Misc documentation and formatting tweaks.

CHANGES.md

@@ -81,6 +81,12 @@
 
   - <https://github.com/georust/gdal/pull/370>
 
+- Split `spatial_ref` module into more feature-specific submodules.
+  **Breaking** `SpatialRef::to_c_hsrs` is now `unsafe` since it returns a raw C pointer, as is the convention with 
+  `Dataset::c_dataset`, `Geometry::c_geometry`, etc.  
+
+  - <https://github.com/georust/gdal/pull/395>
+
 ## 0.14
 
 - Added new content to `README.md` and the root docs.

examples/spatial_reference.rs

@@ -1,6 +1,5 @@
 use gdal::errors::Result;
-use gdal::spatial_ref::SpatialRef;
-use gdal::spatial_ref::CoordTransform;
+use gdal::spatial_ref::{CoordTransform, SpatialRef};
 use gdal::vector::Geometry;
 
 fn run() -> Result<()> {

src/dataset.rs

@@ -438,7 +438,7 @@ impl Dataset {
     #[cfg(major_ge_3)]
     /// Set the spatial reference system for this dataset.
     pub fn set_spatial_ref(&mut self, spatial_ref: &SpatialRef) -> Result<()> {
-        let rv = unsafe { gdal_sys::GDALSetSpatialRef(self.c_dataset, spatial_ref.c_handle()) };
+        let rv = unsafe { gdal_sys::GDALSetSpatialRef(self.c_dataset, spatial_ref.to_c_hsrs()) };
         if rv != CPLErr::CE_None {
             return Err(_last_cpl_err(rv));
         }
@@ -683,7 +683,7 @@ impl Dataset {
 
         let c_layer = unsafe {
             let c_srs = match options.srs {
-                Some(srs) => srs.c_handle(),
+                Some(srs) => srs.to_c_hsrs(),
                 None => null_mut(),
             };
             // The C function takes `char **papszOptions` without mention of `const`, and this is

src/spatial_ref/mod.rs

@@ -1,11 +1,18 @@
-//! GDAL Spatial Reference System Functions
+//! GDAL Spatial Reference System
 //!
-//! <https://gdal.org/api/ogr_srs_api.html>
+//! See: [Spatial Reference System C API](https://gdal.org/api/ogr_srs_api.html).
+//!
+//! See also: [OGR Coordinate Reference Systems and Coordinate Transformation Tutorial](https://gdal.org/tutorials/osr_api_tut.html)
 
 mod srs;
 mod transform;
 mod transform_opts;
 
-pub use srs::{AxisOrientationType, SpatialRef};
+/// Axis orientation options
+///
+/// See [`OGRAxisOrientation`](https://gdal.org/api/ogr_srs_api.html#_CPPv418OGRAxisOrientation).
+pub type AxisOrientationType = gdal_sys::OGRAxisOrientation::Type;
+
+pub use srs::SpatialRef;
 pub use transform::CoordTransform;
 pub use transform_opts::CoordTransformOptions;

src/spatial_ref/srs.rs

@@ -1,23 +1,19 @@
 use crate::utils::{_last_null_pointer_err, _string};
 use gdal_sys::{self, OGRErr};
-use libc::{c_char, c_int};
 use std::ffi::{CStr, CString};
 use std::ptr::{self};
 use std::str::FromStr;
 
 use crate::errors::*;
 
-#[derive(Debug, Clone)]
-pub struct AreaOfUse {
-    pub west_lon_degree: f64,
-    pub south_lat_degree: f64,
-    pub east_lon_degree: f64,
-    pub north_lat_degree: f64,
-    pub name: String,
-}
-
-pub type AxisOrientationType = gdal_sys::OGRAxisOrientation::Type;
-
+/// A OpenGIS Spatial Reference System definition.
+///
+/// Used in geo-referencing raster and vector data, and in coordinate transformations.
+///
+/// # Notes
+/// * See also: [OGR Coordinate Reference Systems and Coordinate Transformation Tutorial](https://gdal.org/tutorials/osr_api_tut.html)
+/// * Consult the [OGC WKT Coordinate System Issues](https://gdal.org/tutorials/wktproblems.html)
+/// page for implementation details of WKT in OGR.
 #[derive(Debug)]
 pub struct SpatialRef(gdal_sys::OGRSpatialReferenceH);
 
