Merge pull request #40 from danielinux/fix-queue-wraparound

queue_pop: properly handle wrap-around

Author: LinuxJedi

src/test/unit/unit.c

@@ -12670,18 +12670,30 @@ END_TEST
 
 START_TEST(test_queue_pop_wraparound) {
     struct queue q;
+    struct {
+        uint8_t buf[8];
+        uint8_t guard[4];
+    } storage;
     uint8_t data[] = {9, 10, 11, 12};
+    uint8_t expected_guard[] = {0xEE, 0xEE, 0xEE, 0xEE};
     uint8_t out[4];
     int len;
-    queue_init(&q, mem, memsz, 0x12345678);
-
-    q.head = memsz - 1;
-    q.tail = memsz - 1;
-    queue_insert(&q, data, 0, sizeof(data));
+    memset(&storage, 0, sizeof(storage));
+    memset(storage.guard, 0xEE, sizeof(storage.guard));
+    queue_init(&q, storage.buf, sizeof(storage.buf), 0x12345678);
+
+    /* Manually set a wrapped queue state: tail near end, head near start. */
+    q.tail = 6;
+    q.head = 2;
+    storage.buf[6] = data[0];
+    storage.buf[7] = data[1];
+    storage.buf[0] = data[2];
+    storage.buf[1] = data[3];
     len = queue_pop(&q, out, sizeof(out));
     ck_assert_int_eq(len, sizeof(out));
     ck_assert_mem_eq(out, data, sizeof(data));
     ck_assert_int_eq(queue_len(&q), 0);
+    ck_assert_mem_eq(storage.guard, expected_guard, sizeof(expected_guard));
 }
 END_TEST
 

src/wolfip.c

@@ -573,11 +573,18 @@ static int queue_insert(struct queue *q, void *data, uint32_t seq, uint32_t len)
 static int queue_pop(struct queue *q, void *data, uint32_t len)
 {
     uint32_t q_len = queue_len(q);
+    uint32_t first_chunk;
     if (q_len == 0)
         return -WOLFIP_EAGAIN;
     if (len > q_len)
         len = q_len;
-    memcpy(data, (const uint8_t *)q->data + q->tail, len);
+    if (q->tail + len > q->size) {
+        first_chunk = q->size - q->tail;
+        memcpy(data, (const uint8_t *)q->data + q->tail, first_chunk);
+        memcpy((uint8_t *)data + first_chunk, (const uint8_t *)q->data, len - first_chunk);
+    } else {
+        memcpy(data, (const uint8_t *)q->data + q->tail, len);
+    }
     q->tail += len;
     q->tail %= q->size;
     q->seq_base += len;