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minmea.c
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minmea.c
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/*
* Copyright © 2014 Kosma Moczek <[email protected]>
* This program is free software. It comes without any warranty, to the extent
* permitted by applicable law. You can redistribute it and/or modify it under
* the terms of the Do What The Fuck You Want To Public License, Version 2, as
* published by Sam Hocevar. See the COPYING file for more details.
*/
#include "minmea.h"
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#define boolstr(s) ((s) ? "true" : "false")
static int hex2int(char c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'A' && c <= 'F')
return c - 'A' + 10;
if (c >= 'a' && c <= 'f')
return c - 'a' + 10;
return -1;
}
uint8_t minmea_checksum(const char *sentence)
{
// Support senteces with or without the starting dollar sign.
if (*sentence == '$')
sentence++;
uint8_t checksum = 0x00;
// The optional checksum is an XOR of all bytes between "$" and "*".
while (*sentence && *sentence != '*')
checksum ^= *sentence++;
return checksum;
}
bool minmea_check(const char *sentence, bool strict)
{
uint8_t checksum = 0x00;
// A valid sentence starts with "$".
if (*sentence++ != '$')
return false;
// The optional checksum is an XOR of all bytes between "$" and "*".
while (*sentence && *sentence != '*' && isprint((unsigned char) *sentence))
checksum ^= *sentence++;
// If checksum is present...
if (*sentence == '*') {
// Extract checksum.
sentence++;
int upper = hex2int(*sentence++);
if (upper == -1)
return false;
int lower = hex2int(*sentence++);
if (lower == -1)
return false;
int expected = upper << 4 | lower;
// Check for checksum mismatch.
if (checksum != expected)
return false;
} else if (strict) {
// Discard non-checksummed frames in strict mode.
return false;
}
// The only stuff allowed at this point is a newline.
while (*sentence == '\r' || *sentence == '\n') {
sentence++;
}
if (*sentence) {
return false;
}
return true;
}
bool minmea_scan(const char *sentence, const char *format, ...)
{
bool result = false;
bool optional = false;
if (sentence == NULL)
return false;
va_list ap;
va_start(ap, format);
const char *field = sentence;
#define next_field() \
do { \
/* Progress to the next field. */ \
while (minmea_isfield(*sentence)) \
sentence++; \
/* Make sure there is a field there. */ \
if (*sentence == ',') { \
sentence++; \
field = sentence; \
} else { \
field = NULL; \
} \
} while (0)
while (*format) {
char type = *format++;
if (type == ';') {
// All further fields are optional.
optional = true;
continue;
}
if (!field && !optional) {
// Field requested but we ran out if input. Bail out.
goto parse_error;
}
switch (type) {
case 'c': { // Single character field (char).
char value = '\0';
if (field && minmea_isfield(*field))
value = *field;
*va_arg(ap, char *) = value;
} break;
case 'd': { // Single character direction field (int).
int value = 0;
if (field && minmea_isfield(*field)) {
switch (*field) {
case 'N':
case 'E':
value = 1;
break;
case 'S':
case 'W':
value = -1;
break;
default:
goto parse_error;
}
}
*va_arg(ap, int *) = value;
} break;
case 'f': { // Fractional value with scale (struct minmea_float).
int sign = 0;
int_least32_t value = -1;
int_least32_t scale = 0;
if (field) {
while (minmea_isfield(*field)) {
if (*field == '+' && !sign && value == -1) {
sign = 1;
} else if (*field == '-' && !sign && value == -1) {
sign = -1;
} else if (isdigit((unsigned char) *field)) {
int digit = *field - '0';
if (value == -1)
value = 0;
if (value > (INT_LEAST32_MAX-digit) / 10) {
/* we ran out of bits, what do we do? */
if (scale) {
/* truncate extra precision */
break;
} else {
/* integer overflow. bail out. */
goto parse_error;
}
}
value = (10 * value) + digit;
if (scale)
scale *= 10;
} else if (*field == '.' && scale == 0) {
scale = 1;
} else if (*field == ' ') {
/* Allow spaces at the start of the field. Not NMEA
* conformant, but some modules do this. */
if (sign != 0 || value != -1 || scale != 0)
goto parse_error;
} else {
goto parse_error;
}
field++;
}
}
if ((sign || scale) && value == -1)
goto parse_error;
if (value == -1) {
/* No digits were scanned. */
value = 0;
scale = 0;
} else if (scale == 0) {
/* No decimal point. */
scale = 1;
}
if (sign)
value *= sign;
*va_arg(ap, struct minmea_float *) = (struct minmea_float) {value, scale};
} break;
case 'i': { // Integer value, default 0 (int).
