Check read_array return value in drain_rx_buffer_

Replace byte-at-a-time read() calls with batched read_array() in all
four UART read sites: receive_telegram_(), receive_encrypted_telegram_(),
and two drain loops. Each read() internally chains through
read_array(data, 1) -> check_read_timeout_(1) -> available(), resulting
in ~3 UART driver calls per byte. Batching into a 64-byte stack buffer
reduces this to ~3 calls per batch regardless of byte count.

Extract drain_rx_buffer_() helper to deduplicate the two drain sites
in ready_to_request_data_() and stop_requesting_data_().

esphome/components/debug/debug_esp8266.cpp

@@ -1,7 +1,6 @@
 #include "debug_component.h"
 #ifdef USE_ESP8266
 #include "esphome/core/log.h"
-#include "esphome/core/progmem.h"
 #include <Esp.h>
 
 extern "C" {
@@ -20,38 +19,27 @@ namespace debug {
 
 static const char *const TAG = "debug";
 
-// PROGMEM string table for reset reasons, indexed by reason code (0-6), with "Unknown" as fallback
-// clang-format off
-PROGMEM_STRING_TABLE(ResetReasonStrings,
-  "Power On",                  // 0 = REASON_DEFAULT_RST
-  "Hardware Watchdog",         // 1 = REASON_WDT_RST
-  "Exception",                 // 2 = REASON_EXCEPTION_RST
-  "Software Watchdog",         // 3 = REASON_SOFT_WDT_RST
-  "Software/System restart",   // 4 = REASON_SOFT_RESTART
-  "Deep-Sleep Wake",           // 5 = REASON_DEEP_SLEEP_AWAKE
-  "External System",           // 6 = REASON_EXT_SYS_RST
-  "Unknown"                    // 7 = fallback
-);
-// clang-format on
-static_assert(REASON_DEFAULT_RST == 0, "Reset reason enum values must match table indices");
-static_assert(REASON_WDT_RST == 1, "Reset reason enum values must match table indices");
-static_assert(REASON_EXCEPTION_RST == 2, "Reset reason enum values must match table indices");
-static_assert(REASON_SOFT_WDT_RST == 3, "Reset reason enum values must match table indices");
-static_assert(REASON_SOFT_RESTART == 4, "Reset reason enum values must match table indices");
-static_assert(REASON_DEEP_SLEEP_AWAKE == 5, "Reset reason enum values must match table indices");
-static_assert(REASON_EXT_SYS_RST == 6, "Reset reason enum values must match table indices");
-
-// PROGMEM string table for flash chip modes, indexed by mode code (0-3), with "UNKNOWN" as fallback
-PROGMEM_STRING_TABLE(FlashModeStrings, "QIO", "QOUT", "DIO", "DOUT", "UNKNOWN");
-static_assert(FM_QIO == 0, "Flash mode enum values must match table indices");
-static_assert(FM_QOUT == 1, "Flash mode enum values must match table indices");
-static_assert(FM_DIO == 2, "Flash mode enum values must match table indices");
-static_assert(FM_DOUT == 3, "Flash mode enum values must match table indices");
-
 // Get reset reason string from reason code (no heap allocation)
 // Returns LogString* pointing to flash (PROGMEM) on ESP8266
 static const LogString *get_reset_reason_str(uint32_t reason) {
-  return ResetReasonStrings::get_log_str(static_cast<uint8_t>(reason), ResetReasonStrings::LAST_INDEX);
+  switch (reason) {
+    case REASON_DEFAULT_RST:
+      return LOG_STR("Power On");
+    case REASON_WDT_RST:
+      return LOG_STR("Hardware Watchdog");
+    case REASON_EXCEPTION_RST:
+      return LOG_STR("Exception");
+    case REASON_SOFT_WDT_RST:
+      return LOG_STR("Software Watchdog");
+    case REASON_SOFT_RESTART:
+      return LOG_STR("Software/System restart");
+    case REASON_DEEP_SLEEP_AWAKE:
+      return LOG_STR("Deep-Sleep Wake");
+    case REASON_EXT_SYS_RST:
+      return LOG_STR("External System");
+    default:
+      return LOG_STR("Unknown");
+  }
 }
 
 // Size for core version hex buffer
@@ -104,9 +92,23 @@ size_t DebugComponent::get_device_info_(std::span<char, DEVICE_INFO_BUFFER_SIZE>
   constexpr size_t size = DEVICE_INFO_BUFFER_SIZE;
   char *buf = buffer.data();
 
