[consider merging] Fixing two problems with layer mapping

1. Mapping "[*/*] 100/0:0/0" (for example) created 0/0
   two times when the input contains 100/0 and 0/0. Now
   it is a single layer only
2. The mapping table generated from strings now uses
   layer indexes from a range that should not collide
   with existing layer indexes.

src/db/db/dbStreamLayers.cc

@@ -236,7 +236,19 @@ LayerMap::substitute_placeholder (const db::LayerProperties &p, const std::set<u
       lp_new.layer = db::ld_combine (p.layer, lp_ph.layer);
       lp_new.datatype = db::ld_combine (p.datatype, lp_ph.datatype);
 
-      unsigned int l_new = layout.insert_layer (lp_new);
+      //  if the placeholder-extrapolated layer is a target layer, go to that one
+      unsigned int l_new = std::numeric_limits<unsigned int>::max ();
+      for (std::map<unsigned int, db::LayerProperties>::const_iterator t = m_target_layers.begin (); t != m_target_layers.end (); ++t) {
+        if (t->second.log_equal (lp_new) && layout.is_valid_layer (t->first)) {
+          l_new = t->first;
+          break;
+        }
+      }
+
+      if (l_new == std::numeric_limits<unsigned int>::max ()) {
+        l_new = layout.insert_layer (lp_new);
+      }
+
       map (p, l_new, lp_new);
       res.insert (l_new);
 
@@ -929,7 +941,10 @@ db::LayerMap
 LayerMap::from_string_file_format (const std::string &s)
 {
   db::LayerMap lm;
-  unsigned int l = 0;
+  //  NOTE: this should be outside the normal layer index range of a Layout and below
+  //  the space reserved for placeholders. With numbers like this we don't get messed
+  //  up with existing layers.
+  unsigned int l = std::numeric_limits<unsigned int>::max () / 2;
 
   int lnr = 0;
 

src/db/unit_tests/dbStreamLayerTests.cc

@@ -577,3 +577,33 @@ TEST(8)
   EXPECT_EQ (db::LayerMap::from_string_file_format (lm.to_string_file_format ()).to_string (), lm.to_string ());
 }
 
+//  mapping of relative target to real target
+TEST(9)
+{
+  db::Layout ly;
+  db::LayerMap lm;
+
+  EXPECT_EQ (layers_to_string (ly), "");
+  unsigned int l0 = ly.insert_layer (db::LayerProperties (0, 0));
+  unsigned int l101 = ly.insert_layer (db::LayerProperties (101, 0));
+
+  unsigned int n = std::numeric_limits<unsigned int>::max () / 2;
+  lm.map_expr ("*/* : */*", n++);
+  lm.map_expr ("100/0 : 0/0", n++);
+
+  lm.prepare (ly);
+
+  std::pair<bool, unsigned int> p;
+  p = lm.first_logical (db::LayerProperties (100, 0), ly);
+  EXPECT_EQ (p.first, true);
+  EXPECT_EQ (p.second, l0);
+
+  p = lm.first_logical (db::LayerProperties (101, 0), ly);
+  EXPECT_EQ (p.first, true);
+  EXPECT_EQ (p.second, l101);
+
+  //  maps to the target 0/0
+  p = lm.first_logical (db::LayerProperties (0, 0), ly);
+  EXPECT_EQ (p.first, true);
+  EXPECT_EQ (p.second, l0);
+}

src/plugins/streamers/gds2/unit_tests/dbGDS2ReaderTests.cc

@@ -417,9 +417,8 @@ TEST(3_AdvancedMapping)
   }
 
   EXPECT_EQ (lm_read.to_string_file_format (),
-    "1/10 : 1/0\n"
+    "1/0,10 : 1/0\n"
     "2/0-1 : 2/0\n"
-    "1/0 : 1/0\n"
     "1/1 : 1/1\n"
     "1/20 : 1/1020\n"
     "1/21 : 1/1021\n"