sqlitegis 0.1.0

SQLiteGIS: PostGIS-style spatial functions for SQLite in pure Rust.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241

//! Spatial operations
//!
//! ST_Union, ST_Intersection, ST_Difference, ST_SymDifference, ST_Buffer

use geo::algorithm::bool_ops::BooleanOps;
use geo::algorithm::Buffer;
use geo::{Geometry, MultiPolygon};

use crate::core::error::{Result, SqliteGisError};
use crate::core::ewkb::{parse_ewkb, parse_ewkb_pair, write_ewkb};
use crate::core::functions::emptiness::is_empty_geometry;

/// Extract a Polygon or MultiPolygon from a geometry, converting single
/// Polygons into MultiPolygon for uniform BooleanOps handling.
fn require_multi_polygon(geom: Geometry<f64>) -> Result<MultiPolygon<f64>> {
    match geom {
        Geometry::Polygon(p) => Ok(MultiPolygon::new(vec![p])),
        Geometry::MultiPolygon(mp) => Ok(mp),
        other => Err(SqliteGisError::wrong_type(
            "Polygon or MultiPolygon",
            &other,
        )),
    }
}

fn binary_polygon_op<F>(a: &[u8], b: &[u8], op: F) -> Result<Vec<u8>>
where
    F: FnOnce(&MultiPolygon<f64>, &MultiPolygon<f64>) -> MultiPolygon<f64>,
{
    let (ga, gb, srid) = parse_ewkb_pair(a, b)?;
    let ma = require_multi_polygon(ga)?;
    let mb = require_multi_polygon(gb)?;
    let result = op(&ma, &mb);
    write_ewkb(&Geometry::MultiPolygon(result), srid)
}

/// ST_Union: compute the geometric union of two polygon geometries.
///
/// # Example
///
/// ```
/// use sqlitegis::core::functions::operations::st_union;
/// use sqlitegis::core::functions::io::geom_from_text;
/// use sqlitegis::core::functions::measurement::st_area;
///
/// let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
/// let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
/// let u = st_union(&a, &b).unwrap();
/// assert!((st_area(&u).unwrap() - 6.0).abs() < 1e-10);
/// ```
pub fn st_union(a: &[u8], b: &[u8]) -> Result<Vec<u8>> {
    binary_polygon_op(a, b, |ma, mb| ma.union(mb))
}

/// ST_Intersection: compute the geometric intersection of two polygon geometries.
///
/// # Example
///
/// ```
/// use sqlitegis::core::functions::operations::st_intersection;
/// use sqlitegis::core::functions::io::geom_from_text;
/// use sqlitegis::core::functions::measurement::st_area;
///
/// let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
/// let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
/// let i = st_intersection(&a, &b).unwrap();
/// assert!((st_area(&i).unwrap() - 2.0).abs() < 1e-10);
/// ```
pub fn st_intersection(a: &[u8], b: &[u8]) -> Result<Vec<u8>> {
    binary_polygon_op(a, b, |ma, mb| ma.intersection(mb))
}

/// ST_Difference: compute the geometric difference (A minus B) of two polygon geometries.
///
/// # Example
///
/// ```
/// use sqlitegis::core::functions::operations::st_difference;
/// use sqlitegis::core::functions::io::geom_from_text;
/// use sqlitegis::core::functions::measurement::st_area;
///
/// let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
/// let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
/// let d = st_difference(&a, &b).unwrap();
/// assert!((st_area(&d).unwrap() - 2.0).abs() < 1e-10);
/// ```
pub fn st_difference(a: &[u8], b: &[u8]) -> Result<Vec<u8>> {
    binary_polygon_op(a, b, |ma, mb| ma.difference(mb))
}

/// ST_SymDifference: compute the symmetric difference (XOR) of two polygon geometries.
///
/// # Example
///
/// ```
/// use sqlitegis::core::functions::operations::st_sym_difference;
/// use sqlitegis::core::functions::io::geom_from_text;
/// use sqlitegis::core::functions::measurement::st_area;
///
/// let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
/// let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
/// let sd = st_sym_difference(&a, &b).unwrap();
/// assert!((st_area(&sd).unwrap() - 4.0).abs() < 1e-10);
/// ```
pub fn st_sym_difference(a: &[u8], b: &[u8]) -> Result<Vec<u8>> {
    binary_polygon_op(a, b, |ma, mb| ma.xor(mb))
}

