Make raster index usize

CHANGES.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- **Breaking**: `Dataset::raster_count` now returns an `usize` and `Dataset::rasterband` now takes `usize` instead of `isize`
+
+  - <https://github.com/georust/gdal/pull/433>
+
  - **Breaking**: `ExtendedDataType` no longer implements `Clone`, `PartialEq` and `Eq`
 
    - <https://github.com/georust/gdal/pull/451>

src/raster/rasterband.rs

@@ -23,9 +23,16 @@ use crate::errors::*;
 impl Dataset {
     /// Fetch a band object for a dataset.
     ///
-    /// Applies to raster datasets, and fetches the
-    /// rasterband at the given _1-based_ index.
-    pub fn rasterband(&self, band_index: isize) -> Result<RasterBand> {
+    /// Applies to raster datasets, and fetches the band at the given _1-based_ index.
+    ///
+    /// # Errors
+    /// Returns an error if the band cannot be read, including in the case the index is 0.
+    ///
+    /// # Panics
+    /// Panics if the band index is greater than `c_int::MAX`.
+    pub fn rasterband(&self, band_index: usize) -> Result<RasterBand> {
+        assert!(band_index <= c_int::MAX as usize);
+
         unsafe {
             let c_band = gdal_sys::GDALGetRasterBand(self.c_dataset(), band_index as c_int);
             if c_band.is_null() {
@@ -69,8 +76,8 @@ impl Dataset {
     }
 
     /// Fetch the number of raster bands on this dataset.
-    pub fn raster_count(&self) -> isize {
-        (unsafe { gdal_sys::GDALGetRasterCount(self.c_dataset()) }) as isize
+    pub fn raster_count(&self) -> usize {
+        (unsafe { gdal_sys::GDALGetRasterCount(self.c_dataset()) }) as usize
     }
 
     /// Returns the raster dimensions: (width, height).

src/raster/rasterize.rs

@@ -161,7 +161,7 @@ mod tests {
 /// may be of any GDAL supported datatype.
 pub fn rasterize(
     dataset: &mut Dataset,
-    bands: &[isize],
+    bands: &[usize],
     geometries: &[Geometry],
     burn_values: &[f64],
     options: Option<RasterizeOptions>,
@@ -178,8 +178,9 @@ pub fn rasterize(
             geometries.len()
         )));
     }
+    let raster_count = dataset.raster_count();
     for band in bands {
-        let is_good = *band > 0 && *band <= dataset.raster_count();
+        let is_good = *band > 0 && *band <= raster_count;
         if !is_good {
             return Err(GdalError::BadArgument(format!(
                 "Band index {} is out of bounds",