0026419: [Regression?] Export of a reversed face leads to crash in 6.9.0 although proceeded in 6.8.0

Take basis surface from trimmed surfaces during IGES writing, because pcurves will be transformed, so trim will be shifted, accorded to new face bounds,
fix updating of seam edge,
change condition of using Segment during exporting periodic BSpline surfaces to IGES (if bounds are not in one period).

Test cases for issue CR26419

src/BRepToIGES/BRepToIGES_BRShell.cxx

@@ -132,13 +132,19 @@ Handle(IGESData_IGESEntity) BRepToIGES_BRShell ::TransferFace(const TopoDS_Face&
     BRep_Builder B;
     TopLoc_Location aLoc;
     Handle(Geom_Surface) aSurf = BRep_Tool::Surface(start, aLoc);
+    while (aSurf->IsKind(STANDARD_TYPE(Geom_RectangularTrimmedSurface)))
+    {
+      // take basis surface, because pcurves will be transformed, so trim will be shifted,
+      // accorded to new face bounds
+      Handle(Geom_RectangularTrimmedSurface) aTrimmedSurf = 
+        Handle(Geom_RectangularTrimmedSurface)::DownCast(aSurf);
+      aSurf = aTrimmedSurf->BasisSurface();
+    }
     aSurf = aSurf->UReversed();
-    Standard_Real U1, U2, V1, V2;
-    aSurf->Bounds(U1, U2, V1, V2);
     Standard_Real aTol = BRep_Tool::Tolerance(start);
     B.MakeFace(myface, aSurf, aLoc ,aTol);
     // set specifics flags of a Face
-	  B.NaturalRestriction(myface, BRep_Tool::NaturalRestriction(start));
+    B.NaturalRestriction(myface, BRep_Tool::NaturalRestriction(start));
     //add wires
     TopoDS_Wire anOuter = TopoDS::Wire(ShapeAlgo::AlgoContainer()->OuterWire(start));
     TopExp_Explorer ex;
@@ -155,7 +161,14 @@ Handle(IGESData_IGESEntity) BRepToIGES_BRShell ::TransferFace(const TopoDS_Face&
         B.Add(myface, W);
       }
     }
+
     // mirror pcurves
+    Standard_Real U1, U2, V1, V2;
+    aSurf->Bounds(U1, U2, V1, V2);
+    Standard_Real aCenter = 0.5 * (U1 + U2);
+    gp_Trsf2d T;
+    gp_Ax2d axis(gp_Pnt2d(aCenter, V1), gp_Dir2d(0.,1.));
+    T.SetMirror(axis);
     NCollection_Map<TopoDS_Shape, TopTools_ShapeMapHasher> aMap (101, new NCollection_IncAllocator);
     for (ex.Init(myface,TopAbs_EDGE);ex.More(); ex.Next()) {
       TopoDS_Edge anEdge = TopoDS::Edge(ex.Current());
@@ -166,9 +179,6 @@ Handle(IGESData_IGESEntity) BRepToIGES_BRShell ::TransferFace(const TopoDS_Face&
       Handle(Geom2d_Curve) aCurve1, aCurve2;
       aCurve1 = BRep_Tool::CurveOnSurface(anEdge, start, f, l);
       aTol = BRep_Tool::Tolerance(anEdge);
-      gp_Trsf2d T;
-      gp_Ax2d axis(gp_Pnt2d(0.5 * (U1 + U2), V1), gp_Dir2d(0.,1.));
-      T.SetMirror(axis);
       if (!aCurve1.IsNull()) {
         aCurve1 = Handle(Geom2d_Curve)::DownCast(aCurve1->Transformed(T));
         if (BRepTools::IsReallyClosed(anEdge, start)) {
@@ -176,7 +186,10 @@ Handle(IGESData_IGESEntity) BRepToIGES_BRShell ::TransferFace(const TopoDS_Face&
           aCurve2 = BRep_Tool::CurveOnSurface(revEdge, start, f, l);
           if (!aCurve2.IsNull()) {
             aCurve2 = Handle(Geom2d_Curve)::DownCast(aCurve2->Transformed(T));
-            B.UpdateEdge(anEdge, aCurve1, aCurve2, myface, aTol);
+            if (anEdge.Orientation() == TopAbs_FORWARD)
+              B.UpdateEdge(anEdge, aCurve1, aCurve2, myface, aTol);
+            else
+              B.UpdateEdge(anEdge, aCurve2, aCurve1, myface, aTol);
           }
           else {
             B.UpdateEdge(anEdge, aCurve1, myface, aTol);

