gd_strings — retrieve a list of string values from a Dirfile
const char **gd_strings(DIRFILE *dirfile);
const char **gd_mstrings(DIRFILE *dirfile, const char *parent);
The gd_strings() function queries a dirfile(5) database specified by dirfile and compiles a read-only list of values of the all STRING type fields defined in the database, excluding /META subfields.
The gd_mstrings() function produces the same list, but for STRING meta subfields of the indicated parent field.
The dirfile argument must point to a valid DIRFILE object previously created by a call to gd_open(3).
Upon successful completion, gd_strings() returns a pointer to an array of strings containing the values of all the STRING fields defined in the dirfile database. Similarly, gd_mstrings() returns a pointer to an array of strings containing the values of all the STRING metafields under parent.
The returned array is terminated by a NULL pointer. A valid pointer is always returned if this function does not encounter an error. If there are no string values to return, a pointer to an array consisting of only the NULL pointer 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, although it is guaranteed to be in the same order as the list of STRING fields returned by gd_field_list_by_type(3). The array is terminated by a NULL pointer. The number of strings in the array can be obtained from a call to gd_nfields_by_type(3).
The caller may not modify any strings in the array, or the array itself. Doing so may cause database corruption. The pointer returned is guaranteed to be valid until gd_strings() or gd_mstrings() is called again with the same arguments, or until the array is de-allocated by a call to gd_close(3) or gd_discard(3).
On error, these functions return NULL and store 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.
- (gd_mstrings() only) The supplied parent field code was not found, or referred to a metafield itself.
- The supplied dirfile was invalid.
A descriptive error string for the error may be obtained by calling gd_error_string(3).
The get_strings() function appeared in GetData-0.3.0.
The get_mstrings() function appeared in GetData-0.4.0.
In GetData-0.7.0, these functions were renamed to gd_strings() and gd_mstrings().
|25 December 2016||Version 0.10.0|