eqemu

annotate src/objfile.cc @ 5:9b5bb05ae53a

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foo
author John Tsiombikas <nuclear@member.fsf.org>
date Fri, 18 Jul 2014 00:42:15 +0300
parents 3d3656360a82
children 977bc1cb055b
rev   line source
nuclear@3 1 #include <stdlib.h>
nuclear@3 2 #include <string.h>
nuclear@3 3 #include <ctype.h>
nuclear@3 4 #include <limits.h>
nuclear@4 5 #include <assert.h>
nuclear@3 6 #include <vector>
nuclear@3 7 #include <map>
nuclear@3 8 #include <string>
nuclear@3 9 #include <sstream>
nuclear@3 10 #include <iomanip>
nuclear@3 11 #include "scene.h"
nuclear@3 12
nuclear@3 13 using namespace std;
nuclear@3 14
nuclear@3 15 #define COMMANDS \
nuclear@3 16 CMD(V), \
nuclear@3 17 CMD(VN), \
nuclear@3 18 CMD(VT), \
nuclear@3 19 CMD(F), \
nuclear@3 20 CMD(O), \
nuclear@3 21 CMD(G), \
nuclear@3 22 CMD(MTLLIB), \
nuclear@3 23 CMD(USEMTL), \
nuclear@3 24 CMD(NEWMTL), \
nuclear@3 25 CMD(KA), \
nuclear@3 26 CMD(KD), \
nuclear@3 27 CMD(KS), \
nuclear@3 28 CMD(NS), \
nuclear@3 29 CMD(NI), \
nuclear@3 30 CMD(D), \
nuclear@3 31 CMD(TR), \
nuclear@3 32 CMD(MAP_KD), \
nuclear@3 33 CMD(MAP_KS), \
nuclear@3 34 CMD(MAP_NS), \
nuclear@3 35 CMD(MAP_D), \
nuclear@3 36 CMD(REFL), \
nuclear@3 37 CMD(BUMP)
nuclear@3 38
nuclear@3 39 #define CMD(x) CMD_##x
nuclear@3 40 enum {
nuclear@3 41 COMMANDS,
nuclear@3 42 CMD_UNK
nuclear@3 43 };
nuclear@3 44 #undef CMD
nuclear@3 45
nuclear@3 46 #define CMD(x) #x
nuclear@3 47 static const char *cmd_names[] = {
nuclear@3 48 COMMANDS,
nuclear@3 49 0
nuclear@3 50 };
nuclear@3 51 #undef CMD
nuclear@3 52
nuclear@3 53
nuclear@3 54 struct ObjFace {
nuclear@3 55 int elem;
nuclear@3 56 int v[4], n[4], t[4];
nuclear@3 57 };
nuclear@3 58
nuclear@3 59 struct ObjFile {
nuclear@3 60 string cur_obj, cur_mat;
nuclear@3 61 vector<Vector3> v, vn;
nuclear@3 62 vector<Vector2> vt;
nuclear@3 63 vector<ObjFace> f;
nuclear@3 64 };
nuclear@3 65
nuclear@3 66 typedef Vector3 Color;
nuclear@3 67
nuclear@3 68 struct ObjMat {
nuclear@3 69 string name; // newmtl <name>
nuclear@3 70 Color ambient, diffuse, specular; // Ka, Kd, Ks
nuclear@3 71 float shininess; // Ns
nuclear@3 72 float ior; // Ni
nuclear@3 73 float alpha; // d, Tr
nuclear@3 74
nuclear@3 75 string tex_dif, tex_spec, tex_shin, tex_alpha; // map_Kd, map_Ks, map_Ns, map_d
nuclear@3 76 string tex_refl; // refl -type sphere|cube file
nuclear@3 77 string tex_bump; // bump
nuclear@3 78
nuclear@3 79 ObjMat() { reset(); }
nuclear@3 80
nuclear@3 81 void reset() {
nuclear@3 82 ambient = diffuse = Color(0.5, 0.5, 0.5);
nuclear@3 83 specular = Color(0.0, 0.0, 0.0);
nuclear@3 84 name = tex_dif = tex_spec = tex_shin = tex_alpha = tex_refl = tex_bump = "";
