[socket] Eliminate heap allocations in set_sockaddr()

Co-authored-by: Clyde Stubbs <2366188+clydebarrow@users.noreply.github.com>

esphome/components/lvgl/lv_validation.py

@@ -413,6 +413,7 @@ class TextValidator(LValidator):
                 str_args = [str(x) for x in value[CONF_ARGS]]
                 arg_expr = cg.RawExpression(",".join(str_args))
                 format_str = cpp_string_escape(format_str)
+                # str_sprintf justified: user-defined format, can't optimize without permanent RAM cost
                 sprintf_str = f"str_sprintf({format_str}, {arg_expr}).c_str()"
                 if nanval := value.get(CONF_IF_NAN):
                     nanval = cpp_string_escape(nanval)

esphome/components/lvgl/lvgl_esphome.cpp

@@ -65,7 +65,10 @@ std::string lv_event_code_name_for(uint8_t event_code) {
   if (event_code < sizeof(EVENT_NAMES) / sizeof(EVENT_NAMES[0])) {
     return EVENT_NAMES[event_code];
   }
-  return str_sprintf("%2d", event_code);
+  // max 4 bytes: "%u" with uint8_t (max 255, 3 digits) + null
+  char buf[4];
+  snprintf(buf, sizeof(buf), "%u", event_code);
+  return buf;
 }
 
 static void rounder_cb(lv_disp_drv_t *disp_drv, lv_area_t *area) {

esphome/components/socket/socket.cpp

@@ -107,9 +107,9 @@ std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol) {
 #endif /* USE_NETWORK_IPV6 */
 }
 
-socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port) {
+socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_address, uint16_t port) {
 #if USE_NETWORK_IPV6
-  if (ip_address.find(':') != std::string::npos) {
+  if (strchr(ip_address, ':') != nullptr) {
     if (addrlen < sizeof(sockaddr_in6)) {
       errno = EINVAL;
       return 0;
@@ -121,14 +121,14 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::stri
 
 #ifdef USE_SOCKET_IMPL_BSD_SOCKETS
     // Use standard inet_pton for BSD sockets
-    if (inet_pton(AF_INET6, ip_address.c_str(), &server->sin6_addr) != 1) {
+    if (inet_pton(AF_INET6, ip_address, &server->sin6_addr) != 1) {
       errno = EINVAL;
       return 0;
     }
 #else
     // Use LWIP-specific functions
     ip6_addr_t ip6;
-    inet6_aton(ip_address.c_str(), &ip6);
+    inet6_aton(ip_address, &ip6);
     memcpy(server->sin6_addr.un.u32_addr, ip6.addr, sizeof(ip6.addr));
 #endif
     return sizeof(sockaddr_in6);
@@ -141,7 +141,7 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::stri
   auto *server = reinterpret_cast<sockaddr_in *>(addr);
   memset(server, 0, sizeof(sockaddr_in));
   server->sin_family = AF_INET;
-  server->sin_addr.s_addr = inet_addr(ip_address.c_str());
+  server->sin_addr.s_addr = inet_addr(ip_address);
   server->sin_port = htons(port);
   return sizeof(sockaddr_in);
 }

esphome/components/socket/socket.h

@@ -87,7 +87,17 @@ std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol
 std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol);
 
 /// Set a sockaddr to the specified address and port for the IP version used by socket_ip().
-socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port);
+/// @param addr Destination sockaddr structure
+/// @param addrlen Size of the addr buffer
+/// @param ip_address Null-terminated IP address string (IPv4 or IPv6)
+/// @param port Port number in host byte order
+/// @return Size of the sockaddr structure used, or 0 on error
+socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_address, uint16_t port);
+
+/// Convenience overload for std::string (backward compatible).
+inline socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port) {
+  return set_sockaddr(addr, addrlen, ip_address.c_str(), port);
+}
 
 /// Set a sockaddr to the any address and specified port for the IP version used by socket_ip().
 socklen_t set_sockaddr_any(struct sockaddr *addr, socklen_t addrlen, uint16_t port);