src/GeomToIGES/GeomToIGES_GeomSurface.cxx

@@ -274,7 +274,7 @@ Handle(IGESData_IGESEntity) GeomToIGES_GeomSurface::TransferSurface(const Handle
     Vmin += vShift;
     Vmax += vShift;
   }
-  if ( Abs(uShift) > Precision::PConfusion() || Abs(vShift) > Precision::PConfusion()) {
+  if (PeriodU || PeriodV) {
     Standard_Boolean isNeedSegment = Standard_True;
     isNeedSegment = Abs(Umax-Umin) > Precision::PConfusion() && 
                     Abs(Vmax-Vmin) > Precision::PConfusion();
@@ -283,7 +283,7 @@ Handle(IGESData_IGESEntity) GeomToIGES_GeomSurface::TransferSurface(const Handle
     vMaxShift = ShapeAnalysis::AdjustToPeriod(Vfin, V0, V1);
     isNeedSegment &= 
       (PeriodU && Abs(uShift - uMaxShift) > Precision::PConfusion()) ||
-      (PeriodV && Abs(vShift - vMaxShift) > Precision::PConfusion());           
+      (PeriodV && Abs(vShift - vMaxShift) > Precision::PConfusion());
     if (isNeedSegment) {
       try {
         OCC_CATCH_SIGNALS
@@ -294,7 +294,7 @@ Handle(IGESData_IGESEntity) GeomToIGES_GeomSurface::TransferSurface(const Handle
             PeriodU = Standard_False;
           if ((V1 - V0) - (Vmax - Vmin) > Precision::PConfusion())
             PeriodV = Standard_False;
-	        mysurface = bspl;
+            mysurface = bspl;
         }
       }
       catch ( Standard_Failure ) {
@@ -303,10 +303,9 @@ Handle(IGESData_IGESEntity) GeomToIGES_GeomSurface::TransferSurface(const Handle
         cout << "Warning: Exception in Segment(): " ;
         Standard_Failure::Caught()->Print(cout);
         #endif
-    }
+      }
     }
   }
-
   //unperiodize surface to get neccessary for IGES standard number of knots and mults
   if ( mysurface->IsUPeriodic() ) {
     mysurface->SetUNotPeriodic();

src/IGESFile/liriges.c

@@ -94,7 +94,7 @@ int  iges_lire (FILE* lefic, int *numsec, char ligne[100], int modefnes)
   if (ligne[0] == '\0' || ligne[0] == '\n' || ligne[0] == '\r')
     return iges_lire(lefic,numsec,ligne,modefnes); /* 0 */
 
-  if (!sscanf(&ligne[73],"%d",&result) == 0) {
+  if (sscanf(&ligne[73],"%d",&result) != 0) {
     *numsec = result;
     typesec = ligne[72];
     switch (typesec) {

tests/bugs/iges/bug26419_1

@@ -0,0 +1,11 @@
+puts "========"
+puts "OCC26419"
+puts "========"
+puts ""
+#####################################################
+# [Regression?] Export of a reversed face leads to crash in 6.9.0 although proceeded in 6.8.0
+#####################################################
+
+restore [locate_data_file bug26419_a-fwd.brep] af
+
+brepiges af ${imagedir}/bug26419_1.igs

tests/bugs/iges/bug26419_2

@@ -0,0 +1,11 @@
+puts "========"
+puts "OCC26419"
+puts "========"
+puts ""
+#####################################################
+# [Regression?] Export of a reversed face leads to crash in 6.9.0 although proceeded in 6.8.0
+#####################################################
+
+restore [locate_data_file bug26419_a-rev.brep] ar
+
+brepiges ar ${imagedir}/bug26419_2.igs