ntdb: add NTDB_ATTRIBUTE_HASHSIZE

Since we've given up on expansion, let them frob the hashsize again.
We have attributes, so we should use them for optional stuff like
this.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 41 insertions, 2 deletions

diff --git a/lib/ntdb/ntdb.h b/lib/ntdb/ntdb.h
index 09622787d4..8e8458e4d1 100644
--- a/lib/ntdb/ntdb.h
+++ b/lib/ntdb/ntdb.h
@@ -633,7 +633,8 @@ enum ntdb_attribute_type {
 	NTDB_ATTRIBUTE_STATS = 3,
 	NTDB_ATTRIBUTE_OPENHOOK = 4,
 	NTDB_ATTRIBUTE_FLOCK = 5,
-	NTDB_ATTRIBUTE_ALLOCATOR = 6
+	NTDB_ATTRIBUTE_ALLOCATOR = 6,
+	NTDB_ATTRIBUTE_HASHSIZE = 7
 };
 
 /**
@@ -867,6 +868,17 @@ struct ntdb_attribute_flock {
 };
 
 /**
+ * struct ntdb_attribute_hashsize - ntdb hashsize setting.
+ *
+ * This attribute is only settable on ntdb_open; it indicates that we create
+ * a hashtable of the given size, rather than the default.
+ */
+struct ntdb_attribute_hashsize {
+	struct ntdb_attribute_base base; /* .attr = NTDB_ATTRIBUTE_HASHSIZE */
+	uint32_t size;
+};
+
+/**
  * struct ntdb_attribute_allocator - allocator for ntdb to use.
  *
  * You can replace malloc/free with your own allocation functions.
@@ -910,6 +922,7 @@ union ntdb_attribute {
 	struct ntdb_attribute_openhook openhook;
 	struct ntdb_attribute_flock flock;
 	struct ntdb_attribute_allocator alloc;
+	struct ntdb_attribute_hashsize hashsize;
 };
 
 #ifdef  __cplusplus
diff --git a/lib/ntdb/open.c b/lib/ntdb/open.c
index 4b8c45298b..9de9e9b48c 100644
--- a/lib/ntdb/open.c
+++ b/lib/ntdb/open.c
@@ -273,6 +273,7 @@ _PUBLIC_ enum NTDB_ERROR ntdb_set_attribute(struct ntdb_context *ntdb,
 	case NTDB_ATTRIBUTE_HASH:
 	case NTDB_ATTRIBUTE_SEED:
 	case NTDB_ATTRIBUTE_OPENHOOK:
+	case NTDB_ATTRIBUTE_HASHSIZE:
 		return ntdb_logerr(ntdb, NTDB_ERR_EINVAL,
 				   NTDB_LOG_USE_ERROR,
 				   "ntdb_set_attribute:"
@@ -281,7 +282,9 @@ _PUBLIC_ enum NTDB_ERROR ntdb_set_attribute(struct ntdb_context *ntdb,
 				   ? "NTDB_ATTRIBUTE_HASH"
 				   : attr->base.attr == NTDB_ATTRIBUTE_SEED
 				   ? "NTDB_ATTRIBUTE_SEED"
-				   : "NTDB_ATTRIBUTE_OPENHOOK");
+				   : attr->base.attr == NTDB_ATTRIBUTE_OPENHOOK
+				   ? "NTDB_ATTRIBUTE_OPENHOOK"
+				   : "NTDB_ATTRIBUTE_HASHSIZE");
 	case NTDB_ATTRIBUTE_STATS:
 		return ntdb_logerr(ntdb, NTDB_ERR_EINVAL,
 				   NTDB_LOG_USE_ERROR,
@@ -349,6 +352,9 @@ _PUBLIC_ enum NTDB_ERROR ntdb_get_attribute(struct ntdb_context *ntdb,
 		attr->alloc.free = ntdb->free_fn;
 		attr->alloc.priv_data = ntdb->alloc_data;
 		break;
+	case NTDB_ATTRIBUTE_HASHSIZE:
+		attr->hashsize.size = 1 << ntdb->hash_bits;
+		break;
 	default:
 		return ntdb_logerr(ntdb, NTDB_ERR_EINVAL,
 				   NTDB_LOG_USE_ERROR,
@@ -475,6 +481,15 @@ static struct ntdb_context *alloc_ntdb(const union ntdb_attribute *attr,
 	return default_alloc(NULL, len, NULL);
 }
 
+static unsigned int next_pow2(uint64_t size)
+{
+	unsigned int bits = 1;
+
+	while ((1ULL << bits) < size)
+		bits++;
+	return bits;
+}
+
 _PUBLIC_ struct ntdb_context *ntdb_open(const char *name, int ntdb_flags,
 					int open_flags, mode_t mode,
 					union ntdb_attribute *attr)
@@ -528,6 +543,17 @@ _PUBLIC_ struct ntdb_context *ntdb_open(const char *name, int ntdb_flags,
 			ntdb->openhook = attr->openhook.fn;
 			ntdb->openhook_data = attr->openhook.data;
 			break;
+		case NTDB_ATTRIBUTE_HASHSIZE:
+			ntdb->hash_bits = next_pow2(attr->hashsize.size);
+			if (ntdb->hash_bits > 31) {
+				ecode = ntdb_logerr(ntdb, NTDB_ERR_EINVAL,
+						    NTDB_LOG_USE_ERROR,
+						    "ntdb_open: hash_size %u"
+						    " too large",
+						    attr->hashsize.size);
+				goto fail;
+			}
+			break;
 		default:
 			/* These are set as normal. */
 			ecode = ntdb_set_attribute(ntdb, attr);