[In-Progress] Add Geo Commands

Current todo:
  - replace functions in zset.{c,h} with a new unified Redis
    zset access API.

Once we get the zset interface fixed, we can squash
relevant commits in this branch and have one nice commit
to merge into unstable.

This commit adds:
  - Geo commands
  - Tests; runnable with: ./runtest --single unit/geo
  - Geo helpers in deps/geohash-int/
  - src/geo.{c,h} and src/geojson.{c,h} implementing geo commands
  - Updated build configurations to get everything working
  - TEMPORARY: src/zset.{c,h} implementing zset score and zset
    range reading without writing to client output buffers.
  - Modified linkage of one t_zset.c function for use in zset.c

Conflicts:
	src/Makefile
	src/redis.c

Author: mattsta

deps/Makefile

@@ -36,6 +36,7 @@ distclean:
 	-(cd hiredis && $(MAKE) clean) > /dev/null || true
 	-(cd linenoise && $(MAKE) clean) > /dev/null || true
 	-(cd lua && $(MAKE) clean) > /dev/null || true
+	-(cd geohash-int && $(MAKE) clean) > /dev/null || true
 	-(cd jemalloc && [ -f Makefile ] && $(MAKE) distclean) > /dev/null || true
 	-(rm -f .make-*)
 
@@ -81,3 +82,9 @@ jemalloc: .make-prerequisites
 	cd jemalloc && $(MAKE) CFLAGS="$(JEMALLOC_CFLAGS)" LDFLAGS="$(JEMALLOC_LDFLAGS)" lib/libjemalloc.a
 
 .PHONY: jemalloc
+
+geohash-int: .make-prerequisites
+	@printf '%b %b\n' $(MAKECOLOR)MAKE$(ENDCOLOR) $(BINCOLOR)$@$(ENDCOLOR)
+	cd geohash-int && $(MAKE)
+
+.PHONY: geohash-int

deps/geohash-int/Makefile

@@ -0,0 +1,23 @@
+STD=
+WARN= -Wall
+OPT= -Ofast
+
+R_CFLAGS= $(STD) $(WARN) $(OPT) $(DEBUG) $(CFLAGS)
+R_LDFLAGS= $(LDFLAGS)
+DEBUG= -g
+
+R_CC=$(CC) $(R_CFLAGS)
+R_LD=$(CC) $(R_LDFLAGS)
+
+all: geohash.o geohash_helper.o
+
+.PHONY: all
+
+geohash.o: geohash.h geohash.c
+geohash_helper.o: geohash.h geohash_helper.h geohash_helper.c
+
+.c.o:
+	$(R_CC) -c $<
+
+clean:
+	rm -f *.o

