A lean, efficient, accurate geohash encoder and decoder library implemented in C

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Geohash encoder/decoder in C

A lean, efficient, accurate geohash encoder and decoder library implemented in C. It does not depend on the C standard library and is well-suited for use in embedded systems. Care has been taken to ensure results are as accurate as possible within the limitations of IEEE 754 double precision. It's also very fast, decoding ~50 million and encoding ~80 million latlons per second on modern desktop and laptop hardware.

This is the fastest, most correct, and most accurate (to double precision) geohash decoder and encoder currently available.

// Validate and decode a geohash into a lat/lon pair. Returns 1 on success,
// or 0 if the buffer does not contain a valid geohash.
int geohash_decode(double *lat, double *lon, const char *buf, int len);

// Store a 21-byte geohash encoding of a lat/lon pair. Does not write a
// terminating null byte. Truncate as needed.
void geohash_encode(char *buf, double lat, double lon);

Example usage

The source file tests/example.c demonstrates decoding and encoding lat/lon coordinates as command line arguments.

$ ./example -d ezs42 dppn59uz86jzd 000000000000 zzzzzzzzzzzz
ezs42          [email protected] 36' 17.929" N    [email protected] 36' 10.898" W
dppn59uz86jzd  [email protected] 26' 26.160" N   [email protected] 59' 45.239" W
000000000000   [email protected] 59' 59.999" S  [email protected] 59' 59.999" W
zzzzzzzzzzzz   [email protected] 59' 59.999" N  [email protected] 59' 59.999" E

$ ./example -e "[email protected]'26.160\"N [email protected]'45.239\"W"
dppn59uz86jzd  [email protected] 26' 26.160" N   [email protected] 59' 45.239" W
  • Decoding is faster than encoding

    Decoding is faster than encoding

    encode 53.711 M-ops/sec
    decode 61.235 M-ops/sec

    This is the case at least for my machine. I wonder why.

                .-/+oossssoo+/-.               [email protected] 
            `:+ssssssssssssssssss+:`           ----------- 
          -+ssssssssssssssssssyyssss+-         OS: Ubuntu 20.04.2 LTS x86_64 
        .ossssssssssssssssssdMMMNysssso.       Host: HP EliteBook 840 G6 
       /ssssssssssshdmmNNmmyNMMMMhssssss/      Kernel: 5.11.0-25-generic 
      +ssssssssshmydMMMMMMMNddddyssssssss+     Uptime: 3 days, 52 mins 
     /sssssssshNMMMyhhyyyyhmNMMMNhssssssss/    Packages: 2519 (dpkg), 8 (snap) 
    .ssssssssdMMMNhsssssssssshNMMMdssssssss.   Shell: bash 5.0.17 
    +sssshhhyNMMNyssssssssssssyNMMMysssssss+   Resolution: 1920x1080 
    ossyNMMMNyMMhsssssssssssssshmmmhssssssso   DE: GNOME 
    ossyNMMMNyMMhsssssssssssssshmmmhssssssso   WM: Mutter 
    +sssshhhyNMMNyssssssssssssyNMMMysssssss+   WM Theme: Adwaita 
    .ssssssssdMMMNhsssssssssshNMMMdssssssss.   Theme: Yaru-dark [GTK2/3] 
     /sssssssshNMMMyhhyyyyhdNMMMNhssssssss/    Icons: Yaru [GTK2/3] 
      +sssssssssdmydMMMMMMMMddddyssssssss+     Terminal: gnome-terminal 
       /ssssssssssshdmNNNNmyNMMMMhssssss/      CPU: Intel i7-8565U (8) @ 4.600GHz 
        .ossssssssssssssssssdMMMNysssso.       GPU: Intel UHD Graphics 620 
          -+sssssssssssssssssyyyssss+-         Memory: 10658MiB / 15818MiB 
    opened by aquiire 0
Christopher Wellons
Christopher Wellons
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