library: add function to link structure references

gds/library.py

@@ -1,4 +1,6 @@
 from datetime import datetime
+from .elements import SRef
+from .reader import ProgressGetter
 
 class Library(object):
     version = 0
@@ -12,3 +14,45 @@ class Library(object):
     meters_per_unit  = 1
 
     structures = {}
+
+    class LinkError(Exception):
+        element = None
+        pass
+
+    def link_srefs(self, progress_callback=None):
+        class Progress(ProgressGetter):
+            total   = 0
+            current = 0
+
+            def __init__(self, lib):
+                for key, value in lib.structures.items():
+                    self.total += len(value.references)
+
+            def progress(self):
+                return float(self.current) / self.total
+
+            def inc(self):
+                self.current += 1
+
+        count = Progress(self)
+
+        for key, value in self.structures.items():
+            
+            for element in value.references:
+                if isinstance(element, SRef) and isinstance(element.structure, str):
+                    # try to resolve link
+                    try:
+                        ref = self.structures[element.structure]
+                        element.structure = ref
+                    except KeyError:
+                        err = LinkError("dangeling sref (structure {} is not defined in library)".format(element.structure))
+                        err.element = element
+
+                        raise err
+
+                count.inc()
+
+                if progress_callback:
+                    progress_callback(count)
+                    
+                    

gds/structure.py

@@ -6,5 +6,7 @@ class Structure(object):
     last_mod      = datetime.now()
     name          = "NONAME"
 
-    # contains all the elements
+    # contains all the low level elements
     elements = []
+    # contains all sref and aref elements
+    references = []