| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Duplicate multiple files |
| 4 | * |
| 5 | * (c) 2008 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of the mLib utilities library. |
| 11 | * |
| 12 | * mLib is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * mLib is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with mLib; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include <errno.h> |
| 31 | #include <stdlib.h> |
| 32 | |
| 33 | #include <unistd.h> |
| 34 | |
| 35 | #include "mdup.h" |
| 36 | |
| 37 | /*----- Data structures ---------------------------------------------------*/ |
| 38 | |
| 39 | typedef struct mdup_fdinfo { |
| 40 | |
| 41 | mdup_fd *f; |
| 42 | /* Each @fdinfo@ structure refers to one of the caller's @fd@ structures. |
| 43 | * This is it. |
| 44 | */ |
| 45 | |
| 46 | struct mdup_fdinfo *eqnext, *eqprev; |
| 47 | /* The caller's request list can contain more than one entry with any given |
| 48 | * @cur@ descriptor. We group them together into an equivalence class, |
| 49 | * which is doubly linked using these fields. |
| 50 | */ |
| 51 | |
| 52 | struct mdup_fdinfo *up; |
| 53 | /* We require that there be at most one node with any given @want@ |
| 54 | * descriptor (other than @-1@). There is therefore at most one node whose |
| 55 | * @want@ is equal to my @cur@. If such a node exists, @up@ points to it; |
| 56 | * otherwise @up@ is null. |
| 57 | */ |
| 58 | |
| 59 | struct mdup_fdinfo *down; |
| 60 | /* Obviously, @down@ links in the opposite direction from @up@. However, |
| 61 | * there may be several nodes whose @cur@ equals my @want@; therefore |
| 62 | * @down@ simply links to one of the nodes in the equivalence class. |
| 63 | * |
| 64 | * Unsurprisingly, @down@ is the direction we move during the depth-first |
| 65 | * traversal phase of the operation. |
| 66 | */ |
| 67 | |
| 68 | struct mdup_fdinfo *dlink; |
| 69 | /* Nodes with @want == -1@, and nodes where we've broken cycles, are |
| 70 | * considered `dynamic': their @cur@ has been chosen by @dup@ to be |
| 71 | * distinct from any existing descriptor, but may collide with a @want@. |
| 72 | * We check each proposed move against the list of dynamic nodes, and move |
| 73 | * them out of the way as necessary. Note that this is really a list of |
| 74 | * equivalence classes rather than single nodes. |
| 75 | */ |
| 76 | |
| 77 | unsigned state; |
| 78 | /* The current state of this node. One of the @ST@ constants described |
| 79 | * below. |
| 80 | */ |
| 81 | } mdup_fdinfo; |
| 82 | |
| 83 | enum { |
| 84 | ST_READY, |
| 85 | /* Node has not yet been processed. |
| 86 | */ |
| 87 | |
| 88 | ST_MARK, |
| 89 | /* Node has been reached by the depth-first traversal, but its descriptor |
| 90 | * has not yet been moved. This state is used to detect cycles using the |
| 91 | * depth-first traversal. |
| 92 | */ |
| 93 | |
| 94 | ST_DONE, |
| 95 | /* Node has been processed completely. We have @want == -1@ or |
| 96 | * @want == cur@. |
| 97 | */ |
| 98 | |
| 99 | ST_BROKEN, |
| 100 | /* Node has been clobbered in order to break a cycle. The node's |
| 101 | * equivalence class has been remapped to a fresh descriptor which (we |
| 102 | * hope) is not equal to any node's @want@. All broken nodes are put on |
| 103 | * the dynamic list: if our hope turns out to be misplaced we can remap the |
| 104 | * class again. |
| 105 | */ |
| 106 | }; |
| 107 | |
