pools map[uint]*sync.Pool
     mu    sync.Mutex
 }
 
 func NewBufferPoolManager() *BufferPoolManager {
     return &BufferPoolManager{
-        pools: make(map[int]*sync.Pool),
+        pools: make(map[uint]*sync.Pool),
     }
 }
 
-func (bpm *BufferPoolManager) GetBuffer(size int) *([]uint8) {
+func (bpm *BufferPoolManager) GetBuffer(size uint) *([]uint8) {
     bpm.mu.Lock()
     pool, exists := bpm.pools[size]
     if !exists {
@@ -32,7 +32,7 @@ func (bpm *BufferPoolManager) GetBuffer(size int) *([]uint8) {
 }
 
 func (bpm *BufferPoolManager) PutBuffer(buf *([]uint8)) {
-    size := len(*buf)
+    size := uint(len(*buf))
     bpm.mu.Lock()
     pool, exists := bpm.pools[size]
     if !exists {
@@ -41,7 +41,6 @@ func (bpm *BufferPoolManager) PutBuffer(buf *([]uint8)) {
     }
     bpm.mu.Unlock()
     
-    // Reset buffer (optional)
     for i := range *buf {
         (*buf)[i] = 0
     }

pdu/submit.go

@@ -60,9 +60,9 @@ type (
 	SUBMIT_MULTI_RESP struct{}
 )
 
-func (p *SUBMIT_SM) Encode() ([]byte, error) {
-	buf := make([]byte, p.Size())
-	err := p.EncodeInto(&buf)
+func (p *SUBMIT_SM) Encode() (*[]byte, error) {
+	buf := ByteBufferPool.GetBuffer(uint(p.Size()))
+	err := p.EncodeInto(buf)
 	return buf, err
 }
 func (p *SUBMIT_SM) EncodeInto(buf *[]byte) error {