Merge command comments; VCD_TARGET cleanup

1 files changed, 14 insertions, 7 deletions

diff --git a/xdelta3/xdelta3-merge.h b/xdelta3/xdelta3-merge.h
index 72bc892..a09f814 100644
--- a/xdelta3/xdelta3-merge.h
+++ b/xdelta3/xdelta3-merge.h
@@ -492,10 +492,15 @@ xd3_merge_source_copy (xd3_stream *stream,
             }
           else
             {
-              // TODO: this is slow because of the recursion, which
-              // could reach a depth equal to the number of target
-              // copies, and this is compression-inefficient because
-              // it can produce duplicate adds.
+              // Note: A better implementation will construct the
+              // mapping of output ranges, starting from the input
+              // range, applying deltas in forward order, using an
+              // interval tree.  This code uses recursion to construct
+              // each copied range, recursively (using binary search
+              // in xd3_merge_find_position).
+              //
+              // TODO: This code can cause stack overflow. Fix as
+              // described above.
               xd3_winst tinst;
               tinst.type = XD3_CPY;
               tinst.mode = iinst.mode;
@@ -555,12 +560,14 @@ int xd3_merge_inputs (xd3_stream *stream,
           ret = xd3_merge_add (stream, input, iinst);
           break;
         default:
-          /* TODO: VCD_TARGET support is completely untested all
-           * throughout. */
-          if (iinst->mode == 0 || iinst->mode == VCD_TARGET)
+          if (iinst->mode == 0)
             {
               ret = xd3_merge_target_copy (stream, iinst);
             }
+          else if (iinst->mode == VCD_TARGET)
+            {
+              ret = XD3_INVALID_INPUT;
+            }
           else
             {
               ret = xd3_merge_source_copy (stream, source, iinst);