gd_alter_endianness(3)

NAME

gd_alter_endianness—modify the byte sex of fields in a Dirfile

SYNOPSIS

#include <getdata.h>

int gd_alter_endianness(DIRFILE *dirfile, unsigned long byte_sex, int fragment_index, int recode);

DESCRIPTION

The gd_alter_endianness() function sets the byte sex of the format specification fragment given by fragment_index to byte_sex in the dirfile(5) database specified by dirfile. The byte sex of a fragment indicate the endianness of data stored in binary files associated with RAW fields defined in the specified fragment. The byte sex of a fragment containing no RAW fields is ignored.

The byte_sex argument should be one of the following:

0 (zero): Indicating that the byte sex should be the native endianness of the host, whichever that may be.
GD_BIG_ENDIAN: Indicating that the byte sex should be big endian.
GD_LITTLE_ENDIAN: Indicating that the byte sex should be little endian.
(GD_BIG_ENDIAN | GD_LITTLE_ENDIAN): Indicating that the byte sex should be the opposite of the native endianness of the host, whichever that may be.

Furthermore, any of these may be bitwise or'd with GD_ARM_ENDIAN or GD_NOT_ARM_ENDIAN indicating that the floating point data are stored in the ARM middle-endian format.

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

If the recode argument is non-zero, this call will byte swap the binary data of affected RAW fields to account for the change in byte sex. If the encoding of the fragment is endianness insensitive, or if the data type is only one byte in size, no change is made. The I/O pointer of all affected 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_endianness() 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_ARGUMENT: The supplied byte_sex was invalid.
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 byte swap a binary file.
GD_E_PROTECTED: The metadata of the indicated format specification fragment was protected from change, or the binary data of the fragment was protected from change and binary file byte swapping was requested.
GD_E_UNCLEAN_DB: An error occurred while moving the byte-swapped 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 immediately 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 byte swapping.

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 byte swap 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 fragments are updated by specifying GD_ALL_FRAGMENTS, the byte swapping occurs one fragment at a time.

An error code of GD_E_UNCLEAN_DB indicates a system error occurred while moving the byte-swapped 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/local/share/doc/getdata/unclean_database_recovery.txt.

HISTORY

The function dirfile_alter_endianness() appeared in GetData-0.5.0.

In GetData-0.7.0, this function was renamed to gd_alter_endianness(). The GD_E_ARM_ENDIAN and GD_NOT_ARM_ENDIAN flags also appeared in this version.

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