/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@cs.vu.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2013, University of Amsterdam
VU University Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(read_util,
[ read_line_to_codes/2, % +Stream, -Codes (without trailing \n)
read_line_to_codes/3, % +Stream, -Codes, ?Tail
read_stream_to_codes/2, % +Stream, -Codes
read_stream_to_codes/3, % +Stream, -Codes, ?Tail
read_file_to_codes/3, % +File, -Codes, +Options
read_line_to_string/2, % +Stream, -Line (without trailing \n)
read_file_to_string/3, % +File, -Codes, +Options
read_file_to_terms/3 % +File, -Terms, +Options
]).
:- use_module(library(shlib)).
:- use_module(library(error)).
:- use_module(library(option)).
/** <module> Read utilities
This library provides some commonly used reading predicates. As these
predicates have proven to be time-critical in some applications we moved
them to C. For compatibility as well as to reduce system dependency, we
link the foreign code at runtime and fallback to the Prolog
implementation if the shared object cannot be found.
@see library(pure_input) allows for processing files with DCGs.
*/
:- predicate_options(read_file_to_codes/3, 3,
[ tail(list_or_partial_list),
pass_to(system:open/4, 4)
]).
:- predicate_options(read_file_to_string/3, 3,
[ pass_to(system:open/4, 4)
]).
:- predicate_options(read_file_to_terms/3, 3,
[ tail(list_or_partial_list),
pass_to(read_stream_to_terms/4, 4),
pass_to(system:absolute_file_name/3, 3),
pass_to(system:open/4, 4)
]).
:- volatile
read_line_to_codes/2,
read_line_to_codes/3,
read_stream_to_codes/2,
read_stream_to_codes/3.
link_foreign :-
catch(load_foreign_library(foreign(readutil)), _, fail), !.
link_foreign :-
assertz((read_line_to_codes(Stream, Line) :-
pl_read_line_to_codes(Stream, Line))),
assertz((read_line_to_codes(Stream, Line, Tail) :-
pl_read_line_to_codes(Stream, Line, Tail))),
assertz((read_stream_to_codes(Stream, Content) :-
pl_read_stream_to_codes(Stream, Content))),
assertz((read_stream_to_codes(Stream, Content, Tail) :-
pl_read_stream_to_codes(Stream, Content, Tail))),
compile_predicates([ read_line_to_codes/2,
read_line_to_codes/3,
read_stream_to_codes/2,
read_stream_to_codes/3
]).
:- initialization(link_foreign, now).
/*******************************
* LINES *
*******************************/
%% read_line_to_codes(+In:stream, -Line:codes) is det.
%
% Read a line of input from In into a list of character codes.
% Trailing newline and or return are deleted. Upon reaching
% end-of-file Line is unified to the atom =end_of_file=.
pl_read_line_to_codes(Stream, Codes) :-
get_code(Stream, C0),
( C0 == -1
-> Codes0 = end_of_file
; read_1line_to_codes(C0, Stream, Codes0)
),
Codes = Codes0.
read_1line_to_codes(-1, _, []) :- !.
read_1line_to_codes(10, _, []) :- !.
read_1line_to_codes(13, Stream, L) :- !,
get_code(Stream, C2),
read_1line_to_codes(C2, Stream, L).
read_1line_to_codes(C, Stream, [C|T]) :-
get_code(Stream, C2),
read_1line_to_codes(C2, Stream, T).
%% read_line_to_codes(+Stream, -Line, ?Tail) is det.
%
% Read a line of input as a difference list. This should be used
% to read multiple lines efficiently. On reaching end-of-file,
% Tail is bound to the empty list.
pl_read_line_to_codes(Stream, Codes, Tail) :-
get_code(Stream, C0),
read_line_to_codes(C0, Stream, Codes0, Tail),
Codes = Codes0.
read_line_to_codes(-1, _, Tail, Tail) :- !,
Tail = [].
read_line_to_codes(10, _, [10|Tail], Tail) :- !.
read_line_to_codes(C, Stream, [C|T], Tail) :-
get_code(Stream, C2),
read_line_to_codes(C2, Stream, T, Tail).