int value = 0;
if (field) {
char *endptr;
value = strtol(field, &endptr, 10);
if (minmea_isfield(*endptr))
goto parse_error;
}
*va_arg(ap, int *) = value;
} break;
case 's': { // String value (char *).
char *buf = va_arg(ap, char *);
if (field) {
while (minmea_isfield(*field))
*buf++ = *field++;
}
*buf = '\0';
} break;
case 't': { // NMEA talker+sentence identifier (char *).
// This field is always mandatory.
if (!field)
goto parse_error;
if (field[0] != '$')
goto parse_error;
for (int f=0; f<5; f++)
if (!minmea_isfield(field[1+f]))
goto parse_error;
char *buf = va_arg(ap, char *);
memcpy(buf, field+1, 5);
buf[5] = '\0';
} break;
case 'D': { // Date (int, int, int), -1 if empty.
struct minmea_date *date = va_arg(ap, struct minmea_date *);
int d = -1, m = -1, y = -1;
if (field && minmea_isfield(*field)) {
// Always six digits.
for (int f=0; f<6; f++)
if (!isdigit((unsigned char) field[f]))
goto parse_error;
char dArr[] = {field[0], field[1], '\0'};
char mArr[] = {field[2], field[3], '\0'};
char yArr[] = {field[4], field[5], '\0'};
d = strtol(dArr, NULL, 10);
m = strtol(mArr, NULL, 10);
y = strtol(yArr, NULL, 10);
}
date->day = d;
date->month = m;
date->year = y;
} break;
case 'T': { // Time (int, int, int, int), -1 if empty.
struct minmea_time *time_ = va_arg(ap, struct minmea_time *);
int h = -1, i = -1, s = -1, u = -1;
if (field && minmea_isfield(*field)) {
// Minimum required: integer time.
for (int f=0; f<6; f++)
if (!isdigit((unsigned char) field[f]))
goto parse_error;
char hArr[] = {field[0], field[1], '\0'};
char iArr[] = {field[2], field[3], '\0'};
char sArr[] = {field[4], field[5], '\0'};
h = strtol(hArr, NULL, 10);
i = strtol(iArr, NULL, 10);
s = strtol(sArr, NULL, 10);
field += 6;
// Extra: fractional time. Saved as microseconds.
if (*field++ == '.') {
uint32_t value = 0;
uint32_t scale = 1000000LU;
while (isdigit((unsigned char) *field) && scale > 1) {
value = (value * 10) + (*field++ - '0');
scale /= 10;
}
u = value * scale;
} else {
u = 0;
}
}
time_->hours = h;
time_->minutes = i;
time_->seconds = s;
time_->microseconds = u;
} break;
case '_': { // Ignore the field.
} break;
default: { // Unknown.
goto parse_error;
}
}
next_field();
}
result = true;
parse_error:
va_end(ap);
return result;
}
bool minmea_talker_id(char talker[3], const char *sentence)
{
char type[6];
if (!minmea_scan(sentence, "t", type))
return false;
talker[0] = type[0];
talker[1] = type[1];
talker[2] = '\0';
return true;
}
enum minmea_sentence_id minmea_sentence_id(const char *sentence, bool strict)
{
if (!minmea_check(sentence, strict))
return MINMEA_INVALID;
char type[6];
if (!minmea_scan(sentence, "t", type))
return MINMEA_INVALID;
if (!strcmp(type+2, "GBS"))
return MINMEA_SENTENCE_GBS;
if (!strcmp(type+2, "GGA"))
return MINMEA_SENTENCE_GGA;
if (!strcmp(type+2, "GLL"))
return MINMEA_SENTENCE_GLL;
if (!strcmp(type+2, "GSA"))
return MINMEA_SENTENCE_GSA;
if (!strcmp(type+2, "GST"))
return MINMEA_SENTENCE_GST;
if (!strcmp(type+2, "GSV"))
return MINMEA_SENTENCE_GSV;
if (!strcmp(type+2, "RMC"))
return MINMEA_SENTENCE_RMC;
if (!strcmp(type+2, "VTG"))
return MINMEA_SENTENCE_VTG;
if (!strcmp(type+2, "ZDA"))
return MINMEA_SENTENCE_ZDA;
return MINMEA_UNKNOWN;
}
bool minmea_parse_gbs(struct minmea_sentence_gbs *frame, const char *sentence)
{
