diff --git a/portability/endian.h b/portability/endian.h
new file mode 100644
index 0000000..a9cc380
--- /dev/null
+++ b/portability/endian.h
@@ -0,0 +1,61 @@
+/* endian.h - portable endian routines
+ *
+ * Copyright (C) 2005-2008 Natanael Copa <n@tanael.org>
+ * Copyright (C) 2008-2011 Timo Teräs <timo.teras@iki.fi>
+ * Copyright (C) 2011 Rich Felker
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#ifdef __linux__
+# include_next <endian.h>
+#else
+
+#pragma once
+#include <stdint.h>
+
+static __inline uint16_t __portable_bswap16(uint16_t __x)
+{
+	return (__x<<8) | (__x>>8);
+}
+
+static __inline uint32_t __portable_bswap32(uint32_t __x)
+{
+	return (__x>>24) | (__x>>8&0xff00) | (__x<<8&0xff0000) | (__x<<24);
+}
+
+static __inline uint64_t __portable_bswap64(uint64_t __x)
+{
+	return (__portable_bswap32(__x)+0ULL)<<32 | __portable_bswap32(__x>>32);
+}
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+# define htobe16(x) __portable_bswap16(x)
+# define be16toh(x) __portable_bswap16(x)
+# define htobe32(x) __portable_bswap32(x)
+# define be32toh(x) __portable_bswap32(x)
+# define htobe64(x) __portable_bswap64(x)
+# define be64toh(x) __portable_bswap64(x)
+# define htole16(x) (uint16_t)(x)
+# define le16toh(x) (uint16_t)(x)
+# define htole32(x) (uint32_t)(x)
+# define le32toh(x) (uint32_t)(x)
+# define htole64(x) (uint64_t)(x)
+# define le64toh(x) (uint64_t)(x)
+#else
+# define htobe16(x) (uint16_t)(x)
+# define be16toh(x) (uint16_t)(x)
+# define htobe32(x) (uint32_t)(x)
+# define be32toh(x) (uint32_t)(x)
+# define htobe64(x) (uint64_t)(x)
+# define be64toh(x) (uint64_t)(x)
+# define htole16(x) __portable_bswap16(x)
+# define le16toh(x) __portable_bswap16(x)
+# define htole32(x) __portable_bswap32(x)
+# define le32toh(x) __portable_bswap32(x)
+# define htole64(x) __portable_bswap64(x)
+# define le64toh(x) __portable_bswap64(x)
+#endif
+
+#endif