nuclear@3 85 shininess = 0;
nuclear@3 86 ior = alpha = 1;
nuclear@3 87 }
nuclear@3 88 };
nuclear@3 89
nuclear@3 90 static bool read_materials(FILE *fp, vector<ObjMat> *vmtl);
nuclear@3 91 static Object *cons_object(ObjFile *obj);
nuclear@3 92
nuclear@3 93 static int get_cmd(char *str);
nuclear@3 94 static bool is_int(const char *str);
nuclear@3 95 static bool is_float(const char *str);
nuclear@3 96 static bool parse_vec(Vector3 *vec);
nuclear@3 97 static bool parse_color(Color *col);
nuclear@3 98 static bool parse_face(ObjFace *face);
nuclear@3 99 static const char *parse_map();
nuclear@3 100
nuclear@3 101
nuclear@3 102 static map<string, Material> matlib;
nuclear@3 103
nuclear@3 104
nuclear@3 105 #define INVALID_IDX INT_MIN
nuclear@3 106
nuclear@3 107 #define SEP " \t\n\r\v"
nuclear@3 108 #define BUF_SZ 512
nuclear@3 109 bool Scene::load_obj(FILE *fp)
nuclear@3 110 {
nuclear@3 111 static int seq;
nuclear@3 112 char cur_name[16];
nuclear@3 113 stringstream sstr;
nuclear@3 114
nuclear@3 115 ObjFile obj;
nuclear@3 116
nuclear@3 117 sprintf(cur_name, "default%02d.obj", seq++);
nuclear@3 118 obj.cur_obj = cur_name;
nuclear@3 119
nuclear@3 120 int prev_cmd = 0, obj_added = 0;
nuclear@3 121 for(;;) {
nuclear@3 122 Vector3 vec;
nuclear@3 123 ObjFace face;
nuclear@3 124
nuclear@3 125 char line[BUF_SZ];
nuclear@3 126 fgets(line, sizeof line, fp);
nuclear@3 127 if(feof(fp)) {
nuclear@3 128 break;
nuclear@3 129 }
nuclear@3 130
nuclear@3 131 char *tok;
nuclear@3 132 if(!(tok = strtok(line, SEP))) {
nuclear@3 133 continue; // ignore empty lines
nuclear@3 134 }
nuclear@3 135
nuclear@3 136 int cmd;
nuclear@3 137 if((cmd = get_cmd(tok)) == -1) {
nuclear@3 138 continue; // ignore unknown commands ...
nuclear@3 139 }
nuclear@3 140
nuclear@3 141 switch(cmd) {
nuclear@3 142 case CMD_V:
nuclear@3 143 if(!parse_vec(&vec)) {
nuclear@3 144 continue;
nuclear@3 145 }
nuclear@3 146 obj.v.push_back(vec);
nuclear@3 147 break;
nuclear@3 148
nuclear@3 149 case CMD_VN:
nuclear@3 150 if(!parse_vec(&vec)) {
nuclear@3 151 continue;
nuclear@3 152 }
nuclear@3 153 obj.vn.push_back(vec);
nuclear@3 154 break;
nuclear@3 155
nuclear@3 156 case CMD_VT:
nuclear@3 157 if(!parse_vec(&vec)) {
nuclear@3 158 continue;
nuclear@3 159 }
nuclear@3 160 vec.y = 1.0 - vec.y;
nuclear@3 161 obj.vt.push_back(Vector2(vec.x, vec.y));
nuclear@3 162 break;
nuclear@3 163
nuclear@3 164 case CMD_O:
nuclear@3 165 case CMD_G:
nuclear@3 166 if(prev_cmd == CMD_O || prev_cmd == CMD_G) {
nuclear@3 167 break; // just in case we've got both of them in a row
nuclear@3 168 }
nuclear@3 169 /* if we have any previous data, group them up, add the object
nuclear@3 170 * and continue with the new one...
