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mercury/library/version_array.m
Zoltan Somogyi a12692a0de Replace /* */ comments with // in the library. 
Keep the old style comments where they do not go to the end of the line,
or where it is important that the comment line not have a // on it.
2018-06-21 18:55:08 +02:00

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%---------------------------------------------------------------------------%
% vim: ts=4 sw=4 et ft=mercury
%---------------------------------------------------------------------------%
% Copyright (C) 2004-2012 The University of Melbourne.
% Copyright (C) 2014-2018 The Mercury Team.
% This file is distributed under the terms specified in COPYING.LIB.
%---------------------------------------------------------------------------%
%
% File: version_array.m.
% Author: Ralph Becket <rafe@cs.mu.oz.au>.
% Stability: low.
%
% Version types are efficient pure implementations of typically imperative
% structures, subject to the following caveat: efficient access is only
% guaranteed for the "latest" version of a given structure. An older version
% incurs an access cost proportional to the number of its descendants.
%
% For example, if A0 is a version array, and A1 is created by updating A0,
% and A2 is created by updating A1, ..., and An is created by updating An-1,
% then accesses to An cost O(1) (assuming no further versions of the array
% have been created from An), but accesses to A0 cost O(n).
%
% Updates to older versions of the structure (for example A(n-1)) may have
% additional costs, for arrays this cost is O(m) where m is the size of the
% array, as the whole array is copied to make a new version array.
%
% Most version data structures come with impure, unsafe means to "rewind"
% to an earlier version, restoring that version's O(1) access times, but
% leaving later versions undefined (i.e. only do this if you are discarding
% all later versions of the structure.)
%
% The motivation for using version types is that they are ordinary ground
% structures and do not depend upon uniqueness, while in many circumstances
% offering similar levels of performance.
%
% This module implements version arrays. A version array provides O(1)
% access and update for the "latest" version of the array. "Older"
% versions of the array incur an O(k) penalty on accesses where k is
% the number of updates that have been made since.
%
% The advantage of version arrays is that in the common, singly threaded,
% case, they are almost as fast as unique arrays, but can be treated as
% ordinary ground values rather than unique values.
%
% Version arrays are zero based.
%
% NOTE_TO_IMPLEMENTORS XXX This implementation is not yet guaranteed to work
% NOTE_TO_IMPLEMENTORS with the agc (accurate garbage collection) grades.
% NOTE_TO_IMPLEMENTORS Specifically, MR_deep_copy and MR_agc_deep_copy
% NOTE_TO_IMPLEMENTORS currently do not recognise version arrays.
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
:- module version_array.
:- interface.
:- import_module list.
:- import_module pretty_printer.
%---------------------------------------------------------------------------%
:- type version_array(T).
% An `version_array.index_out_of_bounds' is the exception thrown
% on out-of-bounds array accesses. The string describes
% the predicate or function reporting the error.
%
:- type version_array.index_out_of_bounds
---> version_array.index_out_of_bounds(string).
%---------------------------------------------------------------------------%
% empty_array returns the empty array.
%
:- func empty = version_array(T).
% init(N, X) returns an array of size N with each item initialised to X.
%
:- func init(int, T) = version_array(T).
% Same as empty/0 except the resulting version_array is not thread safe.
%
% That is your program can crash or behave strangely if you attempt to
% concurrently access or update the array from different threads, or any
% two arrays produced from operations on the same original array.
% However this version is much quicker if you guarantee that you never
% concurrently access the version array.
%
:- func unsafe_empty = version_array(T).
% Same as init(N, X) except the resulting version_array is not thread safe.
%
% That is your program can crash or behave strangely if you attempt to
% concurrently access or update the array from different threads, or any
% two arrays produced from operations on the same original array.
% However this version is much quicker if you guarantee that you never
% concurrently access the version array.
%
:- func unsafe_init(int, T) = version_array(T).
% An obsolete synonym for the above.
%
:- pragma obsolete(unsafe_new/2).
:- func unsafe_new(int, T) = version_array(T).
% version_array(Xs) returns an array constructed from the items in the list
% Xs.
%
:- func version_array(list(T)) = version_array(T).
% A synonym for the above.
%
:- func from_list(list(T)) = version_array(T).
% from_reverse_list(Xs) returns an array constructed from the items in the
% list Xs in reverse order.
%
:- func from_reverse_list(list(T)) = version_array(T).
% lookup(A, I) = X iff the I'th member of A is X.
% (The first item has index 0).
%
:- func lookup(version_array(T), int) = T.
% A ^ elem(I) = lookup(A, I)
%
:- func version_array(T) ^ elem(int) = T.
% set(I, X, A0, A): A is a copy of array A0 with item I updated to be X.
% An exception is thrown if I is out of bounds.
%
:- pred set(int::in, T::in, version_array(T)::in, version_array(T)::out)
is det.
% (A0 ^ elem(I) := X) = A is equivalent to set(I, X, A0, A).
%
:- func (version_array(T) ^ elem(int) := T) = version_array(T).
% size(A) = N if A contains N items (i.e. the valid indices for A
% range from 0 to N - 1).
%
:- func size(version_array(T)) = int.
% max(Z) = size(A) - 1.
% Returns -1 for an empty array.
%
:- func max(version_array(T)) = int.
% is_empty(Array) is true iff Array is the empty array.
%
:- pred is_empty(version_array(T)::in) is semidet.
% resize(A, N, X) returns a new array whose items from
% 0..min(size(A), N - 1) are taken from A and whose items
% from min(size(A), N - 1)..(N - 1) (if any) are initialised to X.
% A predicate version is also provided.
%
:- func resize(version_array(T), int, T) = version_array(T).
:- pred resize(int::in, T::in, version_array(T)::in, version_array(T)::out)
is det.
% copy(A) is a copy of array A. Access to the copy is O(1).
%
:- func copy(version_array(T)) = version_array(T).
% list(A) = Xs where Xs is the list of items in A
% (i.e. A = version_array(Xs)).
%
:- func list(version_array(T)) = list(T).
% A synonym for the above.
%
:- func to_list(version_array(T)) = list(T).
% foldl(F, A, X) is equivalent to list.foldl(F, list(A), X).
