NAME

       gd_open_limit — set a Dirfile's allowed number of open files

SYNOPSIS

       #include <getdata.h>

       long gd_open_limit(DIRFILE *dirfile, long limit);

DESCRIPTION

       The  gd_open_limit()  function  can  be  used  to  limit the number of RAW file descriptors which GetData
       simultaneously holds open in the open dirfile(5) database specified by dirfile.  This function  can  also
       be  used  to  report the current number of open files, or the current limit.  When limiting is active, to
       stay below the limit, GetData will automatically close the least recently  accessed  RAW  fields  (as  if
       gd_raw_close(3) were called), when needed.

       The  default  value  for  the limit is zero, indicating that limiting is disabled.  In this case, GetData
       will never automatically close open RAW fields.  To enable limiting call this function  with  a  positive
       value  for  limit.   If  limited, the minimum limit is two; if this function is passed a limit of one, it
       will behave as if the value 2 were passed instead.

       When setting a limit, this function will  immediately  close  enough  RAW  fields  to  remain  below  the
       specified limit.

       The argument limit may alternately be one of the following special values:

       GD_OLIMIT_NONE (=0)
               Disable limiting, if it was previously active.

       GD_OLIMIT_CURRENT
               Do nothing other than report the current limit.  This is equivalent to calling this function with
               limit equal to the current limit.

       GD_OLIMIT_COUNT
               Instead of returning the current limit, return the current  number  filed  descriptors  for  this
               dirfile.  The current limit is not changed.

RETURN VALUE

       If  limit  is  GD_OLIMIT_COUNT,  then  the  current  number of file descriptors in use by this dirfile is
       returned, or zero if limiting is disabled (i.e. the limit is zero).

       For other values of limit, if successful, this function returns the  open  field  limit,  after  possibly
       modifying it.  This limit is never negative.  It will be zero if limiting is disabled.

       If  limit  is  one of the special values GD_OLIMIT_COUNT, GD_OLIMIT_CURRENT, or GD_OLIMIT_NONE (=0), then
       this function always succeeds.  Otherwise, on error,  gd_open_limit()  returns  a  negative-valued  error
       code.  Possible error codes are:

       GD_E_ALLOC
               The library was unable to allocate memory.

       GD_E_BAD_DIRFILE
               The supplied dirfile was invalid.

       GD_E_IO An  I/O  error occurred while trying to write modified data to disk as a result in a reduction of
               the open field limit.

       The error code is also stored in the DIRFILE object and may be retrieved after this function  returns  by
       calling   gd_error(3).    A   descriptive  error  string  for  the  error  may  be  obtained  by  calling
       gd_error_string(3).

NOTES

       The file descriptors tracked by this functionality are only those associated with RAW  fields  which  are
       held open across function calls.  During the course of any library call, GetData may temporarily exceed a
       file descriptor limit set with this function without triggering an automatic  close.   Some  headroom  is
       always a good idea.

       Furthermore,  this  limit  is  specific to the specified dirfile.  It is not a global limit for the whole
       GetData library.  If a process has multiple DIRFILEs open,  each  of  them  has  its  own  limit  (or  is
       unlimited), even though they all draw from the same limited pool of file descriptors.

       In  some cases, usually when writing to a compressed RAW field, two file descriptors may be held open for
       a single field.

HISTORY

       The gd_open_limit() function appeared in GetData-0.11.0.

SEE ALSO

       gd_error(3), gd_error_string(3), gd_open(3), gd_raw_close(3), getrlimit(3), ulimit(3), dirfile(5)