nuclear@3 171 */
nuclear@3 172 if(!obj.f.empty()) {
nuclear@3 173 Object *robj = cons_object(&obj);
nuclear@3 174 robj->mtl = matlib[obj.cur_mat];
nuclear@3 175 add_object(robj);
nuclear@3 176 obj_added++;
nuclear@3 177
nuclear@3 178 obj.f.clear(); // clean the face list
nuclear@3 179 }
nuclear@3 180 if((tok = strtok(0, SEP))) {
nuclear@3 181 obj.cur_obj = tok;
nuclear@3 182 } else {
nuclear@3 183 sprintf(cur_name, "default%02d.obj", seq++);
nuclear@3 184 obj.cur_obj = cur_name;
nuclear@3 185 }
nuclear@3 186 break;
nuclear@3 187
nuclear@3 188 case CMD_MTLLIB:
nuclear@3 189 if((tok = strtok(0, SEP))) {
nuclear@3 190 FILE *mfile;
nuclear@3 191 if(!(mfile = fopen(tok, "rb"))) {
nuclear@3 192 fprintf(stderr, "failed to open material library: %s\n", tok);
nuclear@3 193 continue;
nuclear@3 194 }
nuclear@3 195
nuclear@3 196 // load all materials of the mtl file into a vector
nuclear@3 197 vector<ObjMat> vmtl;
nuclear@3 198 if(!read_materials(mfile, &vmtl)) {
nuclear@3 199 continue;
nuclear@3 200 }
nuclear@3 201 fclose(mfile);
nuclear@3 202
nuclear@3 203 // and add them all to the scene
nuclear@3 204 for(size_t i=0; i<vmtl.size(); i++) {
nuclear@3 205 Material mat;
nuclear@3 206 mat.ambient = vmtl[i].ambient;
nuclear@3 207 mat.diffuse = vmtl[i].diffuse;
nuclear@3 208 mat.specular = vmtl[i].specular;
nuclear@3 209 mat.shininess = vmtl[i].shininess;
nuclear@3 210 mat.alpha = vmtl[i].alpha;
nuclear@3 211
nuclear@5 212 if(vmtl[i].tex_dif.length()) {
nuclear@5 213 mat.tex[TEX_DIFFUSE] = load_texture(vmtl[i].tex_dif.c_str());
nuclear@5 214 }
nuclear@5 215 if(vmtl[i].tex_refl.length()) {
nuclear@5 216 mat.tex[TEX_ENVMAP] = load_texture(vmtl[i].tex_refl.c_str());
nuclear@5 217 }
nuclear@3 218
nuclear@3 219 matlib[vmtl[i].name] = mat;
nuclear@3 220 }
nuclear@3 221 }
nuclear@3 222 break;
nuclear@3 223
nuclear@3 224 case CMD_USEMTL:
nuclear@3 225 if((tok = strtok(0, SEP))) {
nuclear@3 226 obj.cur_mat = tok;
nuclear@3 227 } else {
nuclear@3 228 obj.cur_mat = "";
nuclear@3 229 }
nuclear@3 230 break;
nuclear@3 231
nuclear@3 232 case CMD_F:
nuclear@3 233 if(!parse_face(&face)) {
nuclear@3 234 continue;
nuclear@3 235 }
nuclear@3 236
nuclear@3 237 // convert negative indices to regular indices
nuclear@3 238 for(int i=0; i<4; i++) {
nuclear@3 239 if(face.v[i] < 0 && face.v[i] != INVALID_IDX) {
nuclear@3 240 face.v[i] = obj.v.size() + face.v[i];
nuclear@3 241 }
nuclear@3 242 if(face.n[i] < 0 && face.n[i] != INVALID_IDX) {
nuclear@3 243 face.n[i] = obj.vn.size() + face.n[i];
nuclear@3 244 }
nuclear@3 245 if(face.t[i] < 0 && face.t[i] != INVALID_IDX) {
nuclear@3 246 face.t[i] = obj.vt.size() + face.t[i];
nuclear@3 247 }
nuclear@3 248 }
nuclear@3 249
nuclear@3 250 // break quads into triangles if needed
nuclear@3 251 obj.f.push_back(face);
nuclear@3 252 if(face.elem == 4) {
nuclear@3 253 face.v[1] = face.v[2];
nuclear@3 254 face.n[1] = face.n[2];
nuclear@3 255 face.t[1] = face.t[2];
nuclear@3 256
nuclear@3 257 face.v[2] = face.v[3];
nuclear@3 258 face.n[2] = face.n[3];
nuclear@3 259 face.t[2] = face.t[3];
nuclear@3 260
nuclear@3 261 obj.f.push_back(face);
nuclear@3 262 }
nuclear@3 263 break;
nuclear@3 264
nuclear@3 265 default:
nuclear@3 266 break; // ignore unknown commands
nuclear@3 267 }
nuclear@3 268
nuclear@3 269 prev_cmd = cmd;
nuclear@3 270 }
nuclear@3 271
nuclear@3 272 // reached end of file...