%
:- func foldl(func(T1, T2) = T2, version_array(T1), T2) = T2.
% foldl(P, A, !X) is equivalent to list.foldl(P, list(A), !X).
%
:- pred foldl(pred(T1, T2, T2), version_array(T1), T2, T2).
:- mode foldl(pred(in, in, out) is det, in, in, out) is det.
:- mode foldl(pred(in, mdi, muo) is det, in, mdi, muo) is det.
:- mode foldl(pred(in, di, uo) is det, in, di, uo) is det.
:- mode foldl(pred(in, in, out) is semidet, in, in, out) is semidet.
:- mode foldl(pred(in, mdi, muo) is semidet, in, mdi, muo) is semidet.
:- mode foldl(pred(in, di, uo) is semidet, in, di, uo) is semidet.
% foldl2(P, A, !Acc1, !Acc2) is equivalent to
% list.foldl2(P, list(A), !Acc1, !Acc2) but more efficient.
%
:- pred foldl2(pred(T1, T2, T2, T3, T3), version_array(T1), T2, T2, T3, T3).
:- mode foldl2(pred(in, in, out, in, out) is det, in, in, out, in, out)
is det.
:- mode foldl2(pred(in, in, out, mdi, muo) is det, in, in, out, mdi, muo)
is det.
:- mode foldl2(pred(in, in, out, di, uo) is det, in, in, out, di, uo)
is det.
:- mode foldl2(pred(in, in, out, in, out) is semidet, in,
in, out, in, out) is semidet.
:- mode foldl2(pred(in, in, out, mdi, muo) is semidet, in,
in, out, mdi, muo) is semidet.
:- mode foldl2(pred(in, in, out, di, uo) is semidet, in,
in, out, di, uo) is semidet.
% foldr(F, A, X) is equivalent to list.foldr(F, list(A), Xs).
%
:- func foldr(func(T1, T2) = T2, version_array(T1), T2) = T2.
:- pred foldr(pred(T1, T2, T2), version_array(T1), T2, T2).
:- mode foldr(pred(in, in, out) is det, in, in, out) is det.
:- mode foldr(pred(in, mdi, muo) is det, in, mdi, muo) is det.
:- mode foldr(pred(in, di, uo) is det, in, di, uo) is det.
:- mode foldr(pred(in, in, out) is semidet, in, in, out) is semidet.
:- mode foldr(pred(in, mdi, muo) is semidet, in, mdi, muo) is semidet.
:- mode foldr(pred(in, di, uo) is semidet, in, di, uo) is semidet.
:- pred foldr2(pred(T1, T2, T2, T3, T3), version_array(T1), T2, T2, T3, T3).
:- mode foldr2(pred(in, in, out, in, out) is det, in, in, out, in, out)
is det.
:- mode foldr2(pred(in, in, out, mdi, muo) is det, in, in, out, mdi, muo)
is det.
:- mode foldr2(pred(in, in, out, di, uo) is det, in, in, out, di, uo)
is det.
:- mode foldr2(pred(in, in, out, in, out) is semidet, in,
in, out, in, out) is semidet.
:- mode foldr2(pred(in, in, out, mdi, muo) is semidet, in,
in, out, mdi, muo) is semidet.
:- mode foldr2(pred(in, in, out, di, uo) is semidet, in,
in, out, di, uo) is semidet.
% version_array.all_true(Pred, Array):
% True iff Pred is true for every element of Array.
%
:- pred all_true(pred(T)::in(pred(in) is semidet), version_array(T)::in)
is semidet.
% version_array.all_false(Pred, Array):
% True iff Pred is false for every element of Array.
%
:- pred all_false(pred(T)::in(pred(in) is semidet), version_array(T)::in)
is semidet.
% unsafe_rewind(A) produces a version of A for which all accesses are O(1).
% Invoking this predicate renders A and all later versions undefined that
% were derived by performing individual updates. Only use this when you are
% absolutely certain there are no live references to A or later versions
% of A. (A predicate version is also provided.)
%
:- func unsafe_rewind(version_array(T)) = version_array(T).
:- pred unsafe_rewind(version_array(T)::in, version_array(T)::out) is det.
% Convert a version_array to a pretty_printer.doc for formatting.
%
:- func version_array_to_doc(version_array(T)) = pretty_printer.doc.
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
% The first implementation of version arrays used nb_references.
% This incurred three memory allocations for every update. This version
% works at a lower level, but only performs one allocation per update.
%---------------------------------------------------------------------------%
:- implementation.
:- import_module int.
:- import_module exception.
:- import_module string.
%---------------------------------------------------------------------------%
:- pragma foreign_proc("C",
version_array.empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
MR_Word array;
MR_incr_hp_type_msg(VA, struct ML_va,
MR_ALLOC_ID, ""version_array.version_array/1"");
MR_incr_hp_msg(array, 1,
MR_ALLOC_ID, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = 0;
#ifdef MR_THREAD_SAFE
MR_incr_hp_type_msg(VA->lock, MercuryLock, MR_ALLOC_ID, NULL);
pthread_mutex_init(VA->lock, MR_MUTEX_ATTR);
#endif
").
:- pragma foreign_proc("C#",
version_array.empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = new version_array.ML_sva(version_array.ML_uva.empty());
").
:- pragma foreign_proc("Java",
version_array.empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = new ML_sva(ML_uva.empty());
").
:- pragma foreign_proc("C",
version_array.unsafe_empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
MR_Word array;
MR_incr_hp_type_msg(VA, struct ML_va,
MR_ALLOC_ID, ""version_array.version_array/1"");
MR_incr_hp_msg(array, 1,
MR_ALLOC_ID, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = 0;
#ifdef MR_THREAD_SAFE
VA->lock = NULL;
#endif
").
:- pragma foreign_proc("C#",
version_array.unsafe_empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = version_array.ML_uva.empty();
").
:- pragma foreign_proc("Java",
version_array.unsafe_empty = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = ML_uva.empty();
").
