+ return (0);
+}
+
+/*----- Job table manipulation --------------------------------------------*/
+
+#define JOB_SHIFT 16
+#define JOB_INDEXMASK ((1ul << JOB_SHIFT) - 1)
+#define JOB_SEQMASK ((1ul << (32 - JOB_SHIFT)) - 1)
+
+#define JOB_END 0xfffffffful
+
+static unsigned long a_joboffset;
+
+/* --- @a_jobidencode@ --- *
+ *
+ * Arguments: @admin_svcop *svc@ = pointer to a service operation
+ *
+ * Returns: A jobid for this job, in an internal static buffer.
+ *
+ * Use: Constructs a jobid. In order to dissuade people from
+ * predicting jobids, we obfuscate them.
+ *
+ * A `raw' jobid consists of two 16-bit fields. The low 16 bits
+ * are an index into a big array. The high 16 bits are a
+ * sequence number recording how many times that slot has been
+ * reused.
+ *
+ * This `raw' jobid is then obfuscated by adding a randomly-
+ * generated offset, and multiplying (mod %$2^{32}$%) by a fixed
+ * odd constant.
+ */
+
+static const char *a_jobidencode(admin_svcop *svc)
+{
+ admin_jobtable *j = &svc->prov->j;
+ static char buf[10];
+ unsigned long pre;
+ unsigned seq;
+
+ assert(svc->index <= JOB_INDEXMASK);
+ seq = j->v[svc->index].seq;
+ assert(seq <= JOB_SEQMASK);
+ pre = (unsigned long)svc->index | ((unsigned long)seq << JOB_SHIFT);
+ sprintf(buf, "J%08lx", ((pre + a_joboffset) * 0x0f87a7a3ul) & 0xffffffff);
+ return (buf);
+}
+
+/* --- @a_jobiddecode@ --- *
+ *
+ * Arguments: @admin_jobtable *j@ = pointer to a job table
+ * @const char *jid@ = pointer to a jobid string
+ *
+ * Returns: A pointer to the job's @svcop@ structure.
+ */
+
+static admin_svcop *a_jobiddecode(admin_jobtable *j, const char *jid)
+{
+ unsigned i;
+ unsigned long pre;
+
+ if (jid[0] != 'J')
+ return (0);
+ for (i = 1; i < 9; i++) {
+ if (!isxdigit((unsigned char)jid[i]))
+ return (0);
+ }
+ if (jid[9] != 0)
+ return (0);
+ pre = strtoul(jid + 1, 0, 16);
+ pre = ((pre * 0xbd11c40bul) - a_joboffset) & 0xffffffff;
+ i = pre & JOB_INDEXMASK;
+ if (i >= j->n || j->v[i].seq != (pre >> JOB_SHIFT))
+ return (0);
+ return (j->v[i].u.op);
+}
+
+/* --- @a_jobcreate@ --- *
+ *
+ * Arguments: @admin *a@ = pointer to administration client
+ *
+ * Returns: A pointer to a freshly-allocated @svcop@, or null.
+ *
+ * Use: Allocates a fresh @svcop@ and links it into a job table.
+ */
+
+static admin_svcop *a_jobcreate(admin *a)
+{
+ admin_svcop *svc;
+ unsigned i;
+ unsigned sz;
+ admin_jobtable *j = &a->j;
+
+ if (j->free != JOB_END) {
+ i = j->free;
+ j->free = j->v[i].u.next;
+ } else {
+ if (j->n == j->sz) {
+ if (j->sz > JOB_INDEXMASK)
+ return (0);
+ sz = j->sz;
+ if (!sz) {
+ j->sz = 16;
+ j->v = xmalloc(j->sz * sizeof(*j->v));
+ } else {
+ j->sz = sz << 1;
+ j->v = xrealloc(j->v, j->sz * sizeof(*j->v), sz * sizeof(*j->v));
+ }
+ }
+ i = j->n++;
+ j->v[i].seq = 0;
+ }
+ svc = xmalloc(sizeof(*svc));
+ svc->index = i;
+ svc->prov = a;
+ svc->next = j->active;
+ svc->prev = 0;
+ if (j->active) j->active->prev = svc;
+ j->active = svc;
+ j->v[i].u.op = svc;
+ IF_TRACING(T_ADMIN, {
+ trace(T_ADMIN, "admin: created job %s (%u)", a_jobidencode(svc), i);
+ })
+ return (svc);
+}
+
+/* --- @a_jobdestroy@ --- *
+ *
+ * Arguments: @admin_svcop *svc@ = pointer to job block
+ *
+ * Returns: ---
+ *
+ * Use: Frees up a completed (or cancelled) job.
