/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2001-2022, University of Amsterdam VU University Amsterdam CWI, Amsterdam SWI-Prolog Solutions b.v. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- 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 ]). :- autoload(library(error),[must_be/2]). :- autoload(library(option),[option/3]). /** 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. @see library(lazy_lists) for creating lazy lists from input. */ :- 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) ]). :- predicate_options(read_stream_to_terms/4, 4, [ pass_to(read_term/3, 3) ]). :- volatile read_line_to_codes/2, read_line_to_codes/3, read_stream_to_codes/2, read_stream_to_codes/3. link_foreign :- catch(use_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(+Stream, -Line:codes) is det. % % Read the next line of input from Stream. Unify content of the lines % as a list of character codes with Line _after_ the line has been % read. A line is ended by a newline character or end-of-file. Unlike % read_line_to_codes/3, this predicate removes a trailing newline % character. 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. % % Difference-list version to read an input line to a list of character % codes. Reading stops at the newline or end-of-file character, but % unlike read_line_to_codes/2, the newline is retained in the output. % This predicate is especially useful for reading a block of lines up % to some delimiter. The following example reads an HTTP header ended % by a blank line: % % ``` % read_header_data(Stream, Header) :- % read_line_to_codes(Stream, Header, Tail), % read_header_data(Header, Stream, Tail). % % read_header_data("\r\n", _, _) :- !. % read_header_data("\n", _, _) :- !. % read_header_data("", _, _) :- !. % read_header_data(_, Stream, Tail) :- % read_line_to_codes(Stream, Tail, NewTail), % read_header_data(Tail, Stream, NewTail). % ``` 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)).