thodg/got/lib/commit_graph.c

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• Show log

  Commit

• Author : Stefan Sperling
  Date : 2018-09-24 11:57:04
  Hash : 93e45b7c
  Message : use commit graph for path filtering in 'tog log'

• lib/commit_graph.c

• /*
   * Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/queue.h>
  #include <sys/stdint.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sha1.h>
  #include <zlib.h>
  #include <ctype.h>
  
  #include "got_error.h"
  #include "got_object.h"
  #include "got_commit_graph.h"
  
  #include "got_lib_delta.h"
  #include "got_lib_inflate.h"
  #include "got_lib_object.h"
  #include "got_lib_object_idset.h"
  #include "got_lib_path.h"
  
  struct got_commit_graph_node {
  	struct got_object_id id;
  
  	/*
  	 * Each graph node corresponds to a commit object.
  	 * Graph vertices are modelled with an adjacency list.
  	 * Adjacencies of a graph node are parent (older) commits.
  	 */
  	int nparents;
  	struct got_object_id_queue parent_ids;
  
  	time_t commit_timestamp;
  
  	/* Used during graph iteration. */
  	TAILQ_ENTRY(got_commit_graph_node) entry;
  };
  
  TAILQ_HEAD(got_commit_graph_iter_list, got_commit_graph_node);
  
  struct got_commit_graph_branch_tip {
  	struct got_object_id id;
  	struct got_commit_graph_node *node;
  };
  
  struct got_commit_graph {
  	/* The set of all commits we have traversed. */
  	struct got_object_idset *node_ids;
  
  	/* The commit at which traversal began (youngest commit in node_ids). */
  	struct got_commit_graph_node *head_node;
  
  	int flags;
  #define GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL		0x01
  
  	/*
  	 * A set of object IDs of known parent commits which we have not yet
  	 * traversed. Each commit ID in this set represents a branch in commit
  	 * history: Either the first-parent branch of the head node, or another
  	 * branch corresponding to a traversed merge commit for which we have
  	 * not traversed a branch point commit yet.
  	 *
  	 * Whenever we add a commit with a matching ID to the graph, we remove
  	 * its corresponding element from this set, and add new elements for
  	 * each of that commit's parent commits which were not traversed yet.
  	 *
  	 * When API users ask us to fetch more commits, we fetch commits from
  	 * all currently open branches. This allows API users to process
  	 * commits in linear order even though the history contains branches.
  	 */
  	struct got_object_idset *open_branches;
  
  	/* Copy of known branch tips for fetch_commits_from_open_branches(). */
  	struct got_commit_graph_branch_tip *tips;
  	size_t ntips;
  #define GOT_COMMIT_GRAPH_MIN_TIPS 10	/* minimum amount of tips to allocate */
  
  	/* Path of tree entry of interest to the API user. */
  	char *path;
  
  	/* The next commit to return when the API user asks for one. */
  	struct got_commit_graph_node *iter_node;
  
  	/* The graph iteration list contains all nodes in sorted order. */
  	struct got_commit_graph_iter_list iter_list;
  };
  
  static struct got_commit_graph *
  alloc_graph(const char *path)
  {
  	struct got_commit_graph *graph;
  
  	graph = calloc(1, sizeof(*graph));
  	if (graph == NULL)
  		return NULL;
  
  	graph->path = strdup(path);
  	if (graph->path == NULL) {
  		free(graph);
  		return NULL;
  	}
  
  	graph->node_ids = got_object_idset_alloc();
  	if (graph->node_ids == NULL) {
  		free(graph->path);
  		free(graph);
  		return NULL;
  	}
  
  	graph->open_branches = got_object_idset_alloc();
  	if (graph->open_branches == NULL) {
  		got_object_idset_free(graph->node_ids);
  		free(graph->path);
  		free(graph);
  		return NULL;
  	}
  