:- pragma foreign_proc("C",
version_array.init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
MR_Integer i;
MR_Word array;
MR_incr_hp_type_msg(VA, struct ML_va,
MR_ALLOC_ID, ""version_array.version_array/1"");
MR_incr_hp_msg(array, N + 1,
MR_ALLOC_ID, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = N;
for (i = 0; i < N; i++) {
VA->rest.array->elements[i] = X;
}
#ifdef MR_THREAD_SAFE
MR_incr_hp_type_msg(VA->lock, MercuryLock, MR_ALLOC_ID, NULL);
pthread_mutex_init(VA->lock, MR_MUTEX_ATTR);
#endif
").
:- pragma foreign_proc("C#",
version_array.init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = new version_array.ML_sva(version_array.ML_uva.init(N, X));
").
:- pragma foreign_proc("Java",
version_array.init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = new ML_sva(ML_uva.init(N, X));
").
:- pragma foreign_proc("C",
version_array.unsafe_init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
MR_Integer i;
MR_Word array;
MR_incr_hp_type_msg(VA, struct ML_va,
MR_ALLOC_ID, ""version_array.version_array/1"");
MR_incr_hp_msg(array, N + 1,
MR_ALLOC_ID, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = N;
for (i = 0; i < N; i++) {
VA->rest.array->elements[i] = X;
}
#ifdef MR_THREAD_SAFE
VA->lock = NULL;
#endif
").
:- pragma foreign_proc("C#",
version_array.unsafe_init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = version_array.ML_uva.init(N, X);
").
:- pragma foreign_proc("Java",
version_array.unsafe_init(N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = ML_uva.init(N, X);
").
unsafe_new(N, X) = unsafe_init(N, X).
%---------------------------------------------------------------------------%
version_array([]) = version_array.empty.
version_array([X | Xs]) = VA :-
VA0 = version_array.init(1 + list.length(Xs), X),
version_array_loop(1, Xs, VA0, VA).
:- pred version_array_loop(int::in, list(T)::in,
version_array(T)::in, version_array(T)::out) is det.
version_array_loop(_, [], !VA).
version_array_loop(I, [X | Xs], !VA) :-
set(I, X, !VA),
version_array_loop(I + 1, Xs, !VA).
from_list(Xs) = version_array(Xs).
from_reverse_list([]) = version_array.empty.
from_reverse_list([X | Xs]) = VA :-
NumElems = 1 + list.length(Xs),
VA0 = version_array.init(NumElems, X),
from_reverse_list_loop(NumElems - 2, Xs, VA0, VA).
:- pred from_reverse_list_loop(int::in, list(T)::in,
version_array(T)::in, version_array(T)::out) is det.
from_reverse_list_loop(_, [], !VA).
from_reverse_list_loop(I, [X | Xs], !VA) :-
set(I, X, !VA),
from_reverse_list_loop(I - 1, Xs, !VA).
%---------------------------------------------------------------------------%
lookup(VA, I) = X :-
( if get_if_in_range(VA, I, X0) then
X = X0
else
out_of_bounds_error(I, max(VA), "version_array.lookup")
).
:- pragma inline(version_array.elem/2).
VA ^ elem(I) =
lookup(VA, I).
%---------------------------------------------------------------------------%
set(I, X, !VA) :-
( if set_if_in_range(I, X, !VA) then
true
else
out_of_bounds_error(I, max(!.VA), "version_array.set")
).
:- pragma inline(version_array.'elem :='/3).
(VA0 ^ elem(I) := X) = VA :-
set(I, X, VA0, VA).
%---------------------------------------------------------------------------%
:- pragma foreign_proc("C",
size(VA::in) = (N::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
N = ML_va_size_dolock(VA);
").
:- pragma foreign_proc("C#",
size(VA::in) = (N::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
N = VA.size();
").
:- pragma foreign_proc("Java",
size(VA::in) = (N::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
N = VA.size();
").
max(VA) = size(VA) - 1.
is_empty(VA) :-
size(VA) = 0.
:- pragma foreign_proc("C",
resize(VA0::in, N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = ML_va_resize_dolock(VA0, N, X, MR_ALLOC_ID);
").
:- pragma foreign_proc("C#",
resize(VA0::in, N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = VA0.resize(N, X);
").
:- pragma foreign_proc("Java",
resize(VA0::in, N::in, X::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness, may_not_duplicate],
"
VA = VA0.resize(N, X);
").
resize(N, X, VA, resize(VA, N, X)).
%---------------------------------------------------------------------------%
copy(VA) =
( if size(VA) = 0 then
VA
else
resize(VA, size(VA), lookup(VA, 0))
).
%---------------------------------------------------------------------------%
list(VA) = foldr(list.cons, VA, []).
to_list(VA) = list(VA).
%---------------------------------------------------------------------------%
foldl(F, VA, Acc) = do_foldl_func(F, VA, Acc, 0, size(VA)).
:- func do_foldl_func(func(T1, T2) = T2, version_array(T1), T2, int, int) = T2.
do_foldl_func(F, VA, Acc, Lo, Hi) =
( if Lo < Hi then
do_foldl_func(F, VA, F(lookup(VA, Lo), Acc), Lo + 1, Hi)
else
Acc
).
%---------------------------------------------------------------------------%
foldl(P, VA, !Acc) :-
do_foldl_pred(P, VA, 0, size(VA), !Acc).
:- pred do_foldl_pred(pred(T1, T2, T2), version_array(T1), int, int, T2, T2).
:- mode do_foldl_pred(pred(in, in, out) is det, in, in, in, in, out) is det.
:- mode do_foldl_pred(pred(in, mdi, muo) is det, in, in, in, mdi, muo) is det.
:- mode do_foldl_pred(pred(in, di, uo) is det, in, in, in, di, uo) is det.
:- mode do_foldl_pred(pred(in, in, out) is semidet, in, in, in, in, out)
is semidet.
:- mode do_foldl_pred(pred(in, mdi, muo) is semidet, in, in, in, mdi, muo)
is semidet.
:- mode do_foldl_pred(pred(in, di, uo) is semidet, in, in, in, di, uo)
is semidet.
do_foldl_pred(P, VA, Lo, Hi, !Acc) :-
( if Lo < Hi then
P(lookup(VA, Lo), !Acc),
do_foldl_pred(P, VA, Lo + 1, Hi, !Acc)
else
true
).