| 108 | /*----- Main code ---------------------------------------------------------*/ |
| 109 | |
| 110 | /* --- @DO_EQUIVS@ --- * |
| 111 | * |
| 112 | * Perform @body@ once for each @g@ in the equivalence class of @f@. |
| 113 | */ |
| 114 | |
| 115 | #define DO_EQUIVS(g, f, body) do { \ |
| 116 | mdup_fdinfo *f_ = (f), *g_ = f_; \ |
| 117 | do { mdup_fdinfo *g = g_; g_ = g_->eqnext; body; } while (g_ != f_); \ |
| 118 | } while (0) |
| 119 | |
| 120 | /* --- @dump@ --- * |
| 121 | * |
| 122 | * Arguments: @mdup_fdinfo *v@ = pointer to info vector |
| 123 | * @size_t n@ = size of vector |
| 124 | * |
| 125 | * Returns: --- |
| 126 | * |
| 127 | * Use: Dumps a scary-looking description of the state of @mdup@'s |
| 128 | * workings. |
| 129 | */ |
| 130 | |
| 131 | #ifdef DEBUG |
| 132 | |
| 133 | #include <stdarg.h> |
| 134 | #include <stdio.h> |
| 135 | |
| 136 | #include "macros.h" |
| 137 | |
| 138 | #define D(x) x |
| 139 | |
| 140 | static void PRINTF_LIKE(4, 5) IGNORABLE |
| 141 | dump(mdup_fdinfo *v, size_t n, mdup_fdinfo *dhead, const char *fmt, ...) |
| 142 | { |
| 143 | int i; |
| 144 | mdup_fdinfo *f, *g; |
| 145 | static const char *state[] = { "READY", "MARK", "DONE", "BROKEN" }; |
| 146 | va_list ap; |
| 147 | |
| 148 | #define INDEX(p) ((p) ? (int)((p) - (v)) : -1) |
| 149 | |
| 150 | /* --- Dump the items, fairly raw --- */ |
| 151 | |
| 152 | va_start(ap, fmt); |
| 153 | fputs("*** ", stdout); |
| 154 | vprintf(fmt, ap); |
| 155 | putchar('\n'); |
| 156 | for (i = 0; i < n; i++) { |
| 157 | f = &v[i]; |
| 158 | printf("%3d: %-6s %3d -> %3d; " |
| 159 | "equivs: %3d, %3d; up: %3d; down: %3d; dyn: %3d\n", |
| 160 | i, state[f->state], f->f->cur, f->f->want, |
| 161 | INDEX(f->eqprev), INDEX(f->eqnext), |
| 162 | INDEX(f->up), INDEX(f->down), INDEX(f->dlink)); |
| 163 | } |
| 164 | putchar('\n'); |
| 165 | va_end(ap); |
| 166 | |
| 167 | #undef INDEX |
| 168 | } |
| 169 | |
| 170 | #else |
| 171 | |
| 172 | #define D(x) |
| 173 | |
| 174 | #endif |
| 175 | |
| 176 | /* --- @dfs@ --- * |
| 177 | * |
| 178 | * Arguments: @mdup_fdinfo *f@ = which node to process |
| 179 | * @mdup_fdinfo **dhead, ***dtail@ = the dynamic list |
| 180 | * |
| 181 | * Returns: Zero on success, @-1@ on some OS failure. |
| 182 | * |
| 183 | * Use: Recursive depth-first traversal of the descriptor graph. |
| 184 | * |
| 185 | * On exit, the node @f@ will be in state @ST_DONE@ or |
| 186 | * @ST_BROKEN@. |
| 187 | */ |
| 188 | |
| 189 | static int dfs(mdup_fdinfo *f, mdup_fdinfo **dhead, mdup_fdinfo ***dtail) |
| 190 | { |
| 191 | mdup_fdinfo *d; |
| 192 | mdup_fd *ff; |
| 193 | int can_close_p = 1; |
| 194 | int fd, ofd; |
| 195 | int e; |
| 196 | |
| 197 | /* --- Null pointers need no processing --- * |
| 198 | * |
| 199 | * Null pointers mark the end of descending chains. |
| 200 | */ |
| 201 | |
| 202 | if (!f) |
| 203 | return (0); |
| 204 | |
| 205 | /* --- Otherwise our behaviour depends on the node's state --- */ |
| 206 | |
| 207 | switch (f->state) { |
| 208 | |
| 209 | /* --- The standard processing, in several phases --- */ |
| 210 | |
| 211 | case ST_READY: |
| 212 | |
| 213 | /* --- Mark the class as being in-progress --- */ |
| 214 | |
| 215 | DO_EQUIVS(g, f, { g->state = ST_MARK; }); |
| 216 | |
| 217 | /* --- Ensure that the our proposed destination is clear --- * |
| 218 | * |
| 219 | * The depth-first traversal will leave the node in @ST_DONE@ or |