  	TAILQ_INIT(&graph->iter_list);
  	return graph;
  }
  
  #if 0
  static int
  is_head_node(struct got_commit_graph_node *node)
  {
  	return node->nchildren == 0;
  }
  
  int
  is_branch_point(struct got_commit_graph_node *node)
  {
  	return node->nchildren > 1;
  }
  
  static int
  is_root_node(struct got_commit_graph_node *node)
  {
  	return node->nparents == 0;
  }
  #endif
  
  static int
  is_merge_point(struct got_commit_graph_node *node)
  {
  	return node->nparents > 1;
  }
  
  static const struct got_error *
  detect_changed_path(int *changed, struct got_commit_object *commit,
      struct got_object_id *commit_id, const char *path,
      struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	struct got_commit_object *pcommit = NULL;
  	struct got_tree_object *tree = NULL, *ptree = NULL;
  	struct got_object_qid *pid;
  
  	if (got_path_is_root_dir(path)) {
  		*changed = 1;
  		return NULL;
  	}
  
  	*changed = 0;
  
  	err = got_object_open_as_tree(&tree, repo, commit->tree_id);
  	if (err)
  		return err;
  
  	pid = SIMPLEQ_FIRST(&commit->parent_ids);
  	if (pid == NULL) {
  		struct got_object_id *obj_id;
  		err = got_object_id_by_path(&obj_id, repo, commit_id, path);
  		if (err)
  			err = NULL;
  		else
  			*changed = 1;
  		free(obj_id);
  		goto done;
  	}
  
  	err = got_object_open_as_commit(&pcommit, repo, pid->id);
  	if (err)
  		goto done;
  
  	err = got_object_open_as_tree(&ptree, repo, pcommit->tree_id);
  	if (err)
  		goto done;
  
  	err = got_object_tree_path_changed(changed, tree, ptree, path, repo);
  done:
  	if (tree)
  		got_object_tree_close(tree);
  	if (ptree)
  		got_object_tree_close(ptree);
  	if (pcommit)
  		got_object_commit_close(pcommit);
  	return err;
  }
  
  static void
  add_node_to_iter_list(struct got_commit_graph *graph,
      struct got_commit_graph_node *node,
      struct got_commit_graph_node *child_node)
  {
  	struct got_commit_graph_node *n, *next;
  
  	if (TAILQ_EMPTY(&graph->iter_list)) {
  		TAILQ_INSERT_HEAD(&graph->iter_list, node, entry);
  		graph->iter_node = node;
  		return;
  	}
  
  	n = graph->iter_node;
  	/* Ensure that an iteration in progress will see this new commit. */
  	while (n) {
  		next = TAILQ_NEXT(n, entry);
  		if (next && node->commit_timestamp >= next->commit_timestamp) {
  			TAILQ_INSERT_BEFORE(next, node, entry);
  			return;
  		}
  		n = next;
  	}
  	TAILQ_INSERT_TAIL(&graph->iter_list, node, entry);
  }
  
  static const struct got_error *
  add_vertex(struct got_object_id_queue *ids, struct got_object_id *id)
  {
  	struct got_object_qid *qid;
  
  	qid = calloc(1, sizeof(*qid));
  	if (qid == NULL)
  		return got_error_from_errno();
  
  	qid->id = got_object_id_dup(id);
  	if (qid->id == NULL) {
  		const struct got_error *err = got_error_from_errno();
  		got_object_qid_free(qid);
  		return err;
  	}
  
  	SIMPLEQ_INSERT_TAIL(ids, qid, entry);
  	return NULL;
  }
  
  static const struct got_error *
  close_branch(struct got_commit_graph *graph, struct got_object_id *commit_id)
  {
  	const struct got_error *err;
  
  	err = got_object_idset_remove(NULL, graph->open_branches, commit_id);
  	if (err && err->code != GOT_ERR_NO_OBJ)
  		return err;
  	return NULL;
  }
  
  static const struct got_error *
  advance_branch(struct got_commit_graph *graph,
      struct got_commit_graph_node *node,
      struct got_object_id *commit_id, struct got_commit_object *commit,
      struct got_repository *repo)
  {
  	const struct got_error *err;
  	struct got_object_qid *qid;
  
  	err = close_branch(graph, commit_id);
  	if (err)
  		return err;
  
  	if (graph->flags & GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL) {
  		qid = SIMPLEQ_FIRST(&commit->parent_ids);
  		if (qid == NULL)
  			return NULL;
  		err = got_object_idset_add(NULL, graph->open_branches, qid->id,
  		    node);
  		if (err && err->code != GOT_ERR_OBJ_EXISTS)
  			return err;
  		return NULL;
  	}
  
