1 /*
2  * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/types.h>
18 #include <sys/stat.h>
19 #include <sys/queue.h>
20 #include <sys/stdint.h>
21 
22 #include <limits.h>
23 #include <stdio.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include <sha1.h>
27 #include <zlib.h>
28 #include <ctype.h>
29 
30 #include "got_error.h"
31 #include "got_object.h"
32 #include "got_cancel.h"
33 #include "got_commit_graph.h"
34 #include "got_path.h"
35 
36 #include "got_lib_delta.h"
37 #include "got_lib_inflate.h"
38 #include "got_lib_object.h"
39 #include "got_lib_object_idset.h"
40 
41 struct got_commit_graph_node {
42 	struct got_object_id id;
43 	time_t timestamp;
44 
45 	/* Used during graph iteration. */
46 	TAILQ_ENTRY(got_commit_graph_node) entry;
47 };
48 
49 TAILQ_HEAD(got_commit_graph_iter_list, got_commit_graph_node);
50 
51 struct got_commit_graph_branch_tip {
52 	struct got_object_id *commit_id;
53 	struct got_commit_object *commit;
54 	struct got_commit_graph_node *new_node;
55 	int changed;
56 	int branch_done;
57 };
58 
59 struct got_commit_graph {
60 	/* The set of all commits we have traversed. */
61 	struct got_object_idset *node_ids;
62 
63 	int flags;
64 #define GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL		0x01
65 
66 	/*
67 	 * A set of object IDs of known parent commits which we have not yet
68 	 * traversed. Each commit ID in this set represents a branch in commit
69 	 * history: Either the first-parent branch of the head node, or another
70 	 * branch corresponding to a traversed merge commit for which we have
71 	 * not traversed a branch point commit yet.
72 	 *
73 	 * Whenever we add a commit with a matching ID to the graph, we remove
74 	 * its corresponding element from this set, and add new elements for
75 	 * each of that commit's parent commits which were not traversed yet.
76 	 *
77 	 * When API users ask us to fetch more commits, we fetch commits from
78 	 * all currently open branches. This allows API users to process
79 	 * commits in linear order even though the history contains branches.
80 	 */
81 	struct got_object_idset *open_branches;
82 
83 	/* Array of branch tips for fetch_commits_from_open_branches(). */
84 	struct got_commit_graph_branch_tip *tips;
85 	int ntips;
86 
87 	/* Path of tree entry of interest to the API user. */
88 	char *path;
89 
90 	/* The next commit to return when the API user asks for one. */
91 	struct got_commit_graph_node *iter_node;
92 
93 	/* The graph iteration list contains all nodes in sorted order. */
94 	struct got_commit_graph_iter_list iter_list;
95 };
96 
97 static const struct got_error *
98 detect_changed_path(int *changed, struct got_commit_object *commit,
99     struct got_object_id *commit_id, const char *path,
100     struct got_repository *repo)
101 {
102 	const struct got_error *err = NULL;
103 	struct got_commit_object *pcommit = NULL;
104 	struct got_tree_object *tree = NULL, *ptree = NULL;
105 	struct got_object_qid *pid;
106 
107 	if (got_path_is_root_dir(path)) {
108 		*changed = 1;
109 		return NULL;
110 	}
111 
112 	*changed = 0;
113 
114 	pid = SIMPLEQ_FIRST(&commit->parent_ids);
115 	if (pid == NULL) {
116 		struct got_object_id *obj_id;
117 		err = got_object_id_by_path(&obj_id, repo, commit_id, path);
118 		if (err) {
119 			if (err->code == GOT_ERR_NO_TREE_ENTRY)
120 				err = NULL;
121 		} else
122 			*changed = 1; /* The path was created in this commit. */
123 		free(obj_id);
124 		return err;
125 	}
126 
127 	err = got_object_open_as_tree(&tree, repo, commit->tree_id);
