Array Utils: Add find_all_ranges function

This functions returns a vector of all the index ranges for which the
span contains consecutive values that equal to the value given.

Pull Request: https://projects.blender.org/blender/blender/pulls/110265

source/blender/blenlib/BLI_array_utils.hh

@@ -169,4 +169,29 @@ inline BooleanMix booleans_mix_calc(const VArray<bool> &varray)
   return booleans_mix_calc(varray, varray.index_range());
 }
 
+/**
+ * Finds all the index ranges for which consecutive values in \a span equal \a value.
+ */
+template<typename T> inline Vector<IndexRange> find_all_ranges(const Span<T> span, const T &value)
+{
+  if (span.is_empty()) {
+    return Vector<IndexRange>();
+  }
+  Vector<IndexRange> ranges;
+  int64_t length = (span.first() == value) ? 1 : 0;
+  for (const int64_t i : span.index_range().drop_front(1)) {
+    if (span[i - 1] == value && span[i] != value) {
+      ranges.append(IndexRange(i - length, length));
+      length = 0;
+    }
+    else if (span[i] == value) {
+      length++;
+    }
+  }
+  if (length > 0) {
+    ranges.append(IndexRange(span.size() - length, length));
+  }
+  return ranges;
+}
+
 }  // namespace blender::array_utils

source/blender/blenlib/tests/BLI_array_utils_test.cc

@@ -5,6 +5,7 @@
 #include "testing/testing.h"
 
 #include "BLI_array_utils.h"
+#include "BLI_array_utils.hh"
 #include "BLI_utildefines.h"
 #include "BLI_utildefines_stack.h"
 
@@ -241,3 +242,52 @@ TEST(array_utils, DeduplicateOrdered3)
 }
 
 #undef DEDUPLICATE_ORDERED_TEST
+
+static void find_all_ranges_test(const blender::Span<bool> data,
+                                 const blender::Span<blender::IndexRange> data_cmp)
+{
+  using namespace blender;
+  Vector<IndexRange> ranges = array_utils::find_all_ranges(data, true);
+  EXPECT_EQ(ranges.size(), data_cmp.size());
+  EXPECT_EQ_ARRAY(data_cmp.data(), ranges.as_span().data(), data_cmp.size());
+}
+
+TEST(array_utils, FindAllRanges1)
+{
+  using namespace blender;
+  const std::array data = {false};
+  Vector<IndexRange> ranges = array_utils::find_all_ranges(Span(data.data(), data.size()), true);
+  EXPECT_EQ(ranges.size(), 0);
+}
+
+TEST(array_utils, FindAllRanges2)
+{
+  using namespace blender;
+  const std::array data = {true, true, true};
+  const std::array data_cmp = {IndexRange(0, 3)};
+  find_all_ranges_test(data, data_cmp);
+}
+
+TEST(array_utils, FindAllRanges3)
+{
+  using namespace blender;
+  const std::array data = {true, false};
+  const std::array data_cmp = {IndexRange(0, 1)};
+  find_all_ranges_test(data, data_cmp);
+}
+
+TEST(array_utils, FindAllRanges4)
+{
+  using namespace blender;
+  const std::array data = {false, true};
+  const std::array data_cmp = {IndexRange(1, 1)};
+  find_all_ranges_test(data, data_cmp);
+}
+
+TEST(array_utils, FindAllRanges5)
+{
+  using namespace blender;
+  const std::array data = {true, false, false, true, true, false, true};
+  const std::array data_cmp = {IndexRange(0, 1), IndexRange(3, 2), IndexRange(6, 1)};
+  find_all_ranges_test(data, data_cmp);
+}