@@ -63,11 +59,21 @@ impl SpatialRef {
         }
     }
 
-    /// Get the handle to underlying C API data
-    pub(crate) unsafe fn c_handle(&self) -> gdal_sys::OGRSpatialReferenceH {
+    /// Returns a C pointer to the allocated [`gdal_sys::OGRSpatialReferenceH`] memory.
+    ///
+    /// # Safety
+    /// This method returns a raw C pointer
+    pub unsafe fn to_c_hsrs(&self) -> gdal_sys::OGRSpatialReferenceH {
         self.0
     }
 
+    /// Set spatial reference from various text formats.
+    ///
+    /// This method will examine the provided input, and try to deduce the format,
+    /// and then use it to initialize the spatial reference system. See the [C++ API docs][CPP]
+    /// for details on these forms.
+    ///
+    /// [CPP]: https://gdal.org/api/ogrspatialref.html#_CPPv4N19OGRSpatialReference16SetFromUserInputEPKc
     pub fn from_definition(definition: &str) -> Result<SpatialRef> {
         let c_obj = unsafe { gdal_sys::OSRNewSpatialReference(ptr::null()) };
         if c_obj.is_null() {
@@ -96,7 +102,7 @@ impl SpatialRef {
     pub fn from_epsg(epsg_code: u32) -> Result<SpatialRef> {
         let null_ptr = ptr::null_mut();
         let c_obj = unsafe { gdal_sys::OSRNewSpatialReference(null_ptr) };
-        let rv = unsafe { gdal_sys::OSRImportFromEPSG(c_obj, epsg_code as c_int) };
+        let rv = unsafe { gdal_sys::OSRImportFromEPSG(c_obj, epsg_code as libc::c_int) };
         if rv != OGRErr::OGRERR_NONE {
             Err(GdalError::OgrError {
                 err: rv,
@@ -124,7 +130,7 @@ impl SpatialRef {
 
     pub fn from_esri(esri_wkt: &str) -> Result<SpatialRef> {
         let c_str = CString::new(esri_wkt)?;
-        let mut ptrs = vec![c_str.as_ptr() as *mut c_char, ptr::null_mut()];
+        let mut ptrs = vec![c_str.as_ptr() as *mut libc::c_char, ptr::null_mut()];
         let null_ptr = ptr::null_mut();
         let c_obj = unsafe { gdal_sys::OSRNewSpatialReference(null_ptr) };
         let rv = unsafe { gdal_sys::OSRImportFromESRI(c_obj, ptrs.as_mut_ptr()) };
@@ -166,7 +172,8 @@ impl SpatialRef {
 
     pub fn to_pretty_wkt(&self) -> Result<String> {
         let mut c_wkt = ptr::null_mut();
-        let rv = unsafe { gdal_sys::OSRExportToPrettyWkt(self.0, &mut c_wkt, false as c_int) };
+        let rv =
+            unsafe { gdal_sys::OSRExportToPrettyWkt(self.0, &mut c_wkt, false as libc::c_int) };
         let res = if rv != OGRErr::OGRERR_NONE {
             Err(GdalError::OgrError {
                 err: rv,
@@ -348,13 +355,17 @@ impl SpatialRef {
         unsafe { gdal_sys::OSRIsVertical(self.0) == 1 }
     }
 
