tdb2: TDB_SEQNUM and tdb_get_seqnum support.

As per TDB1, except that the sequence number is 63 bit.

ccan/tdb2/io.c

@@ -563,6 +563,35 @@ static void *tdb_direct(struct tdb_context *tdb, tdb_off_t off, size_t len,
 	return (char *)tdb->file->map_ptr + off;
 }
 
+void tdb_inc_seqnum(struct tdb_context *tdb)
+{
+	tdb_off_t seq;
+
+	if (likely(!(tdb->flags & TDB_CONVERT))) {
+		int64_t *direct;
+
+		direct = tdb->methods->direct(tdb,
+					      offsetof(struct tdb_header,
+						       seqnum),
+					      sizeof(*direct), true);
+		if (likely(direct)) {
+			/* Don't let it go negative, even briefly */
+			if (unlikely((*direct) + 1) < 0)
+				*direct = 0;
+			(*direct)++;
+			return;
+		}
+	}
+
+	seq = tdb_read_off(tdb, offsetof(struct tdb_header, seqnum));
+	if (!TDB_OFF_IS_ERR(seq)) {
+		seq++;
+		if (unlikely((int64_t)seq < 0))
+			seq = 0;
+		tdb_write_off(tdb, offsetof(struct tdb_header, seqnum), seq);
+	}
+}
+
 void add_stat_(struct tdb_context *tdb, uint64_t *s, size_t val)
 {
 	if ((uintptr_t)s < (uintptr_t)tdb->stats + tdb->stats->size)

ccan/tdb2/open.c

@@ -107,6 +107,7 @@ static enum TDB_ERROR tdb_new_database(struct tdb_context *tdb,
 					 tdb->hash_priv);
 	newdb.hdr.recovery = 0;
 	newdb.hdr.features_used = newdb.hdr.features_offered = TDB_FEATURE_MASK;
+	newdb.hdr.seqnum = 0;
 	memset(newdb.hdr.reserved, 0, sizeof(newdb.hdr.reserved));
 	/* Initial hashes are empty. */
 	memset(newdb.hdr.hashtable, 0, sizeof(newdb.hdr.hashtable));
@@ -243,7 +244,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	}
 
 	if (tdb_flags & ~(TDB_INTERNAL | TDB_NOLOCK | TDB_NOMMAP | TDB_CONVERT
-			  | TDB_NOSYNC)) {
+			  | TDB_NOSYNC | TDB_SEQNUM)) {
 		ecode = tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
 				   "tdb_open: unknown flags %u", tdb_flags);
 		goto fail;

ccan/tdb2/private.h

@@ -246,7 +246,9 @@ struct tdb_header {
 	uint64_t features_used; /* Features all writers understand */
 	uint64_t features_offered; /* Features offered */
 
-	tdb_off_t reserved[24];
+	uint64_t seqnum; /* Sequence number for TDB_SEQNUM */
+
+	tdb_off_t reserved[23];
 
 	/* Top level hash table. */
 	tdb_off_t hashtable[1ULL << TDB_TOPLEVEL_HASH_BITS];
@@ -523,6 +525,9 @@ enum TDB_ERROR tdb_write_convert(struct tdb_context *tdb, tdb_off_t off,
 enum TDB_ERROR tdb_read_convert(struct tdb_context *tdb, tdb_off_t off,
 				void *rec, size_t len);
 
+/* Bump the seqnum (caller checks for tdb->flags & TDB_SEQNUM) */
+void tdb_inc_seqnum(struct tdb_context *tdb);
+
 /* Adds a stat, if it's in range. */
 void add_stat_(struct tdb_context *tdb, uint64_t *stat, size_t val);
 #define add_stat(tdb, statname, val)					\

ccan/tdb2/tdb.c

@@ -63,7 +63,9 @@ static enum TDB_ERROR replace_data(struct tdb_context *tdb,
 		return ecode;
 	}
 
