mirror of
https://github.com/Mercury-Language/mercury.git
synced 2025-12-13 21:04:00 +00:00
a1ef1bf468
Estimated hours taken: 0.5
Branches: main
Fix a problem where the licensing on some of the files in the Mercury
standard library was not explicitly stated.
library/bitmap.m:
library/hash_table.m:
library/pprint.m:
Update the comments about the copyright and license for these files:
mark them as copyright by the University of Melbourne, since they
have been donated to the Mercury project, and license them under the
LGPL.
Also update the layout of the %-------...-------% lines to match
our usual coding convention, so that they get formatted nicely
in the Mercury library reference manual.
Also delete "ff=unix" from the vim line for bitmap.m.
Add "stability:" comments for bitmap.m and hash_table.m
("low" since they make use of unique modes in a way that will
change when we implement ui modes and nested unique modes properly).
404 lines
13 KiB
Mathematica
404 lines
13 KiB
Mathematica
%-----------------------------------------------------------------------------%
|
|
% Copyright (C) 2001-2002 The University of Melbourne
|
|
% This file may only be copied under the terms of the GNU Library General
|
|
% Public License - see the file COPYING.LIB in the Mercury distribution.
|
|
%-----------------------------------------------------------------------------%
|
|
% vim: ts=4 sw=4 et tw=0 wm=0 ft=mercury
|
|
%-----------------------------------------------------------------------------%
|
|
%
|
|
% File: bitmap.m
|
|
% Main author: rafe
|
|
% Stability: low
|
|
%
|
|
% Efficient bitmap implementation.
|
|
%
|
|
% CAVEAT: the user is referred to the documentation in the header
|
|
% of array.m regarding programming with unique objects (the compiler
|
|
% does not currently recognise them, hence we are forced to use
|
|
% non-unique modes until the situation is rectified; this places
|
|
% a small burden on the programmer to ensure the correctness of his
|
|
% code that would otherwise be assured by the compiler.)
|
|
%
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- module bitmap.
|
|
|
|
:- interface.
|
|
|
|
:- import_module array, int, bool.
|
|
|
|
|
|
|
|
:- type bitmap.
|
|
|
|
:- inst bitmap == array.
|
|
:- inst uniq_bitmap == uniq_array.
|
|
:- mode bitmap_ui == array_ui.
|
|
:- mode bitmap_di == array_di.
|
|
:- mode bitmap_uo == array_uo.
|
|
|
|
% new(N, B) creates a bitmap of size N (indexed 0 .. N-1)
|
|
% setting each bit if B = yes and clearing each bit if B = no.
|
|
% An exception is thrown if N is negative.
|
|
%
|
|
:- func new(int, bool) = bitmap.
|
|
:- mode new(in, in) = bitmap_uo is det.
|
|
|
|
% Returns the number of bits in a bitmap.
|
|
%
|
|
:- func num_bits(bitmap) = int.
|
|
:- mode num_bits(bitmap_ui) = out is det.
|
|
:- mode num_bits(in) = out is det.
|
|
|
|
% set(BM, I), clear(BM, I) and flip(BM, I) set, clear and flip
|
|
% bit I in BM respectively.
|
|
%
|
|
:- func set(bitmap, int) = bitmap.
|
|
:- mode set(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
:- func clear(bitmap, int) = bitmap.
|
|
:- mode clear(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
:- func flip(bitmap, int) = bitmap.
|
|
:- mode flip(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
% Unsafe versions of the above: if the index is out of range
|
|
% then behaviour is undefined and bad things are likely to happen.
|
|
%
|
|
:- func unsafe_set(bitmap, int) = bitmap.
|
|
:- mode unsafe_set(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
:- func unsafe_clear(bitmap, int) = bitmap.
|
|
:- mode unsafe_clear(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
:- func unsafe_flip(bitmap, int) = bitmap.
|
|
:- mode unsafe_flip(bitmap_di, in) = bitmap_uo is det.
|
|
|
|
% is_set(BM, I) and is_clear(BM, I) succeed iff bit I in BM
|
|
% is set or clear respectively.