-    pub fn axis_orientation(&self, target_key: &str, axis: i32) -> Result<AxisOrientationType> {
+    pub fn axis_orientation(
+        &self,
+        target_key: &str,
+        axis: i32,
+    ) -> Result<super::AxisOrientationType> {
         let mut orientation = gdal_sys::OGRAxisOrientation::OAO_Other;
         let c_ptr = unsafe {
             gdal_sys::OSRGetAxis(
                 self.0,
                 CString::new(target_key)?.as_ptr(),
-                axis as c_int,
+                axis as libc::c_int,
                 &mut orientation,
             )
         };
@@ -375,7 +386,7 @@ impl SpatialRef {
             gdal_sys::OSRGetAxis(
                 self.0,
                 CString::new(target_key)?.as_ptr(),
-                axis as c_int,
+                axis as libc::c_int,
                 ptr::null_mut(),
             )
         };
@@ -413,6 +424,9 @@ impl SpatialRef {
     }
 
     #[cfg(major_ge_3)]
+    /// Get the valid use bounding area for this `SpatialRef`.
+    ///
+    /// See: [`OSRGetAreaOfUse`](https://gdal.org/api/ogr_srs_api.html#_CPPv415OSRGetAreaOfUse20OGRSpatialReferenceHPdPdPdPdPPKc)
     pub fn area_of_use(&self) -> Option<AreaOfUse> {
         let mut c_area_name: *const libc::c_char = ptr::null_mut();
         let (mut w_long, mut s_lat, mut e_long, mut n_lat): (f64, f64, f64, f64) =
@@ -442,6 +456,18 @@ impl SpatialRef {
     }
 }
 
+#[derive(Debug, Clone)]
+/// Defines the bounding area of valid use for a [`SpatialRef`].
+///
+/// See [`area_of_use`][SpatialRef::area_of_use].
+pub struct AreaOfUse {
+    pub west_lon_degree: f64,
+    pub south_lat_degree: f64,
+    pub east_lon_degree: f64,
+    pub north_lat_degree: f64,
+    pub name: String,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/spatial_ref/transform.rs

@@ -1,13 +1,13 @@
-use gdal_sys::{CPLErr, OGRCoordinateTransformationH};
-use libc::c_int;
-use std::ptr::null_mut;
 use crate::errors;
 use crate::errors::GdalError;
 use crate::spatial_ref::{CoordTransformOptions, SpatialRef};
 use crate::utils::{_last_cpl_err, _last_null_pointer_err};
+use gdal_sys::{CPLErr, OGRCoordinateTransformationH};
+use libc::c_int;
+use std::ptr::null_mut;
 
 #[derive(Debug)]
-/// Defines a coordinate transformation from one SRS to another.
+/// Defines a coordinate transformation from one [`SpatialRef`] to another.
 pub struct CoordTransform {
     inner: OGRCoordinateTransformationH,
     from: String,
@@ -21,8 +21,13 @@ impl Drop for CoordTransform {
 }
 
 impl CoordTransform {
+    /// Constructs a new transformation from `source` to `target`.
+    ///
+    /// See: [OCTNewCoordinateTransformation](https://gdal.org/api/ogr_srs_api.html#_CPPv430OCTNewCoordinateTransformation20OGRSpatialReferenceH20OGRSpatialReferenceH)
     pub fn new(source: &SpatialRef, target: &SpatialRef) -> errors::Result<CoordTransform> {
-        let c_obj = unsafe { gdal_sys::OCTNewCoordinateTransformation(source.c_handle(), target.c_handle()) };
+        let c_obj = unsafe {
+            gdal_sys::OCTNewCoordinateTransformation(source.to_c_hsrs(), target.to_c_hsrs())
+        };
         if c_obj.is_null() {
             return Err(_last_null_pointer_err("OCTNewCoordinateTransformation"));
         }
@@ -33,13 +38,21 @@ impl CoordTransform {
         })
     }
 
