Add spsc_q data structure library

This data structure is designed to support the use cases of the L1,
i.e., provide a queue which can be quickly used to order L1 jobs in FIFO
order with simple iteration of jobs to treat. It is a Single-Consumer
Single-Producer queue library.

Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>

common/utils/ds/spsc_q.c

@@ -0,0 +1,112 @@
+/*
+ * SPDX-License-Identifier: LicenseRef-CSSL-1.0
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "spsc_q.h"
+
+#define rb_lock(LOCK) if (pthread_mutex_lock(LOCK) != 0) abort()
+#define rb_unlock(LOCK) if (pthread_mutex_unlock(LOCK) != 0) abort()
+
+spsc_q_t spsc_q_alloc(size_t cnt, size_t elsiz)
+{
+  /* internally, use one element more: the ringbuffer is full if
+   * (write_idx + 1) % cnt == read_idx, so it's full if one element is still
+   * free (because otherwise write_idx == read_idx, but this is the empty
+   * condition) */
+  cnt += 1;
+  spsc_q_t rb = {.cnt = cnt, .elsiz = elsiz};
+  rb.buf = calloc(cnt, elsiz);
+  pthread_mutex_init(&rb.mtx, NULL);
+  return rb;
+}
+
+void spsc_q_free(spsc_q_t *rb)
+{
+  free(rb->buf);
+  pthread_mutex_destroy(&rb->mtx);
+  memset(rb, 0, sizeof(*rb));
+}
+
+bool spsc_q_put(spsc_q_t *rb, const void *src, size_t elsiz)
+{
+  assert(elsiz == rb->elsiz);
+  rb_lock(&rb->mtx);
+  if ((rb->write_idx + 1) % rb->cnt == rb->read_idx) {
+    rb_unlock(&rb->mtx);
+    return false;
+  }
+
+  uint8_t *bufpos = &rb->buf[rb->write_idx * rb->elsiz];
+  memcpy(bufpos, src, elsiz);
+  rb->write_idx = (rb->write_idx + 1) % rb->cnt;
+  rb_unlock(&rb->mtx);
+  return true;
+}
+
+bool spsc_q_get_if(spsc_q_t *rb, pred p, void *user, void *dest, size_t elsiz)
+{
+  assert(elsiz == rb->elsiz);
+  rb_lock(&rb->mtx);
+  if (rb->write_idx == rb->read_idx) {
+    rb_unlock(&rb->mtx);
+    return false;
+  }
+
+  uint8_t *bufpos = &rb->buf[rb->read_idx * rb->elsiz];
+  if (!p(bufpos, user)) {
+    rb_unlock(&rb->mtx);
+    return false;
+  }
+
+  memcpy(dest, bufpos, elsiz);
+  rb->read_idx = (rb->read_idx + 1) % rb->cnt;
+  rb_unlock(&rb->mtx);
+  return true;
+}
+
+static bool always(const void *data, void *user)
+{
+  (void) data;
+  (void) user;
+  return true;
+}
+bool spsc_q_get(spsc_q_t *rb, void *dest, size_t elsiz)
+{
+  return spsc_q_get_if(rb, always, NULL, dest, elsiz);
+}
+
+int spsc_q_get_while(spsc_q_t *rb, pred p, void *user, void *dest, size_t elsiz, size_t max_len)
+{
+  assert(elsiz == rb->elsiz);
+  rb_lock(&rb->mtx);
+  size_t count = 0;
+  while (rb->write_idx != rb->read_idx && count < max_len) {
+    uint8_t *bufpos = &rb->buf[rb->read_idx * rb->elsiz];
+    if (!p(bufpos, user))
+      break;
+    memcpy(dest + count * elsiz, bufpos, elsiz);
+    count++;
+    rb->read_idx = (rb->read_idx + 1) % rb->cnt;
+  }
+  rb_unlock(&rb->mtx);
+  return count;
+}
+
+int spsc_q_drop_while(spsc_q_t *rb, pred p, void *user)
+{
+  rb_lock(&rb->mtx);
+  size_t dropped = 0;
+  while (rb->write_idx != rb->read_idx) {
+    uint8_t *bufpos = &rb->buf[rb->read_idx * rb->elsiz];
+    if (!p(bufpos, user))
+      break;
+    dropped++;
+    rb->read_idx = (rb->read_idx + 1) % rb->cnt;
+  }
+  rb_unlock(&rb->mtx);
+  return dropped;
+}