hamnet70/impl/src/jsonlogger.c

#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>

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

#include "jsonlogger.h"

#define LOG_OR_RETURN(...) \
	if(dprintf(m_fifo_fd, __VA_ARGS__) < 0) { \
		return false; \
	}

static int m_fifo_fd = -1;
static char m_fifo_path[1024];

static bool start_message(void)
{
	if(m_fifo_fd < 0) {
		// FIFO was not opened yet. Try to open it now.
		m_fifo_fd = open(m_fifo_path, O_WRONLY | O_NONBLOCK);
		if(m_fifo_fd < 0) {
			if(errno != ENXIO) {
				perror("open");
			}
			return false;
		}
	}

	ssize_t ret = write(m_fifo_fd, "{", 1);
	if(ret < 0) {
		// FIFO is not writable or other error
		switch(errno) {
			case EAGAIN: // FIFO not ready for writing -> drop message
				break;

			case EPIPE: // FIFO was closed on the other side
				close(m_fifo_fd);
				m_fifo_fd = -1;
				break;

			default: // other errors are logged to stderr
				perror("write");
				break;
		}

		return false;
	}

	return true;
}

static bool end_message(void)
{
	ssize_t ret = write(m_fifo_fd, "}\n", 2);
	if(ret < 0) {
		// FIFO is not writable or other error
		if(errno != EAGAIN) {
			perror("write");
		}

		return false;
	}

	return true;
}


bool jsonlogger_init(const char *fifoname)
{
	// try to create the named FIFO
	int ret = mkfifo(fifoname, 0666);
	if(ret < 0) {
		if(errno != EEXIST) {
			perror("mkfifo");
			return false;
		}
	}

	strncpy(m_fifo_path, fifoname, sizeof(m_fifo_path));

	m_fifo_fd = -1; // open on demand

	return true;
}


void jsonlogger_shutdown(void)
{
	close(m_fifo_fd);
}


bool jsonlogger_log_simple_integer(const char *msg_type, int64_t value)
{
	if(!start_message()) {
		return false;
	}

	LOG_OR_RETURN("\"%s\": %ld", msg_type, value);

	return end_message();
}


bool jsonlogger_log_simple_double(const char *msg_type, double value)
{
	if(!start_message()) {
		return false;
	}

	LOG_OR_RETURN("\"%s\": %g", msg_type, value);

	return end_message();
}


bool jsonlogger_log_rx_stats(const rx_stats_t *rx_stats)
{
	if(!start_message()) {
		return false;
	}

	LOG_OR_RETURN("\"preambles_found\": %zd, ", rx_stats->preambles_found);
	LOG_OR_RETURN("\"successful_decodes\": %zd, ", rx_stats->successful_decodes);
	LOG_OR_RETURN("\"failed_decodes\": %zd, ", rx_stats->failed_decodes);
	LOG_OR_RETURN("\"header_errors\": %zd", rx_stats->header_errors);

	return end_message();
}