shared: add unaligned.h

The file, imported from systemd sources, contains macros for accessing
potentially unaligned data in a safe way (i.e. byte-wise).

Makefile.am

@@ -102,6 +102,7 @@ EXTRA_DIST = \
 	shared/nm-utils/nm-vpn-plugin-macros.h \
 	shared/nm-utils/nm-vpn-plugin-utils.c \
 	shared/nm-utils/nm-vpn-plugin-utils.h \
+	shared/nm-utils/unaligned.h \
 	shared/nm-version-macros.h.in \
 	\
 	$(NULL)

shared/nm-utils/unaligned.h

@@ -0,0 +1,129 @@
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Tom Gundersen
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <endian.h>
+#include <stdint.h>
+
+/* BE */
+
+static inline uint16_t unaligned_read_be16(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint16_t) u[0]) << 8) |
+                ((uint16_t) u[1]);
+}
+
+static inline uint32_t unaligned_read_be32(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint32_t) unaligned_read_be16(u)) << 16) |
+                ((uint32_t) unaligned_read_be16(u + 2));
+}
+
+static inline uint64_t unaligned_read_be64(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint64_t) unaligned_read_be32(u)) << 32) |
+                ((uint64_t) unaligned_read_be32(u + 4));
+}
+
+static inline void unaligned_write_be16(void *_u, uint16_t a) {
+        uint8_t *u = _u;
+
+        u[0] = (uint8_t) (a >> 8);
+        u[1] = (uint8_t) a;
+}
+
+static inline void unaligned_write_be32(void *_u, uint32_t a) {
+        uint8_t *u = _u;
+
+        unaligned_write_be16(u, (uint16_t) (a >> 16));
+        unaligned_write_be16(u + 2, (uint16_t) a);
+}
+
+static inline void unaligned_write_be64(void *_u, uint64_t a) {
+        uint8_t *u = _u;
+
+        unaligned_write_be32(u, (uint32_t) (a >> 32));
+        unaligned_write_be32(u + 4, (uint32_t) a);
+}
+
+/* LE */
+
+static inline uint16_t unaligned_read_le16(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint16_t) u[1]) << 8) |
+                ((uint16_t) u[0]);
+}
+
+static inline uint32_t unaligned_read_le32(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint32_t) unaligned_read_le16(u + 2)) << 16) |
+                ((uint32_t) unaligned_read_le16(u));
+}
+
+static inline uint64_t unaligned_read_le64(const void *_u) {
+        const uint8_t *u = _u;
+
+        return (((uint64_t) unaligned_read_le32(u + 4)) << 32) |
+                ((uint64_t) unaligned_read_le32(u));
+}
+
+static inline void unaligned_write_le16(void *_u, uint16_t a) {
+        uint8_t *u = _u;
+
+        u[0] = (uint8_t) a;
+        u[1] = (uint8_t) (a >> 8);
+}
+
+static inline void unaligned_write_le32(void *_u, uint32_t a) {
+        uint8_t *u = _u;
+
+        unaligned_write_le16(u, (uint16_t) a);
+        unaligned_write_le16(u + 2, (uint16_t) (a >> 16));
+}
+
+static inline void unaligned_write_le64(void *_u, uint64_t a) {
+        uint8_t *u = _u;
+
+        unaligned_write_le32(u, (uint32_t) a);
+        unaligned_write_le32(u + 4, (uint32_t) (a >> 32));
+}
+
+#if __BYTE_ORDER == __BIG_ENDIAN
+#define unaligned_read_ne16 unaligned_read_be16
+#define unaligned_read_ne32 unaligned_read_be32
+#define unaligned_read_ne64 unaligned_read_be64
+
+#define unaligned_write_ne16 unaligned_write_be16
+#define unaligned_write_ne32 unaligned_write_be32
+#define unaligned_write_ne64 unaligned_write_be64
+#else
+#define unaligned_read_ne16 unaligned_read_le16
+#define unaligned_read_ne32 unaligned_read_le32
+#define unaligned_read_ne64 unaligned_read_le64
+
+#define unaligned_write_ne16 unaligned_write_le16
+#define unaligned_write_ne32 unaligned_write_le32
+#define unaligned_write_ne64 unaligned_write_le64
+#endif