// $GNGBS,170556.00,3.0,2.9,8.3,,,,*5C
char type[6];
if (!minmea_scan(sentence, "tTfffifff",
type,
&frame->time,
&frame->err_latitude,
&frame->err_longitude,
&frame->err_altitude,
&frame->svid,
&frame->prob,
&frame->bias,
&frame->stddev
))
return false;
if (strcmp(type+2, "GBS"))
return false;
return true;
}
bool minmea_parse_rmc(struct minmea_sentence_rmc *frame, const char *sentence)
{
// $GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62
char type[6];
char validity;
int latitude_direction;
int longitude_direction;
int variation_direction;
if (!minmea_scan(sentence, "tTcfdfdffDfd",
type,
&frame->time,
&validity,
&frame->latitude, &latitude_direction,
&frame->longitude, &longitude_direction,
&frame->speed,
&frame->course,
&frame->date,
&frame->variation, &variation_direction))
return false;
if (strcmp(type+2, "RMC"))
return false;
frame->valid = (validity == 'A');
frame->latitude.value *= latitude_direction;
frame->longitude.value *= longitude_direction;
frame->variation.value *= variation_direction;
return true;
}
bool minmea_parse_gga(struct minmea_sentence_gga *frame, const char *sentence)
{
// $GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
char type[6];
int latitude_direction;
int longitude_direction;
if (!minmea_scan(sentence, "tTfdfdiiffcfcf_",
type,
&frame->time,
&frame->latitude, &latitude_direction,
&frame->longitude, &longitude_direction,
&frame->fix_quality,
&frame->satellites_tracked,
&frame->hdop,
&frame->altitude, &frame->altitude_units,
&frame->height, &frame->height_units,
&frame->dgps_age))
return false;
if (strcmp(type+2, "GGA"))
return false;
frame->latitude.value *= latitude_direction;
frame->longitude.value *= longitude_direction;
return true;
}
bool minmea_parse_gsa(struct minmea_sentence_gsa *frame, const char *sentence)
{
// $GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39
char type[6];
if (!minmea_scan(sentence, "tciiiiiiiiiiiiifff",
type,
&frame->mode,
&frame->fix_type,
&frame->sats[0],
&frame->sats[1],
&frame->sats[2],
&frame->sats[3],
&frame->sats[4],
&frame->sats[5],
&frame->sats[6],
&frame->sats[7],
&frame->sats[8],
&frame->sats[9],
&frame->sats[10],
&frame->sats[11],
&frame->pdop,
&frame->hdop,
&frame->vdop))
return false;
if (strcmp(type+2, "GSA"))
return false;
return true;
}
bool minmea_parse_gll(struct minmea_sentence_gll *frame, const char *sentence)
{
// $GPGLL,3723.2475,N,12158.3416,W,161229.487,A,A*41$;
char type[6];
int latitude_direction;
int longitude_direction;
if (!minmea_scan(sentence, "tfdfdTc;c",
type,
&frame->latitude, &latitude_direction,
&frame->longitude, &longitude_direction,
&frame->time,
&frame->status,
&frame->mode))
return false;
if (strcmp(type+2, "GLL"))
return false;
frame->latitude.value *= latitude_direction;
frame->longitude.value *= longitude_direction;
return true;
}
bool minmea_parse_gst(struct minmea_sentence_gst *frame, const char *sentence)
{
// $GPGST,024603.00,3.2,6.6,4.7,47.3,5.8,5.6,22.0*58
char type[6];
if (!minmea_scan(sentence, "tTfffffff",
type,
&frame->time,
&frame->rms_deviation,
&frame->semi_major_deviation,
&frame->semi_minor_deviation,
&frame->semi_major_orientation,
&frame->latitude_error_deviation,
&frame->longitude_error_deviation,
&frame->altitude_error_deviation))
return false;
if (strcmp(type+2, "GST"))
return false;
return true;
}
