NAME¶

gd_alter_endianness — modify the byte sex of fields in a dirfile

SYNOPSIS¶

#include <getdata.h>

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

RETURN VALUE¶

Upon successful completion, gd_alter_endianness() returns zero. On error, it returns -1 and sets the dirfile error to a non-zero error value. Possible error values 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_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_RAW_IO

An I/O error occurred while attempting to byte swap a binary file.

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 dirfile error may be retrieved by calling gd_error(3). A descriptive error string for the last error encountered can be obtained from a call to 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/share/doc/getdata/unclean_database_recovery.txt.

SEE ALSO¶

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