%% read_line_to_string(+Stream, -String) is det.
%
% Read the next line from Stream into String. String does not
% contain the line terminator. String is unified with the _atom_
% end_of_file if the end of the file is reached.
%
% @see read_string/5 can be used to read lines with separated
% records without creating intermediate strings.
read_line_to_string(Stream, String) :-
read_string(Stream, '\n', '\r', Sep, String0),
( Sep \== -1
-> String = String0
; String0 == ""
-> String = end_of_file
; String = String0
).
/*******************************
* STREAM (ENTIRE INPUT) *
*******************************/
%% read_stream_to_codes(+Stream, -Codes) is det.
%% read_stream_to_codes(+Stream, -Codes, ?Tail) is det.
%
% Read input from Stream to a list of character codes. The version
% read_stream_to_codes/3 creates a difference-list.
pl_read_stream_to_codes(Stream, Codes) :-
pl_read_stream_to_codes(Stream, Codes, []).
pl_read_stream_to_codes(Stream, Codes, Tail) :-
get_code(Stream, C0),
read_stream_to_codes(C0, Stream, Codes0, Tail),
Codes = Codes0.
read_stream_to_codes(-1, _, Tail, Tail) :- !.
read_stream_to_codes(C, Stream, [C|T], Tail) :-
get_code(Stream, C2),
read_stream_to_codes(C2, Stream, T, Tail).
%% read_stream_to_terms(+Stream, -Terms, ?Tail, +Options) is det.
read_stream_to_terms(Stream, Terms, Tail, Options) :-
read_term(Stream, C0, Options),
read_stream_to_terms(C0, Stream, Terms0, Tail, Options),
Terms = Terms0.
read_stream_to_terms(end_of_file, _, Tail, Tail, _) :- !.
read_stream_to_terms(C, Stream, [C|T], Tail, Options) :-
read_term(Stream, C2, Options),
read_stream_to_terms(C2, Stream, T, Tail, Options).
/*******************************
* FILE (ENTIRE INPUT) *
*******************************/
%% read_file_to_codes(+Spec, -Codes, +Options) is det.
%
% Read the file Spec into a list of Codes. Options is split into
% options for absolute_file_name/3 and open/4. In addition, the
% following option is provided:
%
% * tail(?Tail)
% Read the data into a _difference list_ Codes\Tail.
%
% @see phrase_from_file/3 and read_file_to_string/3.
read_file_to_codes(Spec, Codes, Options) :-
must_be(list, Options),
option(tail(Tail), Options, []),
absolute_file_name(Spec,
[ access(read)
| Options
],
Path),
setup_call_cleanup(
open(Path, read, Stream, Options),
read_stream_to_codes(Stream, Codes, Tail),
close(Stream)).
%% read_file_to_string(+Spec, -String, +Options) is det.
%
% Read the file Spec into a the string String. Options is split
% into options for absolute_file_name/3 and open/4.
%
% @see phrase_from_file/3 and read_file_to_codes/3.
read_file_to_string(Spec, Codes, Options) :-
must_be(list, Options),
absolute_file_name(Spec,
[ access(read)
| Options
],
Path),
setup_call_cleanup(
open(Path, read, Stream, Options),
read_string(Stream, _Len, Codes),
close(Stream)).
%% read_file_to_terms(+Spec, -Terms, +Options) is det.
%
% Read the file Spec into a list of terms. Options is split over
% absolute_file_name/3, open/4 and read_term/3. In addition, the
% following option is processed:
%
% * tail(?Tail)
% If present, Terms\Tail forms a _difference list_.
%
% Note that the `output' options of read_term/3, such as
% =variable_names= or =subterm_positions= will cause
% read_file_to_terms/3 to fail if Spec contains multiple terms
% because the values for the different terms will not unify.
read_file_to_terms(Spec, Terms, Options) :-
must_be(list, Options),
option(tail(Tail), Options, []),
absolute_file_name(Spec,
[ access(read)
| Options
],
Path),
setup_call_cleanup(
open(Path, read, Stream, Options),
read_stream_to_terms(Stream, Terms, Tail, Options),
close(Stream)).