NAME

       cap_copy_ext, cap_size, cap_copy_int - capability state external representation translation

SYNOPSIS

       #include <sys/capability.h>

       ssize_t cap_size(cap_t cap_p);
       ssize_t cap_copy_ext(void *ext_p, cap_t cap_p, ssize_t size);
       cap_t cap_copy_int(const void * ext_p);

       Link with -lcap.

DESCRIPTION

       These  functions  translate  between  internal  and  external representations of a capability state.  The
       external representation is an exportable, contiguous, persistent representation of a capability state  in
       user-managed  space.   The  internal  representation  is  managed  by the capability functions in working
       storage.

       cap_size() returns the total length (in bytes) that the capability state in working storage identified by
       cap_p would require when converted by cap_copy_ext().  This function is used primarily to  determine  the
       amount  of  buffer  space  that  must  be  provided  to  the cap_copy_ext() function in order to hold the
       capability data record created from cap_p.

       cap_copy_ext() copies a capability state in working storage, identified  by  cap_p,  from  system-managed
       space  to  user-managed  space (pointed to by ext_p) and returns the length of the resulting data record.
       The size  parameter  represents  the  maximum  size,  in  bytes,  of  the  resulting  data  record.   The
       cap_copy_ext()  function  will  do  any  conversions  necessary  to convert the capability state from the
       undefined internal format to an exportable, contiguous, persistent data record.  It is the responsibility
       of the user to allocate a buffer large enough to hold the copied data.  The  buffer  length  required  to
       hold the copied data may be obtained by a call to the cap_size() function.

       cap_copy_int()  copies  a  capability  state from a capability data record in user-managed space to a new
       capability state in working storage, allocating any memory necessary, and  returning  a  pointer  to  the
       newly  created  capability  state.   The  function  initializes  the capability state and then copies the
       capability state from the record pointed to by ext_p into the capability state, converting, if necessary,
       the data from a contiguous, persistent format  to  an  undefined,  internal  format.   Once  copied  into
       internal  format,  the  object  can  be  manipulated  by the capability state manipulation functions (see
       cap_clear(3)).  Note that the record pointed to by  ext_p  must  have  been  obtained  from  a  previous,
       successful  call  to  cap_copy_ext()  for this function to work successfully.  The caller should free any
       releasable memory, when the capability state in  working  storage  is  no  longer  required,  by  calling
       cap_free() with the cap_t as an argument.

RETURN VALUE

       cap_size() returns the length required to hold a capability data record on success, and -1 on failure.

       cap_copy_ext()  returns  the  number  of  bytes  placed  in the user managed space pointed to by ext_p on
       success, and -1 on failure.

       cap_copy_int() returns a pointer to the newly created capability state in working storage on success, and
       NULL on failure.

       On failure, errno is set to EINVAL, ENOMEM, or ERANGE.

CONFORMING TO

       These functions are specified in the withdrawn POSIX.1e draft specification.

SEE ALSO

       libcap(3), cap_clear(3), cap_from_text(3), cap_get_file(3), cap_get_proc(3), cap_init(3), capabilities(7)

                                                   2021-03-06                                    CAP_COPY_EXT(3)