Feat: add reusable lens map files

tests/test_frame.c

@@ -1,4 +1,5 @@
 #include "frame.h"
+#include "lens_map.h"
 #include "optics.h"
 
 #include <math.h>
@@ -6,6 +7,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 static int mesh_has_hanging_vertex(const FrameLensMesh *mesh) {
   for (size_t triangle = 0; triangle < mesh->triangle_count; ++triangle)
@@ -84,6 +86,55 @@ int main(void) {
     fputs("flat-space inverse lens-map regression failed\n", stderr);
     goto done;
   }
+  /* A finalized mesh can be persisted independently of spacetime and then
+   * drive the exact same catalog inverse-map and PSF pass. */
+  const char *lens_map_path = "/tmp/gr_lens_map_test.grlens";
+  const LensMapFrame saved_frame = {.frame_id = 7,
+                                    .coordinate_time = 3.0,
+                                    .proper_time = 2.0,
+                                    .mesh = mesh};
+  LensMap loaded_map = {0};
+  double *roundtrip_hdr = calloc((size_t)width * height * 3, sizeof *roundtrip_hdr);
+  if (roundtrip_hdr == NULL ||
+      lens_map_write(lens_map_path, width, height, 30.0, &saved_frame, 1) ||
+      lens_map_read(lens_map_path, &loaded_map) || loaded_map.frame_count != 1 ||
+      loaded_map.frames[0].frame_id != 7 || loaded_map.width != width ||
+      loaded_map.height != height ||
+      loaded_map.frames[0].mesh.vertex_count != mesh.vertex_count ||
+      frame_splat_catalog(&loaded_map.frames[0].mesh, &catalog, roundtrip_hdr,
+                          width, height, test_exposure, &psf, NULL, INFINITY,
+                          1.0, psf_relative_tail, 0.0, 0, 1, NULL, NULL, NULL) != images) {
+    fputs("lens-map round-trip regression failed\n", stderr);
+    free(roundtrip_hdr); lens_map_destroy(&loaded_map); unlink(lens_map_path);
+    goto done;
+  }
+  for (int value = 0; value < width * height * 3; ++value)
+    if (hdr[value] != roundtrip_hdr[value]) {
+      fputs("lens-map round-trip HDR regression failed\n", stderr);
+      free(roundtrip_hdr); lens_map_destroy(&loaded_map); unlink(lens_map_path);
+      goto done;
+    }
+  free(roundtrip_hdr);
+  lens_map_destroy(&loaded_map);
+  /* A damaged payload must not be mistaken for a reusable physical map. */
+  FILE *damaged = fopen(lens_map_path, "r+b");
+  int damage_failed = damaged == NULL;
+  if (!damage_failed) {
+    if (fseek(damaged, -5L, SEEK_END))
+      damage_failed = 1;
+    const int original = damage_failed ? EOF : fgetc(damaged);
+    if (damage_failed || fseek(damaged, -5L, SEEK_END) || original == EOF ||
+        fputc(original ^ 0xff, damaged) == EOF)
+      damage_failed = 1;
+  }
+  if (damaged != NULL && fclose(damaged))
+    damage_failed = 1;
+  if (damage_failed || !lens_map_read(lens_map_path, &loaded_map)) {
+    fputs("lens-map corruption rejection regression failed\n", stderr);
+    lens_map_destroy(&loaded_map); unlink(lens_map_path);
+    goto done;
+  }
+  unlink(lens_map_path);
   memset(hdr, 0, (size_t)width * height * 3 * sizeof *hdr);
   PsfSplatStats min_y_stats = {0};
   if (frame_splat_catalog(&mesh, &catalog, hdr, width, height, test_exposure,