%---------------------------------------------------------------------------%
foldl2(P, VA, !Acc1, !Acc2) :-
do_foldl2(P, VA, 0, size(VA), !Acc1, !Acc2).
:- pred do_foldl2(pred(T1, T2, T2, T3, T3), version_array(T1), int, int,
T2, T2, T3, T3).
:- mode do_foldl2(pred(in, in, out, in, out) is det, in, in, in,
in, out, in, out) is det.
:- mode do_foldl2(pred(in, in, out, mdi, muo) is det, in, in, in,
in, out, mdi, muo) is det.
:- mode do_foldl2(pred(in, in, out, di, uo) is det, in, in, in,
in, out, di, uo) is det.
:- mode do_foldl2(pred(in, in, out, in, out) is semidet, in, in, in,
in, out, in, out) is semidet.
:- mode do_foldl2(pred(in, in, out, mdi, muo) is semidet, in, in, in,
in, out, mdi, muo) is semidet.
:- mode do_foldl2(pred(in, in, out, di, uo) is semidet, in, in, in,
in, out, di, uo) is semidet.
do_foldl2(P, VA, Lo, Hi, !Acc1, !Acc2) :-
( if Lo < Hi then
P(lookup(VA, Lo), !Acc1, !Acc2),
do_foldl2(P, VA, Lo + 1, Hi, !Acc1, !Acc2)
else
true
).
%---------------------------------------------------------------------------%
foldr(F, VA, Acc) = do_foldr_func(F, VA, Acc, version_array.max(VA)).
:- func do_foldr_func(func(T1, T2) = T2, version_array(T1), T2, int) = T2.
do_foldr_func(F, VA, Acc, Hi) =
( if 0 =< Hi then
do_foldr_func(F, VA, F(lookup(VA, Hi), Acc), Hi - 1)
else
Acc
).
%---------------------------------------------------------------------------%
foldr(P, VA, !Acc) :-
do_foldr_pred(P, VA, version_array.max(VA), !Acc).
:- pred do_foldr_pred(pred(T1, T2, T2), version_array(T1), int, T2, T2).
:- mode do_foldr_pred(pred(in, in, out) is det, in, in, in, out) is det.
:- mode do_foldr_pred(pred(in, mdi, muo) is det, in, in, mdi, muo) is det.
:- mode do_foldr_pred(pred(in, di, uo) is det, in, in, di, uo) is det.
:- mode do_foldr_pred(pred(in, in, out) is semidet, in, in, in, out)
is semidet.
:- mode do_foldr_pred(pred(in, mdi, muo) is semidet, in, in, mdi, muo)
is semidet.
:- mode do_foldr_pred(pred(in, di, uo) is semidet, in, in, di, uo)
is semidet.
do_foldr_pred(P, VA, I, !Acc) :-
( if I >= 0 then
P(lookup(VA, I), !Acc),
do_foldr_pred(P, VA, I - 1, !Acc)
else
true
).
%---------------------------------------------------------------------------%
foldr2(P, VA, !Acc1, !Acc2) :-
do_foldr2(P, VA, version_array.max(VA), !Acc1, !Acc2).
:- pred do_foldr2(pred(T1, T2, T2, T3, T3), version_array(T1), int,
T2, T2, T3, T3).
:- mode do_foldr2(pred(in, in, out, in, out) is det, in, in,
in, out, in, out) is det.
:- mode do_foldr2(pred(in, in, out, mdi, muo) is det, in, in,
in, out, mdi, muo) is det.
:- mode do_foldr2(pred(in, in, out, di, uo) is det, in, in,
in, out, di, uo) is det.
:- mode do_foldr2(pred(in, in, out, in, out) is semidet, in, in,
in, out, in, out) is semidet.
:- mode do_foldr2(pred(in, in, out, mdi, muo) is semidet, in, in,
in, out, mdi, muo) is semidet.
:- mode do_foldr2(pred(in, in, out, di, uo) is semidet, in, in,
in, out, di, uo) is semidet.
do_foldr2(P, VA, I, !Acc1, !Acc2) :-
( if I >= 0 then
P(lookup(VA, I), !Acc1, !Acc2),
do_foldr2(P, VA, I - 1, !Acc1, !Acc2)
else
true
).
%---------------------------------------------------------------------------%
all_true(Pred, VA) :-
do_all_true(Pred, 0, size(VA), VA).
:- pred do_all_true(pred(T)::in(pred(in) is semidet), int::in, int::in,
version_array(T)::in) is semidet.
do_all_true(Pred, I, N, VA) :-
( if I < N then
Elem = VA ^ elem(I),
Pred(Elem),
do_all_true(Pred, I + 1, N, VA)
else
true
).
all_false(Pred, VA) :-
do_all_false(Pred, 0, size(VA), VA).
:- pred do_all_false(pred(T)::in(pred(in) is semidet), int::in, int::in,
version_array(T)::in) is semidet.
do_all_false(Pred, I, N, VA) :-
( if I < N then
Elem = VA ^ elem(I),
not Pred(Elem),
do_all_false(Pred, I + 1, N, VA)
else
true
).
%---------------------------------------------------------------------------%
unsafe_rewind(VA, unsafe_rewind(VA)).
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
% Sordid stuff below this point...
%
% The `thread_safe' attributes are justified:
% - creating new version arrays is thread-safe
% - thread-safe version arrays are protected by their own locks so do not need
% the global lock
% - the whole point of providing non-thread-safe version arrays is to avoid
% locking when the user "knows", and supposedly guarantees, that it is safe
% to do so.
:- pragma foreign_type("C", version_array(T), "struct ML_va *")
where
equality is eq_version_array,
comparison is cmp_version_array.
:- pragma foreign_type("C#", version_array(T), "version_array.ML_va")
where
equality is eq_version_array,
comparison is cmp_version_array.
:- pragma foreign_type("Java", version_array(T),
"jmercury.version_array.ML_va")
where
equality is eq_version_array,
comparison is cmp_version_array.
% This is necessary for the library to compile in the il and java
% grades.
:- type version_array(T)
---> version_array(T).
:- pred eq_version_array(version_array(T)::in, version_array(T)::in)
is semidet.
