漫话Redis源码之六十

geo相关的函数，直接跳过吧，无非就是position相关的转换，没啥好看的。对理解整体的作用不大。

int geohashDecode(const GeoHashRange long_range, const GeoHashRange lat_range,
                   const GeoHashBits hash, GeoHashArea *area) {
    if (HASHISZERO(hash) || NULL == area || RANGEISZERO(lat_range) ||
        RANGEISZERO(long_range)) {
        return 0;
    }
 
    area->hash = hash;
    uint8_t step = hash.step;
    uint64_t hash_sep = deinterleave64(hash.bits); /* hash = [LAT][LONG] */
 
    double lat_scale = lat_range.max - lat_range.min;
    double long_scale = long_range.max - long_range.min;
 
    uint32_t ilato = hash_sep;       /* get lat part of deinterleaved hash */
    uint32_t ilono = hash_sep >> 32; /* shift over to get long part of hash */
 
    /* divide by 2**step.
     * Then, for 0-1 coordinate, multiply times scale and add
       to the min to get the absolute coordinate. */
    area->latitude.min =
        lat_range.min + (ilato * 1.0 / (1ull << step)) * lat_scale;
    area->latitude.max =
        lat_range.min + ((ilato + 1) * 1.0 / (1ull << step)) * lat_scale;
    area->longitude.min =
        long_range.min + (ilono * 1.0 / (1ull << step)) * long_scale;
    area->longitude.max =
        long_range.min + ((ilono + 1) * 1.0 / (1ull << step)) * long_scale;
 
    return 1;
}
 
int geohashDecodeType(const GeoHashBits hash, GeoHashArea *area) {
    GeoHashRange r[2] = {{0}};
    geohashGetCoordRange(&r[0], &r[1]);
    return geohashDecode(r[0], r[1], hash, area);
}
 
int geohashDecodeWGS84(const GeoHashBits hash, GeoHashArea *area) {
    return geohashDecodeType(hash, area);
}
 
int geohashDecodeAreaToLongLat(const GeoHashArea *area, double *xy) {
    if (!xy) return 0;
    xy[0] = (area->longitude.min + area->longitude.max) / 2;
    if (xy[0] > GEO_LONG_MAX) xy[0] = GEO_LONG_MAX;
    if (xy[0] < GEO_LONG_MIN) xy[0] = GEO_LONG_MIN;
    xy[1] = (area->latitude.min + area->latitude.max) / 2;
    if (xy[1] > GEO_LAT_MAX) xy[1] = GEO_LAT_MAX;
    if (xy[1] < GEO_LAT_MIN) xy[1] = GEO_LAT_MIN;
    return 1;
}
 
int geohashDecodeToLongLatType(const GeoHashBits hash, double *xy) {
    GeoHashArea area = {{0}};
    if (!xy || !geohashDecodeType(hash, &area))
        return 0;
    return geohashDecodeAreaToLongLat(&area, xy);
}
 
int geohashDecodeToLongLatWGS84(const GeoHashBits hash, double *xy) {
    return geohashDecodeToLongLatType(hash, xy);
}
 
static void geohash_move_x(GeoHashBits *hash, int8_t d) {
    if (d == 0)
        return;
 
    uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaULL;
    uint64_t y = hash->bits & 0x5555555555555555ULL;
 
    uint64_t zz = 0x5555555555555555ULL >> (64 - hash->step * 2);
 
    if (d > 0) {
        x = x + (zz + 1);
    } else {
        x = x | zz;
        x = x - (zz + 1);
    }
 
    x &= (0xaaaaaaaaaaaaaaaaULL >> (64 - hash->step * 2));
    hash->bits = (x | y);
}
 
static void geohash_move_y(GeoHashBits *hash, int8_t d) {
    if (d == 0)
        return;
 
    uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaULL;
    uint64_t y = hash->bits & 0x5555555555555555ULL;
 
    uint64_t zz = 0xaaaaaaaaaaaaaaaaULL >> (64 - hash->step * 2);
    if (d > 0) {
        y = y + (zz + 1);
    } else {
        y = y | zz;
        y = y - (zz + 1);
    }
    y &= (0x5555555555555555ULL >> (64 - hash->step * 2));
    hash->bits = (x | y);
}
 
void geohashNeighbors(const GeoHashBits *hash, GeoHashNeighbors *neighbors) {
    neighbors->east = *hash;
    neighbors->west = *hash;
    neighbors->north = *hash;
    neighbors->south = *hash;
    neighbors->south_east = *hash;
    neighbors->south_west = *hash;
    neighbors->north_east = *hash;
    neighbors->north_west = *hash;
 
    geohash_move_x(&neighbors->east, 1);
    geohash_move_y(&neighbors->east, 0);
 
    geohash_move_x(&neighbors->west, -1);
    geohash_move_y(&neighbors->west, 0);
 
    geohash_move_x(&neighbors->south, 0);
    geohash_move_y(&neighbors->south, -1);
 
    geohash_move_x(&neighbors->north, 0);
    geohash_move_y(&neighbors->north, 1);
 
    geohash_move_x(&neighbors->north_west, -1);
    geohash_move_y(&neighbors->north_west, 1);
 
    geohash_move_x(&neighbors->north_east, 1);
    geohash_move_y(&neighbors->north_east, 1);
 
    geohash_move_x(&neighbors->south_east, 1);
    geohash_move_y(&neighbors->south_east, -1);
 
    geohash_move_x(&neighbors->south_west, -1);
    geohash_move_y(&neighbors->south_west, -1);
}