1 files changed, 43 insertions, 0 deletions
diff --git a/circuitpython/shared/runtime/buffer_helper.c b/circuitpython/shared/runtime/buffer_helper.c
new file mode 100644
index 0000000..facd05e
--- /dev/null
+++ b/circuitpython/shared/runtime/buffer_helper.c
@@ -0,0 +1,43 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "shared/runtime/buffer_helper.h"
+
+void normalize_buffer_bounds(int32_t *start, int32_t end, size_t *length) {
+    if (end < 0) {
+        end += *length;
+    } else if (((size_t)end) > *length) {
+        end = *length;
+    }
+    if (*start < 0) {
+        *start += *length;
+    }
+    if (end < *start) {
+        *length = 0;
+    } else {
+        *length = end - *start;
+    }
+}