gd_alter_encoding(3)

NAME

gd_alter_encoding—modify the binary encoding of data in a Dirfile

SYNOPSIS

#include <getdata.h>

int gd_alter_encoding(DIRFILE *dirfile, unsigned int encoding, int fragment_index, int recode);

DESCRIPTION

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

The encoding argument should be one of the following symbols:

GD_UNENCODED, GD_BZIP2_ENCODED, GD_FLAC_ENCODED, GD_GZIP_ENCODED, GD_LZMA_ENCODED, GD_SLIM_ENCODED, GD_SIE_ENCODED, GD_TEXT_ENCODED.

See gd_open(3) and dirfile-encoding(5) for the meanings of these symbols and details on the supported encoding schemes.

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

If the recode argument is non-zero, this call will recode the binary data of affected RAW fields to account for the change in binary encoding. If the encoding of the fragment is encoding 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_encoding() 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 recode 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 recoding was requested.
GD_E_UNCLEAN_DB: An error occurred while moving the recoded 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 recoding.

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 recoding 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 recoding occurs one fragment at a time.

An error code of GD_E_UNCLEAN_DB indicates a system error occurred while moving the re-encoded 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_encoding() appeared in GetData-0.5.0.

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

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