Initial rewrite of the file accessors from Perl to C++.

This is especially important for the extremely slow AMF parser.
Also there is a new file handler for the Prusa Control 'PRUS' format.

xs/src/libslic3r/Format/OBJ.cpp

@@ -0,0 +1,79 @@
+#include "../libslic3r.h"
+#include "../Model.hpp"
+#include "../TriangleMesh.hpp"
+
+#include "OBJ.hpp"
+#include "objparser.hpp"
+
+#include <string>
+
+#ifdef _WIN32
+#define DIR_SEPARATOR '\\'
+#else
+#define DIR_SEPARATOR '/'
+#endif
+
+namespace Slic3r {
+
+bool load_obj(const char *path, Model *model, const char *object_name_in)
+{
+    // Parse the OBJ file.
+    ObjParser::ObjData data;
+    if (! ObjParser::objparse(path, data)) {
+//    die "Failed to parse $file\n" if !-e $path;
+        return false;
+    }
+
+    // Count the faces and verify, that all faces are triangular.
+    size_t num_faces = 0;
+    for (size_t i = 0; i < data.vertices.size(); ) {
+        size_t j = i;
+        for (; j < data.vertices.size() && data.vertices[j].coordIdx != -1; ++ j) ;
+        if (i == j)
+            continue;
+        if (j - i != 3) {
+            // Non-triangular faces are not supported as of now.
+            return false;
+        }
+        num_faces ++;
+        i = j;
+    }
+
+    // Convert ObjData into STL.
+    TriangleMesh mesh;
+    stl_file &stl = mesh.stl;
+    stl.stats.type = inmemory;
+    stl.stats.number_of_facets = num_faces;
+    stl.stats.original_num_facets = num_faces;
+    stl_allocate(&stl);
+    size_t i_face = 0;
+    for (size_t i = 0; i < data.vertices.size(); ++ i) {
+        if (data.vertices[i].coordIdx == -1)
+            continue;
+        stl_facet &facet = stl.facet_start[i_face ++];
+        for (unsigned int v = 0; v < 3; ++ v) {
+            const ObjParser::ObjVertex &vertex = data.vertices[i++];
+            memcpy(&facet.vertex[v].x, &data.coordinates[vertex.coordIdx*4], 3 * sizeof(float));
+            if (vertex.normalIdx != -1)
+                memcpy(&facet.normal.x, &data.normals[vertex.normalIdx*3], 3 * sizeof(float));
+        }
+    }
+    stl_get_size(&stl);
+    mesh.repair();
+    if (mesh.facets_count() == 0) {
+        // die "This STL file couldn't be read because it's empty.\n"
+        return false;
+    }
+
+    std::string  object_name;
+    if (object_name_in == nullptr) {
+        const char *last_slash = strrchr(path, DIR_SEPARATOR);
+        object_name.assign((last_slash == nullptr) ? path : last_slash + 1);
+    } else
+       object_name.assign(object_name_in);
+
+    model->add_object(object_name.c_str(), path, std::move(mesh));
+    return true;
+}
+
+}; // namespace Slic3r