gd_alter_spec(3)

NAME
gd_alter_spec, gd_malter_spec — modify a field in a dirfile

SYNOPSIS
#include <getdata.h>

int gd_alter_spec(DIRFILE *dirfile, const char *line, int recode);

int gd_malter_spec(DIRFILE *dirfile, const char *line, const char *parent, int recode);

DESCRIPTION
The gd_alter_spec() function modifies the field described by the field specification line in line to the dirfile specified by dirfile. The gd_malter_spec() function behaves similarly, but modifies the metafield under the field indicated by the field code parent. Field specification lines are described in detail in dirfile-format(5).

The name of the field to be modified, which must already exist, will be obtained from the field specification line. When adding a metafield, line should only contain a field specification, and not a /META directive.

If the modified field is of type RAW and the recode argument is non-zero, the binary file associated with the field will be converted for changes in data type and samples-per-frame. In this case, the field's I/O pointer will be reset to the beginning-of-frame. If recode is zero, no binary file conversion will take place.

If the modified field is of type LINTERP and the recode argument is non-zero, the look-up table file will be moved if line specifies a different path, overwriting an existing file with the new pathname, if present. If the field specified by field_code is of type other than RAW or LINTERP, the recode argument is ignored.

Passing these functions a directive line instead of a field specification line will result in a syntax error. These functions never call the registered parser callback function, even if line contains a syntax error.

RETURN VALUE
On success, gd_alter_spec() and gd_malter_spec() return zero. On error, -1 is returned and the dirfile error is set 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_CODE
    The field specified in line was not found, or the parent field code was not found.

GD_E_BAD_DIRFILE
    The supplied dirfile was invalid.

GD_E_FORMAT
    A syntax error was encountered in line.

GD_E_IO
    An I/O error occurred while translating the binary file associated with a modified RAW field, or an I/O error occurred while attempting to rename a LINTERP table file.

GD_E_LINE_TOO_LONG
    The supplied line was longer than the parser was able to deal with. Lines are limited by the storage size of ssize_t. On 32-bit systems, this limits line to 2**31 bytes. The limit is larger on 64-bit systems.

GD_E_PROTECTED
    The metadata of the fragment was protected from change. Or, a request to translate the binary file associated with a RAW field was attempted, but the data of the fragment was protected.

GD_E_UNKNOWN_ENCODING
    The encoding scheme of the indicated format specification fragment is not known to the library. As a result, the library was unable to translate the binary file be associated with a modified RAW field.

GD_E_UNSUPPORTED
    The encoding scheme of the indicated format specification fragment does not support translating the empty binary file associated with a modified RAW field.

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).

SEE ALSO
gd_alter_bit(3), gd_alter_const(3), gd_alter_entry(3), gd_alter_lincom(3), gd_alter_linterp(3), gd_alter_multiply(3), gd_alter_phase(3), gd_alter_raw(3), gd_alter_spec(3), gd_metaflush(3), gd_open(3), gd_error(3), gd_error_string(3), dirfile-format(5)