bool minmea_parse_gsv(struct minmea_sentence_gsv *frame, const char *sentence)
{
// $GPGSV,3,1,11,03,03,111,00,04,15,270,00,06,01,010,00,13,06,292,00*74
// $GPGSV,3,3,11,22,42,067,42,24,14,311,43,27,05,244,00,,,,*4D
// $GPGSV,4,2,11,08,51,203,30,09,45,215,28*75
// $GPGSV,4,4,13,39,31,170,27*40
// $GPGSV,4,4,13*7B
char type[6];
if (!minmea_scan(sentence, "tiii;iiiiiiiiiiiiiiii",
type,
&frame->total_msgs,
&frame->msg_nr,
&frame->total_sats,
&frame->sats[0].nr,
&frame->sats[0].elevation,
&frame->sats[0].azimuth,
&frame->sats[0].snr,
&frame->sats[1].nr,
&frame->sats[1].elevation,
&frame->sats[1].azimuth,
&frame->sats[1].snr,
&frame->sats[2].nr,
&frame->sats[2].elevation,
&frame->sats[2].azimuth,
&frame->sats[2].snr,
&frame->sats[3].nr,
&frame->sats[3].elevation,
&frame->sats[3].azimuth,
&frame->sats[3].snr
)) {
return false;
}
if (strcmp(type+2, "GSV"))
return false;
return true;
}
bool minmea_parse_vtg(struct minmea_sentence_vtg *frame, const char *sentence)
{
// $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K*48
// $GPVTG,156.1,T,140.9,M,0.0,N,0.0,K*41
// $GPVTG,096.5,T,083.5,M,0.0,N,0.0,K,D*22
// $GPVTG,188.36,T,,M,0.820,N,1.519,K,A*3F
char type[6];
char c_true, c_magnetic, c_knots, c_kph, c_faa_mode;
if (!minmea_scan(sentence, "t;fcfcfcfcc",
type,
&frame->true_track_degrees,
&c_true,
&frame->magnetic_track_degrees,
&c_magnetic,
&frame->speed_knots,
&c_knots,
&frame->speed_kph,
&c_kph,
&c_faa_mode))
return false;
if (strcmp(type+2, "VTG"))
return false;
// values are only valid with the accompanying characters
if (c_true != 'T')
frame->true_track_degrees.scale = 0;
if (c_magnetic != 'M')
frame->magnetic_track_degrees.scale = 0;
if (c_knots != 'N')
frame->speed_knots.scale = 0;
if (c_kph != 'K')
frame->speed_kph.scale = 0;
frame->faa_mode = (enum minmea_faa_mode)c_faa_mode;
return true;
}
bool minmea_parse_zda(struct minmea_sentence_zda *frame, const char *sentence)
{
// $GPZDA,201530.00,04,07,2002,00,00*60
char type[6];
if(!minmea_scan(sentence, "tTiiiii",
type,
&frame->time,
&frame->date.day,
&frame->date.month,
&frame->date.year,
&frame->hour_offset,
&frame->minute_offset))
return false;
if (strcmp(type+2, "ZDA"))
return false;
// check offsets
if (abs(frame->hour_offset) > 13 ||
frame->minute_offset > 59 ||
frame->minute_offset < 0)
return false;
return true;
}
int minmea_getdatetime(struct tm *tm, const struct minmea_date *date, const struct minmea_time *time_)
{
if (date->year == -1 || time_->hours == -1)
return -1;
memset(tm, 0, sizeof(*tm));
if (date->year < 80) {
tm->tm_year = 2000 + date->year - 1900; // 2000-2079
} else if (date->year >= 1900) {
tm->tm_year = date->year - 1900; // 4 digit year, use directly
} else {
tm->tm_year = date->year; // 1980-1999
}
tm->tm_mon = date->month - 1;
tm->tm_mday = date->day;
tm->tm_hour = time_->hours;
tm->tm_min = time_->minutes;
tm->tm_sec = time_->seconds;
return 0;
}
int minmea_gettime(struct timespec *ts, const struct minmea_date *date, const struct minmea_time *time_)
{
struct tm tm;
if (minmea_getdatetime(&tm, date, time_))
return -1;
time_t timestamp = timegm(&tm); /* See README.md if your system lacks timegm(). */
if (timestamp != (time_t)-1) {
ts->tv_sec = timestamp;
ts->tv_nsec = time_->microseconds * 1000;
return 0;
} else {
return -1;
}
}
/* vim: set ts=4 sw=4 et: */