+    /// Constructs a new transformation from `source` to `target` with additional extended options
+    /// defined by `options`: [`CoordTransformOptions`].
+    ///
+    /// See: [OCTNewCoordinateTransformation](https://gdal.org/api/ogr_srs_api.html#_CPPv432OCTNewCoordinateTransformationEx20OGRSpatialReferenceH20OGRSpatialReferenceH35OGRCoordinateTransformationOptionsH)
     pub fn new_with_options(
         source: &SpatialRef,
         target: &SpatialRef,
         options: &CoordTransformOptions,
     ) -> errors::Result<CoordTransform> {
         let c_obj = unsafe {
-            gdal_sys::OCTNewCoordinateTransformationEx(source.c_handle(), target.c_handle(), options.c_options())
+            gdal_sys::OCTNewCoordinateTransformationEx(
+                source.to_c_hsrs(),
+                target.to_c_hsrs(),
+                options.c_options(),
+            )
         };
         if c_obj.is_null() {
             return Err(_last_null_pointer_err("OCTNewCoordinateTransformation"));
@@ -56,15 +69,21 @@ impl CoordTransform {
     ///
     /// # Arguments
     /// * `bounds` - array of [axis0_min, axis1_min, axis0_max, axis1_max],
-    ///            interpreted in the axis order of the source SpatialRef,
-    ///            typically [xmin, ymin, xmax, ymax]
+    ///              interpreted in the axis order of the source SpatialRef,
+    ///              typically [xmin, ymin, xmax, ymax]
     /// * `densify_pts` - number of points per edge (recommended: 21)
     ///
     /// # Returns
     /// `Ok([f64; 4])` with bounds in axis order of target SpatialRef
     /// `Err` if there is an error.
+    ///
+    /// See: [OCTTransformBounds](https://gdal.org/api/ogr_srs_api.html#_CPPv418OCTTransformBounds28OGRCoordinateTransformationHKdKdKdKdPdPdPdPdKi)
     #[cfg(all(major_ge_3, minor_ge_4))]
-    pub fn transform_bounds(&self, bounds: &[f64; 4], densify_pts: i32) -> errors::Result<[f64; 4]> {
+    pub fn transform_bounds(
+        &self,
+        bounds: &[f64; 4],
+        densify_pts: i32,
+    ) -> errors::Result<[f64; 4]> {
         let mut out_xmin: f64 = 0.;
         let mut out_ymin: f64 = 0.;
         let mut out_xmax: f64 = 0.;
@@ -109,7 +128,14 @@ impl CoordTransform {
     /// * `x` - slice of x coordinates
     /// * `y` - slice of y coordinates (must match x in length)
     /// * `z` - slice of z coordinates, or an empty slice to ignore
-    pub fn transform_coords(&self, x: &mut [f64], y: &mut [f64], z: &mut [f64]) -> errors::Result<()> {
+    ///
+    /// See: [OCTTransform](https://gdal.org/api/ogr_srs_api.html#_CPPv412OCTTransform28OGRCoordinateTransformationHiPdPdPd)
+    pub fn transform_coords(
+        &self,
+        x: &mut [f64],
+        y: &mut [f64],
+        z: &mut [f64],
+    ) -> errors::Result<()> {
         let nb_coords = x.len();
         assert_eq!(
             nb_coords,
@@ -166,16 +192,20 @@ impl CoordTransform {
             .expect("Coordinate transform failed")
     }
 
-    pub fn to_c_hct(&self) -> OGRCoordinateTransformationH {
+    /// Returns a C pointer to the allocated [`gdal_sys::OGRCoordinateTransformationH`] memory.
+    ///
+    /// # Safety
+    /// This method returns a raw C pointer
+    pub unsafe fn to_c_hct(&self) -> OGRCoordinateTransformationH {
         self.inner
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use super::*;
     use crate::assert_almost_eq;
     use crate::vector::Geometry;
-    use super::*;
 
