Provided by: libgetdata-dev_0.7.3-6_i386
gd_alter_entry — modify the metadata of a dirfile field
int gd_alter_entry(DIRFILE *dirfile, const char *field_code, const
gd_entry_t *entry, int recode);
The gd_alter_entry() function modifies the field specified by
field_code in the dirfile specified by dirfile to correspond to the new
parameters specified by entry. In addition to specifying a regular
field, field_code may also refer to a metafield by specifying it using
its full (slashed) field code. However, field_code should never
contain a representation suffix.
The form of entry is described in detail in the get_entry(3) man page.
The entry->field and entry->fragment_index members are ignored by this
function and need not be initialised. All other members appropriate to
the field type of field_code should be initialised, except as noted
below. To change the fragment index of a field, use gd_move(3). To
change the name of a field, use gd_rename(3).
If field_code specifies a RAW field 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. If recode is zero, no
binary file conversion will take place.
If field_code specifies a LINTERP field and the recode argument is non-
zero, the look-up table file will be moved if entry->table specifies a
different path. If a file with the new pathname already exists, it
will be overwritten. If the field specified by field_code is of type
other than RAW or LINTERP, the recode argument is ignored.
If field_code specified a LINCOM or POLYNOM field, the value of
entry->comp_scal indicates whether the purely real scalar lists
(entry->a, or entry->b and entry->m) or the complex valued lists
(entry->ca, or entry->cb and entry->cm) will be used. The unused
counterparts need not be initialised.
The entry->field_type member must correspond to the field type of
field_code. This interface cannot be used to change the type of a
given field. To do so, delete the old field first with gd_delete(3),
and then create a new field of the desired type with gd_add(3).
Some field parameters have special values which indicate no change
should be made to the parameter. Specifically, if any of the string
parameters, or the parameters
(entry->a, entry->b, entry->m, entry->ca, entry->cb, or entry->cm) are
NULL, the old values will be retained. Similarly, if entry->spf,
entry->n_fields, or entry->numbits is zero, or if entry->bitnum is -1,
or if entry->data_type, or entry->const_type are equal to GD_NULL,
these parameters will not be modified.
All entry->scalar elements relevant for the given field type must be
initialised to one of the following values:
· a pointer to a field code indicating a new scalar field to be used
for the corresponding field parameter. If the parameter was
previously a literal number, it will be replaced by the specified
field code. If the parameter was previously a field code, the new
field code will replace the old one. If the field code specifies a
CARRAY field, the corresponding entry->scalar_ind element should
also be set.
· a pointer the empty string (""). In this case, no change is made
to the field code for the corresponding field parameter: if one
already existed, it is kept, otherwise the corresponding literal
numerical parameter is used. If the value of the corresponding
numerical entry member is the special value listed above indicating
no change, no change is made to the field parameter at all.
· the NULL pointer. If the corresponding field parameter was
previously a field code, the field code will be deleted and a
literal number used instead. In the special case when a scalar
element is NULL and the corresponding numerical entry member
contains a special value indicating no change listed above, GetData
will de-reference the previous field code value and convert it into
a literal number before removing the field code from the entry.
On success, gd_alter_entry() returns zero. On error, -1 is returned
and the dirfile error is set to a non-zero error value. Possible error
The specified dirfile was opened read-only.
The library was unable to allocate memory.
The field specified by field_code was not found. This error
may also result from attempting to dereference a scalar field
code which indicates a non-existent field.
The supplied dirfile was invalid.
One or more of the parameters specified in entry was invalid.
The entry->field_type parameter did not correspond to the type
of the field specified by field_code, or an attempt was made to
modify the immutable INDEX field. This error may also result
from attempting to dereference a scalar field code which does
not indicate a CONST or CARRAY field.
The entry->data_type parameter provided with a RAW entry, or
the entry->const_type parameter provided with a CONST or CARRAY
entry, was invalid.
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
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.
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.
The encoding scheme of the indicated format specification
fragment does not support translating the 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).
gd_alter_bit(3), gd_alter_carray(3), gd_alter_const(3),
gd_alter_divide(3), gd_alter_lincom(3), gd_alter_linterp(3),
gd_alter_multiply(3), gd_alter_phase(3), gd_alter_polynom(3),
gd_alter_raw(3), gd_alter_recip(3), gd_alter_spec(3), gd_delete(3),
gd_error(3), gd_error_string(3), gd_malter_spec(3), gd_metaflush(3),
gd_move(3), gd_open(3), gd_rename(3), dirfile-format(5)