gd_carrays, gd_mcarrays—retrieve a list of CARRAY values from a Dirfile


#include <getdata.h>

const gd_carray_t *gd_carrays(DIRFILE *dirfile, gd_type_t return_type);

const gd_carray_t *gd_mcarrays(DIRFILE *dirfile, const char *parent, gd_type_t return_type);


The gd_carrays() function queries a dirfile(5) database specified by dirfile and generates a read-only list of values of the all top-level CARRAY fields defined in the database, after type conversion to the data type specified by return_type. For a list of valid symbols to use for return_type, see the gd_get_carray(3) manual page.

The gd_mcarrays() function behaves similarly, but creates a list of values of CARRAY subfields under the parent field parent.

The dirfile argument must point to a valid DIRFILE object previously created by a call to gd_open(3).

A corresponding list of names for these fields may be obtained by calling gd_field_list_by_type(3) or gd_mfield_list_by_type(3).


Upon successful completion, gd_carrays() and gd_mcarrays(3) return a pointer to an array of gd_carray_t objects containing the values of all the CARRAYs defined in the dirfile database. The gd_carray_t structure is defined as:

typedef struct {
  size_t       n;              /* array_len */
  void        *d;              /* CARRAY data */
} gd_carray_t;

where n specifies the length of the CARRAY data, and d is an array of the data values themselves. If return_type was GD_NULL, d will be NULL. Otherwise, the caller should cast the void pointer to a type appropriate for the return_type specified. The list is terminated by an end-of-list marker consisting of a gd_carray_t item with n set to zero.

If no CARRAYs are defined in the database, a list containing only the end-of-list marker is returned.

The array returned will be de-allocated by a call to gd_close(3) and should not be de-allocated by the caller. The list returned should not be assumed to be in any particular order, except that it is guaranteed to be in the same order as the list of CARRAY fields returned by gd_field_list_by_type(3) or gd_mfield_list_by_type(3). The number of values in the array can be obtained from a call to gd_nfields_by_type(3) or gd_nmfields_by_type(3).

The caller may not modify any values in the array, nor the array itself. Doing so may cause database corruption. The pointer returned is guaranteed to be valid only until the function is called again, or until the dirfile's metadata is modified (by adding, modifying or deleting an entry), or until the array is de-allocated by a call to gd_close(3) or gd_discard(3).

On error, gd_carrays() returns NULL and stores a negative-valued error code in the DIRFILE object which may be retrieved by a subsequent call to gd_error(3). Possible error codes are:

The library was unable to allocate memory.
The supplied dirfile was invalid.
The return_type specified was invalid.
An internal error occurred in the library while trying to perform the task. This indicates a bug in the library. Please report the incident to the GetData developers.

A descriptive error string for the error may be obtained by calling gd_error_string(3).


The gd_carrays() and gd_mcarrays() functions appeared in GetData-0.7.0.


dirfile(5), gd_error(3), gd_error_string(3), gd_field_list_by_type(3), gd_get_carray(3), gd_mfield_list_by_type(3), gd_nfields_by_type(3) gd_nmfields_by_type(3) gd_open(3)

Last updated on 25 December 2016 for GetData Version 0.10.0.