Avoid strlen for logger on all platforms that support it

esphome/components/logger/logger.cpp

@@ -65,7 +65,7 @@ void HOT Logger::log_vprintf_(uint8_t level, const char *tag, int line, const ch
     uint16_t buffer_at = 0;                         // Initialize buffer position
     this->format_log_to_buffer_with_terminator_(level, tag, line, format, args, console_buffer, &buffer_at,
                                                 MAX_CONSOLE_LOG_MSG_SIZE);
-    this->write_msg_(console_buffer);
+    this->write_msg_(console_buffer, buffer_at);
   }
 
   // Reset the recursion guard for this task
@@ -136,11 +136,11 @@ void Logger::log_vprintf_(uint8_t level, const char *tag, int line, const __Flas
                                               &this->tx_buffer_at_, this->tx_buffer_size_);
 
   // Write to console and send callback starting at the msg_start
-  if (this->baud_rate_ > 0) {
-    this->write_msg_(this->tx_buffer_ + msg_start);
-  }
   size_t msg_length =
       this->tx_buffer_at_ - msg_start;  // Don't subtract 1 - tx_buffer_at_ is already at the null terminator position
+  if (this->baud_rate_ > 0) {
+    this->write_msg_(this->tx_buffer_ + msg_start, msg_length);
+  }
   this->log_callback_.call(level, tag, this->tx_buffer_ + msg_start, msg_length);
 
   global_recursion_guard_ = false;
@@ -224,7 +224,7 @@ void Logger::process_messages_() {
       // Note: Messages may appear slightly out of order due to async processing, but
       // this is preferred over corrupted/interleaved console output
       if (this->baud_rate_ > 0) {
-        this->write_msg_(this->tx_buffer_);
+        this->write_msg_(this->tx_buffer_, msg_len);
       }
     }
   } else {

esphome/components/logger/logger.h

@@ -161,7 +161,7 @@ class Logger : public Component {
 
  protected:
   void process_messages_();
-  void write_msg_(const char *msg);
+  void write_msg_(const char *msg, size_t len);
 
   // Format a log message with printf-style arguments and write it to a buffer with header, footer, and null terminator
   // It's the caller's responsibility to initialize buffer_at (typically to 0)
@@ -194,7 +194,7 @@ class Logger : public Component {
                                                 this->tx_buffer_size_);
 
     if (this->baud_rate_ > 0) {
-      this->write_msg_(this->tx_buffer_);  // If logging is enabled, write to console
+      this->write_msg_(this->tx_buffer_, this->tx_buffer_at_);  // If logging is enabled, write to console
     }
     this->log_callback_.call(level, tag, this->tx_buffer_, this->tx_buffer_at_);
   }

esphome/components/logger/logger_esp32.cpp

@@ -166,7 +166,7 @@ void Logger::pre_setup() {
 }
 
 #ifdef USE_ESP_IDF
-void HOT Logger::write_msg_(const char *msg) {
+void HOT Logger::write_msg_(const char *msg, size_t len) {
   if (
 #if defined(USE_LOGGER_USB_CDC) && !defined(USE_LOGGER_USB_SERIAL_JTAG)
       this->uart_ == UART_SELECTION_USB_CDC
@@ -178,16 +178,26 @@ void HOT Logger::write_msg_(const char *msg) {
       /* DISABLES CODE */ (false)  // NOLINT
 #endif
   ) {
+    // For USB CDC/Serial JTAG, we use puts() which adds '\n' automatically.
+    // This is safe because the buffer is always null-terminated by format_log_to_buffer_with_terminator_.
+    // The VFS layer handles newline conversion (adding '\r' if configured) in its write function.
+    // While puts() likely calculates strlen internally, the VFS write function already processes
+    // character-by-character for newline conversion, so using puts() is efficient here.
     puts(msg);
   } else {
-    // Use tx_buffer_at_ if msg points to tx_buffer_, otherwise fall back to strlen
-    size_t len = (msg == this->tx_buffer_) ? this->tx_buffer_at_ : strlen(msg);
     uart_write_bytes(this->uart_num_, msg, len);
+    // ESP-IDF uses only '\n' for historical reasons, while Arduino platforms use '\r\n'
     uart_write_bytes(this->uart_num_, "\n", 1);
   }
 }
 #else
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Arduino's println() writes the message followed by "\r\n" (CRLF).
+  // Previously, println() would call write(msg) which uses strlen() internally.
+  // By using write(buffer, size) directly, we avoid the strlen() call.
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>(msg), len);
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>("\r\n"), 2);
+}
 #endif
 
 const char *const UART_SELECTIONS[] = {

esphome/components/logger/logger_esp8266.cpp

@@ -33,7 +33,13 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Arduino's println() writes the message followed by "\r\n" (CRLF).
+  // Previously, println() would call write(msg) which uses strlen() internally.
+  // By using write(buffer, size) directly, we avoid the strlen() call.
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>(msg), len);
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>("\r\n"), 2);
+}
 
 const char *const UART_SELECTIONS[] = {"UART0", "UART1", "UART0_SWAP"};
 

esphome/components/logger/logger_host.cpp

@@ -3,7 +3,7 @@
 
 namespace esphome::logger {
 
-void HOT Logger::write_msg_(const char *msg) {
+void HOT Logger::write_msg_(const char *msg, size_t len) {
   time_t rawtime;
   struct tm *timeinfo;
   char buffer[80];

esphome/components/logger/logger_libretiny.cpp

@@ -49,7 +49,13 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Arduino's println() writes the message followed by "\r\n" (CRLF).
+  // Previously, println() would call write(msg) which uses strlen() internally.
+  // By using write(buffer, size) directly, we avoid the strlen() call.
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>(msg), len);
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>("\r\n"), 2);
+}
 
 const char *const UART_SELECTIONS[] = {"DEFAULT", "UART0", "UART1", "UART2"};
 

esphome/components/logger/logger_rp2040.cpp

@@ -27,7 +27,13 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Arduino's println() writes the message followed by "\r\n" (CRLF).
+  // Previously, println() would call write(msg) which uses strlen() internally.
+  // By using write(buffer, size) directly, we avoid the strlen() call.
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>(msg), len);
+  this->hw_serial_->write(reinterpret_cast<const uint8_t *>("\r\n"), 2);
+}
 
 const char *const UART_SELECTIONS[] = {"UART0", "UART1", "USB_CDC"};
 

esphome/components/logger/logger_zephyr.cpp

@@ -63,16 +63,15 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) {
+void HOT Logger::write_msg_(const char *msg, size_t len) {
 #ifdef CONFIG_PRINTK
   printk("%s\n", msg);
 #endif
   if (nullptr == this->uart_dev_) {
     return;
   }
-  while (*msg) {
+  for (size_t i = 0; i < len; i++) {
-    uart_poll_out(this->uart_dev_, *msg);
+    uart_poll_out(this->uart_dev_, msg[i]);
-    ++msg;
   }
   uart_poll_out(this->uart_dev_, '\n');
 }