nuclear@3 273 if(!obj.f.empty()) {
nuclear@3 274 Object *robj = cons_object(&obj);
nuclear@3 275 robj->mtl = matlib[obj.cur_mat];
nuclear@3 276 add_object(robj);
nuclear@3 277 obj_added++;
nuclear@3 278 }
nuclear@3 279
nuclear@3 280 return obj_added > 0;
nuclear@3 281 }
nuclear@3 282
nuclear@3 283 static Object *cons_object(ObjFile *obj)
nuclear@3 284 {
nuclear@3 285 Object *robj;
nuclear@3 286 Vector3 *varr, *narr;
nuclear@3 287 Vector2 *tarr;
nuclear@3 288
nuclear@3 289 int nelem = obj->f.size() * 3;
nuclear@3 290
nuclear@4 291 assert(sizeof(Vector3) == 3 * sizeof(float));
nuclear@4 292 assert(sizeof(Vector2) == 2 * sizeof(float));
nuclear@4 293
nuclear@3 294 try {
nuclear@3 295 robj = new Object;
nuclear@3 296 varr = new Vector3[nelem];
nuclear@3 297 narr = new Vector3[nelem];
nuclear@3 298 tarr = new Vector2[nelem];
nuclear@3 299 }
nuclear@3 300 catch(...) {
nuclear@3 301 return 0;
nuclear@3 302 }
nuclear@4 303 if(obj->cur_obj.length() > 0) {
nuclear@3 304 robj->set_name(obj->cur_obj.c_str());
nuclear@4 305 }
nuclear@3 306
nuclear@3 307 // need at least one of each element
nuclear@3 308 bool added_norm = false, added_tc = false;
nuclear@3 309 if(obj->vn.empty()) {
nuclear@3 310 obj->vn.push_back(Vector3(0, 0, 0));
nuclear@4 311 added_norm = true;
nuclear@3 312 }
nuclear@3 313 if(obj->vt.empty()) {
nuclear@3 314 obj->vt.push_back(Vector2(0, 0));
nuclear@3 315 added_tc = true;
nuclear@3 316 }
nuclear@3 317
nuclear@3 318 for(size_t i=0; i<obj->f.size(); i++) {
nuclear@3 319 for(int j=0; j<3; j++) {
nuclear@3 320 int idx = i * 3 + j;
nuclear@3 321 ObjFace *f = &obj->f[i];
nuclear@3 322
nuclear@3 323 varr[idx] = obj->v[f->v[j]];
nuclear@3 324 narr[idx] = obj->vn[f->n[j] < 0 ? 0 : f->n[j]];
nuclear@3 325
nuclear@3 326 float t = obj->vt[f->t[j] < 0 ? 0 : f->t[j]].x;
nuclear@3 327 float s = obj->vt[f->t[j] < 0 ? 0 : f->t[j]].y;
nuclear@3 328 tarr[idx] = Vector2(t, s);
nuclear@3 329 }
nuclear@3 330 }
nuclear@3 331
nuclear@3 332 if(added_norm) {
nuclear@3 333 obj->vn.pop_back();
nuclear@3 334 }
nuclear@3 335 if(added_tc) {
nuclear@3 336 obj->vt.pop_back();
nuclear@3 337 }
nuclear@3 338
nuclear@4 339 Mesh *mesh = new Mesh;
nuclear@3 340 mesh->set_attrib(MESH_ATTR_VERTEX, nelem, 3, &varr->x);
nuclear@3 341 mesh->set_attrib(MESH_ATTR_NORMAL, nelem, 3, &narr->x);
nuclear@3 342 mesh->set_attrib(MESH_ATTR_TEXCOORD, nelem, 2, &tarr->x);
nuclear@4 343 robj->set_mesh(mesh);
nuclear@4 344
nuclear@4 345 printf("loaded object %s: %d faces\n", obj->cur_obj.c_str(), nelem / 3);
nuclear@3 346
nuclear@3 347 delete [] varr;
nuclear@3 348 delete [] narr;
nuclear@3 349 delete [] tarr;
nuclear@3 350 return robj;
nuclear@3 351 }
nuclear@3 352
nuclear@3 353 static bool read_materials(FILE *fp, vector<ObjMat> *vmtl)
nuclear@3 354 {
nuclear@3 355 ObjMat mat;
nuclear@3 356
