Use common "revision.h" header for both fsck and rev-tree.

It's really a very generic thing: the notion of one sha1 revision
referring to another one. "fsck" uses it for all nodes, and "rev-tree"
only tracks commit-node relationships, but the code was already
the same - now we just make that explicit by moving it to a common
header file.

1 files changed, 114 insertions, 0 deletions

diff --git a/revision.h b/revision.h
new file mode 100644
index 000000000..4f140ca61
--- /dev/null
+++ b/revision.h
@@ -0,0 +1,114 @@
+#ifndef REVISION_H
+#define REVISION_H
+
+/*
+ * The low 16 bits of the "flags" field shows whether
+ * a commit is part of the path to the root for that
+ * parent.
+ *
+ * Bit 16 is an internal flag that we've seen the
+ * definition for this rev, and not just seen it as
+ * a parent target.
+ */
+#define marked(rev)	((rev)->flags & 0xffff)
+#define SEEN 0x10000
+#define USED 0x20000
+#define REACHABLE 0x40000
+
+struct parent {
+	struct revision *parent;
+	struct parent *next;
+};
+
+struct revision {
+	unsigned int flags;
+	unsigned char sha1[20];
+	unsigned long date;
+	struct parent *parent;
+};
+
+static struct revision **revs;
+static int nr_revs, rev_allocs;
+
+static int find_rev(unsigned char *sha1)
+{
+	int first = 0, last = nr_revs;
+
+	while (first < last) {
+		int next = (first + last) / 2;
+		struct revision *rev = revs[next];
+		int cmp;
+
+		cmp = memcmp(sha1, rev->sha1, 20);
+		if (!cmp)
+			return next;
+		if (cmp < 0) {
+			last = next;
+			continue;
+		}
+		first = next+1;
+	}
+	return -first-1;
+}
+
+static struct revision *lookup_rev(unsigned char *sha1)
+{
+	int pos = find_rev(sha1);
+	struct revision *n;
+
+	if (pos >= 0)
+		return revs[pos];
+	
+	pos = -pos-1;
+
+	if (rev_allocs == nr_revs) {
+		rev_allocs = alloc_nr(rev_allocs);
+		revs = realloc(revs, rev_allocs * sizeof(struct revision *));
+	}
+	n = malloc(sizeof(struct revision));
+
+	n->flags = 0;
+	memcpy(n->sha1, sha1, 20);
+	n->parent = NULL;
+
+	/* Insert it into the right place */
+	memmove(revs + pos + 1, revs + pos, (nr_revs - pos) * sizeof(struct revision *));
+	revs[pos] = n;
+	nr_revs++;
+
+	return n;
+}
+
+static struct revision *add_relationship(struct revision *rev, unsigned char *needs)
+{
+	struct revision *parent_rev = lookup_rev(needs);
+	struct parent **pp = &rev->parent, *p;
+
+	while ((p = *pp) != NULL) {
+		if (p->parent == parent_rev)
+			return parent_rev;
+		pp = &p->next;
+	}
+
+	p = malloc(sizeof(*p));
+	p->parent = parent_rev;
+	p->next = NULL;
+	*pp = p;
+	return parent_rev;
+}
+
+static void mark_reachable(struct revision *rev)
+{
+	struct parent *p = rev->parent;
+
+	/* If we've been here already, don't bother */
+	if (rev->flags & REACHABLE)
+		return;
+	rev->flags |= REACHABLE | USED;
+	while (p) {
+		mark_reachable(p->parent);
+		p = p->next;
+	}
+}
+
+#endif /* REVISION_H */