-  const LogString *flash_mode = FlashModeStrings::get_log_str(
-      static_cast<uint8_t>(ESP.getFlashChipMode()),  // NOLINT(readability-static-accessed-through-instance)
-      FlashModeStrings::LAST_INDEX);
+  const LogString *flash_mode;
+  switch (ESP.getFlashChipMode()) {  // NOLINT(readability-static-accessed-through-instance)
+    case FM_QIO:
+      flash_mode = LOG_STR("QIO");
+      break;
+    case FM_QOUT:
+      flash_mode = LOG_STR("QOUT");
+      break;
+    case FM_DIO:
+      flash_mode = LOG_STR("DIO");
+      break;
+    case FM_DOUT:
+      flash_mode = LOG_STR("DOUT");
+      break;
+    default:
+      flash_mode = LOG_STR("UNKNOWN");
+  }
   uint32_t flash_size = ESP.getFlashChipSize() / 1024;       // NOLINT(readability-static-accessed-through-instance)
   uint32_t flash_speed = ESP.getFlashChipSpeed() / 1000000;  // NOLINT(readability-static-accessed-through-instance)
   ESP_LOGD(TAG, "Flash Chip: Size=%" PRIu32 "kB Speed=%" PRIu32 "MHz Mode=%s", flash_size, flash_speed,

esphome/components/dsmr/dsmr.cpp

@@ -40,9 +40,7 @@ bool Dsmr::ready_to_request_data_() {
       this->start_requesting_data_();
     }
     if (!this->requesting_data_) {
-      while (this->available()) {
-        this->read();
-      }
+      this->drain_rx_buffer_();
     }
   }
   return this->requesting_data_;
@@ -115,13 +113,21 @@ void Dsmr::stop_requesting_data_() {
     } else {
       ESP_LOGV(TAG, "Stop reading data from P1 port");
     }
-    while (this->available()) {
-      this->read();
-    }
+    this->drain_rx_buffer_();
     this->requesting_data_ = false;
   }
 }
 
+void Dsmr::drain_rx_buffer_() {
+  uint8_t buf[64];
+  int avail;
+  while ((avail = this->available()) > 0) {
+    if (!this->read_array(buf, std::min(static_cast<size_t>(avail), sizeof(buf)))) {
+      break;
+    }
+  }
+}
+
 void Dsmr::reset_telegram_() {
   this->header_found_ = false;
   this->footer_found_ = false;
@@ -133,120 +139,144 @@ void Dsmr::reset_telegram_() {
 
 void Dsmr::receive_telegram_() {
   while (this->available_within_timeout_()) {
-    const char c = this->read();
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    int avail = this->available();
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read))
+        return;
+      avail -= to_read;
 
-    // Find a new telegram header, i.e. forward slash.
-    if (c == '/') {
-      ESP_LOGV(TAG, "Header of telegram found");
-      this->reset_telegram_();
-      this->header_found_ = true;
-    }
-    if (!this->header_found_)
-      continue;
+      for (size_t i = 0; i < to_read; i++) {
+        const char c = static_cast<char>(buf[i]);
 
-    // Check for buffer overflow.
-    if (this->bytes_read_ >= this->max_telegram_len_) {
-      this->reset_telegram_();
-      ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
-      return;
-    }
+        // Find a new telegram header, i.e. forward slash.
+        if (c == '/') {
+          ESP_LOGV(TAG, "Header of telegram found");
+          this->reset_telegram_();
+          this->header_found_ = true;
+        }
+        if (!this->header_found_)
+          continue;
 
-    // Some v2.2 or v3 meters will send a new value which starts with '('
-    // in a new line, while the value belongs to the previous ObisId. For
-    // proper parsing, remove these new line characters.
-    if (c == '(') {
-      while (true) {
-        auto previous_char = this->telegram_[this->bytes_read_ - 1];
-        if (previous_char == '\n' || previous_char == '\r') {
-          this->bytes_read_--;
-        } else {
-          break;
+        // Check for buffer overflow.
+        if (this->bytes_read_ >= this->max_telegram_len_) {
+          this->reset_telegram_();
+          ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
+          return;
+        }
+
+        // Some v2.2 or v3 meters will send a new value which starts with '('
+        // in a new line, while the value belongs to the previous ObisId. For
+        // proper parsing, remove these new line characters.
+        if (c == '(') {
+          while (true) {
+            auto previous_char = this->telegram_[this->bytes_read_ - 1];
+            if (previous_char == '\n' || previous_char == '\r') {
+              this->bytes_read_--;
+            } else {
+              break;
+            }
+          }
+        }
+
+        // Store the byte in the buffer.
+        this->telegram_[this->bytes_read_] = c;
+        this->bytes_read_++;
+
+        // Check for a footer, i.e. exclamation mark, followed by a hex checksum.
+        if (c == '!') {
+          ESP_LOGV(TAG, "Footer of telegram found");
+          this->footer_found_ = true;
+          continue;
+        }
+        // Check for the end of the hex checksum, i.e. a newline.
+        if (this->footer_found_ && c == '\n') {
+          // Parse the telegram and publish sensor values.
+          this->parse_telegram();
+          this->reset_telegram_();
+          return;
         }
       }
     }
-
-    // Store the byte in the buffer.
-    this->telegram_[this->bytes_read_] = c;
-    this->bytes_read_++;
-
-    // Check for a footer, i.e. exclamation mark, followed by a hex checksum.
-    if (c == '!') {
-      ESP_LOGV(TAG, "Footer of telegram found");
-      this->footer_found_ = true;
-      continue;
-    }
-    // Check for the end of the hex checksum, i.e. a newline.
-    if (this->footer_found_ && c == '\n') {
-      // Parse the telegram and publish sensor values.
-      this->parse_telegram();
-      this->reset_telegram_();
-      return;
-    }
   }
 }
 