|
|
%
|
|
:- pred is_set(bitmap, int).
|
|
:- mode is_set(bitmap_ui, in) is semidet.
|
|
:- mode is_set(in, in) is semidet.
|
|
|
|
:- pred is_clear(bitmap, int).
|
|
:- mode is_clear(bitmap_ui, in) is semidet.
|
|
:- mode is_clear(in, in) is semidet.
|
|
|
|
% Unsafe versions of the above: if the index is out of range
|
|
% then behaviour is undefined and bad things are likely to happen.
|
|
%
|
|
:- pred unsafe_is_set(bitmap, int).
|
|
:- mode unsafe_is_set(bitmap_ui, in) is semidet.
|
|
:- mode unsafe_is_set(in, in) is semidet.
|
|
|
|
:- pred unsafe_is_clear(bitmap, int).
|
|
:- mode unsafe_is_clear(bitmap_ui, in) is semidet.
|
|
:- mode unsafe_is_clear(in, in) is semidet.
|
|
|
|
% get(BM, I) returns `yes' if is_set(BM, I) and `no' otherwise.
|
|
%
|
|
:- func get(bitmap, int) = bool.
|
|
:- mode get(bitmap_ui, in) = out is det.
|
|
:- mode get(in, in) = out is det.
|
|
|
|
% Unsafe versions of the above: if the index is out of range
|
|
% then behaviour is undefined and bad things are likely to happen.
|
|
%
|
|
:- func unsafe_get(bitmap, int) = bool.
|
|
:- mode unsafe_get(bitmap_ui, in) = out is det.
|
|
:- mode unsafe_get(in, in) = out is det.
|
|
|
|
% Create a new copy of a bitmap.
|
|
%
|
|
:- func copy(bitmap) = bitmap.
|
|
:- mode copy(bitmap_ui) = bitmap_uo is det.
|
|
|
|
% Set operations; the second argument is altered in all cases.
|
|
%
|
|
:- func complement(bitmap) = bitmap.
|
|
:- mode complement(bitmap_di) = bitmap_uo is det.
|
|
|
|
:- func union(bitmap, bitmap) = bitmap.
|
|
:- mode union(bitmap_ui, bitmap_di) = bitmap_uo is det.
|
|
|
|
:- func intersect(bitmap, bitmap) = bitmap.
|
|
:- mode intersect(bitmap_ui, bitmap_di) = bitmap_uo is det.
|
|
|
|
:- func difference(bitmap, bitmap) = bitmap.
|
|
:- mode difference(bitmap_ui, bitmap_di) = bitmap_uo is det.
|
|
|
|
% resize(BM, N, B) resizes bitmap BM to have N bits; if N is
|
|
% smaller than the current number of bits in BM then the excess
|
|
% are discarded. If N is larger than the current number of bits
|
|
% in BM then the new bits are set if B = yes and cleared if
|
|
% B = no.
|
|
%
|
|
:- func resize(bitmap, int, bool) = bitmap.
|
|
:- mode resize(bitmap_di, in, in) = bitmap_uo is det.
|
|
|
|
%-----------------------------------------------------------------------------%
|
|
%-----------------------------------------------------------------------------%
|
|
|
|
:- implementation.
|
|
|
|
:- import_module exception, require.
|
|
|
|
% A bitmap is represented as an array of ints where each int stores
|
|
% int__bits_per_int bits. The first element of the array (index 0)
|
|
% is used to hold the number of bits in the bitmap. This avoids
|
|
% having to create a new bitmap cell on each update.
|
|
%
|
|
% NOTE: the `filler' bits in the last element of the array *must*
|
|
% be clear (i.e. zero). This makes the set operations simpler to
|
|
% implement.
|
|
|
|
:- type bitmap == array(int).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
new(N, B) = BM :-
|
|
( if N < 0 then
|
|
throw(software_error("bitmap__new: negative size"))
|
|
else
|
|
X = initializer(B),
|
|
BM0 = (array__init(num_ints_required(N), X) ^ elem(0) := N),
|
|
BM = clear_filler_bits(BM0)
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
resize(BM0, N, B) = BM :-
|
|
( if N =< 0 then
|
|
BM = new(N, B)
|
|
else
|
|
X = initializer(B),
|
|
NumInts = num_ints_required(N),
|
|
BM1 = array__resize(BM0, NumInts, X),
|
|
|
|
% Now we need to ensure that bits N, N+1, N+2, ... up to
|
|
% the word boundary are initialized properly.