128 	if (err)
129 		return err;
130 
131 	err = got_object_open_as_commit(&pcommit, repo, pid->id);
132 	if (err)
133 		goto done;
134 
135 	err = got_object_open_as_tree(&ptree, repo, pcommit->tree_id);
136 	if (err)
137 		goto done;
138 
139 	err = got_object_tree_path_changed(changed, tree, ptree, path, repo);
140 done:
141 	if (tree)
142 		got_object_tree_close(tree);
143 	if (ptree)
144 		got_object_tree_close(ptree);
145 	if (pcommit)
146 		got_object_commit_close(pcommit);
147 	return err;
148 }
149 
150 static void
151 add_node_to_iter_list(struct got_commit_graph *graph,
152     struct got_commit_graph_node *node,
153     struct got_commit_graph_node *child_node)
154 {
155 	struct got_commit_graph_node *n, *next;
156 
157 	if (TAILQ_EMPTY(&graph->iter_list)) {
158 		TAILQ_INSERT_HEAD(&graph->iter_list, node, entry);
159 		graph->iter_node = node;
160 		return;
161 	}
162 
163 	n = graph->iter_node;
164 	/* Ensure that an iteration in progress will see this new commit. */
165 	while (n) {
166 		next = TAILQ_NEXT(n, entry);
167 		if (next && node->timestamp >= next->timestamp) {
168 			TAILQ_INSERT_BEFORE(next, node, entry);
169 			return;
170 		}
171 		n = next;
172 	}
173 	TAILQ_INSERT_TAIL(&graph->iter_list, node, entry);
174 }
175 
176 static const struct got_error *
177 close_branch(struct got_commit_graph *graph, struct got_object_id *commit_id)
178 {
179 	const struct got_error *err;
180 
181 	err = got_object_idset_remove(NULL, graph->open_branches, commit_id);
182 	if (err && err->code != GOT_ERR_NO_OBJ)
183 		return err;
184 	return NULL;
185 }
186 
187 static const struct got_error *
188 advance_branch(struct got_commit_graph *graph,
189     struct got_commit_graph_node *node,
190     struct got_object_id *commit_id, struct got_commit_object *commit,
191     struct got_repository *repo)
192 {
193 	const struct got_error *err;
194 	struct got_object_qid *qid;
195 
196 	err = close_branch(graph, commit_id);
197 	if (err)
198 		return err;
199 
200 	if (graph->flags & GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL) {
201 		qid = SIMPLEQ_FIRST(&commit->parent_ids);
202 		if (qid == NULL ||
203 		    got_object_idset_get(graph->open_branches, qid->id))
204 			return NULL;
205 		return got_object_idset_add(graph->open_branches,
206 		    qid->id, node);
207 	}
208 
209 	/*
210 	 * If we are graphing commits for a specific path, skip branches
211 	 * which do not contribute any content to this path.
212 	 */
213 	if (commit->nparents > 1 && !got_path_is_root_dir(graph->path)) {
214 		struct got_object_id *merged_id, *prev_id = NULL;
215 		int branches_differ = 0;
216 
217 		err = got_object_id_by_path(&merged_id, repo, commit_id,
218 		    graph->path);
219 		if (err)
220 			return err;
221 
222 		SIMPLEQ_FOREACH(qid, &commit->parent_ids, entry) {
223 			struct got_object_id *id;
224 
225 			if (got_object_idset_get(graph->open_branches, qid->id))
226 				continue;
227 
228 			err = got_object_id_by_path(&id, repo, qid->id,
229 			    graph->path);
230 			if (err) {
231 				if (err->code == GOT_ERR_NO_TREE_ENTRY) {
232 					branches_differ = 1;
233 					continue;
234 				}
235 				free(merged_id);
236 				free(prev_id);
237 				return err;
238 			}
239 
240 			if (prev_id) {
241 				if (!branches_differ &&
242 				    got_object_id_cmp(id, prev_id) != 0)
243 					branches_differ = 1;
244 				free(prev_id);
245 			}
246 			prev_id = id;
247 
248 			/*
249 			 * If a branch has created the merged content we can
250 			 * skip any other branches.
