Use fixed-point meter parsing and early-exit on complete frame

src/meter_driver.cpp

@@ -24,6 +24,7 @@ static uint32_t g_frames_parse_fail = 0;
 static uint32_t g_rx_overflow = 0;
 static uint32_t g_rx_timeout = 0;
 static uint32_t g_last_log_ms = 0;
+static constexpr uint32_t METER_FIXED_FRAC_MAX_DIV = 10000;
 
 void meter_init() {
 #ifdef ARDUINO_ARCH_ESP32
@@ -72,35 +73,91 @@ static ObisField detect_obis_field(const char *line) {
   return ObisField::None;
 }
 
+static bool parse_decimal_fixed(const char *start, const char *end, float &out_value) {
+  if (!start || !end || end <= start) {
+    return false;
+  }
+
+  const char *cur = start;
+  bool started = false;
+  bool negative = false;
+  bool in_fraction = false;
+  bool saw_digit = false;
+  uint64_t int_part = 0;
+  uint32_t frac_part = 0;
+  uint32_t frac_div = 1;
+
+  while (cur < end) {
+    char c = *cur++;
+    if (!started) {
+      if (c == '+' || c == '-') {
+        started = true;
+        negative = (c == '-');
+        continue;
+      }
+      if (c >= '0' && c <= '9') {
+        started = true;
+        saw_digit = true;
+        int_part = static_cast<uint64_t>(c - '0');
+        continue;
+      }
+      if (c == '.' || c == ',') {
+        started = true;
+        in_fraction = true;
+        continue;
+      }
+      continue;
+    }
+
+    if (c >= '0' && c <= '9') {
+      saw_digit = true;
+      uint32_t digit = static_cast<uint32_t>(c - '0');
+      if (!in_fraction) {
+        if (int_part <= (UINT64_MAX - digit) / 10ULL) {
+          int_part = int_part * 10ULL + digit;
+        }
+      } else if (frac_div < METER_FIXED_FRAC_MAX_DIV) {
+        frac_part = frac_part * 10U + digit;
+        frac_div *= 10U;
+      }
+      continue;
+    }
+
+    if ((c == '.' || c == ',') && !in_fraction) {
+      in_fraction = true;
+      continue;
+    }
+
+    break;
+  }
+
+  if (!saw_digit) {
+    return false;
+  }
+  double value = static_cast<double>(int_part);
+  if (frac_div > 1U) {
+    value += static_cast<double>(frac_part) / static_cast<double>(frac_div);
+  }
+  if (negative) {
+    value = -value;
+  }
+  out_value = static_cast<float>(value);
+  return true;
+}
+
 static bool parse_obis_ascii_payload_value(const char *line, float &out_value) {
   const char *lparen = strchr(line, '(');
   if (!lparen) {
     return false;
   }
-  const char *cur = lparen + 1;
-  char num_buf[24];
-  size_t n = 0;
-  while (*cur && *cur != ')' && *cur != '*') {
-    char c = *cur++;
-    if ((c >= '0' && c <= '9') || c == '-' || c == '+' || c == '.' || c == ',') {
-      if (c == ',') {
-        c = '.';
+  const char *end = lparen + 1;
+  while (*end && *end != ')' && *end != '*') {
+    ++end;
   }
-      if (n + 1 < sizeof(num_buf)) {
-        num_buf[n++] = c;
-      }
-    } else if (n == 0) {
-      continue;
-    } else {
-      break;
-    }
-  }
-  if (n == 0) {
+  if (end <= lparen + 1) {
     return false;
   }
-  num_buf[n] = '\0';
-  out_value = static_cast<float>(atof(num_buf));
-  return true;
+  return parse_decimal_fixed(lparen + 1, end, out_value);
 }
 
 static bool parse_obis_ascii_unit_scale(const char *line, float &value) {
@@ -342,6 +399,12 @@ bool meter_parse_frame(const char *frame, size_t len, MeterData &data) {
           break;
       }
 
+      if (energy_ok && total_p_ok && p1_ok && p2_ok && p3_ok && data.meter_seconds_valid) {
+        data.valid = true;
+        g_frames_ok++;
+        return true;
+      }
+
       line_len = 0;
       continue;
     }