diff options
| -rw-r--r-- | commit.c | 107 | ||||
| -rw-r--r-- | commit.h | 13 |
2 files changed, 120 insertions, 0 deletions
@@ -3,6 +3,22 @@ #include "commit.h" #include "cache.h" +struct sort_node +{ + /* + * the number of children of the associated commit + * that also occur in the list being sorted. + */ + unsigned int indegree; + + /* + * reference to original list item that we will re-use + * on output. + */ + struct commit_list * list_item; + +}; + const char *commit_type = "commit"; enum cmit_fmt get_commit_format(const char *arg) @@ -346,3 +362,94 @@ int count_parents(struct commit * commit) return count; } +/* + * Performs an in-place topological sort on the list supplied. + */ +void sort_in_topological_order(struct commit_list ** list) +{ + struct commit_list * next = *list; + struct commit_list * work = NULL; + struct commit_list ** pptr = list; + struct sort_node * nodes; + struct sort_node * next_nodes; + int count = 0; + + /* determine the size of the list */ + while (next) { + next = next->next; + count++; + } + /* allocate an array to help sort the list */ + nodes = xcalloc(count, sizeof(*nodes)); + /* link the list to the array */ + next_nodes = nodes; + next=*list; + while (next) { + next_nodes->list_item = next; + next->item->object.util = next_nodes; + next_nodes++; + next = next->next; + } + /* update the indegree */ + next=*list; + while (next) { + struct commit_list * parents = next->item->parents; + while (parents) { + struct commit * parent=parents->item; + struct sort_node * pn = (struct sort_node *)parent->object.util; + + if (pn) + pn->indegree++; + parents=parents->next; + } + next=next->next; + } + /* + * find the tips + * + * tips are nodes not reachable from any other node in the list + * + * the tips serve as a starting set for the work queue. + */ + next=*list; + while (next) { + struct sort_node * node = (struct sort_node *)next->item->object.util; + + if (node->indegree == 0) { + commit_list_insert(next->item, &work); + } + next=next->next; + } + /* process the list in topological order */ + while (work) { + struct commit * work_item = pop_commit(&work); + struct sort_node * work_node = (struct sort_node *)work_item->object.util; + struct commit_list * parents = work_item->parents; + + while (parents) { + struct commit * parent=parents->item; + struct sort_node * pn = (struct sort_node *)parent->object.util; + + if (pn) { + /* + * parents are only enqueued for emission + * when all their children have been emitted thereby + * guaranteeing topological order. + */ + pn->indegree--; + if (!pn->indegree) + commit_list_insert(parent, &work); + } + parents=parents->next; + } + /* + * work_item is a commit all of whose children + * have already been emitted. we can emit it now. + */ + *pptr = work_node->list_item; + pptr = &(*pptr)->next; + *pptr = NULL; + work_item->object.util = NULL; + } + free(nodes); +} @@ -54,4 +54,17 @@ struct commit *pop_most_recent_commit(struct commit_list **list, struct commit *pop_commit(struct commit_list **stack); int count_parents(struct commit * commit); + +/* + * Performs an in-place topological sort of list supplied. + * + * Pre-conditions: + * all commits in input list and all parents of those + * commits must have object.util == NULL + * + * Post-conditions: + * invariant of resulting list is: + * a reachable from b => ord(b) < ord(a) + */ +void sort_in_topological_order(struct commit_list ** list); #endif /* COMMIT_H */ |