Special case read with length zero

Author: erlend-aasland

Modules/_sqlite/blob.c

@@ -139,7 +139,7 @@ static PyObject *
 read_multiple(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));
+    assert(offset < sqlite3_blob_bytes(self->blob));
 
     PyObject *buffer = PyBytes_FromStringAndSize(NULL, length);
     if (buffer == NULL) {
@@ -191,6 +191,11 @@ blob_read_impl(pysqlite_Blob *self, int length)
         length = max_read_len;
     }
 
+    assert(length >= 0);
+    if (length == 0) {
+        return PyBytes_FromStringAndSize(NULL, 0);
+    }
+
     PyObject *buffer = read_multiple(self, length, self->offset);
     if (buffer == NULL) {
         return NULL;