gd_mcarrays(3)

NAME
gd_constants — retrieve a list of CARRAY values from a dirfile

SYNOPSIS
#include <getdata.h>

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

DESCRIPTION
The gd_mcarrays() function queries a dirfile(5) database specified by dirfile and returns a read-only list of values of the all CARRAY metafields for the supplied parent field, 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) man page. The dirfile argument must point to a valid DIRFILE object previously created by a call to gd_open(3). 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_mfield_list_by_type(3). The number of values in the array can be obtained from a call to 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 gd_mcarrays() 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). A corresponding list of names for these fields may be obtained by calling gd_field_list_by_type(3).

RETURN VALUE
Upon successful completion, gd_mcarrays() returns 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 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. 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. On error, gd_mcarrays() returns NULL and sets the dirfile error to a non-zero error value. Possible error values are:

GD_E_ALLOC
    The library was unable to allocate memory.

GD_E_BAD_CODE
    The supplied parent field code was not found, or referred to a metafield itself.

GD_E_BAD_DIRFILE
    The supplied dirfile was invalid.

GD_E_BAD_TYPE
    The return_type specified was invalid.

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