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ENHANCED: dedicated faster branches for repositionable streams

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rebis-dev makes the speed difference especially apparent due to the
linear scan of strings on the heap in partial_string_tail/2 which is
now avoided for repositionable streams, notably files.

This addresses #2888 reported and analyzed by @haijinSk. Many thanks!
This commit is contained in:
Markus Triska
2025-04-17 22:14:37 +02:00
committed by Mark Thom
parent 4c46f0e54d
commit bf31d3f9a9
1 changed files with 22 additions and 14 deletions
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36
src/lib/pio.pl
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@@ -39,7 +39,8 @@
% represented as a list of characters.
phrase_from_stream(GRBody, Stream) :-
stream_to_lazy_list(Stream, Ls),
stream_property(Stream, reposition(Reposition)),
stream_to_lazy_list(Reposition, Stream, Ls),
phrase(GRBody, Ls).
%% phrase_from_file(+GRBody, +File)
@@ -64,7 +65,7 @@ phrase_from_file(NT, File, Options) :-
; Type = text
),
setup_call_cleanup(
open(File, read, Stream, Options),
open(File, read, Stream, [reposition(true)|Options]),
phrase_from_stream(NT, Stream),
close(Stream)
)
@@ -73,34 +74,41 @@ phrase_from_file(NT, File, Options) :-
% How many chars to read from stream and buffer in each step
chars_to_read(4096).
stream_to_lazy_list(Stream, Ls) :-
get_stream_buffer_position(Stream, Pos),
freeze(Ls, render_step(Stream, Pos, Ls)).
stream_to_lazy_list(Reposition, Stream, Ls) :-
get_stream_buffer_position(Reposition, Stream, Pos),
freeze(Ls, render_step(Reposition, Stream, Pos, Ls)).
render_step(Stream, Pos, Ls) :-
set_stream_buffer_position(Stream, Pos),
( buffer_at_end_of_stream(Stream) ->
render_step(Reposition, Stream, Pos, Ls) :-
set_stream_buffer_position(Reposition, Stream, Pos),
( buffer_at_end_of_stream(Reposition, Stream) ->
Ls = []
; chars_to_read(CharsToRead),
buffer_get_n_chars(Stream, CharsToRead, Chars),
buffer_get_n_chars(Reposition, Stream, CharsToRead, Chars),
partial_string(Chars, Ls, Ls0),
stream_to_lazy_list(Stream, Ls0)
stream_to_lazy_list(Reposition, Stream, Ls0)
).
buffer_at_end_of_stream(Stream) :-
buffer_at_end_of_stream(true, Stream) :- at_end_of_stream(Stream).
buffer_at_end_of_stream(false, Stream) :-
stream_bufferids(Stream, _, BufferPosId, _),
bb_get(BufferPosId, Pos),
Pos = eof.
get_stream_buffer_position(Stream, Pos) :-
get_stream_buffer_position(true, Stream, Pos) :-
stream_property(Stream, position(Pos)).
get_stream_buffer_position(false, Stream, Pos) :-
stream_bufferids(Stream, _, BufferPosId, _),
bb_get(BufferPosId, Pos).
set_stream_buffer_position(Stream, Pos) :-
set_stream_buffer_position(true, Stream, Pos) :-
set_stream_position(Stream, Pos).
set_stream_buffer_position(false, Stream, Pos) :-
stream_bufferids(Stream, _, BufferPosId, _),
bb_put(BufferPosId, Pos).
buffer_get_n_chars(Stream, N, Chars) :-
buffer_get_n_chars(true, Stream, N, Chars) :-
get_n_chars(Stream, N, Chars).
buffer_get_n_chars(false, Stream, N, Chars) :-
stream_bufferids(Stream, BufferId, BufferPosId, BufferLenId),
buffer_prepare_for_n(Stream, BufferId, BufferPosId, BufferLenId, N),
bb_get(BufferId, Buffer),