-	/* FIXME: tdb_increment_seqnum(tdb); */
+	if (tdb->flags & TDB_SEQNUM)
+		tdb_inc_seqnum(tdb);
+
 	return TDB_SUCCESS;
 }
 
@@ -79,6 +81,9 @@ static enum TDB_ERROR update_data(struct tdb_context *tdb,
 		/* Put a zero in; future versions may append other data. */
 		ecode = tdb->methods->twrite(tdb, off + dbuf.dsize, "", 1);
 	}
+	if (tdb->flags & TDB_SEQNUM)
+		tdb_inc_seqnum(tdb);
+
 	return ecode;
 }
 
@@ -285,6 +290,9 @@ enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key)
 				+ rec_data_length(&rec)
 				+ rec_extra_padding(&rec));
 
+	if (tdb->flags & TDB_SEQNUM)
+		tdb_inc_seqnum(tdb);
+
 unlock:
 	tdb_unlock_hashes(tdb, h.hlock_start, h.hlock_range, F_WRLCK);
 	return ecode;
@@ -313,6 +321,9 @@ void tdb_add_flag(struct tdb_context *tdb, unsigned flag)
 	case TDB_NOSYNC:
 		tdb->flags |= TDB_NOSYNC;
 		break;
+	case TDB_SEQNUM:
+		tdb->flags |= TDB_SEQNUM;
+		break;
 	default:
 		tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
 			   "tdb_add_flag: Unknown flag %u", flag);
@@ -337,6 +348,9 @@ void tdb_remove_flag(struct tdb_context *tdb, unsigned flag)
 	case TDB_NOSYNC:
 		tdb->flags &= ~TDB_NOSYNC;
 		break;
+	case TDB_SEQNUM:
+		tdb->flags &= ~TDB_SEQNUM;
+		break;
 	default:
 		tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
 			   "tdb_remove_flag: Unknown flag %u", flag);
@@ -433,6 +447,12 @@ const char *tdb_name(const struct tdb_context *tdb)
 	return tdb->name;
 }
 
+int64_t tdb_get_seqnum(struct tdb_context *tdb)
+{
+	return tdb_read_off(tdb, offsetof(struct tdb_header, seqnum));
+}
+	
+
 int tdb_fd(const struct tdb_context *tdb)
 {
 	return tdb->file->fd;

ccan/tdb2/tdb2.h

@@ -78,6 +78,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 #define TDB_NOMMAP   8 /* don't use mmap */
 #define TDB_CONVERT 16 /* convert endian */
 #define TDB_NOSYNC   64 /* don't use synchronous transactions */
+#define TDB_SEQNUM   128 /* maintain a sequence number */
 
 /**
  * tdb_close - close and free a tdb.
@@ -323,6 +324,25 @@ enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
 							 TDB_DATA data,
 							 void *p),
 				 void *p);
+
+/**
+ * tdb_get_seqnum - get a database sequence number
+ * @tdb: the tdb context returned from tdb_open()
+ *
+ * This returns a sequence number: any change to the database from a
+ * tdb context opened with the TDB_SEQNUM flag will cause that number
+ * to increment.  Note that the incrementing is unreliable (it is done
+ * without locking), so this is only useful as an optimization.
+ *
+ * For example, you may have a regular database backup routine which
+ * does not operate if the sequence number is unchanged.  In the
+ * unlikely event of a failed increment, it will be backed up next
+ * time any way.
+ *
+ * Returns an enum TDB_ERROR (ie. negative) on error.
+ */
+int64_t tdb_get_seqnum(struct tdb_context *tdb);
+
 /**
  * tdb_firstkey - get the "first" key in a TDB
  * @tdb: the tdb context returned from tdb_open()

