diff --git a/tag.c b/tag.c
new file mode 100644
index 0000000..f079d83
--- /dev/null
+++ b/tag.c
@@ -0,0 +1,73 @@
+#include "tag.h"
+#include "cache.h"
+
+const char *tag_type = "tag";
+
+struct tag *lookup_tag(unsigned char *sha1)
+{
+        struct object *obj = lookup_object(sha1);
+        if (!obj) {
+                struct tag *ret = xmalloc(sizeof(struct tag));
+                memset(ret, 0, sizeof(struct tag));
+                created_object(sha1, &ret->object);
+                ret->object.type = tag_type;
+                return ret;
+        }
+        if (obj->type != tag_type) {
+                error("Object %s is a %s, not a tree", 
+                      sha1_to_hex(sha1), obj->type);
+                return NULL;
+        }
+        return (struct tag *) obj;
+}
+
+int parse_tag(struct tag *item)
+{
+        char type[20];
+        void *data, *bufptr;
+        unsigned long size;
+        if (item->object.parsed)
+                return 0;
+        item->object.parsed = 1;
+        data = bufptr = read_sha1_file(item->object.sha1, type, &size);
+        if (!data)
+                return error("Could not read %s",
+                             sha1_to_hex(item->object.sha1));
+        if (strcmp(type, tag_type))
+                return error("Object %s not a tag",
+                             sha1_to_hex(item->object.sha1));
+
+	int typelen, taglen;
+	unsigned char object[20];
+	const char *type_line, *tag_line, *sig_line;
+
+	if (size < 64)
+		return -1;
+	if (memcmp("object ", data, 7) || get_sha1_hex(data + 7, object))
+		return -1;
+
+	item->tagged = parse_object(object);
+
+	type_line = data + 48;
+	if (memcmp("\ntype ", type_line-1, 6))
+		return -1;
+
+	tag_line = strchr(type_line, '\n');
+	if (!tag_line || memcmp("tag ", ++tag_line, 4))
+		return -1;
+
+	sig_line = strchr(tag_line, '\n');
+	if (!sig_line)
+		return -1;
+	sig_line++;
+
+	typelen = tag_line - type_line - strlen("type \n");
+	if (typelen >= 20)
+		return -1;
+	taglen = sig_line - tag_line - strlen("tag \n");
+	item->tag = xmalloc(taglen + 1);
+	memcpy(item->tag, tag_line + 4, taglen);
+	item->tag[taglen] = '\0';
+
+	return 0;
+}