/// ST_Buffer: expand or shrink a geometry by a given distance.
///
/// # Example
///
/// ```
/// use sqlitegis::core::functions::operations::st_buffer;
/// use sqlitegis::core::functions::constructors::st_point;
/// use sqlitegis::core::functions::measurement::st_area;
///
/// let pt = st_point(0.0, 0.0, None).unwrap();
/// let buffered = st_buffer(&pt, 1.0).unwrap();
/// let area = st_area(&buffered).unwrap();
/// // Area of a circle with radius 1 approximately  pi
/// assert!((area - std::f64::consts::PI).abs() < 0.1);
/// ```
pub fn st_buffer(blob: &[u8], distance: f64) -> Result<Vec<u8>> {
    let (geom, srid) = parse_ewkb(blob)?;
    if is_empty_geometry(&geom) {
        let empty = Geometry::Polygon(geo::Polygon::new(geo::LineString::new(vec![]), vec![]));
        return write_ewkb(&empty, srid);
    }
    let result = geom.buffer(distance);
    let mut polygons = result.0;
    let out_geom = match polygons.len() {
        0 => Geometry::Polygon(geo::Polygon::new(geo::LineString::new(vec![]), vec![])),
        1 => {
            let polygon = polygons.pop().ok_or_else(|| {
                SqliteGisError::InvalidInput(
                    "buffer result unexpectedly missing single polygon".to_string(),
                )
            })?;
            Geometry::Polygon(polygon)
        }
        _ => Geometry::MultiPolygon(MultiPolygon::new(polygons)),
    };
    write_ewkb(&out_geom, srid)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::core::functions::accessors::{st_geometry_type, st_is_empty};
    use crate::core::functions::constructors::st_point;
    use crate::core::functions::io::geom_from_text;
    use crate::core::functions::measurement::st_area;

    #[test]
    fn union_overlapping() {
        let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
        let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
        let u = st_union(&a, &b).unwrap();
        assert!((st_area(&u).unwrap() - 6.0).abs() < 1e-10);
    }

    #[test]
    fn intersection_overlapping() {
        let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
        let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
        let i = st_intersection(&a, &b).unwrap();
        assert!((st_area(&i).unwrap() - 2.0).abs() < 1e-10);
    }

    #[test]
    fn difference_overlapping() {
        let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
        let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
        let d = st_difference(&a, &b).unwrap();
        assert!((st_area(&d).unwrap() - 2.0).abs() < 1e-10);
    }

    #[test]
    fn sym_difference_overlapping() {
        let a = geom_from_text("POLYGON((0 0,2 0,2 2,0 2,0 0))", None).unwrap();
        let b = geom_from_text("POLYGON((1 0,3 0,3 2,1 2,1 0))", None).unwrap();
        let sd = st_sym_difference(&a, &b).unwrap();
        assert!((st_area(&sd).unwrap() - 4.0).abs() < 1e-10);
    }

    #[test]
    fn buffer_point() {
        let pt = st_point(0.0, 0.0, None).unwrap();
        let buffered = st_buffer(&pt, 1.0).unwrap();
        let area = st_area(&buffered).unwrap();
        assert!((area - std::f64::consts::PI).abs() < 0.1);
        assert_eq!(st_geometry_type(&buffered).unwrap(), "ST_Polygon");
    }

    #[test]
    fn buffer_multipoint_returns_multipolygon_for_disconnected_components() {
        let mp = geom_from_text("MULTIPOINT((0 0),(10 0))", None).unwrap();
        let buffered = st_buffer(&mp, 1.0).unwrap();
        assert_eq!(st_geometry_type(&buffered).unwrap(), "ST_MultiPolygon");
    }

    #[test]
    fn union_wrong_type() {
        let line = geom_from_text("LINESTRING(0 0,1 1)", None).unwrap();
        let poly = geom_from_text("POLYGON((0 0,1 0,1 1,0 1,0 0))", None).unwrap();
        assert!(st_union(&line, &poly).is_err());
    }

    #[test]
    fn union_accepts_multipolygon_inputs() {
        let mp = geom_from_text("MULTIPOLYGON(((0 0,1 0,1 1,0 1,0 0)))", None).unwrap();
        let poly = geom_from_text("POLYGON((1 0,2 0,2 1,1 1,1 0))", None).unwrap();
        let u = st_union(&mp, &poly).unwrap();
        assert!(st_area(&u).unwrap() > 1.0);
    }

    #[test]
    fn buffer_negative_shrinks() {
        let poly = geom_from_text("POLYGON((0 0,10 0,10 10,0 10,0 0))", None).unwrap();
        let shrunk = st_buffer(&poly, -1.0).unwrap();
        let area = st_area(&shrunk).unwrap();
        assert!(area < 100.0 && area > 0.0);
    }

    #[test]
    fn buffer_empty_polygon_returns_empty_polygon() {
        let empty = geom_from_text("POLYGON EMPTY", None).unwrap();
        let buffered = st_buffer(&empty, 1.0).unwrap();
        assert_eq!(st_geometry_type(&buffered).unwrap(), "ST_Polygon");
        assert!(st_is_empty(&buffered).unwrap());
    }

    #[test]
    fn buffer_empty_point_returns_empty_polygon() {
        let empty = geom_from_text("POINT EMPTY", None).unwrap();
        let buffered = st_buffer(&empty, 1.0).unwrap();
        assert_eq!(st_geometry_type(&buffered).unwrap(), "ST_Polygon");
        assert!(st_is_empty(&buffered).unwrap());
    }
}