+ */
+
+static void a_jobdestroy(admin_svcop *svc)
+{
+ admin *a = svc->prov;
+ admin_jobtable *j = &a->j;
+ unsigned i = svc->index;
+
+ IF_TRACING(T_ADMIN, {
+ trace(T_ADMIN, "admin: destroying job %s (%u)", a_jobidencode(svc), i);
+ })
+ assert(j->v[i].u.op = svc);
+ j->v[i].u.next = j->free;
+ j->v[i].seq++;
+ j->free = i;
+ if (svc->next) svc->next->prev = svc->prev;
+ if (svc->prev) svc->prev->next = svc->next;
+ else j->active = svc->next;
+}
+
+/* --- @a_jobtableinit@ --- *
+ *
+ * Arguments: @admin_jobtable *j@ = pointer to job table
+ *
+ * Returns: ---
+ *
+ * Use: Initializes a job table.
+ */
+
+static void a_jobtableinit(admin_jobtable *j)
+{
+ if (!a_joboffset)
+ a_joboffset = GR_RANGE(&rand_global, 0xffffffff) + 1;
+ j->n = j->sz = 0;
+ j->active = 0;
+ j->free = JOB_END;
+ j->v = 0;
+}
+
+/* --- @a_jobtablefinal@ --- *
+ *
+ * Arguments: @admin_jobtable *j@ = pointer to job table
+ *
+ * Returns: ---
+ *
+ * Use: Closes down a job table.
+ */
+
+static void a_jobtablefinal(admin_jobtable *j)
+{
+ admin_svcop *svc, *ssvc;
+
+ for (svc = j->active; svc; svc = ssvc) {
+ ssvc = svc->next;
+ a_bgfail(&svc->bg, "provider-failed", A_END);
+ a_bgrelease(&svc->bg);
+ }
+ if (j->v) xfree(j->v);
+}
+
+/*----- Services infrastructure -------------------------------------------*/
+
+/* --- @a_svcfind@ --- *
+ *
+ * Arguments: @admin *a@ = the requesting client
+ * @const char *name@ = service name wanted
+ *
+ * Returns: The service requested, or null.
+ *
+ * Use: Finds a service; reports an error if the service couldn't be
+ * found.
+ */
+
+static admin_service *a_svcfind(admin *a, const char *name)
+{
+ admin_service *svc;
+
+ if ((svc = sym_find(&a_svcs, name, -1, 0, 0)) == 0) {
+ a_fail(a, "unknown-service", "%s", name, A_END);
+ return (0);
+ }
+ return (svc);
+}
+
+/* --- @a_svcunlink@ --- *
+ *
+ * Arguments: @admin_service *svc@ = pointer to service structure
+ *
+ * Returns: ---
+ *
+ * Use: Unlinks the service from its provider, without issuing a
+ * message or freeing the structure. The version string is
+ * freed, however.
+ */
+
+static void a_svcunlink(admin_service *svc)
+{
+ if (svc->next)
+ svc->next->prev = svc->prev;
+ if (svc->prev)
+ svc->prev->next = svc->next;
+ else
+ svc->prov->svcs = svc->next;
+ xfree(svc->version);
+}
+
+/* --- @a_svcrelease@ --- *
+ *
+ * Arguments: @admin_service *svc@ = pointer to service structure
+ *
+ * Returns: ---
+ *
+ * Use: Releases a service and frees its structure.
+ */
+
+static void a_svcrelease(admin_service *svc)
+{
+ a_notify("SVCRELEASE", "%s", SYM_NAME(svc), A_END);
+ a_svcunlink(svc);
+ sym_remove(&a_svcs, svc);