From 42c8e3daa85b52063966877bf59f626f2b88d90c Mon Sep 17 00:00:00 2001
From: Agisilaos Kounelis <36283973+kounelisagis@users.noreply.github.com>
Date: Sat, 2 Mar 2024 00:02:25 +0200
Subject: [PATCH] Fix Filestore unable to read sizes smaller than offset
 (#1907)

* Fix filestore unable to read sizes smaller than offset
* add test for filestore using small buffer
---
 tiledb/filestore.py            |  2 +-
 tiledb/tests/test_filestore.py | 25 +++++++++++++++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/tiledb/filestore.py b/tiledb/filestore.py
index b3d49cf57c..ced8561459 100644
--- a/tiledb/filestore.py
+++ b/tiledb/filestore.py
@@ -67,7 +67,7 @@ def read(self, offset: int = 0, size: int = -1) -> bytes:
 
         if size == -1:
             size = len(self)
-        size = max(size - offset, 0)
+        size = min(size, len(self) - offset)
 
         return lt.Filestore._buffer_export(
             self._ctx,
diff --git a/tiledb/tests/test_filestore.py b/tiledb/tests/test_filestore.py
index dd8e3da3e2..bde45452aa 100644
--- a/tiledb/tests/test_filestore.py
+++ b/tiledb/tests/test_filestore.py
@@ -35,12 +35,33 @@ def test_buffer(self, capfd):
         schema.attr(0).dump()
         assert_captured(capfd, "Type: BLOB")
 
-        data = b"buffer"
-
         fs = tiledb.Filestore(path)
         fs.write(data)
         assert bytes(data) == fs.read()
 
+    def test_small_buffer(self, capfd):
+        path = self.path("test_small_buffer")
+        # create a 4 byte array
+        data = b"abcd"
+
+        fs = tiledb.Filestore(path)
+
+        with self.assertRaises(tiledb.TileDBError):
+            fs.write(data)
+
+        schema = tiledb.ArraySchema.from_file()
+        tiledb.Array.create(path, schema)
+
+        assert schema.attr(0).name == "contents"
+        assert schema.attr(0).dtype == np.bytes_
+
+        schema.attr(0).dump()
+        assert_captured(capfd, "Type: BLOB")
+
+        fs = tiledb.Filestore(path)
+        fs.write(data)
+        assert data[3:4] == fs.read(offset=3, size=1)
+
     def test_uri(self, text_fname):
         path = self.path("test_uri")
         schema = tiledb.ArraySchema.from_file(text_fname)