251 			 */
252 			if (got_object_id_cmp(merged_id, id) == 0) {
253 				err = got_object_idset_add(graph->open_branches,
254 				    qid->id, node);
255 				free(merged_id);
256 				free(id);
257 				return err;
258 			}
259 		}
260 
261 		free(prev_id);
262 		prev_id = NULL;
263 		free(merged_id);
264 		merged_id = NULL;
265 
266 		/*
267 		 * If the path's content is the same on all branches,
268 		 * follow the first parent only.
269 		 */
270 		if (!branches_differ) {
271 			qid = SIMPLEQ_FIRST(&commit->parent_ids);
272 			if (qid == NULL)
273 				return NULL;
274 			if (got_object_idset_get(graph->open_branches, qid->id))
275 				return NULL;
276 			if (got_object_idset_get(graph->node_ids, qid->id))
277 				return NULL; /* parent already traversed */
278 			return got_object_idset_add(graph->open_branches,
279 			    qid->id, node);
280 		}
281 	}
282 
283 	SIMPLEQ_FOREACH(qid, &commit->parent_ids, entry) {
284 		if (got_object_idset_get(graph->open_branches, qid->id))
285 			continue;
286 		if (got_object_idset_get(graph->node_ids, qid->id))
287 			continue; /* parent already traversed */
288 		err = got_object_idset_add(graph->open_branches, qid->id, node);
289 		if (err)
290 			return err;
291 	}
292 
293 	return NULL;
294 }
295 
296 static const struct got_error *
297 add_node(struct got_commit_graph_node **new_node, int *changed,
298     int *branch_done, struct got_commit_graph *graph,
299     struct got_object_id *commit_id, struct got_commit_object *commit,
300     struct got_commit_graph_node *child_node, struct got_repository *repo)
301 {
302 	const struct got_error *err = NULL;
303 	struct got_commit_graph_node *node;
304 
305 	*new_node = NULL;
306 	*changed = 0;
307 	*branch_done = 0;
308 
309 	node = calloc(1, sizeof(*node));
310 	if (node == NULL)
311 		return got_error_from_errno("calloc");
312 
313 	memcpy(&node->id, commit_id, sizeof(node->id));
314 	node->timestamp = commit->committer_time;
315 
316 	err = got_object_idset_add(graph->node_ids, &node->id, node);
317 	if (err) {
318 		free(node);
319 		return err;
320 	}
321 
322 	err = detect_changed_path(changed, commit, commit_id, graph->path,
323 	    repo);
324 	if (err) {
325 		if (err->code == GOT_ERR_NO_OBJ) {
326 			/*
327 			 * History of the path stops here on the current
328 			 * branch. Keep going on other branches.
