.\" header.tmac. GetData manual macros. .\" .\" Copyright (C) 2016 D. V. Wiebe .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .\" This file is part of the GetData project. .\" .\" Permission is granted to copy, distribute and/or modify this document .\" under the terms of the GNU Free Documentation License, Version 1.2 or .\" any later version published by the Free Software Foundation; with no .\" Invariant Sections, with no Front-Cover Texts, and with no Back-Cover .\" Texts. 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The gd_alter_frameoffset man page. .\" .\" man/gd_alter_frameoffset.3in. Generated from gd_alter_frameoffset.3in.in by configure. .\" .\" Copyright (C) 2008, 2010, 2014, 2016 D. V. Wiebe .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .\" This file is part of the GetData project. .\" .\" Permission is granted to copy, distribute and/or modify this document .\" under the terms of the GNU Free Documentation License, Version 1.2 or .\" any later version published by the Free Software Foundation; with no .\" Invariant Sections, with no Front-Cover Texts, and with no Back-Cover .\" Texts. A copy of the license is included in the `COPYING.DOC' file .\" as part of this distribution. .\" .TH gd_alter_frameoffset 3 "25 December 2016" "Version 0.10.0" "GETDATA" .SH NAME gd_alter_frameoffset \(em modify the starting frame of fields in a Dirfile .SH SYNOPSIS .SC .B #include .HP .BI "int gd_alter_frameoffset(DIRFILE *" dirfile ", off_t " offset , .BI "int " fragment_index ", int " recode ); .EC .SH DESCRIPTION The .FN gd_alter_frameoffset function sets the frame offset of the format specification fragment given by .ARG fragment_index to .ARG offset in the dirfile(5) database specified by .ARG dirfile . The frame offset of a fragment indicate the frame number of the first sample of data stored in binary files associated with .B RAW fields defined in the specified fragment. The frame offset of a fragment containing no .B RAW fields is ignored. The frame offset may not be negative. The .ARG dirfile argument must point to a valid DIRFILE object previously created by a call to .F3 gd_open . In addition to being simply a valid fragment index, .ARG fragment_index may also be the special value .BR GD_ALL_FRAGMENTS , which indicates that the frame offset of all fragments in the database should be changed. If the .ARG recode argument is non-zero, this call will shift the binary data of affected .B RAW fields to account 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 affected .B RAW fields is reset to the beginning-of-frame. If .ARG recode is zero, affected binary files are left untouched. .SH RETURN VALUE Upon successful completion, .FN gd_alter_frameoffset returns zero. On error, it returns a negative-valued error code. Possible error codes are: .DD GD_E_ACCMODE The specified dirfile was opened read-only. .DD GD_E_ALLOC The library was unable to allocate memory. .DD GD_E_BAD_DIRFILE The supplied dirfile was invalid. .DD GD_E_BAD_INDEX The supplied index was out of range. .DD GD_E_IO An I/O error occurred while attempting to shift a binary file. .DD 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. .DD GD_E_RANGE The supplied offset was less than zero. .DD 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 .B NOTES section below for recovery instructions. In this case, the dirfile will be flagged as invalid, to prevent further database corruption. It should be immediately closed. .DD GD_E_UNKNOWN_ENCODING The encoding scheme of the fragment is unknown. .DD GD_E_UNSUPPORTED The encoding scheme of the fragment does not support binary file shifting. .PP The error code is also stored in the .B DIRFILE object and may be retrieved after this function returns by calling .F3 gd_error . A descriptive error string for the error may be obtained by calling .F3 gd_error_string . .SH 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 .B RAW fields in the fragment both before and after translation. If all fragments are updated by specifying .BR GD_ALL_FRAGMENTS , the shifting occurs one fragment at a time. An error code of .B 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 continuing. For recovery instructions, see the file /usr/share/doc/getdata/unclean_database_recovery.txt. .SH HISTORY The function .FN dirfile_alter_frameoffset appeared in GetData-0.5.0. In GetData-0.7.0, this function was renamed to .FN gd_alter_frameoffset . in GetData-0.10.0, the error return from this function changed from -1 to a negative-valued error code. .SH SEE ALSO .F3 gd_open , .F3 gd_error , .F3 gd_error_string , .F3 gd_frameoffset , dirfile(5), dirfile-format(5)