Low-level dispatch module for publish-subscribe mechanism

This module implements a way to send messages from one module to
another, with associated data types.  It does not yet do anything to
ensure that messages are correct, that types match, or that other
forms of consistency are preserved.

1 files changed, 170 insertions, 0 deletions

diff --git a/src/lib/dispatch/dispatch_new.c b/src/lib/dispatch/dispatch_new.c
new file mode 100644
index 0000000000..a2879016a7
--- /dev/null
+++ b/src/lib/dispatch/dispatch_new.c
@@ -0,0 +1,170 @@
+/* Copyright (c) 2001, Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file dispatch_new.c
+ * \brief Code to construct a dispatch_t from a dispatch_cfg_t.
+ **/
+
+#define DISPATCH_PRIVATE
+#include "orconfig.h"
+
+#include "lib/dispatch/dispatch.h"
+#include "lib/dispatch/dispatch_st.h"
+#include "lib/dispatch/dispatch_cfg.h"
+#include "lib/dispatch/dispatch_cfg_st.h"
+
+#include "lib/intmath/cmp.h"
+#include "lib/malloc/malloc.h"
+#include "lib/log/util_bug.h"
+
+#include <string.h>
+
+/** Convert a void* in a smartlist to the corresponding integer. */
+#define VOID_TO_ID(p) ((intptr_t)(p))
+
+/** Given a smartlist full of void* fields encoding intptr_t values,
+ * return the largest intptr_t, or dflt if the list is empty. */
+static intptr_t
+max_in_sl(const smartlist_t *sl, intptr_t dflt)
+{
+  if (!smartlist_len(sl))
+    return dflt;
+  void *as_ptr = smartlist_get(sl, 0);
+  intptr_t max = VOID_TO_ID(as_ptr);
+  SMARTLIST_FOREACH_BEGIN(sl, void *, p) {
+    intptr_t i = VOID_TO_ID(p);
+    if (i > max)
+      max = i;
+  } SMARTLIST_FOREACH_END(p);
+  return max;
+}
+
+/** Helper: Format an unformattable message auxiliary data item: just return a
+* copy of the string <>. */
+static char *
+type_fmt_nop(msg_aux_data_t arg)
+{
+  (void)arg;
+  return tor_strdup("<>");
+}
+
+/** Helper: Free an unfreeable message auxiliary data item: do nothing. */
+static void
+type_free_nop(msg_aux_data_t arg)
+{
+  (void)arg;
+}
+
+/** Type functions to use when no type functions are provided. */
+static dispatch_typefns_t nop_typefns = {
+  .free_fn = type_free_nop,
+  .fmt_fn = type_fmt_nop
+};
+
+/**
+ * Alert function to use when none is configured: do nothing.
+ **/
+static void
+alert_fn_nop(dispatch_t *d, channel_id_t ch, void *arg)
+{
+  (void)d;
+  (void)ch;
+  (void)arg;
+}
+
+/**
+ * Given a list of recvfn_t, create and return a new dtbl_entry_t mapping
+ * to each of those functions.
+ **/
+static dtbl_entry_t *
+dtbl_entry_from_lst(smartlist_t *receivers)
+{
+  if (!receivers)
+    return NULL;
+
+  size_t n_recv = smartlist_len(receivers);
+  dtbl_entry_t *ent;
+  ent = tor_malloc_zero(offsetof(dtbl_entry_t, rcv) +
+                        sizeof(dispatch_rcv_t) * n_recv);
+
+  ent->n_fns = n_recv;
+
+  SMARTLIST_FOREACH_BEGIN(receivers, const dispatch_rcv_t *, rcv) {
+    memcpy(&ent->rcv[rcv_sl_idx], rcv, sizeof(*rcv));
+    if (rcv->enabled) {
+      ++ent->n_enabled;
+    }
+  } SMARTLIST_FOREACH_END(rcv);
+
+  return ent;
+}
+
+/** Create and return a new dispatcher from a given dispatch_cfg_t. */
+dispatch_t *
+dispatch_new(const dispatch_cfg_t *cfg)
+{
+  dispatch_t *d = tor_malloc_zero(sizeof(dispatch_t));
+
+  /* Any message that has a type or a receiver counts towards our messages */
+  const size_t n_msgs = MAX(smartlist_len(cfg->type_by_msg),
+                            smartlist_len(cfg->recv_by_msg)) + 1;
+
+  /* Any channel that any message has counts towards the number of channels. */
+  const size_t n_chans = (size_t) MAX(1, max_in_sl(cfg->chan_by_msg,0)) + 1;
+
+  /* Any type that a message has, or that has functions, counts towards
+   * the number of types. */
+  const size_t n_types = (size_t) MAX(max_in_sl(cfg->type_by_msg,0),
+                                      smartlist_len(cfg->fns_by_type)) + 1;
+
+  d->n_msgs = n_msgs;
+  d->n_queues = n_chans;
+  d->n_types = n_types;
+
+  /* Initialize the array of type-functions. */
+  d->typefns = tor_calloc(n_types, sizeof(dispatch_typefns_t));
+  for (size_t i = 0; i < n_types; ++i) {
+    /* Default to no-op for everything... */
+    memcpy(&d->typefns[i], &nop_typefns, sizeof(dispatch_typefns_t));
+  }
+  SMARTLIST_FOREACH_BEGIN(cfg->fns_by_type, dispatch_typefns_t *, fns) {
+    /* Set the functions if they are provided. */
+    if (fns) {
+      if (fns->free_fn)
+        d->typefns[fns_sl_idx].free_fn = fns->free_fn;
+      if (fns->fmt_fn)
+        d->typefns[fns_sl_idx].fmt_fn = fns->fmt_fn;
+    }
+  } SMARTLIST_FOREACH_END(fns);
+
+  /* Initialize the message queues: one for each channel. */
+  d->queues = tor_calloc(d->n_queues, sizeof(dqueue_t));
+  for (size_t i = 0; i < d->n_queues; ++i) {
+    TOR_SIMPLEQ_INIT(&d->queues[i].queue);
+    d->queues[i].alert_fn = alert_fn_nop;
+  }
+
+  /* Build the dispatch tables mapping message IDs to receivers. */
+  d->table = tor_calloc(d->n_msgs, sizeof(dtbl_entry_t *));
+  SMARTLIST_FOREACH_BEGIN(cfg->recv_by_msg, smartlist_t *, rcv) {
+    d->table[rcv_sl_idx] = dtbl_entry_from_lst(rcv);
+  } SMARTLIST_FOREACH_END(rcv);
+
+  /* Fill in the empty entries in the dispatch tables:
+   * types and channels for each message. */
+  SMARTLIST_FOREACH_BEGIN(cfg->type_by_msg, smartlist_t *, type) {
+    if (d->table[type_sl_idx])
+      d->table[type_sl_idx]->type = VOID_TO_ID(type);
+  } SMARTLIST_FOREACH_END(type);
+
+  SMARTLIST_FOREACH_BEGIN(cfg->chan_by_msg, smartlist_t *, chan) {
+    if (d->table[chan_sl_idx])
+      d->table[chan_sl_idx]->channel = VOID_TO_ID(chan);
+  } SMARTLIST_FOREACH_END(chan);
+
+  return d;
+}