bugfix: use correct offset in inner read/write

python · JelleZijlstra · Apr 22, 2022 · Apr 16, 2022 · Apr 16, 2022 · Apr 16, 2022
commit 233f94074e9c31f5f260d3b890afc581b090d4c7
@@ -1138,6 +1138,13 @@ def test_blob_write_error_length(self):
         with self.assertRaisesRegex(ValueError, "data longer than blob"):
             self.blob.write(b"a" * 1000)
 
+        self.blob.seek(0, SEEK_SET)
+        n = len(self.blob)
+        self.blob.write(b"a" * (n-1))
+        self.blob.write(b"a" * 1)
+        with self.assertRaisesRegex(ValueError, "data longer than blob"):
+            self.blob.write(b"a" * 1)
+
     def test_blob_write_error_row_changed(self):
         self.cx.execute("update test set b='aaaa' where rowid=1")
         with self.assertRaises(sqlite.OperationalError):
@@ -1178,6 +1185,15 @@ def test_blob_set_item(self):
         actual = self.cx.execute("select b from test").fetchone()[0]
         self.assertEqual(actual, expected)
 
+    def test_blob_set_item_with_offset(self):
+        self.blob.seek(0, SEEK_END)
+        self.assertEqual(self.blob.read(), b"")  # verify that we're at EOB
+        self.blob[0] = b"T"
+        self.blob[-1] = b"."
+        self.blob.seek(0, SEEK_SET)
+        expected = b"This blob data string is exactly fifty bytes long."
+        self.assertEqual(self.blob.read(), expected)
+
     def test_blob_set_buffer_object(self):
         from array import array
         self.blob[0] = memoryview(b"1")

@@ -123,7 +123,7 @@ static PyObject *
 inner_read(pysqlite_Blob *self, Py_ssize_t length, Py_ssize_t offset)
 {
     assert(length <= sqlite3_blob_bytes(self->blob));
-    assert(offset <= sqlite3_blob_bytes(self->blob) - self->offset);
+    assert(offset <= sqlite3_blob_bytes(self->blob));
 
     PyObject *buffer = PyBytes_FromStringAndSize(NULL, length);
     if (buffer == NULL) {
@@ -188,13 +188,13 @@ inner_write(pysqlite_Blob *self, const void *buf, Py_ssize_t len,
             Py_ssize_t offset)
 {
     int blob_len = sqlite3_blob_bytes(self->blob);
-    int remaining_len = blob_len - self->offset;
+    int remaining_len = blob_len - offset;
     if (len > remaining_len) {
         PyErr_SetString(PyExc_ValueError, "data longer than blob length");
         return -1;
     }
 
-    assert(offset <= remaining_len);
+    assert(offset <= blob_len);
     int rc;
     Py_BEGIN_ALLOW_THREADS
     rc = sqlite3_blob_write(self->blob, buf, (int)len, (int)offset);