|
|
%
|
|
int__min(num_bits(BM0), N, M),
|
|
Offset = int_offset(M - 1),
|
|
Mask = bitsmask(M - 1), % For bits we need to preserve.
|
|
Bits = \(Mask) /\ X, % Bits we need to fill in.
|
|
BM2 = (( BM1
|
|
^ elem(0) := N )
|
|
^ elem(Offset) := (BM1 ^ elem(Offset) /\ Mask) \/ Bits),
|
|
BM = clear_filler_bits(BM2)
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
:- func clear_filler_bits(bitmap) = bitmap.
|
|
:- mode clear_filler_bits(bitmap_di) = bitmap_uo is det.
|
|
|
|
clear_filler_bits(BM0) = BM :-
|
|
N = num_bits(BM0),
|
|
( if N > 0 then
|
|
Last = int_offset(N - 1), % Offset of last bit.
|
|
Ksam = bitsmask(N - 1), % Masks off the filler bits.
|
|
BM = BM0 ^ elem(Last) := BM0 ^ elem(Last) /\ Ksam
|
|
else
|
|
BM = BM0
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
:- func initializer(bool) = int.
|
|
|
|
initializer(no) = 0.
|
|
initializer(yes) = \(0).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
num_bits(BM) = BM ^ elem(0).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
:- pred in_range(bitmap, int).
|
|
:- mode in_range(bitmap_ui, in) is semidet.
|
|
:- mode in_range(in, in) is semidet.
|
|
|
|
in_range(BM, I) :- 0 =< I, I < num_bits(BM).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
set(BM, I) =
|
|
( if in_range(BM, I)
|
|
then BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) \/ bitmask(I)
|
|
else throw(software_error("bitmap__set: out of range"))
|
|
).
|
|
|
|
clear(BM, I) =
|
|
( if in_range(BM, I)
|
|
then BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) /\ \bitmask(I)
|
|
else throw(software_error("bitmap__clear: out of range"))
|
|
).
|
|
|
|
flip(BM, I) =
|
|
( if in_range(BM, I)
|
|
then BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) `xor` bitmask(I)
|
|
else throw(software_error("bitmap__flip: out of range"))
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
unsafe_set(BM, I) =
|
|
BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) \/ bitmask(I).
|
|
|
|
unsafe_clear(BM, I) =
|
|
BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) /\ \bitmask(I).
|
|
|
|
unsafe_flip(BM, I) =
|
|
BM ^ elem(int_offset(I)) := BM ^ elem(int_offset(I)) `xor` bitmask(I).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
is_set(BM, I) :-
|
|
( if in_range(BM, I)
|
|
then BM ^ elem(int_offset(I)) /\ bitmask(I) \= 0
|
|
else throw(software_error("bitmap__is_set: out of range"))
|
|
).
|
|
|
|
is_clear(BM, I) :-
|
|
( if in_range(BM, I)
|
|
then BM ^ elem(int_offset(I)) /\ bitmask(I) = 0
|
|
else throw(software_error("bitmap__is_clear: out of range"))
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
unsafe_is_set(BM, I) :-
|
|
BM ^ elem(int_offset(I)) /\ bitmask(I) \= 0.
|
|
|
|
unsafe_is_clear(BM, I) :-
|
|
BM ^ elem(int_offset(I)) /\ bitmask(I) = 0.