     #[cfg(all(major_ge_3, minor_ge_4))]
     #[test]
@@ -346,4 +376,4 @@ mod tests {
             panic!("Wrong error type");
         }
     }
-}
+}

src/spatial_ref/transform_opts.rs

@@ -45,8 +45,8 @@ impl CoordTransformOptions {
     /// The west longitude is generally lower than the east longitude, except for areas of interest
     /// that go across the anti-meridian.
     ///
-    /// For more information, see:
-    /// <https://gdal.org/tutorials/osr_api_tut.html#advanced-coordinate-transformation>
+    /// For more information, see
+    /// [Advanced Coordinate Transformation Tutorial](https://gdal.org/tutorials/osr_api_tut.html#advanced-coordinate-transformation).
     ///
     /// # Arguments
     ///
@@ -101,8 +101,9 @@ impl CoordTransformOptions {
 
     /// Sets whether ballpark transformations are allowed.
     ///
-    /// By default, PROJ may generate "ballpark transformations" (see
-    /// <https://proj.org/glossary.html>) when precise datum transformations are missing. For high
+    /// By default, PROJ may generate "ballpark transformations"
+    /// (see [Glossary](https://proj.org/glossary.html))
+    /// when precise datum transformations are missing. For high
     /// accuracy use cases, such transformations might not be allowed.
     ///
     /// If this option is specified with PROJ < 8, the `OGR_CT_OP_SELECTION` configuration option
@@ -131,8 +132,8 @@ impl CoordTransformOptions {
     /// string starting with `+proj=pipeline`), a WKT2 string describing a `CoordinateOperation`,
     /// or a `"urn:ogc:def:coordinateOperation:EPSG::XXXX"` URN.
     ///
-    /// For more information, see:
-    /// <https://gdal.org/tutorials/osr_api_tut.html#advanced-coordinate-transformation>
+    /// For more information, see
+    /// [Advanced Coordinate Transformation Tutorial](https://gdal.org/tutorials/osr_api_tut.html#advanced-coordinate-transformation).
     ///
     /// # Arguments
     ///
@@ -173,7 +174,7 @@ mod tests {
         options.set_ballpark_allowed(false).unwrap();
         let trafo = CoordTransform::new_with_options(&ma, &nl, &options);
         let err = trafo.unwrap_err();
-        assert!(matches!(err, GdalError::NullPointer { .. }), "{:?}", err);
+        assert!(matches!(err, GdalError::NullPointer { .. }), "{err:?}");
     }
 
     #[test]
@@ -189,4 +190,4 @@ mod tests {
         let trafo = CoordTransform::new_with_options(&nad27, &wgs84, &options);
         assert!(trafo.is_ok());
     }
-}
+}

src/vector/geometry.rs

@@ -292,7 +292,7 @@ impl Geometry {
 
     pub fn set_spatial_ref(&mut self, spatial_ref: SpatialRef) {
         unsafe {
-            gdal_sys::OGR_G_AssignSpatialReference(self.c_geometry(), spatial_ref.c_handle())
+            gdal_sys::OGR_G_AssignSpatialReference(self.c_geometry(), spatial_ref.to_c_hsrs())
         };
     }
 

src/vector/layer.rs

@@ -462,7 +462,9 @@ pub trait LayerAccess: Sized {
 
     /// Read batches of columnar [Arrow](https://arrow.apache.org/) data from OGR.
     ///
-    /// Extended options are available via [`CslStringList`]. As defined in the OGR documentation for [`GetArrowStream`](https://gdal.org/api/ogrlayer_cpp.html#_CPPv4N8OGRLayer14GetArrowStreamEP16ArrowArrayStream12CSLConstList), the current options are:
+    /// Extended options are available via [`crate::cpl::CslStringList`].
+    /// As defined in the OGR documentation for [`GetArrowStream`](https://gdal.org/api/ogrlayer_cpp.html#_CPPv4N8OGRLayer14GetArrowStreamEP16ArrowArrayStream12CSLConstList),
+    /// the current options are:
     ///
     /// * `INCLUDE_FID=YES/NO`. Whether to include the FID column. Defaults to YES.
     /// * `MAX_FEATURES_IN_BATCH=integer`. Maximum number of features to retrieve in a ArrowArray batch. Defaults to 65 536.