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


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


     #include <endian.h>
     uint16_t htobe16(uint16_t host_16bits);
     uint16_t htole16(uint16_t host_16bits);
     uint16_t be16toh(uint16_t big_endian_16bits);
     uint16_t le16toh(uint16_t little_endian_16bits);
     uint32_t htobe32(uint32_t host_32bits);
     uint32_t htole32(uint32_t host_32bits);
     uint32_t be32toh(uint32_t big_endian_32bits);
     uint32_t le32toh(uint32_t little_endian_32bits);
     uint64_t htobe64(uint64_t host_64bits);
     uint64_t htole64(uint64_t host_64bits);
     uint64_t be64toh(uint64_t big_endian_64bits);
     uint64_t le64toh(uint64_t little_endian_64bits);
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     htobe16(),   htole16(),  be16toh(),  le16toh(),  htobe32(),  htole32(),
     be32toh(), le32toh(), htobe64(), htole64(), be64toh(), le64toh():
         Since glibc 2.19:
         In glibc up to and including 2.19:


     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.


     These functions were added to glibc in version 2.9.


     These  functions are nonstandard.  Similar functions are present on the
     BSDs, where the required  header  file  is  <sys/endian.h>  instead  of
     <endian.h>.  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").


     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.


     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  <endian.h>  #include <stdint.h> #include <stdio.h> #include
     int main(int argc, char *argv[]) {
         union {
             uint32_t u32;
             uint8_t 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(EXIT_SUCCESS); }


     bswap(3), byteorder(3)


     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at

GNU 2017-09-15 ENDIAN(3)

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