All internal text representation in SWI-Prolog is represented using
char * plus length and allow for 0-bytes in them.
The foreign library supports this by implementing a *_nchars() function
for each applicable *_chars() function. Below we briefly present the
signatures of these functions. For full documentation consult the
*_chars() function.
- int PL_get_atom_nchars(term_t
t, size_t *len, char **s)
- See PL_get_atom_chars().
- int PL_get_list_nchars(term_t
t, size_t *len, char **s)
- See PL_get_list_chars().
- int PL_get_nchars(term_t
t, size_t *len, char **s, unsigned int flags)
- See PL_get_chars().
The len pointer may be
NULL.
- int PL_put_atom_nchars(term_t
t, size_t len, const char *s)
- See PL_put_atom_chars().
- int PL_put_string_nchars(term_t
t, size_t len, const char *s)
- See PL_put_string_chars().
- int PL_put_list_ncodes(term_t
t, size_t len, const char *s)
- See PL_put_list_codes().
- int PL_put_list_nchars(term_t
t, size_t len, const char *s)
- See PL_put_list_chars().
- int PL_unify_atom_nchars(term_t
t, size_t len, const char *s)
- See PL_unify_atom_chars().
- int PL_unify_string_nchars(term_t
t, size_t len, const char *s)
- See PL_unify_string_chars().
- int PL_unify_list_ncodes(term_t
t, size_t len, const char *s)
- See PL_unify_codes().
- int PL_unify_list_nchars(term_t
t, size_t len, const char *s)
- See PL_unify_list_chars().
In addition, the following functions are available for creating and
inspecting atoms:
- atom_t PL_new_atom_nchars(size_t
len, const char *s)
- Create a new atom as PL_new_atom(),
but using the given length and characters. If len is
(size_t)-1,
it is computed from s using strlen(). See PL_new_atom()
for error handling.
- const char * PL_atom_nchars(atom_t
a, size_t *len)
- Extract the text and length of an atom. If you do not need the length,
pass NULL as the value of len. If PL_atom_nchars()
is called for a blob, NULL is returned.