:- pragma terminates(eq_version_array/2).
eq_version_array(VAa, VAb) :-
N = max(VAa),
N = max(VAb),
eq_version_array_2(N, VAa, VAb).
:- pred eq_version_array_2(int::in,
version_array(T)::in, version_array(T)::in) is semidet.
eq_version_array_2(I, VAa, VAb) :-
( if I >= 0 then
lookup(VAa, I) = lookup(VAb, I),
eq_version_array_2(I - 1, VAa, VAb)
else
true
).
:- pred cmp_version_array(comparison_result::uo,
version_array(T)::in, version_array(T)::in) is det.
:- pragma terminates(cmp_version_array/3).
cmp_version_array(R, VAa, VAb) :-
SizeA = VAa ^ size,
SizeB = VAb ^ size,
compare(SizeResult, SizeA, SizeB),
(
SizeResult = (=),
cmp_version_array_2(0, SizeA, VAa, VAb, R)
;
( SizeResult = (<)
; SizeResult = (>)
),
R = SizeResult
).
:- pred cmp_version_array_2(int::in, int::in, version_array(T)::in,
version_array(T)::in, comparison_result::uo) is det.
cmp_version_array_2(I, Size, VAa, VAb, R) :-
( if I >= Size then
R = (=)
else
compare(R0, lookup(VAa, I), lookup(VAb, I)),
(
R0 = (=),
cmp_version_array_2(I + 1, Size, VAa, VAb, R)
;
( R0 = (<)
; R0 = (>)
),
R = R0
)
).
:- pred get_if_in_range(version_array(T)::in, int::in, T::out) is semidet.
:- pragma foreign_proc("C",
get_if_in_range(VA::in, I::in, X::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
SUCCESS_INDICATOR = ML_va_get_dolock(VA, I, &X);
").
:- pragma foreign_proc("C#",
get_if_in_range(VA::in, I::in, X::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
try {
X = VA.get(I);
SUCCESS_INDICATOR = true;
} catch (System.IndexOutOfRangeException) {
X = null;
SUCCESS_INDICATOR = false;
}
").
:- pragma foreign_proc("Java",
get_if_in_range(VA::in, I::in, X::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
try {
X = VA.get(I);
SUCCESS_INDICATOR = true;
} catch (ArrayIndexOutOfBoundsException e) {
X = null;
SUCCESS_INDICATOR = false;
}
").
:- pred set_if_in_range(int::in, T::in,
version_array(T)::in, version_array(T)::out) is semidet.
:- pragma foreign_proc("C",
set_if_in_range(I::in, X::in, VA0::in, VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
SUCCESS_INDICATOR = ML_va_set_dolock(VA0, I, X, &VA, MR_ALLOC_ID);
").
:- pragma foreign_proc("C#",
set_if_in_range(I::in, X::in, VA0::in, VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
try {
VA = VA0.set(I, X);
SUCCESS_INDICATOR = true;
} catch (System.IndexOutOfRangeException) {
VA = null;
SUCCESS_INDICATOR = false;
}
").
:- pragma foreign_proc("Java",
set_if_in_range(I::in, X::in, VA0::in, VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
try {
VA = VA0.set(I, X);
SUCCESS_INDICATOR = true;
} catch (ArrayIndexOutOfBoundsException e) {
VA = null;
SUCCESS_INDICATOR = false;
}
").
:- pragma foreign_proc("C",
unsafe_rewind(VA0::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = ML_va_rewind_dolock(VA0, MR_ALLOC_ID);
").
:- pragma foreign_proc("C#",
unsafe_rewind(VA0::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = VA0.rewind();
").
:- pragma foreign_proc("Java",
unsafe_rewind(VA0::in) = (VA::out),
[will_not_call_mercury, promise_pure, thread_safe, will_not_modify_trail,
does_not_affect_liveness],
"
VA = VA0.rewind();
").
:- pragma foreign_decl("C", "
// If index is -1 then value is undefined and rest is the latest
// array value.
//
// Otherwise value is the overwritten value at index and rest is
// a pointer to the next version in the chain.
typedef struct ML_va *ML_va_ptr;
typedef const struct ML_va *ML_const_va_ptr;
struct ML_va {
MR_Integer index; // -1 for latest, >= 0 for older
MR_Word value; // Valid if index >= 0
union {
MR_ArrayPtr array; // Valid if index == -1
ML_va_ptr next; // Valid if index >= 0
} rest;
#ifdef MR_THREAD_SAFE
MercuryLock *lock; // NULL or lock
#endif
};
// Returns a pointer to the latest version of the array.
extern ML_va_ptr
ML_va_get_latest(ML_const_va_ptr VA);
// Returns the number of items in a version array.
extern MR_Integer
ML_va_size_dolock(ML_const_va_ptr);
// If I is in range then ML_va_get(VA, I, &X) sets X to the I'th item
// in VA (counting from zero) and returns MR_TRUE. Otherwise it
// returns MR_FALSE.
extern MR_bool
ML_va_get_dolock(ML_const_va_ptr, MR_Integer, MR_Word *);
// If I is in range then ML_va_set(VA0, I, X, VA) sets VA to be VA0
// updated with the I'th item as X (counting from zero) and
// returns MR_TRUE. Otherwise it returns MR_FALSE.
extern MR_bool
ML_va_set_dolock(ML_va_ptr, MR_Integer, MR_Word, ML_va_ptr *,
MR_AllocSiteInfoPtr);
// `Rewinds' a version array, invalidating all extant successors
// including the argument.
extern ML_va_ptr
ML_va_rewind_dolock(ML_va_ptr, MR_AllocSiteInfoPtr);
// Resize a version array.
extern ML_va_ptr
ML_va_resize_dolock(ML_va_ptr, MR_Integer, MR_Word, MR_AllocSiteInfoPtr);
").
