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/tests/test_spsc_q_perf.cpp

@@ -0,0 +1,75 @@
+#include "benchmark/benchmark.h"
+#include "stdio.h"
+#include "assert.h"
+#include "pthread.h"
+
+extern "C" {
+#include "spsc_q.h"
+}
+
+typedef struct q_args {
+  spsc_q_t q;
+  int range;
+} q_args_t;
+
+static void *producer(void *arg)
+{
+  q_args_t *a = (q_args_t *) arg;
+  int i = 0;
+  while (i <= a->range) {
+    if (spsc_q_put(&a->q, &i, sizeof(i)))
+      i++;
+  }
+  return NULL;
+}
+
+static void *consumer(void *arg)
+{
+  q_args_t *a = (q_args_t *) arg;
+  int i = 0;
+  while (i != a->range) {
+    int r;
+    if (spsc_q_get(&a->q, &r, sizeof(r))) {
+      assert(r == i);
+      i++;
+    }
+  }
+  return NULL;
+}
+
+static void run_test(int range, int q_size)
+{
+  q_args_t args = {
+    .q = spsc_q_alloc(q_size, sizeof(int)),
+    .range = range,
+  };
+
+  pthread_t p, c;
+  int ret;
+  // start
+  ret = pthread_create(&p, NULL, producer, &args);
+  assert(ret == 0);
+  ret = pthread_create(&c, NULL, consumer, &args);
+  assert(ret == 0);
+
+  ret = pthread_join(p, NULL);
+  assert(ret == 0);
+  ret = pthread_join(c, NULL);
+  assert(ret == 0);
+  // stop
+  // data/time => throughput
+
+  spsc_q_free(&args.q);
+}
+
+static void BM_spsc_q(benchmark::State &state)
+{
+  int range = 500000;
+  int q_size = state.range(0);
+  for (auto _ : state)
+    run_test(range, q_size);
+}
+
+BENCHMARK(BM_spsc_q)->RangeMultiplier(2)->Range(10, 160);
+
+BENCHMARK_MAIN();