Panda: add can_send buffer caching (#19910)

old-commit-hash: 5c58a2618e

selfdrive/boardd/panda.cc

@@ -1,7 +1,7 @@
 #include <stdexcept>
 #include <cassert>
 #include <iostream>
-
+#include <vector>
 #include <unistd.h>
 
 #include "common/swaglog.h"
@@ -303,9 +303,10 @@ void Panda::send_heartbeat(){
 }
 
 void Panda::can_send(capnp::List<cereal::CanData>::Reader can_data_list){
-  int msg_count = can_data_list.size();
+  static std::vector<uint32_t> send;
+  const int msg_count = can_data_list.size();
 
-  uint32_t *send = new uint32_t[msg_count*0x10]();
+  send.resize(msg_count*0x10);
 
   for (int i = 0; i < msg_count; i++) {
     auto cmsg = can_data_list[i];
@@ -320,9 +321,7 @@ void Panda::can_send(capnp::List<cereal::CanData>::Reader can_data_list){
     memcpy(&send[i*4+2], can_data.begin(), can_data.size());
   }
 
-  usb_bulk_write(3, (unsigned char*)send, msg_count*0x10, 5);
-
-  delete[] send;
+  usb_bulk_write(3, (unsigned char*)send.data(), send.size(), 5);
 }
 
 int Panda::can_receive(kj::Array<capnp::word>& out_buf) {