:- pragma foreign_decl("C", local, "
#include ""mercury_types.h""
#include ""mercury_bitmap.h""
// Returns the number of items in a version array.
static MR_Integer
ML_va_size(ML_const_va_ptr);
// If I is in range then ML_va_get(VA, I, &X) sets X to the I'th item
// in VA (counting from zero) and returns MR_TRUE. Otherwise it
// returns MR_FALSE.
static MR_bool
ML_va_get(ML_const_va_ptr VA, MR_Integer I, MR_Word *Xptr);
// If I is in range then ML_va_set(VA0, I, X, VA) sets VA to be VA0
// updated with the I'th item as X (counting from zero) and
// returns MR_TRUE. Otherwise it returns MR_FALSE.
static MR_bool
ML_va_set(ML_va_ptr, MR_Integer, MR_Word, ML_va_ptr *,
MR_AllocSiteInfoPtr alloc_id);
// Create a copy of VA0 as a new array.
static ML_va_ptr
ML_va_flat_copy(ML_const_va_ptr VA0, MR_AllocSiteInfoPtr alloc_id);
// Update the array VA using the override values in VA0
// i.e. recreate the state of the version array as captured in VA0.
static void
ML_va_rewind_into(ML_va_ptr VA, ML_const_va_ptr VA0,
MR_AllocSiteInfoPtr alloc_id);
// `Rewinds' a version array, invalidating all extant successors
// including the argument.
static ML_va_ptr
ML_va_rewind(ML_va_ptr VA, MR_AllocSiteInfoPtr alloc_id);
// Resize a version array.
static ML_va_ptr
ML_va_resize(ML_va_ptr, MR_Integer, MR_Word, MR_AllocSiteInfoPtr);
").
:- pragma foreign_code("C", "
#define ML_va_latest_version(VA) ((VA)->index == -1)
#ifdef MR_THREAD_SAFE
#define ML_maybe_lock(lock) \\
do { \\
if (lock) { \\
MR_LOCK(lock, ""ML_maybe_lock""); \\
} \\
} while (0)
#define ML_maybe_unlock(lock) \\
do { \\
if (lock) { \\
MR_UNLOCK(lock, ""ML_maybe_unlock""); \\
} \\
} while (0)
#else
#define ML_maybe_lock(lock) ((void) 0)
#define ML_maybe_unlock(lock) ((void) 0)
#endif
ML_va_ptr
ML_va_get_latest(ML_const_va_ptr VA)
{
while (!ML_va_latest_version(VA)) {
VA = VA->rest.next;
}
// Cast away the 'const'.
return (ML_va_ptr)VA;
}
MR_Integer
ML_va_size_dolock(ML_const_va_ptr VA)
{
#ifdef MR_THREAD_SAFE
MercuryLock *lock = VA->lock;
#endif
MR_Integer size;
ML_maybe_lock(lock);
size = ML_va_size(VA);
ML_maybe_unlock(lock);
return size;
}
static MR_Integer
ML_va_size(ML_const_va_ptr VA)
{
VA = ML_va_get_latest(VA);
return VA->rest.array->size;
}
int
ML_va_get_dolock(ML_const_va_ptr VA, MR_Integer I, MR_Word *Xptr)
{
#ifdef MR_THREAD_SAFE
MercuryLock *lock = VA->lock;
#endif
int ret;
ML_maybe_lock(lock);
ret = ML_va_get(VA, I, Xptr);
ML_maybe_unlock(lock);
return ret;
}
static int
ML_va_get(ML_const_va_ptr VA, MR_Integer I, MR_Word *Xptr)
{
while (!ML_va_latest_version(VA)) {
if (I == VA->index) {
*Xptr = VA->value;
return MR_TRUE;
}
VA = VA->rest.next;
}
if (0 <= I && I < VA->rest.array->size) {
*Xptr = VA->rest.array->elements[I];
return MR_TRUE;
} else {
return MR_FALSE;
}
}
int
ML_va_set_dolock(ML_va_ptr VA0, MR_Integer I, MR_Word X, ML_va_ptr *VAptr,
MR_AllocSiteInfoPtr alloc_id)
{
#ifdef MR_THREAD_SAFE
MercuryLock *lock = VA0->lock;
#endif
int ret;
ML_maybe_lock(lock);
ret = ML_va_set(VA0, I, X, VAptr, alloc_id);
ML_maybe_unlock(lock);
return ret;
}
static int
ML_va_set(ML_va_ptr VA0, MR_Integer I, MR_Word X, ML_va_ptr *VAptr,
MR_AllocSiteInfoPtr alloc_id)
{
ML_va_ptr VA1;
if (ML_va_latest_version(VA0)) {
if (I < 0 || I >= VA0->rest.array->size) {
return MR_FALSE;
}
MR_incr_hp_type_msg(VA1, struct ML_va, alloc_id,
""version_array.version_array/1"");
VA1->index = -1;
VA1->value = (MR_Word) NULL;
VA1->rest.array = VA0->rest.array;
#ifdef MR_THREAD_SAFE
VA1->lock = VA0->lock;
#endif
VA0->index = I;
VA0->value = VA0->rest.array->elements[I];
VA0->rest.next = VA1;
VA1->rest.array->elements[I] = X;
} else {
VA1 = ML_va_flat_copy(VA0, alloc_id);
if (I < 0 || I >= VA1->rest.array->size) {
return MR_FALSE;
}
VA1->rest.array->elements[I] = X;
}
*VAptr = VA1;
return MR_TRUE;
}
static ML_va_ptr
ML_va_flat_copy(ML_const_va_ptr VA0, MR_AllocSiteInfoPtr alloc_id)
{
ML_va_ptr latest;
ML_va_ptr VA;
MR_Word array;
MR_Integer N;
MR_Integer i;
latest = ML_va_get_latest(VA0);
N = latest->rest.array->size;
MR_incr_hp_type_msg(VA, struct ML_va,
alloc_id, ""version_array.version_array/1"");
MR_incr_hp_msg(array, N + 1,
alloc_id, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = N;
for (i = 0; i < N; i++) {
VA->rest.array->elements[i] = latest->rest.array->elements[i];
}
#ifdef MR_THREAD_SAFE
if (VA0->lock != NULL) {
MR_incr_hp_type_msg(VA->lock, MercuryLock, alloc_id, NULL);
pthread_mutex_init(VA->lock, MR_MUTEX_ATTR);
} else {
VA->lock = NULL;
}
#endif
ML_va_rewind_into(VA, VA0, alloc_id);
return VA;
}
static void
ML_va_rewind_into(ML_va_ptr VA_dest, ML_const_va_ptr VA_src,
MR_AllocSiteInfoPtr alloc_id)
{
MR_Integer I;
MR_Word X;
ML_const_va_ptr cur;
MR_BitmapPtr bitmap;
if (ML_va_latest_version(VA_src)) {
// Shortcut.
return;
}
// Rewind elements from the oldest to the newest, undoing their changes.