deps/geohash-int/geohash.c

@@ -0,0 +1,290 @@
+/*
+ * Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
+ * Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *  * Neither the name of Redis nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without
+ *    specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "geohash.h"
+
+/**
+ * Hashing works like this:
+ * Divide the world into 4 buckets.  Label each one as such:
+ *  -----------------
+ *  |       |       |
+ *  |       |       |
+ *  | 0,1   | 1,1   |
+ *  -----------------
+ *  |       |       |
+ *  |       |       |
+ *  | 0,0   | 1,0   |
+ *  -----------------
+ */
+
+bool geohashGetCoordRange(uint8_t coord_type, GeoHashRange *lat_range,
+                          GeoHashRange *long_range) {
+    switch (coord_type) {
+    case GEO_WGS84_TYPE: {
+        /* These are constraints from EPSG:900913 / EPSG:3785 / OSGEO:41001 */
+        /* We can't geocode at the north/south pole. */
+        lat_range->max = 85.05112878;
+        lat_range->min = -85.05112878;
+        long_range->max = 180.0;
+        long_range->min = -180.0;
+        break;
+    }
+    case GEO_MERCATOR_TYPE: {
+        lat_range->max = 20037726.37;
+        lat_range->min = -20037726.37;
+        long_range->max = 20037726.37;
+        long_range->min = -20037726.37;
+        break;
+    }
+    default: { return false; }
+    }
+    return true;
+}
+
+bool geohashEncode(GeoHashRange *lat_range, GeoHashRange *long_range,
+                   double latitude, double longitude, uint8_t step,
+                   GeoHashBits *hash) {
+    uint8_t i;
+
+    if (NULL == hash || step > 32 || step == 0 || RANGEPISZERO(lat_range) ||
+        RANGEPISZERO(long_range)) {
+        return false;
+    }
+
+    hash->bits = 0;
+    hash->step = step;
+
+    if (latitude < lat_range->min || latitude > lat_range->max ||
+        longitude < long_range->min || longitude > long_range->max) {
+        return false;
+    }
+
+    for (i = 0; i < step; i++) {
+        uint8_t lat_bit, long_bit;
+
+        if (lat_range->max - latitude >= latitude - lat_range->min) {
+            lat_bit = 0;
+            lat_range->max = (lat_range->max + lat_range->min) / 2;
+        } else {
+            lat_bit = 1;
+            lat_range->min = (lat_range->max + lat_range->min) / 2;
+        }
+        if (long_range->max - longitude >= longitude - long_range->min) {
+            long_bit = 0;
+            long_range->max = (long_range->max + long_range->min) / 2;
+        } else {
+            long_bit = 1;
+            long_range->min = (long_range->max + long_range->min) / 2;
+        }
+
+        hash->bits <<= 1;
+        hash->bits += long_bit;
+        hash->bits <<= 1;
+        hash->bits += lat_bit;
+    }
+    return true;
+}
+
+bool geohashEncodeType(uint8_t coord_type, double latitude, double longitude,
+                       uint8_t step, GeoHashBits *hash) {
+    GeoHashRange r[2] = { { 0 } };
+    geohashGetCoordRange(coord_type, &r[0], &r[1]);
+    return geohashEncode(&r[0], &r[1], latitude, longitude, step, hash);
+}
+
+bool geohashEncodeWGS84(double latitude, double longitude, uint8_t step,
+                        GeoHashBits *hash) {
+    return geohashEncodeType(GEO_WGS84_TYPE, latitude, longitude, step, hash);
+}
+
+bool geohashEncodeMercator(double latitude, double longitude, uint8_t step,
+                           GeoHashBits *hash) {
+    return geohashEncodeType(GEO_MERCATOR_TYPE, latitude, longitude, step,
+                             hash);
+}
+
+static inline uint8_t get_bit(uint64_t bits, uint8_t pos) {
+    return (bits >> pos) & 0x01;
+}
+
+bool geohashDecode(const GeoHashRange lat_range, const GeoHashRange long_range,
+                   const GeoHashBits hash, GeoHashArea *area) {
+    uint8_t i;
+
+    if (HASHISZERO(hash) || NULL == area || RANGEISZERO(lat_range) ||
+        RANGEISZERO(long_range)) {
+        return false;
+    }
+
+    area->hash = hash;
+    area->latitude.min = lat_range.min;
+    area->latitude.max = lat_range.max;
+    area->longitude.min = long_range.min;
+    area->longitude.max = long_range.max;
+
+    for (i = 0; i < hash.step; i++) {
+        uint8_t lat_bit, long_bit;
+
+        long_bit = get_bit(hash.bits, (hash.step - i) * 2 - 1);
+        lat_bit = get_bit(hash.bits, (hash.step - i) * 2 - 2);
+
+        if (lat_bit == 0) {
+            area->latitude.max = (area->latitude.max + area->latitude.min) / 2;
+        } else {
+            area->latitude.min = (area->latitude.max + area->latitude.min) / 2;
+        }
+
+        if (long_bit == 0) {
+            area->longitude.max =
+                (area->longitude.max + area->longitude.min) / 2;
+        } else {
+            area->longitude.min =
+                (area->longitude.max + area->longitude.min) / 2;
+        }
+    }
+    return true;
+}
+
+bool geohashDecodeType(uint8_t coord_type, const GeoHashBits hash,
+                       GeoHashArea *area) {
+    GeoHashRange r[2] = { { 0 } };
+    geohashGetCoordRange(coord_type, &r[0], &r[1]);
+    return geohashDecode(r[0], r[1], hash, area);
+}
+
+bool geohashDecodeWGS84(const GeoHashBits hash, GeoHashArea *area) {
+    return geohashDecodeType(GEO_WGS84_TYPE, hash, area);
+}
+
+bool geohashDecodeMercator(const GeoHashBits hash, GeoHashArea *area) {
+    return geohashDecodeType(GEO_MERCATOR_TYPE, hash, area);
+}
+
+bool geohashDecodeAreaToLatLong(const GeoHashArea *area, double *latlong) {
+    double y, x;
+
+    if (!latlong)
+        return false;
+
+    y = (area->latitude.min + area->latitude.max) / 2;
+    x = (area->longitude.min + area->longitude.max) / 2;
+
+    latlong[0] = y;
+    latlong[1] = x;
+    return true;
+}
+
+bool geohashDecodeToLatLongType(uint8_t coord_type, const GeoHashBits hash,
+                                double *latlong) {
+    GeoHashArea area = { { 0 } };
+    if (!latlong || !geohashDecodeType(coord_type, hash, &area))
+        return false;
+    return geohashDecodeAreaToLatLong(&area, latlong);
+}
+
+bool geohashDecodeToLatLongWGS84(const GeoHashBits hash, double *latlong) {
+    return geohashDecodeToLatLongType(GEO_WGS84_TYPE, hash, latlong);
+}
+
+bool geohashDecodeToLatLongMercator(const GeoHashBits hash, double *latlong) {
+    return geohashDecodeToLatLongType(GEO_MERCATOR_TYPE, hash, latlong);
+}
+
+static void geohash_move_x(GeoHashBits *hash, int8_t d) {
+    if (d == 0)
+        return;
+
+    uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaLL;
+    uint64_t y = hash->bits & 0x5555555555555555LL;
+
+    uint64_t zz = 0x5555555555555555LL >> (64 - hash->step * 2);
+
+    if (d > 0) {
+        x = x + (zz + 1);
+    } else {
+        x = x | zz;
+        x = x - (zz + 1);
+    }
+
+    x &= (0xaaaaaaaaaaaaaaaaLL >> (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 & 0xaaaaaaaaaaaaaaaaLL;
+    uint64_t y = hash->bits & 0x5555555555555555LL;
+
+    uint64_t zz = 0xaaaaaaaaaaaaaaaaLL >> (64 - hash->step * 2);
+    if (d > 0) {
+        y = y + (zz + 1);
+    } else {
+        y = y | zz;
+        y = y - (zz + 1);
+    }
+    y &= (0x5555555555555555LL >> (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);
+}