[statsd] Use direct appends and stack buffer instead of str_sprintf

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/modbus_controller/modbus_controller.h

@@ -285,13 +285,8 @@ class ServerRegister {
       case SensorValueType::S_QWORD_R:
         return std::to_string(value);
       case SensorValueType::FP32_R:
-      case SensorValueType::FP32: {
-        // max 48: float with %.1f can be up to 42 chars incl. null (3.4e38 → 38 integer digits + decimal point + 1
-        // decimal digit + optional sign)
-        char buf[48];
-        snprintf(buf, sizeof(buf), "%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
-        return buf;
-      }
+      case SensorValueType::FP32:
+        return str_sprintf("%.1f", bit_cast<float>(static_cast<uint32_t>(value)));
       default:
         return std::to_string(value);
     }

esphome/components/modbus_controller/text_sensor/modbus_textsensor.cpp

@@ -16,20 +16,12 @@ void ModbusTextSensor::parse_and_publish(const std::vector<uint8_t> &data) {
   while ((items_left > 0) && index < data.size()) {
     uint8_t b = data[index];
     switch (this->encode_) {
-      case RawEncoding::HEXBYTES: {
-        // max 3: 2 hex digits + null
-        char hex_buf[3];
-        snprintf(hex_buf, sizeof(hex_buf), "%02x", b);
-        output_str += hex_buf;
+      case RawEncoding::HEXBYTES:
+        output_str += str_snprintf("%02x", 2, b);
         break;
-      }
-      case RawEncoding::COMMA: {
-        // max 5: optional ','(1) + uint8(3) + null, for both ",%d" and "%d"
-        char dec_buf[5];
-        snprintf(dec_buf, sizeof(dec_buf), index != this->offset ? ",%d" : "%d", b);
-        output_str += dec_buf;
+      case RawEncoding::COMMA:
+        output_str += str_sprintf(index != this->offset ? ",%d" : "%d", b);
         break;
-      }
       case RawEncoding::ANSI:
         if (b < 0x20)
           break;

esphome/components/statsd/statsd.cpp

@@ -114,14 +114,23 @@ void StatsdComponent::update() {
     // This implies you can't explicitly set a gauge to a negative number without first setting it to zero.
     if (val < 0) {
       if (this->prefix_) {
-        out.append(str_sprintf("%s.", this->prefix_));
+        out.append(this->prefix_);
+        out.append(".");
       }
-      out.append(str_sprintf("%s:0|g\n", s.name));
+      out.append(s.name);
+      out.append(":0|g\n");
     }
     if (this->prefix_) {
-      out.append(str_sprintf("%s.", this->prefix_));
+      out.append(this->prefix_);
+      out.append(".");
     }
-    out.append(str_sprintf("%s:%f|g\n", s.name, val));
+    out.append(s.name);
+    // Buffer for ":" + value + "|g\n".
+    // %g uses max 13 chars for value (sign + 6 significant digits + e+xxx)
+    // Total: 1 + 13 + 4 = 18 chars + null, use 24 for safety
+    char val_buf[24];
+    snprintf(val_buf, sizeof(val_buf), ":%g|g\n", val);
+    out.append(val_buf);
 
     if (out.length() > SEND_THRESHOLD) {
       this->send_(&out);