329 			 */
330 			err = NULL;
331 			*branch_done = 1;
332 		} else {
333 			got_object_idset_remove(NULL, graph->node_ids,
334 			    &node->id);
335 			free(node);
336 			return err;
337 		}
338 	}
339 
340 	if (*changed)
341 		add_node_to_iter_list(graph, node, child_node);
342 	*new_node = node;
343 	return NULL;
344 }
345 
346 const struct got_error *
347 got_commit_graph_open(struct got_commit_graph **graph,
348     const char *path, int first_parent_traversal)
349 {
350 	const struct got_error *err = NULL;
351 
352 	*graph = calloc(1, sizeof(**graph));
353 	if (*graph == NULL)
354 		return got_error_from_errno("calloc");
355 
356 	(*graph)->path = strdup(path);
357 	if ((*graph)->path == NULL) {
358 		err = got_error_from_errno("strdup");
359 		goto done;
360 	}
361 
362 	(*graph)->node_ids = got_object_idset_alloc();
363 	if ((*graph)->node_ids == NULL) {
364 		err = got_error_from_errno("got_object_idset_alloc");
365 		goto done;
366 	}
367 
368 	(*graph)->open_branches = got_object_idset_alloc();
369 	if ((*graph)->open_branches == NULL) {
370 		err = got_error_from_errno("got_object_idset_alloc");
371 		goto done;
372 	}
373 
374 	TAILQ_INIT(&(*graph)->iter_list);
375 	if (first_parent_traversal)
376 		(*graph)->flags |= GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL;
377 done:
378 	if (err) {
379 		got_commit_graph_close(*graph);
380 		*graph = NULL;
381 	}
382 	return err;
383 }
384 
385 struct add_branch_tip_arg {
386 	struct got_commit_graph_branch_tip *tips;
387 	int ntips;
388 	struct got_repository *repo;
389 	struct got_commit_graph *graph;
390 };
391 
392 static const struct got_error *
393 add_branch_tip(struct got_object_id *commit_id, void *data, void *arg)
394 {
395 	const struct got_error *err;
396 	struct got_commit_graph_node *child_node = data;
397 	struct add_branch_tip_arg *a = arg;
398 	struct got_commit_graph_node *new_node;
399 	struct got_commit_object *commit;
400 	int changed, branch_done;
401 
402 	err = got_object_open_as_commit(&commit, a->repo, commit_id);
403 	if (err)
404 		return err;
405 
406 	err = add_node(&new_node, &changed, &branch_done, a->graph,
407 	    commit_id, commit, child_node, a->repo);
408 	if (err)
409 		return err;
410 
411 	a->tips[a->ntips].commit_id = new_node ? &new_node->id : NULL;
412 	a->tips[a->ntips].commit = commit;
413 	a->tips[a->ntips].new_node = new_node;
414 	a->tips[a->ntips].changed = changed;
415 	a->tips[a->ntips].branch_done = branch_done;
416 	a->ntips++;
417 
418 	return NULL;
419 }
420 
421 static const struct got_error *
422 fetch_commits_from_open_branches(int *nfetched,
423     struct got_object_id **changed_id, struct got_commit_graph *graph,
424     struct got_repository *repo, got_cancel_cb cancel_cb, void *cancel_arg)
425 {
426 	const struct got_error *err;
427 	struct add_branch_tip_arg arg;
428 	int i, ntips;
429 
430 	*nfetched = 0;
431 	if (changed_id)
432 		*changed_id = NULL;
433 
434 	ntips = got_object_idset_num_elements(graph->open_branches);
435 	if (ntips == 0)
436 		return NULL;
437 
438 	/* (Re-)allocate branch tips array if necessary. */
439 	if (graph->ntips < ntips) {
440 		struct got_commit_graph_branch_tip *tips;
441 		tips = recallocarray(graph->tips, graph->ntips, ntips,
442 		    sizeof(*tips));
443 		if (tips == NULL)
444 			return got_error_from_errno("recallocarray");
445 		graph->tips = tips;
446 		graph->ntips = ntips;
447 	}
448 	arg.tips = graph->tips;
449 	arg.ntips = 0; /* add_branch_tip() will increment */
450 	arg.repo = repo;
