Merge pull request #35 from shawnlaffan/dataset_getlayer_method

add a Dataset::GetLayerCount method

Makefile.PL

@@ -21,6 +21,7 @@ WriteMakefile(
     },
     TEST_REQUIRES => {
         'Test::More' => 0,
+        'Test::Exception' => 0,
         'JSON' => 0,
         'Data::Dumper' => 0
     },

lib/Geo/GDAL/FFI/Dataset.pm

@@ -92,11 +92,23 @@ sub GetBands {
     return @bands;
 }
 
+sub GetLayerCount {
+    my ($self) = @_;
+    return Geo::GDAL::FFI::GDALDatasetGetLayerCount($$self);
+}
+
+
 sub GetLayer {
     my ($self, $i) = @_;
     $i //= 0;
-    my $l = Geo::GDAL::FFI::isint($i) ? Geo::GDAL::FFI::GDALDatasetGetLayer($$self, $i) :
-    Geo::GDAL::FFI::GDALDatasetGetLayerByName($$self, $i);
+    my $l = Geo::GDAL::FFI::isint($i)
+      ? Geo::GDAL::FFI::GDALDatasetGetLayer($$self, $i)
+      : Geo::GDAL::FFI::GDALDatasetGetLayerByName($$self, $i);
+    unless ($l) {
+        my $msg = Geo::GDAL::FFI::error_msg()
+          // "Could not access layer $i in data set.";
+        confess $msg if $msg;
+    }
     Geo::GDAL::FFI::_register_parent_ref ($l, $self);
     return bless \$l, 'Geo::GDAL::FFI::Layer';
 }
@@ -504,6 +516,10 @@ SpatialReference are ignored.
 
 =back
 
+=head2 GetLayerCount
+ my $count = $dataset->GetLayerCount();
+
+
 =head2 GetLayer
 
  my $layer = $dataset->GetLayer($name);

t/dataset.t

@@ -0,0 +1,40 @@
+use v5.10;
+use strict;
+use warnings;
+use Carp;
+use Geo::GDAL::FFI qw/GetDriver HaveGEOS/;
+use Test::More;
+use Test::Exception;
+use Data::Dumper;
+
+my $ds = GetDriver('GPKG')->Create('test.gpkg');
+my $sr = Geo::GDAL::FFI::SpatialReference->new(EPSG => 3067);
+foreach my $i (1..3) {
+    my $l = $ds->CreateLayer({
+        Name => "test$i",
+        SpatialReference => $sr,
+        GeometryType => 'Point',
+    });
+    my $d = $l->GetDefn();
+    my $f = Geo::GDAL::FFI::Feature->new($d);
+    $l->CreateFeature($f);
+}
+
+
+is ($ds->GetLayerCount, 3, 'Got expected number of layers');
+
+dies_ok (
+    sub {$ds->GetLayer ('not_exists')},
+    'GetLayer exception for non-existent layer name',
+);
+dies_ok (
+    sub {$ds->GetLayer (23)},
+    'GetLayer exception for too large index',
+);
+dies_ok (
+    sub {$ds->GetLayer (-1)},
+    'GetLayer exception for negative index',
+);
+
+
+done_testing();