Reviewer required changes

NO logic change to buffers yet. Just moving
existing logic into constructor/destructor.

src/fs_io.cc

@@ -37,6 +37,23 @@ static void cxx_xfree(void *ptr)
     xfree(ptr);
 }
 
+dwrite_q::dwrite_q(const size_t aSize, char *aBuffer, FREE *aFree) :
+    buf(aBuffer),
+    len(aSize),
+    free_func(aFree)
+{
+    if (!buf) {
+        buf = static_cast<char *>(xmalloc(len));
+        free_func = cxx_xfree; // dwrite_q buffer xfree()
+    }
+}
+
+dwrite_q::~dwrite_q()
+{
+    if (free_func)
+        free_func(buf);
+}
+
 /*
  * opens a disk file specified by 'path'.  This function always
  * blocks!  There is no callback.
@@ -138,19 +155,12 @@ diskCombineWrites(_fde_disk *fdd)
         for (dwrite_q *q = fdd->write_q; q != nullptr; q = q->next)
             len += q->len - q->buf_offset;
 
-        auto *wq = new dwrite_q;
-        wq->buf = (char *)xmalloc(len);
-        wq->free_func = cxx_xfree; // dwrite_q buffer xfree()
-
+        auto *wq = new dwrite_q(len);
         while (auto *q = fdd->write_q) {
             len = q->len - q->buf_offset;
             memcpy(wq->buf + wq->len, q->buf + q->buf_offset, len);
             wq->len += len;
             fdd->write_q = q->next;
-
-            if (q->free_func)
-                q->free_func(q->buf);
-
             delete q;
         };
 
@@ -237,10 +247,6 @@ diskHandleWrite(int fd, void *)
              */
             while (auto *q = fdd->write_q) {
                 fdd->write_q = q->next;
-
-                if (q->free_func)
-                    q->free_func(q->buf);
-
                 delete q;
             }
         }
@@ -262,10 +268,6 @@ diskHandleWrite(int fd, void *)
         if (q->buf_offset == q->len) {
             /* complete write */
             fdd->write_q = q->next;
-
-            if (q->free_func)
-                q->free_func(q->buf);
-
             delete q;
         }
     }
@@ -318,11 +320,8 @@ file_write(int fd,
     assert(fd >= 0);
     assert(F->flags.open);
     /* if we got here. Caller is eligible to write. */
-    auto *wq = new dwrite_q;
+    auto *wq = new dwrite_q(len, static_cast<char *>(const_cast<void *>(ptr_to_buf)), free_func);
     wq->file_offset = file_offset;
-    wq->buf = (char *)ptr_to_buf;
-    wq->len = len;
-    wq->free_func = free_func;
 
     if (!F->disk.wrt_handle_data) {
         F->disk.wrt_handle = handle;

src/fs_io.h

@@ -33,8 +33,12 @@ class dread_ctrl
 class dwrite_q
 {
     MEMPROXY_CLASS(dwrite_q);
-
 public:
+    dwrite_q() = default;
+    dwrite_q(const size_t, char * = nullptr, FREE * = nullptr);
+    dwrite_q(dwrite_q &&) = delete; // no copying or moving of any kind
+    ~dwrite_q();
+
     off_t file_offset = 0;
     char *buf = nullptr;
     size_t len = 0;