| 220 | * @ST_BROKEN@ afterwards; either way, its @cur@ will not be same as |
| 221 | * our @want@. |
| 222 | * |
| 223 | * Note that this can move @%\emph{us}@ to @ST_BROKEN@. This is not a |
| 224 | * significant problem. |
| 225 | */ |
| 226 | |
| 227 | DO_EQUIVS(g, f, { if (dfs(g->down, dhead, dtail)) return (-1); }); |
| 228 | |
| 229 | /* --- Now the real work can begin --- * |
| 230 | * |
| 231 | * For each node in the class, copy the descriptor from @cur@ to |
| 232 | * @want@. Before doing this, we must move out of the way any (other) |
| 233 | * dynamic nodes whose @cur@ matches our @want@. |
| 234 | * |
| 235 | * Interestingly, this is the only point in the function where we need |
| 236 | * nontrivial error handling: if something goes wrong with one of the |
| 237 | * @dup2@ calls, we must close the descriptors made so far this pass |
| 238 | * before returning. |
| 239 | */ |
| 240 | |
| 241 | ofd = f->f->cur; |
| 242 | DO_EQUIVS(g, f, { |
| 243 | ff = g->f; |
| 244 | for (d = *dhead; d; d = d->dlink) { |
| 245 | if (d != f && d->f->cur == ff->want) { |
| 246 | if ((fd = dup(ff->want)) < 0) |
| 247 | goto fail; |
| 248 | DO_EQUIVS(dd, d, { dd->f->cur = fd; }); |
| 249 | close(ff->want); |
| 250 | } |
| 251 | } |
| 252 | if (ff->cur == ff->want) |
| 253 | can_close_p = 0; |
| 254 | else if (dup2(ofd, ff->want) < 0) |
| 255 | goto fail; |
| 256 | goto ok; |
| 257 | fail: |
| 258 | e = errno; |
| 259 | for (g = g->eqprev; g != f->eqprev; g = g->eqprev) { |
| 260 | if (g->f->want != g->f->cur) |
| 261 | close(g->f->want); |
| 262 | } |
| 263 | errno = e; |
| 264 | return (-1); |
| 265 | ok:; |
| 266 | }); |
| 267 | |
| 268 | /* --- We're done --- * |
| 269 | * |
| 270 | * If the original descriptor isn't wanted by anyone we can (and must) |
| 271 | * close it. Nodes can now move to @ST_DONE@. |
| 272 | */ |
| 273 | |
| 274 | if (can_close_p) |
| 275 | close(ofd); |
| 276 | DO_EQUIVS(g, f, { |
| 277 | g->f->cur = g->f->want; |
| 278 | g->state = ST_DONE; |
| 279 | }); |
| 280 | break; |
| 281 | |
| 282 | /* --- We have encoutered a cycle --- * |
| 283 | * |
| 284 | * The caller wants our descriptor. We therefore shunt this entire |
| 285 | * equivalence class to a new descriptor, and link it onto the dynamic |
| 286 | * list. Mark it as broken so that we don't try to do anything |
| 287 | * complicated to it again. |
| 288 | */ |
| 289 | |
| 290 | case ST_MARK: |
| 291 | ofd = f->f->cur; |
| 292 | if ((fd = dup(ofd)) < 0) |
| 293 | return (-1); |
| 294 | DO_EQUIVS(g, f, { |
| 295 | g->f->cur = fd; |
| 296 | g->state = ST_BROKEN; |
| 297 | }); |
| 298 | f->dlink = **dtail; |
| 299 | **dtail = f; |
| 300 | close(ofd); |
| 301 | break; |
| 302 | |
| 303 | /* --- Nothing to be done here --- * |
| 304 | * |
| 305 | * @ST_DONE@ nodes have already been completely processed; @ST_BROKEN@ |
| 306 | * nodes will be fixed up after the main traversal. |
| 307 | */ |
| 308 | |
| 309 | case ST_DONE: |
| 310 | case ST_BROKEN: |
| 311 | return (0); |
| 312 | |
| 313 | } |
| 314 | return (0); |
| 315 | } |
| 316 | |
| 317 | /* --- @mdup@ --- * |
| 318 | * |
| 319 | * Arguments: @mdup_fd *v@ = pointer to @mdup_fd@ vector |
| 320 | * @size_t n@ = size of vector |
| 321 | * |
| 322 | * Returns: Zero if successful, @-1@ on failure. |
| 323 | * |
| 324 | * Use: Rearranges file descriptors. |
| 325 | * |
| 326 | * The vector @v@ consists of a number of @mdup_fd@ structures. |
| 327 | * Each `slot' in the table represents a file. The slot's @cur@ |