nuclear@3 357 for(;;) {
nuclear@3 358 char line[BUF_SZ];
nuclear@3 359 fgets(line, sizeof line, fp);
nuclear@3 360 if(feof(fp)) {
nuclear@3 361 break;
nuclear@3 362 }
nuclear@3 363
nuclear@3 364 char *tok;
nuclear@3 365 if(!(tok = strtok(line, SEP))) {
nuclear@3 366 continue;
nuclear@3 367 }
nuclear@3 368
nuclear@3 369 int cmd;
nuclear@3 370 if((cmd = get_cmd(tok)) == -1) {
nuclear@3 371 continue;
nuclear@3 372 }
nuclear@3 373
nuclear@3 374 switch(cmd) {
nuclear@3 375 case CMD_NEWMTL:
nuclear@3 376 // add the previous material, and start a new one
nuclear@3 377 if(mat.name.length() > 0) {
nuclear@3 378 vmtl->push_back(mat);
nuclear@3 379 mat.reset();
nuclear@3 380 }
nuclear@3 381 if((tok = strtok(0, SEP))) {
nuclear@3 382 mat.name = tok;
nuclear@3 383 }
nuclear@3 384 break;
nuclear@3 385
nuclear@3 386 case CMD_KA:
nuclear@3 387 parse_color(&mat.ambient);
nuclear@3 388 break;
nuclear@3 389
nuclear@3 390 case CMD_KD:
nuclear@3 391 parse_color(&mat.diffuse);
nuclear@3 392 break;
nuclear@3 393
nuclear@3 394 case CMD_KS:
nuclear@3 395 parse_color(&mat.specular);
nuclear@3 396 break;
nuclear@3 397
nuclear@3 398 case CMD_NS:
nuclear@3 399 if((tok = strtok(0, SEP)) && is_float(tok)) {
nuclear@3 400 mat.shininess = atof(tok);
nuclear@3 401 }
nuclear@3 402 break;
nuclear@3 403
nuclear@3 404 case CMD_NI:
nuclear@3 405 if((tok = strtok(0, SEP)) && is_float(tok)) {
nuclear@3 406 mat.ior = atof(tok);
nuclear@3 407 }
nuclear@3 408 break;
nuclear@3 409
nuclear@3 410 case CMD_D:
nuclear@3 411 case CMD_TR:
nuclear@3 412 {
nuclear@3 413 Color c;
nuclear@3 414 if(parse_color(&c)) {
nuclear@3 415 mat.alpha = cmd == CMD_D ? c.x : 1.0 - c.x;
nuclear@3 416 }
nuclear@3 417 }
nuclear@3 418 break;
nuclear@3 419
nuclear@3 420 case CMD_MAP_KD:
nuclear@3 421 mat.tex_dif = parse_map();
nuclear@3 422 break;
nuclear@3 423
nuclear@3 424 default:
nuclear@3 425 break;
nuclear@3 426 }
nuclear@3 427 }
nuclear@3 428
nuclear@3 429 if(mat.name.length() > 0) {
nuclear@3 430 vmtl->push_back(mat);
nuclear@3 431 }
nuclear@3 432 return true;
nuclear@3 433 }
nuclear@3 434
nuclear@3 435 static int get_cmd(char *str)
nuclear@3 436 {
nuclear@3 437 char *s = str;
nuclear@3 438 while((*s = toupper(*s))) s++;
nuclear@3 439
nuclear@3 440 for(int i=0; cmd_names[i]; i++) {
nuclear@3 441 if(strcmp(str, cmd_names[i]) == 0) {
nuclear@3 442 return i;
nuclear@3 443 }
nuclear@3 444 }
nuclear@3 445 return CMD_UNK;
nuclear@3 446 }
nuclear@3 447
nuclear@3 448 static bool is_int(const char *str)
nuclear@3 449 {
nuclear@3 450 char *tmp;
nuclear@3 451 strtol(str, &tmp, 10);
nuclear@3 452 return tmp != str;
nuclear@3 453 }
nuclear@3 454
nuclear@3 455 static bool is_float(const char *str)
nuclear@3 456 {
nuclear@3 457 char *tmp;
nuclear@3 458 strtod(str, &tmp);
nuclear@3 459 return tmp != str;
nuclear@3 460 }
nuclear@3 461
