dirfile_alter_entry --- modify the metadata of a dirfile field


#include <getdata.h>
int dirfile_alter_entry(DIRFILE *dirfile, const char *field_code, const gd_entry_t *entry, int recode);


The dirfile_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 represenation 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 dirfile_move(3). To change the name of a field, use dirfile_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 dirfile_delete(3), and then create a new field of the desired type with dirfile_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->, 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 CONST 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 paramter was previously a field code, the new field code will replace the old one.
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, otherise the correponding 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, dirfile_alter_entry() returns zero. On error, -1 is returned and the dirfile error is set to a non-zero error value. Possible error values are:
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-existant 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 field.
The entry->data_type parameter provided with a RAW entry, or the entry->const_type parameter provided with a CONST 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 protected.
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 specified format file 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 specified format file fragment does not support translating the empty binary file associated with a modified RAW field. The dirfile error may be retrieved by calling get_error(3). A descriptive error string for the last error encountered can be obtained from a call to get_error_string(3).


dirfile_alter_bit(3), dirfile_alter_clincom(3), dirfile_alter_const(3), dirfile_alter_cpolynom(3), dirfile_alter_lincom(3), dirfile_alter_linterp(3), dirfile_alter_multiply(3), dirfile_alter_phase(3), dirfile_alter_polynom(3), dirfile_alter_raw(3), dirfile_alter_spec(3), dirfile_delete(3), dirfile_malter_spec(3), dirfile_metaflush(3), dirfile_move(3), dirfile_open(3), dirfile_rename(3), get_error(3), get_error_string(3), dirfile-format(5)