CircularLogPrinter - In-Memory Logging with Optional Output

CircularLogPrinter

Path: src/modbus/circular_log_printer.h

Revision History:

• 2023-11-15: Initial documentation

CircularLogPrinter is an Arduino-compatible Print implementation that stores the last N log lines in a circular buffer. It can optionally mirror all output to another stream (like Serial). The component is designed to be 100% reinterpret-cast-free for MISRA/CPPCHECK compliance, making it suitable for industrial applications.

REQUIREMENTS

• FreeRTOS (for optional thread safety)
• ESP32 IDF framework
• Global Serial object (when using default constructor)

PROVIDES

• using LogRingBuffer = char[LOG_BUFFER_LINES][LOG_BUFFER_LINE_LENGTH]
• class CircularLogPrinter: A Print implementation storing log lines in a circular buffer

FEATURES

• Configurable circular buffer size via macros
• Thread-safe operation (optional)
• Ability to attach to ESP-IDF’s logging system
• No pointer type casting (MISRA compliant)
• Retrieves log history by line number
• Optional mirroring to any Print-compatible output
• Efficient multi-byte writes

DEPENDENCIES

• Arduino.h
• Print.h
• esp_log.h

BEHAVIOUR

TODOS

PERFORMANCE

• Consider using a more efficient buffer strategy for high-volume logging
• Potential optimization by pre-allocating buffer space when attaching to ESP-IDF log

SECURITY

• No direct security concerns as this is an output-only component
• Consider adding sanitization for control characters that could affect terminal displays

COMPLIANCE

• Already designed for MISRA/CPPCHECK compliance with no reinterpret casts
• Consider adding formal verification of buffer access bounds

RECOMMENDATIONS

• Adjust LOG_BUFFER_LINES and LOG_BUFFER_LINE_LENGTH based on available memory and application needs
• For performance-critical applications, consider disabling thread safety with LOG_BUFFER_THREAD_SAFE=0
• When using with Modbus, attach to ESP-IDF logging to capture all system messages including Modbus communication logs

Example

#include "circular_log_printer.h"

// Create logger with default output (Serial)
CircularLogPrinter logger;

void setup() {
  Serial.begin(115200);

  // Attach to ESP-IDF logging system
  logger.attachToEspLog();

  // Log some messages
  logger.println("System initializing...");

  // Later, retrieve historical logs
  for (size_t i = 0; i < logger.lines(); i++) {
    Serial.println(logger.getLine(i));
  }
}