dynamically allocate hash table buckets based on init() call

we probably should move to a more tree-like data structure than a hash
table.  But well, lookup is not the most computationally expensive part
compared to the cryptographic operations.

src/auc.h

@@ -31,7 +31,7 @@ struct auc_rec {
 	struct osmo_sub_auth_data auth;
 };
 
-int auc_core_init(void *ctx);
+int auc_core_init(void *ctx, unsigned int nbuckets);
 int auc_add_rec(struct auc_rec *rec);
 int auc_gen_vecs(struct osmo_auth_vector *vec,
 		 const char *imsi, int n_vecs);

src/auc_core.c

@@ -21,18 +21,25 @@
 #include <string.h>
 
 #include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
 #include <osmocom/crypt/auth.h>
 
 #include "auc.h"
 
-#define NBUCKETS 1024
-static struct llist_head auc_buckets[NBUCKETS];
+static struct llist_head *auc_buckets;
+static unsigned int g_nbuckets;
 
-int auc_core_init(void *ctx)
+int auc_core_init(void *ctx, unsigned int nbuckets)
 {
 	int i;
 
-	for (i = 0; i < NBUCKETS; i++)
+	auc_buckets = talloc_array(ctx, struct llist_head, nbuckets);
+	if (!auc_buckets)
+		return -ENOMEM;
+
+	g_nbuckets = nbuckets;
+
+	for (i = 0; i < nbuckets; i++)
 		INIT_LLIST_HEAD(&auc_buckets[i]);
 
 	return 0;
@@ -45,7 +52,7 @@ static unsigned int osmo_auc_hashfn(const char *imsi)
 
 	res = atoi(imsi + len - 6);
 
-	return res % NBUCKETS;
+	return res % g_nbuckets;
 }
 
 int auc_add_rec(struct auc_rec *rec)

src/auc_main.c

@@ -24,6 +24,8 @@
 #include <osmocom/core/talloc.h>
 #include <osmocom/crypt/auth.h>
 
+#include "auc.h"
+
 void *tall_ctx;
 
 static int auc_test(void)
@@ -60,7 +62,7 @@ int main(int argc, char **argv)
 
 	tall_ctx = talloc_zero_size(NULL, 1);
 
-	rc = auc_core_init(tall_ctx);
+	rc = auc_core_init(tall_ctx, 64*1024);
 	if (rc < 0)
 		exit(1);