  	/*
  	 * If we are graphing commits for a specific path, skip branches
  	 * which do not contribute any content to this path.
  	 */
  	if (is_merge_point(node) && !got_path_is_root_dir(graph->path)) {
  		struct got_object_id *id, *merged_id, *prev_id = NULL;
  		int branches_differ = 0;
  
  		err = got_object_id_by_path(&merged_id, repo, commit_id,
  		    graph->path);
  		if (err)
  			return err;
  
  		SIMPLEQ_FOREACH(qid, &commit->parent_ids, entry) {
  			if (got_object_idset_get(graph->node_ids, qid->id))
  				continue; /* parent already traversed */
  
  			err = got_object_id_by_path(&id, repo, qid->id,
  			    graph->path);
  			if (err) {
  				if (err->code == GOT_ERR_NO_OBJ) {
  					branches_differ = 1;
  					continue;
  				}
  				return err;
  			}
  
  			if (prev_id) {
  				if (!branches_differ &&
  				    got_object_id_cmp(merged_id, prev_id) != 0)
  					branches_differ = 1;
  			} else
  				prev_id = id;
  
  			/*
  			 * If a branch has created the merged content we can
  			 * skip any other branches.
  			 */
  			if (got_object_id_cmp(merged_id, id) == 0) {
  				err = got_object_idset_add(NULL,
  				    graph->open_branches, qid->id, node);
  				if (err && err->code != GOT_ERR_OBJ_EXISTS)
  					return err;
  				return NULL;
  			}
  		}
  
  		/*
  		 * If the path's content is the same on all branches,
  		 * follow the first parent only.
  		 */
  		if (!branches_differ) {
  			qid = SIMPLEQ_FIRST(&commit->parent_ids);
  			if (qid == NULL)
  				return NULL;
  			if (got_object_idset_get(graph->node_ids, qid->id))
  				return NULL; /* parent already traversed */
  			err = got_object_idset_add(NULL,
  			    graph->open_branches, qid->id, node);
  			if (err && err->code != GOT_ERR_OBJ_EXISTS)
  				return err;
  			return NULL;
  		}
  	}
  
  	SIMPLEQ_FOREACH(qid, &commit->parent_ids, entry) {
  		if (got_object_idset_get(graph->node_ids, qid->id))
  			continue; /* parent already traversed */
  		err = got_object_idset_add(NULL, graph->open_branches,
  		    qid->id, node);
  		if (err && err->code != GOT_ERR_OBJ_EXISTS)
  			return err;
  	}
  
  	return NULL;
  }
  
  static void
  free_node(struct got_commit_graph_node *node)
  {
  	while (!SIMPLEQ_EMPTY(&node->parent_ids)) {
  		struct got_object_qid *pid = SIMPLEQ_FIRST(&node->parent_ids);
  		SIMPLEQ_REMOVE_HEAD(&node->parent_ids, entry);
  		got_object_qid_free(pid);
  	}
  	free(node);
  }
  
  static const struct got_error *
  add_node(struct got_commit_graph_node **new_node,
      struct got_commit_graph *graph, struct got_object_id *commit_id,
      struct got_commit_object *commit, struct got_commit_graph_node *child_node,
      struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	struct got_commit_graph_node *node;
  	struct got_object_qid *pid;
  	int changed = 0, branch_done = 0;
  
  	*new_node = NULL;
  
  	node = calloc(1, sizeof(*node));
  	if (node == NULL)
  		return got_error_from_errno();
  
  	memcpy(&node->id, commit_id, sizeof(node->id));
  	SIMPLEQ_INIT(&node->parent_ids);
  	SIMPLEQ_FOREACH(pid, &commit->parent_ids, entry) {
  		err = add_vertex(&node->parent_ids, pid->id);
  		if (err) {
  			free_node(node);
  			return err;
  		}
  		node->nparents++;
  	}
  
  	err = got_object_idset_add(NULL, graph->node_ids, &node->id, node);
  	if (err) {
  		if (err->code == GOT_ERR_OBJ_EXISTS)
  			err = NULL;
  		free_node(node);
  		return err;
  	}
  
  	err = detect_changed_path(&changed, commit, commit_id, graph->path,
  	    repo);
  	if (err) {
  		if (err->code == GOT_ERR_NO_OBJ) {
  			/*
  			 * History of the path stops here on the current
  			 * branch. Keep going on other branches.
  			 */
  			err = NULL;
  			branch_done = 1;
  		} else {
  			free_node(node);
  			return err;
  		}
  	}
  
