Support PATH type with geo::LineString

Author: kestred

README.md

@@ -268,6 +268,13 @@ types. The driver currently supports the following conversions:
             </td>
             <td>BOX</td>
         </tr>
+        <tr>
+            <td>
+                <a href="https://github.com/georust/rust-geo">geo::LineString&lt;f64&gt;</a>
+                (<a href="#optional-features">optional</a>)
+            </td>
+            <td>PATH</td>
+        </tr>
     </tbody>
 </table>
 
@@ -340,3 +347,11 @@ support is provided optionally by the `with-geo` feature, which adds `ToSql` and
 
 [BOX](https://www.postgresql.org/docs/9.4/static/datatype-geometric.html#AEN6883)
 support is provided optionally by the `with-geo` feature, which adds `ToSql` and `FromSql` implementations for `geo`'s `Bbox` type.
+
+### PATH type
+
+[PATH](https://www.postgresql.org/docs/9.4/static/datatype-geometric.html#AEN6912)
+support is provided optionally by the `with-geo` feature, which adds `ToSql` and `FromSql` implementations for `geo`'s `LineString` type.
+Paths converted from LineString are always treated as "open" paths. Use the
+[pclose](https://www.postgresql.org/docs/8.2/static/functions-geometry.html#FUNCTIONS-GEOMETRY-FUNC-TABLE)
+geometric function to insert a closed path.

postgres-shared/src/types/geo.rs

@@ -1,7 +1,7 @@
 extern crate geo;
 
 use postgres_protocol::types;
-use self::geo::{Bbox, Point};
+use self::geo::{Bbox, LineString, Point};
 use std::error::Error;
 
 use types::{FromSql, ToSql, IsNull, Type};
@@ -59,3 +59,44 @@ impl ToSql for Bbox<f64> {
     accepts!(Type::Box);
     to_sql_checked!();
 }
+
+impl FromSql for LineString<f64> {
+    fn from_sql(_: &Type, raw: &[u8]) -> Result<Self, Box<Error + Sync + Send>> {
+        if raw.len() < 5 {
+            return Err("invalid message length".into());
+        }
+
+        // let _ = types::bool_from_sql(&raw[0..1])?; // is path open or closed
+        let n_points = types::int4_from_sql(&raw[1..5])? as usize;
+        let raw_points = &raw[5..raw.len()-1];
+        if raw_points.len() != 16 * n_points {
+            return Err("invalid message length".into());
+        }
+
+        let mut points = Vec::with_capacity(n_points);
+        for n in 0..n_points {
+            let x = types::float8_from_sql(&raw[n..n+8])?;
+            let y = types::float8_from_sql(&raw[n+8..n+16])?;
+            points.push(Point::new(x, y));
+        }
+        Ok(LineString(points))
+    }
+
+    accepts!(Type::Path);
+}
+
+impl ToSql for LineString<f64> {
+    fn to_sql(&self, _: &Type, out: &mut Vec<u8>) -> Result<IsNull, Box<Error + Sync + Send>> {
+        let closed = false; // always encode an open path from LineString
+        types::bool_to_sql(closed, out);
+        types::int4_to_sql(self.0.len() as i32, out);
+        for point in &self.0 {
+            types::float8_to_sql(point.x(), out);
+            types::float8_to_sql(point.y(), out);
+        }
+        Ok(IsNull::No)
+    }
+
+    accepts!(Type::Path);
+    to_sql_checked!();
+}