// So that we undo elements in the correct order we use a bitmap to
// ensure that we never update an array slot twice.
cur = VA_src;
MR_allocate_bitmap_msg(bitmap, VA_dest->rest.array->size, alloc_id);
MR_bitmap_zero(bitmap);
while (!ML_va_latest_version(cur)) {
I = cur->index;
X = cur->value;
if (I < VA_dest->rest.array->size && !MR_bitmap_get_bit(bitmap, I)) {
VA_dest->rest.array->elements[I] = X;
MR_bitmap_set_bit(bitmap, I);
}
cur = cur->rest.next;
}
}
ML_va_ptr
ML_va_rewind_dolock(ML_va_ptr VA, MR_AllocSiteInfoPtr alloc_id)
{
#ifdef MR_THREAD_SAFE
MercuryLock *lock = VA->lock;
#endif
ML_maybe_lock(lock);
VA = ML_va_rewind(VA, alloc_id);
ML_maybe_unlock(lock);
return VA;
}
static ML_va_ptr
ML_va_rewind(ML_va_ptr VA, MR_AllocSiteInfoPtr alloc_id)
{
MR_Integer I;
MR_Word X;
ML_va_ptr cur;
MR_ArrayPtr array;
MR_BitmapPtr bitmap;
if (ML_va_latest_version(VA)) {
// Shortcut.
return VA;
}
// Rewind elements from the oldest to the newest, undoing their changes.
// So that we undo elements in the correct order we use a bitmap to
// ensure that we never update an array slot twice.
cur = VA;
array = ML_va_get_latest(VA)->rest.array;
MR_allocate_bitmap_msg(bitmap, array->size, alloc_id);
while (!ML_va_latest_version(cur)) {
I = cur->index;
X = cur->value;
if (!MR_bitmap_get_bit(bitmap, I)) {
array->elements[I] = X;
MR_bitmap_set_bit(bitmap, I);
}
cur = cur->rest.next;
}
VA->rest.array = array;
// This element is no-longer an update element.
VA->index = -1;
VA->value = 0;
return VA;
}
ML_va_ptr
ML_va_resize_dolock(ML_va_ptr VA0, MR_Integer N, MR_Word X,
MR_AllocSiteInfoPtr alloc_id)
{
#ifdef MR_THREAD_SAFE
MercuryLock *lock = VA0->lock;
#endif
ML_va_ptr VA;
ML_maybe_lock(lock);
VA = ML_va_resize(VA0, N, X, alloc_id);
ML_maybe_unlock(lock);
return VA;
}
static ML_va_ptr
ML_va_resize(ML_va_ptr VA0, MR_Integer N, MR_Word X,
MR_AllocSiteInfoPtr alloc_id)
{
ML_va_ptr latest;
ML_va_ptr VA;
MR_Integer i;
MR_Integer size_VA0;
MR_Integer min;
MR_Word array;
latest = ML_va_get_latest(VA0);
size_VA0 = ML_va_size(latest);
min = (N <= size_VA0 ? N : size_VA0);
MR_incr_hp_type_msg(VA, struct ML_va,
alloc_id, ""version_array.version_array/1"");
MR_incr_hp_msg(array, N + 1,
alloc_id, ""version_array.version_array/1"");
VA->index = -1;
VA->value = (MR_Word) NULL;
VA->rest.array = (MR_ArrayPtr) array;
VA->rest.array->size = N;
for (i = 0; i < min; i++) {
VA->rest.array->elements[i] = latest->rest.array->elements[i];
}
#ifdef MR_THREAD_SAFE
if (VA0->lock != NULL) {
MR_incr_hp_type_msg(VA->lock, MercuryLock, alloc_id, NULL);
pthread_mutex_init(VA->lock, MR_MUTEX_ATTR);
} else {
VA->lock = NULL;
}
#endif
ML_va_rewind_into(VA, VA0, alloc_id);
for (i = min; i < N; i++) {
VA->rest.array->elements[i] = X;
}
return VA;
}
").
:- pragma foreign_decl("C#", local, "
using System;
").
:- pragma foreign_code("C#", "
public interface ML_va {
object get(int I);
ML_va set(int I, object X);
ML_va resize(int N, object X);
ML_va rewind();
int size();
}
// An implementation of version arrays that is safe when used in multiple
// threads.
//
// It just wraps the unsafe version is some synchronization logic so
// that only one thread can be accessing the array at one instant.
[System.Serializable]
public class ML_sva : ML_va {
private ML_uva version_array;
private object va_lock;
public ML_sva(ML_uva va) {
version_array = va;
va_lock = new object();
}
private ML_sva() {}
public object get(int I) {
lock (va_lock) {
return version_array.get(I);
}
}
public ML_va set(int I, object X) {
lock (va_lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.set_uva(I, X);
if (result.version_array.isClone()) {
result.version_array.resetIsClone();
result.va_lock = new object();
} else {
result.va_lock = this.va_lock;
}
return result;
}
}
public ML_va resize(int N, object X) {
lock (va_lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.resize_uva(N, X);
result.va_lock = new object();
return result;
}
}
public ML_va rewind()
{
lock (va_lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.rewind_uva();
result.va_lock = this.va_lock;
return result;
}
}
public int size()
{
lock (va_lock) {
return version_array.size();
}
}
}
// An implementation of version arrays that is only safe when used from
// a single thread, but *much* faster than the synchronized version.
