Add big-endian tests for our BSD layer

test/bsd/shm_queue.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#define FRAME_SIZE 1540
+#define FRAME_QUEUE_DEPTH 32
+#define SHM_NAME "/mongoose-shm"
+
+// Keep this SHM ABI semaphore-free. Some S390/Linux headers pull fcntl/socket
+// declarations through <semaphore.h>, colliding with Mongoose BSD prototypes.
+// Each direction is single-producer/single-consumer and polled, so a simple
+// ring is enough for this test path.
+struct shm_frame {
+  size_t len;
+  uint8_t buf[FRAME_SIZE];
+};
+
+struct shm_queue {
+  volatile size_t head;
+  volatile size_t tail;
+  struct shm_frame frames[FRAME_QUEUE_DEPTH];
+};
+
+struct shm_link {
+  struct shm_queue to_tap;
+  struct shm_queue from_tap;
+};
+
+static inline bool shm_queue_push(struct shm_queue *q, const void *buf,
+                                  size_t len) {
+  size_t tail = q->tail, next = (tail + 1) % FRAME_QUEUE_DEPTH;
+  struct shm_frame *f;
+  if (len > sizeof(q->frames[0].buf) || next == q->head) return false;
+  f = &q->frames[tail];
+  memcpy(f->buf, buf, len);
+  f->len = len;
+  __sync_synchronize();
+  q->tail = next;
+  return true;
+}
+
+static inline size_t shm_queue_pop(struct shm_queue *q, void *buf, size_t len) {
+  size_t head = q->head, n;
+  struct shm_frame *f;
+  if (head == q->tail) return 0;
+  __sync_synchronize();
+  f = &q->frames[head];
+  n = f->len;
+  if (n > len) {
+    q->head = (head + 1) % FRAME_QUEUE_DEPTH;
+    return 0;
+  }
+  memcpy(buf, f->buf, n);
+  __sync_synchronize();
+  q->head = (head + 1) % FRAME_QUEUE_DEPTH;
+  return n;
+}