basic: add unaligned macros for little endian

Also add test code for that.

src/basic/unaligned.h

@@ -21,8 +21,11 @@
   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;
 
@@ -64,3 +67,47 @@ static inline void unaligned_write_be64(void *_u, uint64_t a) {
         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));
+}