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
get(BM, I) = ( if is_clear(BM, I) then no else yes ).
|
|
|
|
%------------------------------------------------------------------------------%
|
|
|
|
unsafe_get(BM, I) = ( if unsafe_is_clear(BM, I) then no else yes ).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
copy(BM) = array__copy(BM).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
complement(BM) =
|
|
clear_filler_bits(complement_2(BM ^ elem(0) - 1, BM)).
|
|
|
|
|
|
|
|
:- func complement_2(int, bitmap) = bitmap.
|
|
:- mode complement_2(in, bitmap_di) = bitmap_uo is det.
|
|
|
|
complement_2(WordI, BM) =
|
|
( if WordI =< 0
|
|
then BM
|
|
else complement_2(WordI - 1, BM ^ elem(WordI) := \(BM ^ elem(WordI)))
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
union(BMa, BMb) =
|
|
( if num_bits(BMa) > num_bits(BMb) then
|
|
zip(int_offset(num_bits(BMb) - 1), (\/), BMb, bitmap__copy(BMa))
|
|
else
|
|
zip(int_offset(num_bits(BMa) - 1), (\/), BMa, BMb)
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
intersect(BMa, BMb) =
|
|
( if num_bits(BMa) > num_bits(BMb) then
|
|
zip(int_offset(num_bits(BMb) - 1), (/\), BMb, bitmap__copy(BMa))
|
|
else
|
|
zip(int_offset(num_bits(BMa) - 1), (/\), BMa, BMb)
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
difference(BMa, BMb) =
|
|
( if num_bits(BMa) > num_bits(BMb) then
|
|
zip(int_offset(num_bits(BMb) - 1), Xor, BMb, bitmap__copy(BMa))
|
|
else
|
|
zip(int_offset(num_bits(BMa) - 1), Xor, BMa, BMb)
|
|
)
|
|
:-
|
|
Xor = ( func(X, Y) = (X `xor` Y) ).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
% Applies a function to every corresponding element between +ve I
|
|
% and 1 inclusive, destructively updating the second bitmap.
|
|
%
|
|
:- func zip(int, func(int, int) = int, bitmap, bitmap) = bitmap.
|
|
:- mode zip(in, func(in, in) = out is det, bitmap_ui, bitmap_di) = bitmap_uo
|
|
is det.
|
|
|
|
zip(I, Fn, BMa, BMb) =
|
|
( if I > 0 then
|
|
zip(I - 1, Fn, BMa, BMb ^ elem(I) := Fn(BMb ^ elem(I), BMa ^ elem(I)))
|
|
else
|
|
BMb
|
|
).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
% The size of the array required to hold an N-bit bitmap.
|
|
%
|
|
:- func num_ints_required(int) = int.
|
|
|
|
% We add the 1 on because arrays of size N are indexed 0 .. N - 1.
|
|
%
|
|
num_ints_required(N) = 1 + ( if N > 0 then int_offset(N) else 0 ).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
% The array index containing the given bit.
|
|
%
|
|
:- func int_offset(int) = int.
|
|
|
|
% We add the extra 1 on because elem(0) is used to store the number
|
|
% of bits in the bitmap; the data are stored in the following elements.
|
|
%
|
|
int_offset(I) = 1 + int__quot_bits_per_int(I).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
% Construct the bitmask for a given bit in a word.
|
|
%
|
|
% E.g. assuming int__bits_per_int = 8 and I = 11 then
|
|
% bitmask(I) = 2'00001000
|
|
%
|
|
:- func bitmask(int) = int.
|
|
|
|
% NOTE: it would be nicer to use /\ with a bitmask here rather
|
|
% than rem. Do modern back-ends do the decent thing here if
|
|
% int__bits_per_int is the expected power of two?
|
|
%
|
|
bitmask(I) = 1 `unchecked_left_shift` int__rem_bits_per_int(I).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
|
|
% Construct the bitmask for all the bits up to and including
|
|
% the given bit in a word.
|
|
%
|
|
% E.g. assuming int__bits_per_int = 8 and I = 11 then
|
|
% bitmask(I) = 2'00001111
|
|
%
|
|
:- func bitsmask(int) = int.
|
|
|
|
bitsmask(I) = BitsMask :-
|
|
BitMask = bitmask(I),
|
|
BitsMask = BitMask \/ (BitMask - 1).
|
|
|
|
% ---------------------------------------------------------------------------- %
|
|
% ---------------------------------------------------------------------------- %
|