451 	arg.graph = graph;
452 	err = got_object_idset_for_each(graph->open_branches, add_branch_tip,
453 	    &arg);
454 	if (err)
455 		goto done;
456 
457 	for (i = 0; i < arg.ntips; i++) {
458 		struct got_object_id *commit_id;
459 		struct got_commit_object *commit;
460 		struct got_commit_graph_node *new_node;
461 		int branch_done, changed;
462 
463 		if (cancel_cb) {
464 			err = (*cancel_cb)(cancel_arg);
465 			if (err)
466 				break;
467 		}
468 
469 		commit_id = arg.tips[i].commit_id;
470 		commit = arg.tips[i].commit;
471 		new_node = arg.tips[i].new_node;
472 		branch_done = arg.tips[i].branch_done;
473 		changed = arg.tips[i].changed;
474 
475 		if (branch_done)
476 			err = close_branch(graph, commit_id);
477 		else
478 			err = advance_branch(graph, new_node, commit_id,
479 			    commit, repo);
480 		if (err)
481 			break;
482 		if (changed && changed_id && *changed_id == NULL)
483 			*changed_id = commit_id;
484 	}
485 done:
486 	for (i = 0; i < arg.ntips; i++)
487 		got_object_commit_close(arg.tips[i].commit);
488 	(*nfetched) = arg.ntips;
489 	return err;
490 }
491 
492 static const struct got_error *
493 free_node_iter(struct got_object_id *id, void *data, void *arg)
494 {
495 	struct got_commit_graph_node *node = data;
496 	free(node);
497 	return NULL;
498 }
499 
500 void
501 got_commit_graph_close(struct got_commit_graph *graph)
502 {
503 	if (graph->open_branches)
504 		got_object_idset_free(graph->open_branches);
505 	got_object_idset_for_each(graph->node_ids, free_node_iter, NULL);
506 	if (graph->node_ids)
507 		got_object_idset_free(graph->node_ids);
508 	free(graph->tips);
509 	free(graph->path);
510 	free(graph);
511 }
512 
513 const struct got_error *
514 got_commit_graph_iter_start(struct got_commit_graph *graph,
515     struct got_object_id *id, struct got_repository *repo,
516     got_cancel_cb cancel_cb, void *cancel_arg)
517 {
518 	const struct got_error *err = NULL;
519 	struct got_commit_graph_node *start_node;
520 	struct got_commit_object *commit;
521 	int changed, branch_done;
522 
523 	if (!TAILQ_EMPTY(&graph->iter_list))
524 		return got_error(GOT_ERR_ITER_BUSY);
525 
526 	err = got_object_open_as_commit(&commit, repo, id);
527 	if (err)
528 		return err;
529 
530 	err = add_node(&start_node, &changed, &branch_done, graph, id,
531 	    commit, NULL, repo);
532 	if (err)
533 		goto done;
534 
535 	err = advance_branch(graph, start_node, id, commit, repo);
536 	if (err)
537 		goto done;
538 
539 	if (!changed) {
540 		/* Locate first commit which changed graph->path. */
541 		struct got_object_id *changed_id = NULL;
542 		while (changed_id == NULL) {
543 			int ncommits;
544 			err = fetch_commits_from_open_branches(&ncommits,
545 			    &changed_id, graph, repo, cancel_cb, cancel_arg);
546 			if (err) {
547 				got_object_commit_close(commit);
548 				return err;
549 			}
550 		}
551 		start_node = got_object_idset_get(graph->node_ids, changed_id);
552 	}
553 done:
554 	got_object_commit_close(commit);
555 	if (err == NULL)
556 		graph->iter_node = start_node;
557 	return err;
558 }
559 
560 const struct got_error *
561 got_commit_graph_iter_next(struct got_object_id **id,
562     struct got_commit_graph *graph, struct got_repository *repo,
563     got_cancel_cb cancel_cb, void *cancel_arg)
564 {
565 	const struct got_error *err = NULL;
566 
567 	*id = NULL;
568 
569 	if (graph->iter_node == NULL) {
570 		/* We are done iterating, or iteration was not started. */
571 		return got_error(GOT_ERR_ITER_COMPLETED);
