1 files changed, 39 insertions, 0 deletions
diff --git a/src/python/include/pybind11_diagram_utils.h b/src/python/include/pybind11_diagram_utils.h
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+++ b/src/python/include/pybind11_diagram_utils.h
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+/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
+ *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
+ *    Author(s):       Marc Glisse
+ *
+ *    Copyright (C) 2020 Inria
+ *
+ *    Modification(s):
+ *      - YYYY/MM Author: Description of the modification
+ */
+
+#include <pybind11/pybind11.h>
+#include <pybind11/numpy.h>
+
+#include <boost/range/counting_range.hpp>
+#include <boost/range/adaptor/transformed.hpp>
+
+namespace py = pybind11;
+typedef py::array_t<double> Dgm;
+
+// Get m[i,0] and m[i,1] as a pair
+static auto pairify(void* p, ssize_t h, ssize_t w) {
+  return [=](ssize_t i){
+    char* birth = (char*)p + i * h;
+    char* death = birth + w;
+    return std::make_pair(*(double*)birth, *(double*)death);
+  };
+}
+
+inline auto numpy_to_range_of_pairs(py::array_t<double> dgm) {
+  py::buffer_info buf = dgm.request();
+  // shape (n,2) or (0) for empty
+  if((buf.ndim!=2 || buf.shape[1]!=2) && (buf.ndim!=1 || buf.shape[0]!=0))
+    throw std::runtime_error("Diagram must be an array of size n x 2");
+  // In the case of shape (0), avoid reading non-existing strides[1] even if we won't use it.
+  ssize_t stride1 = buf.ndim == 2 ? buf.strides[1] : 0;
+  auto cnt = boost::counting_range<ssize_t>(0, buf.shape[0]);
+  return boost::adaptors::transform(cnt, pairify(buf.ptr, buf.strides[0], stride1));
+  // Be careful that the returned range cannot contain references to dead temporaries.
+}