CToolBox/include/toolbox/logger.h

#ifndef LOGGER_H
#define LOGGER_H

/* LOGGER RETURN CODE */
#define LOGGER_RC_TYPE unsigned char
extern __thread LOGGER_RC_TYPE logger_errno;
#define LOGGER_RC_OK   ((LOGGER_RC_TYPE) 0L) /* No Error */
#define LOGGER_RC_EFM  ((LOGGER_RC_TYPE) 1L) /* Failed to malloc */
#define LOGGER_RC_EVN  ((LOGGER_RC_TYPE) 2L) /* Value is Null */

#if defined(LOGGER_TYPEDEF) || defined(TYPEDEFS)
typedef struct str str_st;
#endif	/* LOGGER_TYPEDEF || TYPEDEFS */

enum logger_level {
	LL_TRACE,
	LL_DEBUG,
	LL_INFO,
	LL_WARN,
	LL_ERROR,
	LL_FATAL
};

typedef void (*_print_like)(const char *, ...);

struct logger {
	_print_like trace;
	_print_like debug;
	_print_like info;
	_print_like warn;
	_print_like error;
	_print_like fatal;
};


struct logger* logger_create(enum logger_level lvl);
LOGGER_RC_TYPE logger_destroy(struct logger *logger);

#if defined(LOGGER_IMP) || defined(IMPLEMENTATIONS)

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#if defined(LOGGER_LOG) || defined(LOGS)
  #define __LOG(OUT, PFX, TXT) fprintf(OUT, PFX" %s: %s", __func__, TXT)
  #define LOG_ERROR(TXT) __LOG(stderr, "[ERROR]", TXT)
#else
  #define LOG_ERROR(TXT) ;
#endif	/* LOGGER_LOG */

#define TEST_FOR_NULL(POINTER)						\
	if ( POINTER == NULL ) {					\
		LOG_ERROR("Null Pointer Not Expected");		\
		logger_errno = LOGGER_RC_EVN;				\
		return logger_errno;					\
	}

#define CHECK_MALLOC(POINTER, STR_RC)					\
	if ( POINTER == NULL ) {					\
		LOG_ERROR("Failed to malloc");				\
		logger_errno = LOGGER_RC_EFM;				\
		return STR_RC;						\
	}

static void nop(const char *format, ...) {(void) format;}

__attribute__((format(printf, 1, 2)))
static void trace(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stdout, "[TRACE] ");
	vfprintf(stdout, format, vargs);
}

__attribute__((format(printf, 1, 2)))
static void debug(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stdout, "[DEBUG] ");
	vfprintf(stdout, format, vargs);
}

__attribute__((format(printf, 1, 2)))
static void info(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stdout, "[INFO] ");
	vfprintf(stdout, format, vargs);
}

__attribute__((format(printf, 1, 2)))
static void warn(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stdout, "[WARN] ");
	vfprintf(stdout, format, vargs);
}

__attribute__((format(printf, 1, 2)))
static void error(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stderr, "[ERROR] ");
	vfprintf(stderr, format, vargs);
}

__attribute__((format(printf, 1, 2)))
static void fatal(const char *format, ...) {
	va_list vargs;
	va_start(vargs, format);
	fprintf(stderr, "[FATAL] ");
	vfprintf(stderr, format, vargs);
}

struct logger* logger_create(enum logger_level lvl) {
	logger_errno = LOGGER_RC_OK;
	struct logger *ret = malloc(sizeof(struct logger));
	CHECK_MALLOC(ret, NULL)

	ret->trace = *nop;
	ret->debug = *nop;
	ret->info  = *nop;
	ret->warn  = *nop;
	ret->error = *nop;
	ret->fatal = *nop;

	switch (lvl) {
	case LL_TRACE:
		ret->trace = *trace;
		/* fall through */
	case LL_DEBUG:
		ret->debug = *debug;
		/* fall through */
	case LL_INFO:
		ret->info = *info;
		/* fall through */
	case LL_WARN:
		ret->warn = *warn;
		/* fall through */
	case LL_ERROR:
		ret->error = *error;
		/* fall through */
	case LL_FATAL:
		ret->fatal = *fatal;
	}

	return ret;
}

LOGGER_RC_TYPE logger_destroy(struct logger *logger) {
	logger_errno = LOGGER_RC_OK;
	TEST_FOR_NULL(logger);
	free(logger);
	return LOGGER_RC_OK;
}

#undef LOG_ERROR
#undef TEST_FOR_NULL
#undef CHECK_MALLOC

#endif	/* LOGGER_IMP || IMPLEMENTATIONS */

#endif	/* LOGGER_H */