572 	}
573 
574 	if (graph->iter_node ==
575 	    TAILQ_LAST(&graph->iter_list, got_commit_graph_iter_list) &&
576 	    got_object_idset_num_elements(graph->open_branches) == 0) {
577 		/* We are done iterating. */
578 		*id = &graph->iter_node->id;
579 		graph->iter_node = NULL;
580 		return NULL;
581 	}
582 
583 	while (TAILQ_NEXT(graph->iter_node, entry) == NULL &&
584 	    got_object_idset_num_elements(graph->open_branches) > 0) {
585 		int ncommits;
586 		struct got_object_id *changed_id;
587 		err = fetch_commits_from_open_branches(&ncommits,
588 		    &changed_id, graph, repo, cancel_cb, cancel_arg);
589 		if (err)
590 			return err;
591 	}
592 
593 	*id = &graph->iter_node->id;
594 	graph->iter_node = TAILQ_NEXT(graph->iter_node, entry);
595 	return NULL;
596 }
597 
598 const struct got_error *
599 got_commit_graph_find_youngest_common_ancestor(struct got_object_id **yca_id,
600     struct got_object_id *commit_id, struct got_object_id *commit_id2,
601     struct got_repository *repo, got_cancel_cb cancel_cb, void *cancel_arg)
602 {
603 	const struct got_error *err = NULL;
604 	struct got_commit_graph *graph = NULL, *graph2 = NULL;
605 	int completed = 0, completed2 = 0;
606 	struct got_object_idset *commit_ids;
607 
608 	*yca_id = NULL;
609 
610 	commit_ids = got_object_idset_alloc();
611 	if (commit_ids == NULL)
612 		return got_error_from_errno("got_object_idset_alloc");
613 
614 	err = got_commit_graph_open(&graph, "/", 1);
615 	if (err)
616 		goto done;
617 
618 	err = got_commit_graph_open(&graph2, "/", 1);
619 	if (err)
620 		goto done;
621 
622 	err = got_commit_graph_iter_start(graph, commit_id, repo,
623 	    cancel_cb, cancel_arg);
624 	if (err)
625 		goto done;
626 
627 	err = got_commit_graph_iter_start(graph2, commit_id2, repo,
628 	    cancel_cb, cancel_arg);
629 	if (err)
630 		goto done;
631 
632 	for (;;) {
633 		struct got_object_id *id = NULL, *id2 = NULL;
634 
635 		if (cancel_cb) {
636 			err = (*cancel_cb)(cancel_arg);
637 			if (err)
638 				break;
639 		}
640 
641 		if (!completed) {
642 			err = got_commit_graph_iter_next(&id, graph, repo,
643 			    cancel_cb, cancel_arg);
644 			if (err) {
645 				if (err->code != GOT_ERR_ITER_COMPLETED)
646 					break;
647 				err = NULL;
648 				completed = 1;
649 			}
650 		}
651 
652 		if (!completed2) {
653 			err = got_commit_graph_iter_next(&id2, graph2, repo,
654 			    cancel_cb, cancel_arg);
655 			if (err) {
656 				if (err->code != GOT_ERR_ITER_COMPLETED)
657 					break;
658 				err = NULL;
659 				completed2 = 1;
660 			}
661 		}
662 
663 		if (id) {
664 			if (got_object_idset_get(commit_ids, id)) {
665 				*yca_id = got_object_id_dup(id);
666 				if (*yca_id)
667 					break;
668 				err = got_error_from_errno("got_object_id_dup");
669 				break;
670 
671 			}
672 			err = got_object_idset_add(commit_ids, id, id);
673 			if (err)
674 				break;
675 		}
676 		if (id2) {
677 			if (got_object_idset_get(commit_ids, id2)) {
678 				*yca_id = got_object_id_dup(id2);
679 				if (*yca_id)
680 					break;
681 				err = got_error_from_errno("got_object_id_dup");
682 				break;
683 
684 			}
685 			err = got_object_idset_add(commit_ids, id2, id2);
686 			if (err)
687 				break;
688 		}
689 
690 		if (completed && completed2) {
691 			err = got_error(GOT_ERR_ANCESTRY);
692 			break;
693 		}
694 
695 	}
696 done:
697 	got_object_idset_free(commit_ids);
698 	if (graph)
699 		got_commit_graph_close(graph);
700 	if (graph2)
701 		got_commit_graph_close(graph2);
702 	return err;
703 }