From 6bceb4ea5ddd4907fbfba14112ce22c74516c3e1 Mon Sep 17 00:00:00 2001
From: Julien Lamy <lamy@unistra.fr>
Date: Thu, 22 Dec 2016 12:20:51 +0100
Subject: [PATCH] Fix hashing Tags (close #44)

---
 tests/wrappers/test_tag.py | 11 +++++++++++
 wrappers/Tag.cpp           |  6 ++++++
 2 files changed, 17 insertions(+)

diff --git a/tests/wrappers/test_tag.py b/tests/wrappers/test_tag.py
index cf21990c..4f580e87 100644
--- a/tests/wrappers/test_tag.py
+++ b/tests/wrappers/test_tag.py
@@ -83,5 +83,16 @@ def test_str(self):
         tag = odil.Tag(0x1234, 0x5678)
         self.assertEqual(str(tag), "12345678")
 
+    def test_hash(self):
+        tag = odil.Tag(
+            odil.registry.PatientName.group, odil.registry.PatientName.element)
+        d = {tag: True}
+
+        self.assertTrue(tag in d)
+        self.assertTrue(odil.registry.PatientName in d)
+
+        other = odil.Tag(
+            odil.registry.PatientID.group, odil.registry.PatientID.element)
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/wrappers/Tag.cpp b/wrappers/Tag.cpp
index e2014199..26bf3537 100644
--- a/wrappers/Tag.cpp
+++ b/wrappers/Tag.cpp
@@ -10,6 +10,11 @@
 
 #include "odil/Tag.h"
 
+uint32_t hash(odil::Tag const & tag)
+{
+    return ((tag.group<<16)+tag.element);
+}
+
 void wrap_Tag()
 {
     using namespace boost::python;
@@ -29,6 +34,7 @@ void wrap_Tag()
         .def(self <= self)
         .def(self >= self)
         .def("__str__", &Tag::operator std::string)
+        .def("__hash__", &hash)
     ;
     implicitly_convertible<std::string, Tag>();
 }