text: /*
   * Copyright © 2014 Kosma Moczek <kosma@cloudyourcar.com>
   * 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.
   */
  
  #ifndef MINMEA_H
  #define MINMEA_H
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #include <stdio.h>
  #include <stdint.h>
  #include <stdbool.h>
  #include <errno.h>
  #include <time.h>
  #include <math.h>
  
  #ifndef NAN
  #define NAN (0)
  #endif
  
  #define MINMEA_MAX_LENGTH 80
  
  enum minmea_sentence_id {
      MINMEA_INVALID = -1,
      MINMEA_UNKNOWN = 0,
      MINMEA_SENTENCE_RMC,
      MINMEA_SENTENCE_GGA,
      MINMEA_SENTENCE_GSA,
      MINMEA_SENTENCE_GLL,
      MINMEA_SENTENCE_GST,
      MINMEA_SENTENCE_GSV,
  };
  
  struct minmea_float {
      int_least32_t value;
      int_least32_t scale;
  };
  
  struct minmea_date {
      int day;
      int month;
      int year;
  };
  
  struct minmea_time {
      int hours;
      int minutes;
      int seconds;
      int microseconds;
  };
  
  struct minmea_sentence_rmc {
      struct minmea_time time;
      bool valid;
      struct minmea_float latitude;
      struct minmea_float longitude;
      struct minmea_float speed;
      struct minmea_float course;
      struct minmea_date date;
      struct minmea_float variation;
  };
  
  struct minmea_sentence_gga {
      struct minmea_time time;
      struct minmea_float latitude;
      struct minmea_float longitude;
      int fix_quality;
      int satellites_tracked;
      struct minmea_float hdop;
      struct minmea_float altitude; char altitude_units;
      struct minmea_float height; char height_units;
      int dgps_age;
  };
  
  enum minmea_gll_status {
      MINMEA_GLL_STATUS_DATA_VALID = 'A',
      MINMEA_GLL_STATUS_DATA_NOT_VALID = 'V',
  };
  
  enum minmea_gll_mode {
      MINMEA_GLL_MODE_AUTONOMOUS = 'A',
      MINMEA_GLL_MODE_DPGS = 'D',
      MINMEA_GLL_MODE_DR = 'E',
  };
  
  struct minmea_sentence_gll {
      struct minmea_float latitude;
      struct minmea_float longitude;
      struct minmea_time time;
      char status;
      char mode;
  };
  
  struct minmea_sentence_gst {
      struct minmea_time time;
      struct minmea_float rms_deviation;
      struct minmea_float semi_major_deviation;
      struct minmea_float semi_minor_deviation;
      struct minmea_float semi_major_orientation;
      struct minmea_float latitude_error_deviation;
      struct minmea_float longitude_error_deviation;
      struct minmea_float altitude_error_deviation;
  };
  
  enum minmea_gsa_mode {
      MINMEA_GPGSA_MODE_AUTO = 'A',
      MINMEA_GPGSA_MODE_FORCED = 'M',
  };
  
  enum minmea_gsa_fix_type {
      MINMEA_GPGSA_FIX_NONE = 1,
      MINMEA_GPGSA_FIX_2D = 2,
      MINMEA_GPGSA_FIX_3D = 3,
  };
  
  struct minmea_sentence_gsa {
      char mode;
      int fix_type;
      int sats[12];
      struct minmea_float pdop;
      struct minmea_float hdop;
      struct minmea_float vdop;
  };
  
  struct minmea_sat_info {
      int nr;
      int elevation;
      int azimuth;
      int snr;
  };
  
  struct minmea_sentence_gsv {
      int total_msgs;
      int msg_nr;
      int total_sats;
      struct minmea_sat_info sats[4];
  };
  
  /**
   * Calculate raw sentence checksum. Does not check sentence integrity.
   */
  uint8_t minmea_checksum(const char *sentence);
  
  /**
   * Check sentence validity and checksum. Returns true for valid sentences.
   */
  bool minmea_check(const char *sentence, bool strict);
  
  /**
   * Determine talker identifier.
   */
  bool minmea_talker_id(char talker[3], const char *sentence);
  
  /**
   * Determine sentence identifier.
   */
  enum minmea_sentence_id minmea_sentence_id(const char *sentence, bool strict);
  
  /**
   * Scanf-like processor for NMEA sentences. Supports the following formats:
   * c - single character (char *)
   * d - direction, returned as 1/-1, default 0 (int *)
   * f - fractional, returned as value + scale (int *, int *)
   * i - decimal, default zero (int *)
   * s - string (char *)
   * t - talker identifier and type (char *)
   * T - date/time stamp (int *, int *, int *)
   * Returns true on success. See library source code for details.
   */
  bool minmea_scan(const char *sentence, const char *format, ...);
  
  /*
   * Parse a specific type of sentence. Return true on success.
   */
  bool minmea_parse_rmc(struct minmea_sentence_rmc *frame, const char *sentence);
  bool minmea_parse_gga(struct minmea_sentence_gga *frame, const char *sentence);
  bool minmea_parse_gsa(struct minmea_sentence_gsa *frame, const char *sentence);
  bool minmea_parse_gll(struct minmea_sentence_gll *frame, const char *sentence);
  bool minmea_parse_gst(struct minmea_sentence_gst *frame, const char *sentence);
  bool minmea_parse_gsv(struct minmea_sentence_gsv *frame, const char *sentence);
  
  /**
   * Convert GPS UTC date/time representation to a UNIX timestamp.
   */
  int minmea_gettime(struct timespec *ts, const struct minmea_date *date, const struct minmea_time *time_);
  
  /**
   * Rescale a fixed-point value to a different scale. Rounds towards zero.
   */
  static inline int_least32_t minmea_rescale(struct minmea_float *f, int_least32_t new_scale)
  {
      if (f->scale == 0)
          return 0;
      if (f->scale == new_scale)
          return f->value;
      if (f->scale > new_scale)
          return (f->value + ((f->value > 0) - (f->value < 0)) * f->scale/new_scale/2) / (f->scale/new_scale);
      else
          return f->value * (new_scale/f->scale);
  }
  
  /**
   * Convert a fixed-point value to a floating-point value.
   * Returns NaN for "unknown" values.
   */
  static inline float minmea_tofloat(struct minmea_float *f)
  {
      if (f->scale == 0)
          return NAN;
      return (float) f->value / (float) f->scale;
  }
  
  /**
   * Convert a raw coordinate to a floating point DD.DDD... value.
   * Returns NaN for "unknown" values.
   */
  static inline float minmea_tocoord(struct minmea_float *f)
  {
      if (f->scale == 0)
          return NAN;
      int_least32_t degrees = f->value / (f->scale * 100);
      int_least32_t minutes = f->value % (f->scale * 100);
      return (float) degrees + (float) minutes / (60 * f->scale);
  }
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* MINMEA_H */
  
  /* vim: set ts=4 sw=4 et: */
  