| 328 | * member names the current file descriptor for this file; the |
| 329 | * @want@ member is the file descriptor we want to use for it. |
| 330 | * if you want to keep a file alive but don't care which |
| 331 | * descriptor it ends up with, set @want = -1@. Several slots |
| 332 | * may specify the same @cur@ descriptor; but they all have to |
| 333 | * declare different @want@s (except that several slots may have |
| 334 | * @want = -1@. |
| 335 | * |
| 336 | * On successful exit, the function will have rearranged the |
| 337 | * file descriptors as requested. To reflect this, the @cur@ |
| 338 | * members will all be set to match the (non-@-1@) @want@ |
| 339 | * members. |
| 340 | * |
| 341 | * If there is a failure, then some rearrangement may have been |
| 342 | * performed and some not; the @cur@ members are set to reflect |
| 343 | * which file descriptors are to be used. The old file |
| 344 | * descriptors are closed. (This is different from usual @dup@ |
| 345 | * behaviour, of course, but essential for reliable error |
| 346 | * handling.) If you want to keep a particular source file |
| 347 | * descriptor open as well as make a new copy then specify two |
| 348 | * slots with the same @cur@, one with @want = cur@ and one with |
| 349 | * the desired output descriptor. |
| 350 | * |
| 351 | * This function works correctly even if the desired remappings |
| 352 | * contain cycles. |
| 353 | */ |
| 354 | |
| 355 | int mdup(mdup_fd *v, size_t n) |
| 356 | { |
| 357 | size_t i, j; |
| 358 | mdup_fdinfo *vv; |
| 359 | mdup_fdinfo *f, *g, *dhead, **dtail; |
| 360 | mdup_fd *ff; |
| 361 | int rc = -1; |
| 362 | int can_close_p; |
| 363 | int ofd, fd; |
| 364 | |
| 365 | /* --- Allocate and initialize the table of info nodes --- * |
| 366 | * |
| 367 | * Each entry @ff@ in the caller's @v@ array will have a corresponding node |
| 368 | * @f@ in @vv@ with @f->f = ff@. Initially each node's links are null, and |
| 369 | * the node is in the @ST_READY@ state. |
| 370 | * |
| 371 | * We also initialize a list given by @dhead@ and @dtail@ containing the |
| 372 | * entries with `dynamically-assigned' descriptors -- i.e., those whose |
| 373 | * values we made up using @dup@. The list lets us detect collisions with |
| 374 | * explicitly requested descriptors and move the dynamic ones out of the |
| 375 | * way. |
| 376 | */ |
| 377 | |
| 378 | if ((vv = malloc(sizeof(*vv) * n)) == 0) |
| 379 | return (-1); |
| 380 | |
| 381 | dhead = 0; |
| 382 | dtail = &dhead; |
| 383 | for (i = 0; i < n; i++) { |
| 384 | f = &vv[i]; |
| 385 | f->f = &v[i]; |
| 386 | f->up = f->down = 0; |
| 387 | f->eqnext = f->eqprev = 0; |
| 388 | f->state = ST_READY; |
| 389 | } |
| 390 | |
| 391 | /* --- Pass one: link the graph together --- * |
| 392 | * |
| 393 | * Once this pass is complete, the following properties will hold. |
| 394 | * |
| 395 | * * The nodes which have the same @cur@ are linked together by their |
| 396 | * @eqnext@ and @eqprev@ fields into a doubly-linked circular list |
| 397 | * representing this equivalence class. |
| 398 | * |
| 399 | * * @f->up == g@ if and only if @f->f->cur == g->f->want@. (Note that |
| 400 | * @want@ fields are unique according to our interface. We detect |
| 401 | * violations and exit with @errno == EINVAL@.) |
| 402 | * |
| 403 | * * If @f->up == g@ then there exists a @ff@ in the same equivalence |
