Add subscription marking to keep track of things you've read

[blerg.git] / database / database.c

diff --git a/database/database.c b/database/database.c
index a45c92b..e6e8707 100644 (file)
--- a/database/database.c
+++ b/database/database.c
@@ -164,10 +164,17 @@ struct blerg *blerg_open(const char *name) {
                goto open_failed_meta_open;
        }
        fstat(blerg->meta_fd, &st);
-       if (st.st_size == 0) {
-               char *buf = (char *) malloc(sizeof(struct meta));
-               memset(buf, 0, sizeof(struct meta));
-               write(blerg->meta_fd, buf, sizeof(struct meta));
+       if (st.st_size < sizeof(struct meta)) {
+               // Fill the difference in size between sizeof(struct meta) and
+               // the file size with nulls.  This allows seamless upgrades as
+               // long as struct meta only adds members.
+               int len = sizeof(struct meta) - st.st_size;
+               char *buf = (char *) malloc(len);
+               memset(buf, 0, len);
+               int tmpfd = dup(blerg->meta_fd);
+               FILE* tmp = fdopen(tmpfd, "a");
+               fwrite(buf, len, 1, tmp);
+               fclose(tmp);
                free(buf);
        }
        blerg->meta = (struct meta *) mmap(NULL, sizeof(struct meta), PROT_READ | PROT_WRITE, MAP_SHARED, blerg->meta_fd, 0);
@@ -324,3 +331,11 @@ time_t blerg_get_timestamp(struct blerg *blerg, int record) {
 
        return blerg->index[seg_rec].timestamp;
 }
+
+int blerg_set_subscription_mark(struct blerg *blerg) {
+       blerg->meta->subscription_mark = subscription_count_items(blerg->name);
+}
+
+uint64_t blerg_get_subscription_mark(struct blerg *blerg) {
+       return blerg->meta->subscription_mark;
+}