NAME

       gd_alter_frameoffset — modify the starting frame of fields in a Dirfile

SYNOPSIS

       #include <getdata.h>

       int gd_alter_frameoffset(DIRFILE *dirfile, off_t offset, int fragment_index, int recode);

DESCRIPTION

       The  gd_alter_frameoffset()  function sets the frame offset of the format specification fragment given by
       fragment_index to offset in the dirfile(5) database specified by dirfile.  The frame offset of a fragment
       indicate the frame number of the first sample of data stored in binary files associated with  RAW  fields
       defined  in  the specified fragment.  The frame offset of a fragment containing no RAW fields is ignored.
       The frame offset may not be negative.

       The dirfile argument must point to a valid DIRFILE object previously created by a call to gd_open(3).

       In addition to being simply a valid  fragment  index,  fragment_index  may  also  be  the  special  value
       GD_ALL_FRAGMENTS,  which  indicates  that  the  frame  offset  of all fragments in the database should be
       changed.

       If the recode argument is non-zero, this call will shift the binary data of affected RAW  fields  to  ac‐
       count  for the change in frame offset.  If the new frame offset is larger than the old frame offset, this
       will result in permanent deletion of data from the database.  If the new frame offset is smaller than the
       old frame offset, the binary file will be padded at the front with zeroes.  The I/O pointer  of  all  af‐
       fected RAW fields is reset to the beginning-of-frame.

       If recode is zero, affected binary files are left untouched.

RETURN VALUE

       Upon  successful completion, gd_alter_frameoffset() returns zero.  On error, it returns a negative-valued
       error code.  Possible error codes are:

       GD_E_ACCMODE
               The specified dirfile was opened read-only.

       GD_E_ALLOC
               The library was unable to allocate memory.

       GD_E_BAD_DIRFILE
               The supplied dirfile was invalid.

       GD_E_BAD_INDEX
               The supplied index was out of range.

       GD_E_IO An I/O error occurred while attempting to shift a binary file.

       GD_E_PROTECTED
               The metadata of the given format specification fragment was protected from change, or the  binary
               data of the fragment was protected from change and binary file shifting was requested.

       GD_E_RANGE
               The supplied offset was less than zero.

       GD_E_UNCLEAN_DB
               An  error occurred while moving the shifted file into place.  As a result, the database may be in
               an unclean state.  See the NOTES section below for recovery  instructions.   In  this  case,  the
               dirfile will be flagged as invalid, to prevent further database corruption.  It should be immedi‐
               ately closed.

       GD_E_UNKNOWN_ENCODING
               The encoding scheme of the fragment is unknown.

       GD_E_UNSUPPORTED
               The encoding scheme of the fragment does not support binary file shifting.

       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

       A binary file shift occurs out-of-place.  As a result, sufficient space must be present on the filesystem
       for  the  binary files of all RAW fields in the fragment both before and after translation.  If all frag‐
       ments are updated by specifying GD_ALL_FRAGMENTS, the shifting occurs one fragment at a time.

       An error code of GD_E_UNCLEAN_DB indicates a system error occurred while moving the shifted  binary  data
       into place or when deleting the old data.  If this happens, the database may be left in an unclean state.
       The caller should check the filesystem directly to ascertain the state of the dirfile data before contin‐
       uing.  For recovery instructions, see the file /usr/share/doc/getdata/unclean_database_recovery.txt.

HISTORY

       The function dirfile_alter_frameoffset() appeared in GetData-0.5.0.

       In GetData-0.7.0, this function was renamed to gd_alter_frameoffset().

       in GetData-0.10.0, the error return from this function changed from -1 to a negative-valued error code.

SEE ALSO

       gd_open(3), gd_error(3), gd_error_string(3), gd_frameoffset(3), dirfile(5), dirfile-format(5)

Version 0.10.0                                  25 December 2016                         gd_alter_frameoffset(3)