ll_scan.c

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/******************************************************************************
 G_lat_scan (buf, lat)
     char *buf;
     double *lat;
 
 G_lon_scan (buf, lon)
     char *buf;
     double *lon;
 
 G_llres_scan (buf, res)
     char *buf;
     double *res;
 
 Convert ascii string representations of latitude/longitude to a double.
 The string format is:
 
       dd:mm:ss.ffh
 
 where:
       dd is degrees, 0-90 for latitude, 0-180 for longitude
       mm is minutes, 0-59
       ss is seconds, 0-59
       ff is fractions of a second, >= 0
       h  is 'n' or 's' for latitude,
             'e' or 'w' for longitude.
             missing for resolution
 
 lat (or lon) is set to the double value for the lat/lon represented in buf.
 
 lat is always in the range  -90 thru  90,
 lon is always in the range -180 thru 180.
 
 note: southern latitude and western longitude are returned as negative values.
 
 returns 1 if input format is ok, 0 otherwise.
******************************************************************************/
#include <grass/gis.h>
 
#define LL_TOLERANCE 10
 
static int scan_ll(const char *, const char *, double *, int);
static int check_minutes(const char *);
static int check_seconds(const char *);
 
int G_lat_scan(const char *buf, double *lat)
{
    return scan_ll(buf, "sn", lat, 90 + LL_TOLERANCE);
}
 
int G_lon_scan(const char *buf, double *lon)
{
    return scan_ll(buf, "we", lon, 360 + LL_TOLERANCE);
}
 
int G_llres_scan(const char *buf, double *res)
{
    char tbuf[100];
 
    snprintf(tbuf, sizeof(tbuf), "%se", buf);
    return scan_ll(tbuf, "we", res, 0);
}
 
#define MARKER 1
static int scan_ll(const char *buf, const char *dir, double *result, int max)
{
    char h[100];
    int d, m, s;
    char ps[20], *pps;
    double p, f;
    double pm = 0.0;
    char tbuf[100];
 
    snprintf(tbuf, sizeof(tbuf), "%s%c", buf,
             MARKER); /* add a marker at end of string */
    buf = tbuf;
 
    if (sscanf(buf, "%d:%d:%d.%[0123456789]%[^\n]", &d, &m, &s, ps, h) == 5) {
        p = 0.0;
        f = .1;
        for (pps = ps; *pps; pps++) {
            p += (*pps - '0') * f;
            f /= 10.0;
        }
    }
    else if (sscanf(buf, "%d:%d:%d%[^\n]", &d, &m, &s, h) == 4) {
        p = 0.0;
    }
    else if (sscanf(buf, "%d:%d.%[0123456789]%[^\n]", &d, &m, ps, h) == 4) {
        s = 0;
        p = 0.0;
        f = .1;
        for (pps = ps; *pps; pps++) {
            pm += (*pps - '0') * f;
            f /= 10.0;
        }
    }
    else if (sscanf(buf, "%d:%d%[^\n]", &d, &m, h) == 3) {
        p = 0.0;
        s = 0;
    }
    else if (sscanf(buf, "%d%[^\n]", &d, h) == 2) {
        p = 0.0;
        s = m = 0;
    }
    else
        return 0;
 
    if (d < 0)
        return 0;
    if (m < 0 || m >= 60)
        return 0;
    if (s < 0 || s >= 60)
        return 0;
 
    if (max) {
        if (d > max)
            return 0;
        if (d == max && (m > 0 || s > 0 || p > 0.0))
            return 0;
    }
 
    if (m && !check_minutes(buf))
        return 0;
    if (s && !check_seconds(buf))
        return 0;
 
    *result = d + (m + pm) / 60.0 + (s + p) / 3600.0;
 
    G_strip(h);
 
    if (*result == 0.0 && *h == MARKER)
        return (1);
 
    if (*h >= 'A' && *h <= 'Z')
        *h += 'a' - 'A';
 
    if (*h != dir[0] && *h != dir[1])
        return 0;
 
    if (h[1] != MARKER)
        return 0;
 
    if (*h == dir[0] && *result != 0.0)
        *result = -(*result);
 
    return 1;
}
 
static int check_minutes(const char *buf)
{
    /* skip over degrees */
    while (*buf != ':')
        if (*buf++ == 0)
            return 1;
    buf++;
 
    /* must have 2 digits for minutes */
    if (*buf < '0' || *buf > '9')
        return 0;
    buf++;
    if (*buf < '0' || *buf > '9')
        return 0;
    buf++;
    return (*buf < '0' || *buf > '9');
}
 
static int check_seconds(const char *buf)
{
    /* skip over degrees */
    while (*buf != ':')
        if (*buf++ == 0)
            return 1;
    buf++;
    /* skip over minutes */
    while (*buf != ':')
        if (*buf++ == 0)
            return 1;
    buf++;
 
    /* must have 2 digits for seconds */
    if (*buf < '0' || *buf > '9')
        return 0;
    buf++;
    if (*buf < '0' || *buf > '9')
        return 0;
    buf++;
    return (*buf < '0' || *buf > '9');
}