  	node->commit_timestamp = mktime(&commit->tm_committer);
  	if (node->commit_timestamp == -1) {
  		free_node(node);
  		return got_error_from_errno();
  	}
  
  	if (changed && !is_merge_point(node))
  		add_node_to_iter_list(graph, node, child_node);
  
  	if (branch_done)
  		err = close_branch(graph, commit_id);
  	else
  		err = advance_branch(graph, node, commit_id, commit, repo);
  	if (err)
  		free_node(node);
  	else
  		*new_node = node;
  
  	return err;
  }
  
  const struct got_error *
  got_commit_graph_open(struct got_commit_graph **graph,
      struct got_object_id *commit_id, const char *path,
      int first_parent_traversal, struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	struct got_commit_object *commit;
  
  	*graph = NULL;
  
  	err = got_object_open_as_commit(&commit, repo, commit_id);
  	if (err)
  		return err;
  
  	/* The path must exist in our initial commit. */
  	if (!got_path_is_root_dir(path)) {
  		struct got_object_id *obj_id;
  		err = got_object_id_by_path(&obj_id, repo, commit_id, path);
  		if (err)
  			return err;
  		free(obj_id);
  	}
  
  	*graph = alloc_graph(path);
  	if (*graph == NULL) {
  		got_object_commit_close(commit);
  		return got_error_from_errno();
  	}
  
  	if (first_parent_traversal)
  		(*graph)->flags |= GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL;
  
  	err = add_node(&(*graph)->head_node, *graph, commit_id, commit, NULL,
  	    repo);
  	got_object_commit_close(commit);
  	if (err) {
  		got_commit_graph_close(*graph);
  		*graph = NULL;
  		return err;
  	}
  	
  	return NULL;
  }
  
  struct gather_branch_tips_arg {
  	struct got_commit_graph_branch_tip *tips;
  	int ntips;
  };
  
  static void
  gather_branch_tips(struct got_object_id *id, void *data, void *arg)
  {
  	struct gather_branch_tips_arg *a = arg;
  	memcpy(&a->tips[a->ntips].id, id, sizeof(*id));
  	a->tips[a->ntips].node = data;
  	a->ntips++;
  }
  
  static const struct got_error *
  fetch_commits_from_open_branches(int *ncommits, int *wanted_id_added,
      struct got_object_id **changed_id, struct got_commit_graph *graph,
      struct got_repository *repo, struct got_object_id *wanted_id)
  {
  	const struct got_error *err;
  	struct gather_branch_tips_arg arg;
  	int i;
  
  	*ncommits = 0;
  	if (wanted_id_added)
  		*wanted_id_added = 0;
  	if (changed_id)
  		*changed_id = NULL;
  
  	arg.ntips = got_object_idset_num_elements(graph->open_branches);
  	if (arg.ntips == 0)
  		return NULL;
  
  	/*
  	 * Adding nodes to the graph might change the graph's open
  	 * branches state. Create a local copy of the current state.
  	 */
  	if (graph->ntips < arg.ntips) {
  		struct got_commit_graph_branch_tip *tips;
  		if (arg.ntips < GOT_COMMIT_GRAPH_MIN_TIPS)
  			arg.ntips = GOT_COMMIT_GRAPH_MIN_TIPS;
  		tips = reallocarray(graph->tips, arg.ntips, sizeof(*tips));
  		if (tips == NULL)
  			return got_error_from_errno();
  		graph->tips = tips;
  		graph->ntips = arg.ntips;
  	}
  	arg.ntips = 0; /* reset; gather_branch_tips() will increment */
  	arg.tips = graph->tips;
  	got_object_idset_for_each(graph->open_branches,
  	    gather_branch_tips, &arg);
  
  	for (i = 0; i < arg.ntips; i++) {
  		struct got_object_id *commit_id;
  		struct got_commit_graph_node *child_node, *new_node;
  		struct got_commit_object *commit;
  		int changed;
  
  		commit_id = &graph->tips[i].id;
  		child_node = graph->tips[i].node;
  
  		err = got_object_open_as_commit(&commit, repo, commit_id);
  		if (err)
  			break;
  
