.

wcfs/internal/wcfs_virtmem.cpp

@@ -362,7 +362,40 @@ void Conn::_pin1(PinReq *req) {
 
 // XXX Conn::mmap
 
-// XXX Conn::resync
+// resync resyncs connection and its mappings onto different database view.
+void Conn::resync(Tid at) { // XXX void -> err?
+    Conn &wconn = *this;
+
+    // XXX locking
+
+    for foid, f in wconn._filetab.items():
+        // XXX if file has no mappings and was not used during whole prev
+        // cycle - forget and stop watching it
+
+        // update f.headfsize and remmap to head/f zero regions that are now covered by head/f
+        _ = os.fstat(f.headf.fileno())
+        assert f.blksize == _.st_blksize    // blksize must not change
+        headfsize = _.st_size
+        assert f.headfsize <= headfsize     // head/file size ↑=
+        assert headfsize % f.blksize == 0
+        for mmap in f.mmaps:
+            print('  resync -> %s: unzero [%d:%d)' % (at, f.headfsize//f.blksize, headfsize//f.blksize))
+            memunzero = mmap.mem[f.headfsize - mmap.blk_start*f.blksize :
+                                 headfsize   - mmap.blk_start*f.blksize]
+            if len(memunzero) > 0:
+                mm.map_into_ro(memunzero, f.headf.fileno(), f.headfsize)
+
+        f.headfsize = headfsize
+
+
+        _ = wconn._wlink.sendReq(context.background(), b"watch %s @%s" % (h(foid), h(at)))
+        if _ != "ok":
+            // XXX unregister f from _filetab
+            // XXX vvv -> errctx?
+            raise RuntimeError("resync @%s -> @%s: f<%s>: %s" % (h(wconn.at), h(at), h(foid), _))
+
+    wconn.at = at
+}
 
 // _remmapblk remmaps mapping memory for file[blk] to be viewing database as of @at state.
 //