2json.c

/* @brief Convert the Abstract Syntax Tree generated by mpc for the DBC file
 * into an equivalent JSON file.
 * @copyright Richard James Howe (2018)
 * @license MIT *
 */
#include "2json.h"
#include "util.h"
#include <assert.h>
#include <time.h>

static int print_escaped(FILE *o, const char *string)
{
	assert(o);
	assert(string);
	char c;
	int r = 0;
	while((c = *(string)++)) {
		switch(c) {
		case '"':  r = fputs("&quot;", o); break;
		case '\'': r = fputs("&apos;", o); break;
		case '<':  r = fputs("&lt;",   o); break;
		case '>':  r = fputs("&gt;",   o); break;
		case '&':  r = fputs("&amp;",  o); break;
		default:
			   r = fputc(c, o);
		}
		if (r < 0)
			return -1;
	}
	return 0;
}

static int indent(FILE *o, unsigned depth)
{
	assert(o);
	while(depth--)
		if (fputc('\t', o) != '\t')
			return -1;
	return 0;
}

enum { INT, STRING, BOOL, FLOAT };

static int pfield(FILE *o, unsigned depth, bool last, int type, const char *node, const char *fmt, ...)
{
	assert(o);
	assert(node);
	assert(fmt);
	va_list args;
	assert(o && node && fmt);
	errno = 0;
	if (indent(o, depth) < 0)
		goto warn;
	if (fprintf(o, "\"%s\" : %s", node, type == STRING ? "\"" : "") < 0)
		goto warn;
	assert(fmt);
	va_start(args, fmt);
	int r = vfprintf(o, fmt, args);
	va_end(args);
	if (r < 0)
		goto warn;
	if (fprintf(o, "%s%s\n", type == STRING ? "\"" : "", !last ? "," : "") < 0)
		goto warn;
	return 0;
warn:
	warning("XML node generation, problem writing to FILE* <%p>: %s", o, emsg());
	return -1;
}

static int signal2json(signal_t *sig, FILE *o, unsigned depth)
{
	assert(sig);
	assert(o);
	indent(o, depth);
	fprintf(o, "\"signal\" : {\n");
	pfield(o, depth+1, false, STRING, "name",      "%s", sig->name);
	pfield(o, depth+1, false, INT,    "startbit",  "%u", sig->start_bit);
	pfield(o, depth+1, false, INT,    "bitlength", "%u", sig->bit_length);
	pfield(o, depth+1, false, STRING, "endianess", "%s", sig->endianess == endianess_motorola_e ? "motorola" : "intel");
	pfield(o, depth+1, false, FLOAT,  "scaling",   "%g", sig->scaling);
	pfield(o, depth+1, false, FLOAT,  "offset",    "%g", sig->offset);
	pfield(o, depth+1, false, FLOAT,  "minimum",   "%g", sig->minimum);
	pfield(o, depth+1, false, FLOAT,  "maximum",   "%g", sig->maximum);
	pfield(o, depth+1, false, BOOL,   "signed",    "%s", sig->is_signed ? "true" : "false");
	pfield(o, depth+1, false, INT,    "floating",  "%u", sig->is_floating ? sig->sigval : 0);

	indent(o, depth+1);
	fprintf(o, "\"units\" : \"");
	print_escaped(o, sig->units);
	fprintf(o, "\"\n");

	indent(o, depth);
	if (fprintf(o, "}") < 0)
		return -1;
	return 0;
}

static int msg2json(can_msg_t *msg, FILE *o, unsigned depth)
{
	assert(msg);
	assert(o);
	indent(o, depth);
	fprintf(o, "{\n");
	pfield(o, depth+1, false, STRING, "name", "%s", msg->name);
	pfield(o, depth+1, false, INT,    "id",   "%u", msg->id);
	pfield(o, depth+1, !(msg->signal_count), INT,    "dlc",  "%u", msg->dlc);

	signal_t *multiplexor = NULL;
	for (size_t i = 0; i < msg->signal_count; i++) {
		signal_t *sig = msg->sigs[i];
		if (sig->is_multiplexor) {
			if (multiplexor) {
				error("multiple multiplexor values detected (only one per CAN msg is allowed) for %s", msg->name);
				return -1;
			}
			multiplexor = sig;
			continue;
		}
		if (sig->is_multiplexed)
			continue;
		if (signal2json(sig, o, depth+1) < 0)
			return -1;
		if ((msg->signal_count && i < (msg->signal_count - 1)) || multiplexor)
			fprintf(o, ",");
		fprintf(o, "\n");
	}

	if (multiplexor) {
		indent(o, depth+1);
		fprintf(o, "\"multiplexor-group\" : {\n");
		indent(o, depth+2);
		fprintf(o, "\"multiplexor\" : {\n");
		if (signal2json(multiplexor, o, depth+3) < 0)
			return -1;
		fprintf(o, "\n");
		indent(o, depth+2);
		fprintf(o, "}%s\n", msg->signal_count ? "," : "");
		size_t multiplexed_count = 0;
		for (size_t i = 0; i < msg->signal_count; i++) {
			signal_t *sig = msg->sigs[i];
			if (sig->is_multiplexed)
				multiplexed_count++;
		}

		for (size_t i = 0, j = 0; i < msg->signal_count; i++) {
			signal_t *sig = msg->sigs[i];
			if (!(sig->is_multiplexed))
				continue;
			j++;
			indent(o, depth+2);
			fprintf(o, "\"multiplexed\" : {\n");
			pfield(o, depth+3, false, INT, "multiplexed-on", "%u",  sig->switchval);
			if (signal2json(sig, o, depth+3) < 0)
				return -1;
			fprintf(o, "\n");
			indent(o, depth+2);
			fprintf(o, "}");
			if (multiplexed_count && j < multiplexed_count)
				fprintf(o, ",");
			fprintf(o, "\n");

		}
		indent(o, depth+1);
		fprintf(o, "}\n");
	}

	indent(o, depth);
	if (fprintf(o, "}") < 0)
		return -1;
	return 0;
}

int dbc2json(dbc_t *dbc, FILE *output, bool use_time_stamps)
{
	assert(dbc);
	assert(output);
	/**@todo print out ECU node information, and the standard XML header */
	time_t rawtime = time(NULL);
	struct tm *timeinfo = localtime(&rawtime);

	fprintf(output, "{\n");
	fprintf(output, "\t\"description\" : \"JSON generated from a CAN DBC file\",\n");
	fprintf(output, "\t\"compiler\" : \"dbcc\",\n");
	fprintf(output, "\t\"site\" : \"https://github.com/howerj/dbcc\",\n");
	if (use_time_stamps)
		fprintf(output, "\t\"generated-on\": %s,", asctime(timeinfo));

	fprintf(output, "\t\"messages\" : [\n");
	for (size_t i = 0; i < dbc->message_count; i++) {
		if (msg2json(dbc->messages[i], output, 2) < 0)
			return -1;
		if (dbc->message_count && i < (dbc->message_count - 1))
			fprintf(output, ",");
		fprintf(output, "\n");
	}
	fprintf(output, "\t]\n");
	if (fprintf(output, "}\n") < 0)
		return -1;
	return 0;
}