Serial logging helper for Arduino programs

serial_logger.h

/**
 * SPDX-License-Identifier: MIT
 *
 * Arduino logging utility (with logging levels)
 * =============================================
 *
 * Settings
 * --------
 * 
 * E_LEVEL: set the desired maximum logging level to be displayed, the default
 *          is E_TRACE.
 * 
 * F_CRASH: function to instantly crash a program, it is used by any FATAL
 *          level message. This can be disabled by setting to `NOOP', the
 *          default is exit(1).
 *
 * Usage
 * -----
 * 
 * Add this into a file called `serial_logger.h' and then include the file in
 * your application with:
 *
 *     #include "serial_logger.h"
 *
 * Settings should be defined using `#define SETTING_NAME' *before* including
 * the logging file.
 */

#ifndef _SERIAL_LOGGER
#define _SERIAL_LOGGER

/* Define log levels */
#define E_FATAL 0
#define E_ERROR 1
#define E_WARN 2
#define E_INFO 3
#define E_DEBUG 4
#define E_TRACE 5

/* Max level to show */
#ifndef E_LEVEL
#define E_LEVEL E_TRACE
#endif

#ifndef F_CRASH
#if F_CRASH == NOOP
#define F_CRASH (void)0
#else
#define F_CRASH exit(1)
#endif
#endif

#if E_LEVEL >= 0
static inline int debug_printf(int level, const char *file, int line, const char *format, ...)
    __attribute__((format(printf, 3, 4))) {
    int bytes = 0;
    char buffer[1024];
    
    va_list list;

    switch(level) {
    case E_TRACE:
        Serial.print("TRACE");
        break;
    case E_DEBUG:
        Serial.print("DEBUG");
        break;
    case E_INFO:
        Serial.print("INFO ");
        break;
    case E_WARN:
        Serial.print("WARN ");
        break;
    case E_ERROR:
        Serial.print("ERROR");
        break;
    case E_TRACE:
    default:
        Serial.print("FATAL");
        break;
    }
    bytes += 5;

    Serial.print(" @ ");
    Serial.print(file);
    Serial.print(":");
    snprintf(buffer, sizeof(buffer), "%d", line);
    Serial.print(buffer);
    Serial.print(": ");

    bytes += 6 + strlen(file) + strlen(buffer);
    
    va_start(list, format);
    bytes += vsnprintf(buffer, sizeof(buffer), format, list);
    Serial.print(buffer);
    va_end(list);

    if (level <= E_FATAL)
        F_CRASH;

    Serial.print("\n");
    return bytes + 1;
}
#endif

#if E_LEVEL >= E_TRACE
#define TRACE(fmt, ...) debug_printf(E_TRACE, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define TRACE_RAW(msg) Serial.print(msg)
#else
#define TRACE(fmt, ...)
#define TRACE_RAW(msg)
#endif
#if E_LEVEL >= E_DEBUG
#define DEBUG(fmt, ...) debug_printf(E_DEBUG, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define DEBUG_RAW(msg) Serial.print(msg)
#else
#define DEBUG(fmt, ...)
#define DEBUG_RAW(msg)
#endif
#if E_LEVEL >= E_INFO
#define INFO(fmt, ...) debug_printf(E_INFO, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define INFO_RAW(msg) Serial.print(msg)
#else
#define INFO(fmt, ...)
#define INFO_RAW(msg)
#endif
#if E_LEVEL >= E_WARN
#define WARN(fmt, ...) debug_printf(E_WARN, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define WARN_RAW(msg) Serial.print(msg)
#else
#define WARN(fmt, ...)
#define WARN_RAW(msg)
#endif
#if E_LEVEL >= E_ERROR
#define ERROR(fmt, ...) debug_printf(E_ERROR, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define ERROR_RAW(msg) Serial.print(msg)
#else
#define ERROR(fmt, ...)
#define ERROR_RAW(msg)
#endif
#if E_LEVEL >= E_FATAL
#define FATAL(fmt, ...) debug_printf(E_FATAL, __FILE__, __LINE__, fmt, ##__VA_ARGS__)
#define FATAL_RAW(msg) Serial.print(msg)
#else
#define FATAL(fmt, ...)
#define FATAL_RAW(msg)
#endif

#endif /* _SERIAL_LOGGER */