ccan/tdb2/test/failtest_helper.h

@@ -4,7 +4,7 @@
 #include <stdbool.h>
 
 /* FIXME: Check these! */
-#define INITIAL_TDB_MALLOC	"open.c", 198, FAILTEST_MALLOC
+#define INITIAL_TDB_MALLOC	"open.c", 199, FAILTEST_MALLOC
 #define URANDOM_OPEN		"open.c", 44, FAILTEST_OPEN
 #define URANDOM_READ		"open.c", 24, FAILTEST_READ
 

ccan/tdb2/test/run-81-seqnum.c

@@ -0,0 +1,71 @@
+#include <ccan/tdb2/tdb.c>
+#include <ccan/tdb2/open.c>
+#include <ccan/tdb2/free.c>
+#include <ccan/tdb2/lock.c>
+#include <ccan/tdb2/io.c>
+#include <ccan/tdb2/hash.c>
+#include <ccan/tdb2/transaction.c>
+#include <ccan/tdb2/traverse.c>
+#include <ccan/tdb2/check.c>
+#include <ccan/tap/tap.h>
+#include "logging.h"
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct tdb_context *tdb;
+	struct tdb_data d = { NULL, 0 }; /* Bogus GCC warning */
+	struct tdb_data key = { (unsigned char *)"key", 3 };
+	struct tdb_data data = { (unsigned char *)"data", 4 };
+	int flags[] = { TDB_INTERNAL, TDB_DEFAULT, TDB_NOMMAP,
+			TDB_INTERNAL|TDB_CONVERT, TDB_CONVERT,
+			TDB_NOMMAP|TDB_CONVERT };
+
+	plan_tests(sizeof(flags) / sizeof(flags[0]) * 15 + 4 * 13);
+	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
+		tdb = tdb_open("run-new_database.tdb", flags[i]|TDB_SEQNUM,
+			       O_RDWR|O_CREAT|O_TRUNC, 0600, &tap_log_attr);
+		if (!ok1(tdb))
+			continue;
+		
+		ok1(tdb_get_seqnum(tdb) == 0);
+		ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+		ok1(tdb_get_seqnum(tdb) == 1);
+		/* Fetch doesn't change seqnum */
+		if (ok1(tdb_fetch(tdb, key, &d) == TDB_SUCCESS))
+			free(d.dptr);
+		ok1(tdb_get_seqnum(tdb) == 1);
+		ok1(tdb_append(tdb, key, data) == TDB_SUCCESS);
+		ok1(tdb_get_seqnum(tdb) == 2);
+
+		ok1(tdb_delete(tdb, key) == TDB_SUCCESS);
+		ok1(tdb_get_seqnum(tdb) == 3);
+		/* Empty append works */
+		ok1(tdb_append(tdb, key, data) == TDB_SUCCESS);
+		ok1(tdb_get_seqnum(tdb) == 4);
+
+		ok1(tdb_wipe_all(tdb) == TDB_SUCCESS);
+		ok1(tdb_get_seqnum(tdb) == 5);
+
+		if (!(flags[i] & TDB_INTERNAL)) {
+			ok1(tdb_transaction_start(tdb) == TDB_SUCCESS);
+			ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+			ok1(tdb_get_seqnum(tdb) == 6);
+			ok1(tdb_append(tdb, key, data) == TDB_SUCCESS);
+			ok1(tdb_get_seqnum(tdb) == 7);
+			ok1(tdb_delete(tdb, key) == TDB_SUCCESS);
+			ok1(tdb_get_seqnum(tdb) == 8);
+			ok1(tdb_transaction_commit(tdb) == TDB_SUCCESS);
+			ok1(tdb_get_seqnum(tdb) == 8);
+
+			ok1(tdb_transaction_start(tdb) == TDB_SUCCESS);
+			ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+			ok1(tdb_get_seqnum(tdb) == 9);
+			tdb_transaction_cancel(tdb);
+			ok1(tdb_get_seqnum(tdb) == 8);
+		}
+		tdb_close(tdb);
+		ok1(tap_log_messages == 0);
+	}
+	return exit_status();
+}