Add callback multiplex support

Change-Id: Iddeb3a1b0e20706e72ec8f74dabc60b342f003ba
Signed-off-by: Dave Barach <dave@barachs.net>

2 files changed, 112 insertions, 0 deletions

diff --git a/src/vppinfra/CMakeLists.txt b/src/vppinfra/CMakeLists.txt
index 02e5322e1fc..a42bcb818a5 100644
--- a/src/vppinfra/CMakeLists.txt
+++ b/src/vppinfra/CMakeLists.txt
@@ -99,6 +99,7 @@ set(VPPINFRA_HEADERS
   bitops.h
   byte_order.h
   cache.h
+  callback.h
   clib_error.h
   clib.h
   cpu.h
diff --git a/src/vppinfra/callback.h b/src/vppinfra/callback.h
new file mode 100644
index 00000000000..595d69d72ab
--- /dev/null
+++ b/src/vppinfra/callback.h
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2019 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/** @file
+ * @brief Callback multiplex scheme
+ * For a fully worked-out example, see .../src/vlib/main.[ch] and
+ * .../src/plugins/perfmon.c
+ */
+
+#ifndef included_callback_h
+#define included_callback_h
+#include <vppinfra/clib.h>
+
+/** @brief Add or remove a callback to the specified callback set
+ *  @param h head of the callback vector
+ *  @param tmp vector to build result
+ *  @param l clib_spinlock_t lock to protect the vector, may be 0
+ *  @param f function to add or remove
+ *  @param enable 1 adds f to the vector, 0 removes f from the vector
+ *
+ * Add or remove a callback from the indicated callback vector.
+ * Caller must provide locking to prevent > 1 concurrent writer
+ * Swaps the head of the callback vector and a tmp vector in one
+ * motion, after a write barrier to ensure that the write is atomic.
+ */
+#define clib_callback_enable_disable(h,tmp,l,f,enable)  \
+do {                                                    \
+  void *tmp2;                                           \
+  clib_spinlock_lock_if_init(&l);                       \
+  vec_reset_length(tmp);                                \
+  vec_append(tmp, h);                                   \
+  if (enable)                                           \
+    vec_add1 (tmp,(void *)f);                           \
+  else                                                  \
+    {                                                   \
+      int i;                                            \
+      for (i = 0; i < vec_len (tmp); i++)               \
+        if (((void *)tmp[i]) == (void *)f)              \
+          {                                             \
+            vec_delete (tmp, 1, i);                     \
+            break;                                      \
+          }                                             \
+    }                                                   \
+  tmp2 = h;                                             \
+  CLIB_MEMORY_STORE_BARRIER();                          \
+  h = tmp;                                              \
+  tmp = tmp2;                                           \
+  clib_spinlock_unlock_if_init(&l);                     \
+} while(0);
+
+/** @brief call the specified callback set
+ * @param h the callback set
+ * @param varargs additional callback parameters
+ */
+#define clib_call_callbacks(h, ... )                    \
+do {                                                    \
+  /*                                                    \
+   * Note: fp exists to shut up gcc-6, which            \
+   * produces a warning not seen with gcc-7 or 8        \
+   */                                                   \
+  void (*fp)(void *a1, ...);                            \
+  int i;                                                \
+  for (i = 0; i < vec_len (h); i++)                     \
+    {                                                   \
+      fp = (void *)(h[i]);                              \
+      (*fp) (__VA_ARGS__);                              \
+    }                                                   \
+ } while (0);
+
+/** @brief predicate function says whether the specified function is enabled
+ * @param h the callback set
+ * @param l clib_spinlock_t lock to protect the vector, may be 0
+ * @param f the function to search for
+ * @return 1 if the function is enabled, 0 if not
+ */
+#define clib_callback_is_set(h,l,f)             \
+({                                              \
+  int _i;                                       \
+  int _found = 0;                               \
+  clib_spinlock_lock_if_init(&l);               \
+  for (_i = 0; _i < vec_len (h); _i++)          \
+    if (((void *)h[_i]) == (void *) f)          \
+      {                                         \
+        _found=1;                               \
+        break;                                  \
+      }                                         \
+  clib_spinlock_unlock_if_init(&l);             \
+  _found;                                       \
+ })
+
+#endif /* included_callback_h */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */