/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@cs.vu.nl
WWW: http://www.swi-prolog.org
Copyright (C): 2009-2012, 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 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(csv,
[ csv//1, % +Rows
csv//2, % +Rows, +Options
csv_read_file/2, % +File, -Data
csv_read_file/3, % +File, -Data, +Options
csv_read_file_row/3, % +File, -Row, +Options
csv_write_file/2, % +File, +Data
csv_write_file/3, % +File, +Data, +Options
csv_write_stream/3 % +Stream, +Data, +Options
]).
:- use_module(library(record)).
:- use_module(library(error)).
:- use_module(library(pure_input)).
:- use_module(library(debug)).
/** <module> Process CSV (Comma-Separated Values) data
This library parses and generates CSV data. CSV data is represented in
Prolog as a list of rows. Each row is a compound term, where all rows
have the same name and arity.
@tbd Implement immediate assert of the data to avoid possible stack
overflows.
@tbd Writing creates an intermediate code-list, possibly overflowing
resources. This waits for pure output!
@see RFC 4180
*/
:- predicate_options(csv//2, 2,
[ separator(nonneg), % mustv be code
strip(boolean),
convert(boolean),
functor(atom),
arity(-nonneg), % actually ?nonneg
match_arity(boolean)
]).
:- predicate_options(csv_read_file/3, 3,
[ pass_to(csv//2, 2),
pass_to(phrase_from_file/3, 3)
]).
:- predicate_options(csv_read_file_row/3, 3,
[ pass_to(csv//2, 2),
pass_to(open/4, 4)
]).
:- predicate_options(csv_write_file/3, 3,
[ pass_to(csv//2, 2),
pass_to(open/4, 4)
]).
:- predicate_options(csv_write_stream/3, 3,
[ pass_to(csv//2, 2)
]).
:- record
csv_options(separator:integer=0',,
strip:boolean=false,
convert:boolean=true,
functor:atom=row,
arity:integer,
match_arity:boolean=true).
%% csv_read_file(+File, -Rows) is det.
%% csv_read_file(+File, -Rows, +Options) is det.
%
% Read a CSV file into a list of rows. Each row is a Prolog term
% with the same arity. Options is handed to csv//2. Remaining
% options are processed by phrase_from_file/3. The default
% separator depends on the file name extension and is =|\t|= for
% =|.tsv|= files and =|,|= otherwise.
%
% Suppose we want to create a predicate table/6 from a CSV file
% that we know contains 6 fields per record. This can be done
% using the code below. Without the option arity(6), this would
% generate a predicate table/N, where N is the number of fields
% per record in the data.
%
% ==
% ?- csv_read_file(File, Rows, [functor(table), arity(6)]),
% maplist(assert, Rows).
% ==
csv_read_file(File, Rows) :-
csv_read_file(File, Rows, []).
csv_read_file(File, Rows, Options) :-
default_separator(File, Options, Options1),
make_csv_options(Options1, Record, RestOptions),
phrase_from_file(csv_roptions(Rows, Record), File, RestOptions).
default_separator(File, Options0, Options) :-
( option(separator(_), Options0)
-> Options = Options0
; file_name_extension(_, Ext0, File),
downcase_atom(Ext0, Ext),
ext_separator(Ext, Sep)
-> Options = [separator(Sep)|Options0]
; Options = Options0
).
ext_separator(csv, 0',).
ext_separator(tsv, 0'\t).
%% csv(?Rows)// is det.
%% csv(?Rows, +Options)// is det.
%
% Prolog DCG to `read/write' CSV data. Options:
%
% * separator(+Code)
% The comma-separator. Must be a character code. Default is
% (of course) the comma. Character codes can be specified
% using the 0' notion. E.g., =|separator(0';)|=.
%
% * strip(+Boolean)
% If =true= (default =false=), strip leading and trailing
% blank space. RFC4180 says that blank space is part of the
% data.
%
% * convert(+Boolean)
% If =true= (default), use name/2 on the field data. This
% translates the field into a number if possible.
%
% * functor(+Atom)
% Functor to use for creating row terms. Default is =row=.
%
% * arity(?Arity)
% Number of fields in each row. This predicate raises
% a domain_error(row_arity(Expected), Found) if a row is
% found with different arity.
%
% * match_arity(+Boolean)
% If =false= (default =true=), do not reject CSV files where
% lines provide a varying number of fields (columns). This
% can be a work-around to use some incorrect CSV files.
csv(Rows) -->
csv(Rows, []).
csv(Rows, Options) -->
{ make_csv_options(Options, Record, _) },
csv_roptions(Rows, Record).
csv_roptions(Rows, Record) -->
{ ground(Rows) }, !,
emit_csv(Rows, Record).
csv_roptions(Rows, Record) -->
csv_data(Rows, Record).
csv_data([], _) -->
eof, !.
csv_data([Row|More], Options) -->
row(Row, Options), !,
{ debug(csv, 'Row: ~p', [Row]) },
csv_data(More, Options).
eof([], []).
row(Row, Options) -->
fields(Fields, Options),
{ csv_options_functor(Options, Functor),
Row =.. [Functor|Fields],
functor(Row, _, Arity),
check_arity(Options, Arity)
}.
check_arity(Options, Arity) :-
csv_options_arity(Options, Arity), !.
check_arity(Options, _) :-
csv_options_match_arity(Options, false), !.
check_arity(Options, Arity) :-
csv_options_arity(Options, Expected),
domain_error(row_arity(Expected), Arity).
fields([F|T], Options) -->
field(F, Options),
( separator(Options)
-> fields(T, Options)
; end_of_record
-> { T = [] }
).
field(Value, Options) -->
{ csv_options_strip(Options, true) }, !,
stripped_field(Value, Options).
field(Value, Options) -->
"\"", !,
string_codes(Codes),
{ make_value(Codes, Value, Options) }.
field(Value, Options) -->
{ csv_options_separator(Options, Sep) },
field_codes(Codes, Sep),
{ make_value(Codes, Value, Options) }.
stripped_field(Value, Options) -->
ws,
( "\""
-> string_codes(Codes),
ws
; { csv_options_separator(Options, Sep) },
field_codes(Codes0, Sep),
{ strip_trailing_ws(Codes0, Codes) }
),
{ make_value(Codes, Value, Options) }.
ws --> " ", !, ws.
ws --> "\t", !, ws.
ws --> "".
strip_trailing_ws(List, Stripped) :-
append(Stripped, WS, List),
all_ws(WS).
all_ws([]).
all_ws([32|T]) :- all_ws(T).
all_ws([9|T]) :- all_ws(T).
%% string_codes(-Codes)
%
% Process a double-quotes string where the quote is escaped by
% doubling it. Eats the terminating double-quote.
string_codes(List) -->
[H],
( { H == 0'" }
-> ( "\""
-> { List = [H|T] },
string_codes(T)
; { List = [] }
)
; { List = [H|T] },
string_codes(T)
).
field_codes([], Sep), [Sep] --> [Sep], !.
field_codes([], _), "\n" --> "\r\n", !.
field_codes([], _), "\n" --> "\n", !.
field_codes([H|T], Sep) --> [H], !, field_codes(T, Sep).
field_codes([], _) --> []. % unterminated last record
make_value(Codes, Value, Options) :-
csv_options_convert(Options, true), !,
name(Value, Codes).
make_value(Codes, Value, _) :-
atom_codes(Value, Codes).
separator(Options) -->
{ csv_options_separator(Options, Sep) },
[Sep].
end_of_record --> "\n".
end_of_record --> "\r\n".
end_of_record --> eof. % unterminated last record
%% csv_read_file_row(+File, -Row, +Options) is nondet.
%
% True when Row is a row in File. First unifies Row with the first
% row in File. Backtracking yields the second, ... row. This
% interface is an alternative to csv_read_file/3 that avoids
% loading all rows in memory. Note that this interface does not
% guarantee that all rows in File have the same arity.
%
% In addition to the options of csv_read_file/3, this predicate
% processes the option:
%
% * line(-Line)
% Line is unified with the 1-based line-number from which Row is
% read.
csv_read_file_row(File, Row, Options) :-
default_separator(File, Options, Options1),
make_csv_options(Options1, RecordOptions, Options2),
select_option(line(Line), Options2, RestOptions, _),
setup_call_cleanup(
open(File, read, Stream, RestOptions),
csv_read_stream_row(Stream, Row, Line, RecordOptions),
close(Stream)).
csv_read_stream_row(Stream, Row, Line, Options) :-
between(1, infinite, Line),
read_line_to_codes(Stream, Codes, []),
( Codes == []
-> !,
fail
; phrase(row(Row, Options), Codes),
debug(csv, 'Row: ~p', [Row])
).
/*******************************
* OUTPUT *
*******************************/
%% csv_write_file(+File, +Data) is det.
%% csv_write_file(+File, +Data, +Options) is det.
%
% Write a list of Prolog terms to a CSV file. Options are given
% to csv//2. Remaining options are given to open/4. The default
% separator depends on the file name extension and is =|\t|= for
% =|.tsv|= files and =|,|= otherwise.
csv_write_file(File, Data) :-
csv_write_file(File, Data, []).
csv_write_file(File, Data, Options) :-
default_separator(File, Options, Options1),
make_csv_options(Options1, Record, RestOptions),
phrase(emit_csv(Data, Record), String),
setup_call_cleanup(
open(File, write, Out, RestOptions),
format(Out, '~s', [String]),
close(Out)).
emit_csv([], _) --> [].
emit_csv([H|T], Options) -->
emit_row(H, Options), "\r\n", % RFC 4180 demands \r\n
emit_csv(T, Options).
emit_row(Row, Options) -->
{ Row =.. [_|Fields] },
emit_fields(Fields, Options).
emit_fields([H|T], Options) -->
emit_field(H, Options),
( { T == [] }
-> []
; { csv_options_separator(Options, Sep) },
[Sep],
emit_fields(T, Options)
).
emit_field(H, Options) -->
{ atom(H), !,
atom_codes(H, Codes)
},
( { needs_quotes(H, Options) }
-> "\"", emit_string(Codes), "\""
; emit_codes(Codes)
).
emit_field(H, _) -->
{ number_codes(H,Codes) },
emit_codes(Codes).
needs_quotes(Atom, _) :-
sub_atom(Atom, _, _, _, '"'), !.
needs_quotes(Atom, Options) :-
csv_options_separator(Options, Sep),
char_code(Char, Sep),
sub_atom(Atom, _, _, _, Char), !.
emit_string([]) --> "".
emit_string([0'"|T]) --> !, "\"\"", emit_string(T).
emit_string([H|T]) --> [H], emit_string(T).
emit_codes([]) --> "".
emit_codes([0'"|T]) --> !, "\"\"", emit_codes(T).
emit_codes([H|T]) --> [H], emit_codes(T).
%% csv_write_stream(+Stream, +Data, +Options) is det.
%
% Write the rows in Data to Stream. This is similar to
% csv_write_file/3, but can deal with data that is produced
% incrementally. The example below saves all answers from the
% predicate data/3 to File.
%
% ==
% save_data(File) :-
% setup_call_cleanup(
% open(File, write, Out),
% forall(data(C1,C2,C3),
% csv_write_file(Out, [row(C1,C2,C3)], [])),
% close(Out)),
% ==
csv_write_stream(Stream, Data, Options) :-
make_csv_options(Options, Record, _),
phrase(emit_csv(Data, Record), String),
format(Stream, '~s', [String]).