ENDIAN(3) Linux Programmer's Manual ENDIAN(3)

NAME
       htobe16, htole16, be16toh, le16toh, htobe32, htole32, be32toh, le32toh,
       htobe64, htole64, be64toh, le64toh - convert values  between  host  and
       big-/little-endian byte order

SYNOPSIS
       #define BSDSOURCE             /* See featuretestmacros(7) */
       #include 

       uint16t htobe16(uint16t host16bits);
       uint16t htole16(uint16t host16bits);
       uint16t be16toh(uint16t bigendian16bits);
       uint16t le16toh(uint16t littleendian16bits);

       uint32t htobe32(uint32t host32bits);
       uint32t htole32(uint32t host32bits);
       uint32t be32toh(uint32t bigendian32bits);
       uint32t le32toh(uint32t littleendian32bits);

       uint64t htobe64(uint64t host64bits);
       uint64t htole64(uint64t host64bits);
       uint64t be64toh(uint64t bigendian64bits);
       uint64t le64toh(uint64t littleendian64bits);

DESCRIPTION
       These  functions  convert  the byte encoding of integer values from the
       byte order that the current CPU (the "host") uses, to and from  little-
       endian and big-endian byte order.

       The  number,  nn,  in  the  name of each function indicates the size of
       integer handled by the function, either 16, 32, or 64 bits.

       The functions with names of the form "htobenn" convert from  host  byte
       order to big-endian order.

       The  functions  with names of the form "htolenn" convert from host byte
       order to little-endian order.

       The functions with names of the form "benntoh" convert from  big-endian
       order to host byte order.

       The  functions  with  names  of the form "lenntoh" convert from little-
       endian order to host byte order.

VERSIONS
       These functions were added to glibc in version 2.9.

CONFORMING TO
       These functions are nonstandard.  Similar functions are present on  the
       BSDs,  where  the  required  header  file  is  instead of
       .  Unfortunately, NetBSD, FreeBSD, and glibc haven't followed
       the original OpenBSD naming convention for these functions, whereby the
       nn component always appears at the end of the function name (thus,  for
       example,  in  NetBSD,  FreeBSD,  and  glibc, the equivalent of OpenBSDs
       "betoh32" is "be32toh").

NOTES
       These functions are similar to the older byteorder(3) family  of  func‐
       tions.  For example, be32toh() is identical to ntohl().

       The  advantage  of the byteorder(3) functions is that they are standard
       functions available on all UNIX systems.  On the other hand,  the  fact
       that  they  were  designed  for use in the context of TCP/IP means that
       they lack the 64-bit and little-endian variants described in this page.

EXAMPLE
       The program below display the results of  converting  an  integer  from
       host byte order to both little-endian and big-endian byte order.  Since
       host byte order is either little-endian  or  big-endian,  only  one  of
       these  conversions  will have an effect.  When we run this program on a
       little-endian system such as x86-32, we see the following:

           $ ./a.out
           x.u32 = 0x44332211
           htole32(x.u32) = 0x44332211
           htobe32(x.u32) = 0x11223344

   Program source

       #include 
       #include 
       #include 
       #include 

       int
       main(int argc, char *argv[])
       {
           union {
            uint32t u32;
            uint8t arr[4];
           } x;

           x.arr[0] = 0x11;     /* Lowest-address byte */
           x.arr[1] = 0x22;
           x.arr[2] = 0x33;
           x.arr[3] = 0x44;     /* Highest-address byte */

           printf("x.u32 = 0x%x\n", x.u32);
           printf("htole32(x.u32) = 0x%x\n", htole32(x.u32));
           printf("htobe32(x.u32) = 0x%x\n", htobe32(x.u32));

           exit(EXITSUCCESS);
       }

SEE ALSO
       byteorder(3)

COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2010-09-10                         ENDIAN(3)