X-Git-Url: https://git.verplant.org/?a=blobdiff_plain;f=commit.c;h=caee5bc218f6db03ec4c8f16f39b892ebb7c762c;hb=d48a72f337fa8edfb7a09e620e75cbbb2a5fe836;hp=254c902716e08266a89a9df245bcda5808737b6a;hpb=f755494cec27fed8c9693bb91c26762061518b0b;p=git.git

diff --git a/commit.c b/commit.c
index 254c9027..caee5bc2 100644
--- a/commit.c
+++ b/commit.c
@@ -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)
@@ -36,8 +52,9 @@ struct commit *lookup_commit_reference(const unsigned char *sha1)
 
 	if (!obj)
 		return NULL;
-	if (obj->type == tag_type)
-		obj = ((struct tag *)obj)->tagged;
+	while (obj->type == tag_type)
+		obj = parse_object(((struct tag *)obj)->tagged->sha1);
+
 	return check_commit(obj, sha1);
 }
 
@@ -346,3 +363,94 @@ 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);
+}