From 7a14591e5707c4c3611ce5e9626293b6082c9beb Mon Sep 17 00:00:00 2001
From: Ryan Walter Murray <rywm@dhigroup.com>
Date: Fri, 23 Jan 2026 11:24:21 +0100
Subject: [PATCH 1/2] Minimal test exposing bug

---
 tests/test_dfs0.py | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tests/test_dfs0.py b/tests/test_dfs0.py
index c2c40be..4e50450 100644
--- a/tests/test_dfs0.py
+++ b/tests/test_dfs0.py
@@ -25,6 +25,33 @@ class Dfs0Tests(unittest.TestCase):
     #    maxValue = examples_dfs0.FindMaxValue("testdata/data_ndr_roese.dfs0", 4);
     #    assert_equal(1.0754467248916626, maxValue);
 
+    def test_many_open_closes_1(self):
+        fn = r"testdata\Rain_accumulated.dfs0"
+
+        for i in range(1000):
+            dfs = DfsFile()
+            dfs.Open(fn)
+
+            # if you close, then this does not error
+            #dfs.Close()
+
+    def test_many_open_closes_2(self):
+        fn = r"testdata\Rain_accumulated.dfs0"
+
+        files = []
+
+        # if this exceeds 509, we get problem.
+        # probably related to 512 limit of max number of files open at one time
+        # https://stackoverflow.com/questions/870173/is-there-a-limit-on-number-of-open-files-in-windows
+        for i in range(509):
+            dfs = DfsFile()
+            dfs.Open(fn)
+            files.append(dfs)
+
+        for dfs in files:
+            dfs.Close()
+
+
     def test_Read_non_ascii_itemname(self):
         dfs = DfsFile()
         dfs.Open("testdata/TS_non_ascii.dfs0")

From 23b6a4e3bd268c0b03d6c6e8bb6a6137a2f61fc2 Mon Sep 17 00:00:00 2001
From: Ryan Walter Murray <rywm@dhigroup.com>
Date: Fri, 23 Jan 2026 12:47:35 +0100
Subject: [PATCH 2/2] Fix path to test data

---
 tests/test_dfs0.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/test_dfs0.py b/tests/test_dfs0.py
index 4e50450..81d861c 100644
--- a/tests/test_dfs0.py
+++ b/tests/test_dfs0.py
@@ -26,7 +26,7 @@ class Dfs0Tests(unittest.TestCase):
     #    assert_equal(1.0754467248916626, maxValue);
 
     def test_many_open_closes_1(self):
-        fn = r"testdata\Rain_accumulated.dfs0"
+        fn = "testdata/Rain_accumulated.dfs0"
 
         for i in range(1000):
             dfs = DfsFile()
@@ -36,7 +36,7 @@ def test_many_open_closes_1(self):
             #dfs.Close()
 
     def test_many_open_closes_2(self):
-        fn = r"testdata\Rain_accumulated.dfs0"
+        fn = "testdata/Rain_accumulated.dfs0"
 
         files = []