nuclear@3 462 static bool parse_vec(Vector3 *vec)
nuclear@3 463 {
nuclear@3 464 for(int i=0; i<3; i++) {
nuclear@3 465 char *tok;
nuclear@3 466
nuclear@3 467 if(!(tok = strtok(0, SEP)) || !is_float(tok)) {
nuclear@3 468 if(i < 2) {
nuclear@3 469 return false;
nuclear@3 470 }
nuclear@3 471 vec->z = 0.0;
nuclear@3 472 } else {
nuclear@3 473 (*vec)[i] = atof(tok);
nuclear@3 474 }
nuclear@3 475 }
nuclear@3 476 return true;
nuclear@3 477 }
nuclear@3 478
nuclear@3 479 static bool parse_color(Color *col)
nuclear@3 480 {
nuclear@3 481 for(int i=0; i<3; i++) {
nuclear@3 482 char *tok;
nuclear@3 483
nuclear@3 484 if(!(tok = strtok(0, SEP)) || !is_float(tok)) {
nuclear@3 485 col->y = col->z = col->x;
nuclear@3 486 return i > 0 ? true : false;
nuclear@3 487 }
nuclear@3 488 (*col)[i] = atof(tok);
nuclear@3 489 }
nuclear@3 490 return true;
nuclear@3 491 }
nuclear@3 492
nuclear@3 493 static bool parse_face(ObjFace *face)
nuclear@3 494 {
nuclear@3 495 char *tok[] = {0, 0, 0, 0};
nuclear@3 496 face->elem = 0;
nuclear@3 497
nuclear@3 498 for(int i=0; i<4; i++) {
nuclear@3 499 if((!(tok[i] = strtok(0, SEP)) || !is_int(tok[i]))) {
nuclear@3 500 if(i < 3) return false; // less than 3 verts? not a polygon
nuclear@3 501 } else {
nuclear@3 502 face->elem++;
nuclear@3 503 }
nuclear@3 504 }
nuclear@3 505
nuclear@3 506 for(int i=0; i<4; i++) {
nuclear@3 507 char *subtok = tok[i];
nuclear@3 508
nuclear@3 509 if(!subtok || !*subtok || !is_int(subtok)) {
nuclear@3 510 if(i < 3) {
nuclear@3 511 return false;
nuclear@3 512 }
nuclear@3 513 face->v[i] = INVALID_IDX;
nuclear@3 514 } else {
nuclear@3 515 face->v[i] = atoi(subtok);
nuclear@3 516 if(face->v[i] > 0) face->v[i]--; /* convert to 0-based */
nuclear@3 517 }
nuclear@3 518
nuclear@3 519 while(subtok && *subtok && *subtok != '/') {
nuclear@3 520 subtok++;
nuclear@3 521 }
nuclear@3 522 if(subtok && *subtok && *++subtok && is_int(subtok)) {
nuclear@3 523 face->t[i] = atoi(subtok);
nuclear@3 524 if(face->t[i] > 0) face->t[i]--; /* convert to 0-based */
nuclear@3 525 } else {
nuclear@3 526 face->t[i] = INVALID_IDX;
nuclear@3 527 }
nuclear@3 528
nuclear@3 529 while(subtok && *subtok && *subtok != '/') {
nuclear@3 530 subtok++;
nuclear@3 531 }
nuclear@3 532 if(subtok && *subtok && *++subtok && is_int(subtok)) {
nuclear@3 533 face->n[i] = atoi(subtok);
nuclear@3 534 if(face->n[i] > 0) face->n[i]--; /* convert to 0-based */
nuclear@3 535 } else {
nuclear@3 536 face->n[i] = INVALID_IDX;
nuclear@3 537 }
nuclear@3 538 }
nuclear@3 539
nuclear@3 540 return true;
nuclear@3 541 }
nuclear@3 542
nuclear@3 543 static const char *parse_map()
nuclear@3 544 {
nuclear@3 545 char *tok, *prev = 0;
nuclear@3 546
nuclear@3 547 while((tok = strtok(0, SEP))) {
nuclear@3 548 prev = tok;
nuclear@3 549 }
nuclear@3 550
nuclear@3 551 return prev ? prev : "";
nuclear@3 552 }