  		err = detect_changed_path(&changed, commit, commit_id,
  		    graph->path, repo);
  		if (err) {
  			got_object_commit_close(commit);
  			if (err->code != GOT_ERR_NO_OBJ)
  				break;
  			err = close_branch(graph, commit_id);
  			if (err)
  				break;
  			continue;
  		}
  		if (changed && changed_id && *changed_id == NULL)
  			*changed_id = commit_id;
  		err = add_node(&new_node, graph, commit_id, commit, child_node,
  		    repo);
  		got_object_commit_close(commit);
  		if (err)
  			break;
  		if (new_node)
  			(*ncommits)++;
  		if (wanted_id && got_object_id_cmp(commit_id, wanted_id) == 0)
  			*wanted_id_added = 1;
  	}
  
  	return err;
  }
  
  const struct got_error *
  got_commit_graph_fetch_commits(struct got_commit_graph *graph, int limit,
      struct got_repository *repo)
  {
  	const struct got_error *err;
  	int nfetched = 0, ncommits;
  	struct got_object_id *changed_id = NULL;
  
  	while (nfetched < limit) {
  		err = fetch_commits_from_open_branches(&ncommits, NULL,
  		    &changed_id, graph, repo, NULL);
  		if (err)
  			return err;
  		if (ncommits == 0)
  			break;
  		if (changed_id)
  			nfetched += ncommits;
  	}
  
  	return NULL;
  }
  
  static void
  free_node_iter(struct got_object_id *id, void *data, void *arg)
  {
  	struct got_commit_graph_node *node = data;
  	free_node(node);
  }
  
  void
  got_commit_graph_close(struct got_commit_graph *graph)
  {
  	got_object_idset_free(graph->open_branches);
  	got_object_idset_for_each(graph->node_ids, free_node_iter, NULL);
  	got_object_idset_free(graph->node_ids);
  	free(graph->tips);
  	free(graph->path);
  	free(graph);
  }
  
  const struct got_error *
  got_commit_graph_iter_start(struct got_commit_graph *graph,
      struct got_object_id *id, struct got_repository *repo)
  {
  	const struct got_error *err = NULL;
  	struct got_commit_graph_node *start_node;
  	struct got_commit_object *commit;
  	int changed;
  
  	start_node = got_object_idset_get(graph->node_ids, id);
  	if (start_node == NULL)
  		return got_error(GOT_ERR_NO_OBJ);
  
  	err = got_object_open_as_commit(&commit, repo, &start_node->id);
  	if (err)
  		return err;
  
  	err = detect_changed_path(&changed, commit, &start_node->id,
  	    graph->path, repo);
  	if (err) {
  		got_object_commit_close(commit);
  		return err;
  	}
  
  	if (!changed) {
  		/* Locate first commit which changed graph->path. */
  		struct got_object_id *changed_id = NULL;
  		while (changed_id == NULL) {
  			int ncommits;
  			err = fetch_commits_from_open_branches(&ncommits, NULL,
  			    &changed_id, graph, repo, NULL);
  			if (err) {
  				got_object_commit_close(commit);
  				return err;
  			}
  		}
  		start_node = got_object_idset_get(graph->node_ids, changed_id);
  	}
  	got_object_commit_close(commit);
  
  	graph->iter_node = start_node;
  	return NULL;
  }
  
  const struct got_error *
  got_commit_graph_iter_next(struct got_object_id **id,
      struct got_commit_graph *graph)
  {
  	*id = NULL;
  
  	if (graph->iter_node == NULL) {
  		/* We are done iterating, or iteration was not started. */
  		return got_error(GOT_ERR_ITER_COMPLETED);
  	}
  
  	if (graph->iter_node ==
  	    TAILQ_LAST(&graph->iter_list, got_commit_graph_iter_list) &&
  	    got_object_idset_num_elements(graph->open_branches) == 0) {
  		/* We are done iterating. */
  		*id = &graph->iter_node->id;
  		graph->iter_node = NULL;
  		return NULL;
  	}
  
  	if (TAILQ_NEXT(graph->iter_node, entry) == NULL)
  		return got_error(GOT_ERR_ITER_NEED_MORE);
  
  	*id = &graph->iter_node->id;
  	graph->iter_node = TAILQ_NEXT(graph->iter_node, entry);
  	return NULL;
  }