| 404 | * class (and therefore on @f@'s @eqnext@ list) as @f@ with |
| 405 | * @g->down == ff@. |
| 406 | */ |
| 407 | |
| 408 | for (i = 0; i < n; i++) { |
| 409 | f = &vv[i]; |
| 410 | if (!f->eqnext) |
| 411 | f->eqnext = f->eqprev = f; |
| 412 | for (j = 0; j < n; j++) { |
| 413 | if (i == j) |
| 414 | continue; |
| 415 | g = &vv[j]; |
| 416 | if (f->f->cur == g->f->cur) { |
| 417 | if (!g->eqnext) { |
| 418 | g->eqnext = f->eqnext; |
| 419 | g->eqprev = f; |
| 420 | f->eqnext->eqprev = g; |
| 421 | f->eqnext = g; |
| 422 | } |
| 423 | } |
| 424 | if (g->f->want == -1) |
| 425 | /* fine */; |
| 426 | else if (f->f->want == g->f->want) { |
| 427 | errno = EINVAL; |
| 428 | goto fail; |
| 429 | } else if (f->f->cur == g->f->want) { |
| 430 | f->up = g; |
| 431 | if (!g->down) |
| 432 | g->down = f; |
| 433 | } |
| 434 | } |
| 435 | } |
| 436 | |
| 437 | /* --- Pass two: handle don't-care requests --- * |
| 438 | * |
| 439 | * By the end of this pass, we have the following properties. |
| 440 | * |
| 441 | * * Every node will be marked @ST_DONE@. This is a temporary abuse of |
| 442 | * the @ST_DONE@ state which will be rectified during the next pass. |
| 443 | * |
| 444 | * * Every node with @want == -1@ will have @cur@ set to a freshly |
| 445 | * allocated file descriptor distinct from every previously open file. |
| 446 | */ |
| 447 | |
| 448 | for (i = 0; i < n; i++) { |
| 449 | f = &vv[i]; |
| 450 | switch (f->state) { |
| 451 | case ST_DONE: |
| 452 | break; |
| 453 | case ST_READY: |
| 454 | can_close_p = 1; |
| 455 | DO_EQUIVS(g, f, { |
| 456 | ff = g->f; |
| 457 | ofd = ff->cur; |
| 458 | if (ff->want != -1) |
| 459 | can_close_p = 0; |
| 460 | else { |
| 461 | if ((fd = dup(ofd)) < 0) |
| 462 | goto fail; |
| 463 | ff->cur = fd; |
| 464 | } |
| 465 | g->state = ST_DONE; |
| 466 | }); |
| 467 | if (can_close_p) |
| 468 | close(ofd); |
| 469 | break; |
| 470 | } |
| 471 | } |
| 472 | |
| 473 | /* --- Pass three: restore equivalence classes and @down@ links --- * |
| 474 | * |
| 475 | * This pass re-establishes the properties from pass one. Because we've |
| 476 | * changed some @cur@ members, the equivalence classes will have changed, |
| 477 | * so we must fix up the @eqnext@ lists and @down@ links. |
| 478 | * |
| 479 | * Nodes with @want == -1@ are now finished with (modulo tweaking |
| 480 | * dynamically allocated descriptors as we process the others), so we leave |
| 481 | * them in @ST_DONE@; other nodes are restored to @ST_READY@. |
| 482 | */ |
| 483 | |
| 484 | for (i = 0; i < n; i++) { |
| 485 | f = &vv[i]; |
| 486 | ff = f->f; |
| 487 | if (ff->want == -1) { |
| 488 | f->eqnext->eqprev = f->eqprev; |
| 489 | f->eqprev->eqnext = f->eqnext; |
| 490 | f->eqnext = f->eqprev = f; |
| 491 | f->dlink = *dtail; |
| 492 | *dtail = f; |
| 493 | } else |
| 494 | f->state = ST_READY; |
| 495 | } |
| 496 | |
| 497 | /* --- Pass four: main depth-first traversal --- * |
| 498 | * |
| 499 | * See the description of the function @dfs@ above. After this pass, every |
| 500 | * node is in state @ST_DONE@ or @ST_BROKEN@. |
| 501 | */ |
| 502 | |
| 503 | for (i = 0; i < n; i++) { |
| 504 | if (dfs(&vv[i], &dhead, &dtail)) |
| 505 | goto fail; |
| 506 | } |
| 507 | |
| 508 | /* --- Finished --- */ |
| 509 | |
| 510 | rc = 0; |
| 511 | fail: |
| 512 | free(vv); |
| 513 | return (rc); |
| 514 | } |
| 515 | |
| 516 | /*----- That's all, folks -------------------------------------------------*/ |