 void Dsmr::receive_encrypted_telegram_() {
   while (this->available_within_timeout_()) {
-    const char c = this->read();
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    int avail = this->available();
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read))
+        return;
+      avail -= to_read;
 
-    // Find a new telegram start byte.
-    if (!this->header_found_) {
-      if ((uint8_t) c != 0xDB) {
-        continue;
+      for (size_t i = 0; i < to_read; i++) {
+        const char c = static_cast<char>(buf[i]);
+
+        // Find a new telegram start byte.
+        if (!this->header_found_) {
+          if ((uint8_t) c != 0xDB) {
+            continue;
+          }
+          ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
+          this->reset_telegram_();
+          this->header_found_ = true;
+        }
+
+        // Check for buffer overflow.
+        if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
+          this->reset_telegram_();
+          ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
+          return;
+        }
+
+        // Store the byte in the buffer.
+        this->crypt_telegram_[this->crypt_bytes_read_] = c;
+        this->crypt_bytes_read_++;
+
+        // Read the length of the incoming encrypted telegram.
+        if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
+          // Complete header + data bytes
+          this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
+          ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
+        }
+
+        // Check for the end of the encrypted telegram.
+        if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
+          continue;
+        }
+        ESP_LOGV(TAG, "End of encrypted telegram found");
+
+        // Decrypt the encrypted telegram.
+        GCM<AES128> *gcmaes128{new GCM<AES128>()};
+        gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
+        // the iv is 8 bytes of the system title + 4 bytes frame counter
+        // system title is at byte 2 and frame counter at byte 15
+        for (int i = 10; i < 14; i++)
+          this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
+        constexpr uint16_t iv_size{12};
+        gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
+        gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
+                           // the ciphertext start at byte 18
+                           &this->crypt_telegram_[18],
+                           // cipher size
+                           this->crypt_bytes_read_ - 17);
+        delete gcmaes128;  // NOLINT(cppcoreguidelines-owning-memory)
+
+        this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
+        ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
+        ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
+
+        // Parse the decrypted telegram and publish sensor values.
+        this->parse_telegram();
+        this->reset_telegram_();
+        return;
       }
-      ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
-      this->reset_telegram_();
-      this->header_found_ = true;
     }
-
-    // Check for buffer overflow.
-    if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
-      this->reset_telegram_();
-      ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
-      return;
-    }
-
-    // Store the byte in the buffer.
-    this->crypt_telegram_[this->crypt_bytes_read_] = c;
-    this->crypt_bytes_read_++;
-
-    // Read the length of the incoming encrypted telegram.
-    if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
-      // Complete header + data bytes
-      this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
-      ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
-    }
-
-    // Check for the end of the encrypted telegram.
-    if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
-      continue;
-    }
-    ESP_LOGV(TAG, "End of encrypted telegram found");
-
-    // Decrypt the encrypted telegram.
-    GCM<AES128> *gcmaes128{new GCM<AES128>()};
-    gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
-    // the iv is 8 bytes of the system title + 4 bytes frame counter
-    // system title is at byte 2 and frame counter at byte 15
-    for (int i = 10; i < 14; i++)
-      this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
-    constexpr uint16_t iv_size{12};
-    gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
-    gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
-                       // the ciphertext start at byte 18
-                       &this->crypt_telegram_[18],
-                       // cipher size
-                       this->crypt_bytes_read_ - 17);
-    delete gcmaes128;  // NOLINT(cppcoreguidelines-owning-memory)
-
-    this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
-    ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
-    ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
-
-    // Parse the decrypted telegram and publish sensor values.
-    this->parse_telegram();
-    this->reset_telegram_();
-    return;
   }
 }
 

esphome/components/dsmr/dsmr.h

@@ -85,6 +85,7 @@ class Dsmr : public Component, public uart::UARTDevice {
   void receive_telegram_();
   void receive_encrypted_telegram_();
   void reset_telegram_();
+  void drain_rx_buffer_();
 
   /// Wait for UART data to become available within the read timeout.
   ///