First attempt at binding UnitCell struct

pycrystfel/bindings.pyx

@@ -115,3 +115,40 @@ cdef class Detector:
 
     def panel_names(self):
         return [self._img.detgeom.panels[i].name.decode('utf-8') for i in range(self.n_panels)]
+
+
+cdef class UnitCell:
+    cdef crystfel.UnitCell* _ptr
+    cdef bint ptr_owner
+
+    def __cinit__(self):
+        self.ptr_owner = False
+
+    def __dealloc__(self):
+        # De-allocate if not null and flag is set
+        if self._ptr is not NULL and self.ptr_owner is True:
+            crystfel.cell_free(self._ptr)
+            self._ptr = NULL
+
+    @staticmethod
+    cdef UnitCell from_ptr(crystfel.UnitCell* ptr, bint owner=False):
+        # Call to __new__ bypasses __init__ constructor
+        cdef UnitCell cell = UnitCell.__new__(UnitCell)
+        cell._ptr = ptr
+        cell.ptr_owner = True
+        return cell
+
+    @classmethod
+    def from_parameters(cls, double a, double b, double c,
+                        double alpha, double beta, double gamma):
+        cdef crystfel.UnitCell* ptr = crystfel.cell_new_from_parameters(
+            a, b, c, alpha, beta, gamma,
+        )
+        return UnitCell.from_ptr(ptr, owner=True)
+
+    @property
+    def lengths(self):
+         cdef:
+             double a, b, c, alpha, beta, gamma
+         crystfel.cell_get_parameters(self._ptr, &a, &b, &c, &alpha, &beta, &gamma)
+         return np.array([a, b, c])

pycrystfel/crystfel.pxd

@@ -120,3 +120,31 @@ cdef extern from "crystfel/peaks.h":
       int min_pix_count, int max_pix_count, int local_bg_radius, int min_res,
       int max_res, int use_saturated
   )
+
+cdef extern from "crystfel/cell.h":
+  cdef struct rvec:
+    double u, v, w
+
+  ctypedef enum LatticeType:
+    L_TRICLINIC,
+    L_MONOCLINIC,
+    L_ORTHORHROMBIC,
+    L_TETRAGONAL,
+    L_RHOMBOHEDRAL,
+    L_HEXAGONAL,
+    L_CUBIC,
+
+  ctypedef struct UnitCell:
+    pass   # Opaque struct, used through functions
+
+  UnitCell* cell_new()
+  UnitCell* cell_new_from_cell(const UnitCell* orig)
+  UnitCell* cell_new_from_parameters(double a, double b, double c,
+                                     double alpha, double beta, double gamma)
+
+  void cell_free(UnitCell* cell)
+
+  cell_set_parameters(UnitCell* cell, double a, double b, double c,
+                          double alpha, double beta, double gamma)
+  int cell_get_parameters(UnitCell* cell, double* a, double* b, double* c,
+                          double* alpha, double* beta, double* gamma)