You can use the macros defined in kernel.h:
http://www.bruceblinn.com/linuxinfo/ByteOrder.html
The following macros return the value after it has been converted. Note: the linux/kernel.h header file is the header file that should be included in the source files where these macros are used, but it is not the header file where the macros are actually defined.
#include <linux/kernel.h>
__u16 le16_to_cpu(const __le16);
__u32 le32_to_cpu(const __le32);
__u64 le64_to_cpu(const __le64);
__le16 cpu_to_le16(const __u16);
__le32 cpu_to_le32(const __u32);
__le64 cpu_to_le64(const __u64);
__u16 be16_to_cpu(const __be16);
__u32 be32_to_cpu(const __be32);
__u64 be64_to_cpu(const __be64);
__be16 cpu_to_be16(const __u16);
__be32 cpu_to_be32(const __u32);
__be64 cpu_to_be64(const __u64);