[uptime] Use buf_append_printf for ESP8266 flash optimization

esphome/components/syslog/esphome_syslog.cpp

@@ -47,27 +47,29 @@ void Syslog::log_(const int level, const char *tag, const char *message, size_t
   size_t remaining = sizeof(packet);
 
   // Write PRI - abort if this fails as packet would be malformed
-  offset = buf_append_printf(packet, sizeof(packet), 0, "<%d>", pri);
-  if (offset == 0) {
-    return;  // PRI always produces at least "<0>" (3 chars), so 0 means error
+  int ret = snprintf(packet, remaining, "<%d>", pri);
+  if (ret <= 0 || static_cast<size_t>(ret) >= remaining) {
+    return;
   }
-  remaining -= offset;
+  offset = ret;
+  remaining -= ret;
 
   // Write timestamp directly into packet (RFC 5424: use "-" if time not valid or strftime fails)
   auto now = this->time_->now();
   size_t ts_written = now.is_valid() ? now.strftime(packet + offset, remaining, "%b %e %H:%M:%S") : 0;
   if (ts_written > 0) {
     offset += ts_written;
+    remaining -= ts_written;
   } else if (remaining > 0) {
     packet[offset++] = '-';
+    remaining--;
   }
 
   // Write hostname, tag, and message
-  offset = buf_append_printf(packet, sizeof(packet), offset, " %s %s: %.*s", App.get_name().c_str(), tag, (int) len,
-                             message);
-  // Clamp to exclude null terminator position if buffer was filled
-  if (offset >= sizeof(packet)) {
-    offset = sizeof(packet) - 1;
+  ret = snprintf(packet + offset, remaining, " %s %s: %.*s", App.get_name().c_str(), tag, (int) len, message);
+  if (ret > 0) {
+    // snprintf returns chars that would be written; clamp to actual buffer space
+    offset += std::min(static_cast<size_t>(ret), remaining > 0 ? remaining - 1 : 0);
   }
 
   if (offset > 0) {

esphome/components/uptime/text_sensor/uptime_text_sensor.cpp

@@ -9,17 +9,12 @@ namespace uptime {
 
 static const char *const TAG = "uptime.sensor";
 
-// Clamp position to valid buffer range when snprintf indicates truncation
-static size_t clamp_buffer_pos(size_t pos, size_t buf_size) { return pos < buf_size ? pos : buf_size - 1; }
-
 static void append_unit(char *buf, size_t buf_size, size_t &pos, const char *separator, unsigned value,
                         const char *label) {
   if (pos > 0) {
-    pos += snprintf(buf + pos, buf_size - pos, "%s", separator);
-    pos = clamp_buffer_pos(pos, buf_size);
+    pos = buf_append_printf(buf, buf_size, pos, "%s", separator);
   }
-  pos += snprintf(buf + pos, buf_size - pos, "%u%s", value, label);
-  pos = clamp_buffer_pos(pos, buf_size);
+  pos = buf_append_printf(buf, buf_size, pos, "%u%s", value, label);
 }
 
 void UptimeTextSensor::setup() {