[System.Serializable]
public class ML_uva : ML_va {
private int index; // -1 for latest, >= 0 for older
private object value; // Valid if index >= 0
private object rest; // array if index == -1
// next if index >= 0
// True if this is a fresh clone of another ML_uva.
private bool clone = false;
public ML_uva() {}
public static ML_uva empty() {
ML_uva va = new ML_uva();
va.index = -1;
va.value = null;
va.rest = new object[0];
return va;
}
public static ML_uva init(int N, object X) {
ML_uva va = new ML_uva();
va.index = -1;
va.value = null;
va.rest = new object[N];
for (int i = 0; i < N; i++) {
va.array()[i] = X;
}
return va;
}
public ML_va resize(int N, object X) {
return resize_uva(N, X);
}
public ML_uva resize_uva(int N, object X) {
ML_uva VA0 = this;
ML_uva latest;
int size_VA0;
int min;
latest = VA0.latest();
size_VA0 = latest.size();
min = (N <= size_VA0 ? N : size_VA0);
ML_uva VA = new ML_uva();
VA.index = -1;
VA.value = null;
VA.rest = new object[N];
System.Array.Copy(latest.array(), 0, VA.array(), 0, min);
VA0.rewind_into(VA);
for (int i = min; i < N; i++) {
VA.array()[i] = X;
}
return VA;
}
private bool is_latest()
{
return index == -1;
}
private ML_uva latest()
{
ML_uva VA = this;
while (!VA.is_latest()) {
VA = VA.next();
}
return VA;
}
private object[] array()
{
return (object[]) rest;
}
private ML_uva next()
{
return (ML_uva) rest;
}
public int size()
{
return latest().array().Length;
}
public object get(int I)
{
ML_uva VA = this;
while (!VA.is_latest()) {
if (I == VA.index) {
return VA.value;
}
VA = VA.next();
}
return VA.array()[I];
}
public ML_va set(int I, object X)
{
return set_uva(I, X);
}
public ML_uva set_uva(int I, object X)
{
ML_uva VA0 = this;
ML_uva VA1;
if (VA0.is_latest()) {
VA1 = new ML_uva();
VA1.index = -1;
VA1.value = null;
VA1.rest = VA0.array();
VA0.index = I;
VA0.value = VA0.array()[I];
VA0.rest = VA1;
VA1.array()[I] = X;
} else {
VA1 = VA0.flat_copy();
VA1.array()[I] = X;
}
return VA1;
}
private ML_uva flat_copy()
{
ML_uva VA0 = this;
ML_uva latest;
ML_uva VA;
latest = VA0.latest();
VA = new ML_uva();
VA.index = -1;
VA.value = null;
VA.rest = latest.array().Clone();
VA.clone = true;
VA0.rewind_into(VA);
return VA;
}
public bool isClone() {
return clone;
}
public void resetIsClone() {
this.clone = false;
}
private void rewind_into(ML_uva VA)
{
int I;
object X;
ML_uva cur;
mercury.runtime.MercuryBitmap bitmap;
if (this.is_latest()) {
// Shortcut.
return;
}
// Rewind elements from the oldest to the newest, undoing their changes.
// So that we undo elements in the correct order we use a bitmap to
// ensure that we never update an array slot twice.
cur = this;
bitmap = new mercury.runtime.MercuryBitmap(cur.size());
while (!cur.is_latest()) {
I = cur.index;
X = cur.value;
if (I < VA.size() && !bitmap.GetBit(I)) {
VA.array()[I] = X;
bitmap.SetBit(I);
}
cur = cur.next();
}
}
public ML_va rewind()
{
return rewind_uva();
}
public ML_uva rewind_uva()
{
int I;
object X;
ML_uva cur;
mercury.runtime.MercuryBitmap bitmap;
object[] array;
if (is_latest()) {
return this;
}
// Rewind elements from the oldest to the newest, undoing their
// changes. So that we undo elements in the correct order,
// we use a bitmap to ensure that we never update an array slot twice.
cur = this;
array = latest().array();
bitmap = new mercury.runtime.MercuryBitmap(array.Length);
while (!cur.is_latest()) {
I = cur.index;
X = cur.value;
if (!bitmap.GetBit(I)) {
array[I] = X;
bitmap.SetBit(I);
}
cur = cur.next();
}
rest = array;
// This element is no-longer an update element.
index = -1;
value = 0;
return this;
}
}
").
:- pragma foreign_decl("Java", local, "
import jmercury.runtime.MercuryBitmap;
").
:- pragma foreign_code("Java", "
public interface ML_va {
public Object get(int I) throws ArrayIndexOutOfBoundsException;
public ML_va set(int I, Object X);
public ML_va resize(int N, Object X);
public ML_va rewind();
public int size();
}
public static class Lock implements java.io.Serializable {
public Lock() { return; }
}
// An implementation of version arrays that is safe when used in multiple
// threads.
//
// It just wraps the unsafe version is some synchronization logic so
// that only one thread can be accessing the array at one instant.
public static class ML_sva implements ML_va, java.io.Serializable {
private ML_uva version_array;
private Lock lock;
public ML_sva(ML_uva va) {
version_array = va;
lock = new Lock();
}
private ML_sva() {};
public Object get(int I) throws ArrayIndexOutOfBoundsException {
synchronized (lock) {
return version_array.get(I);
}
}
public ML_sva set(int I, Object X) {
synchronized (lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.set(I, X);
if (result.version_array.isClone()) {
result.version_array.resetIsClone();
result.lock = new Lock();
} else {
result.lock = this.lock;
}
return result;
}
}
public ML_sva resize(int N, Object X) {
synchronized (lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.resize(N, X);
result.lock = new Lock();
return result;
}
}
public ML_sva rewind()
{
synchronized (lock) {
ML_sva result = new ML_sva();
result.version_array = version_array.rewind();
result.lock = this.lock;
return result;
}
}
public int size()
{
synchronized (lock) {
return version_array.size();
}
}
}
// An implementation of version arrays that is only safe when used from
// a single thread, but *much* faster than the synchronized version.
public static class ML_uva implements ML_va, java.io.Serializable {
private int index; // -1 for latest, >= 0 for older
private Object value; // Valid if index >= 0
private Object rest; // array if index == -1
// next if index >= 0
private boolean clone = false;
public ML_uva() {}
public static ML_uva empty() {
ML_uva va = new ML_uva();
va.index = -1;
va.value = null;
va.rest = new Object[0];
return va;
}
public static ML_uva init(int N, Object X) {
ML_uva va = new ML_uva();
va.index = -1;
va.value = null;
va.rest = new Object[N];
java.util.Arrays.fill(va.array(), X);
return va;
}
public ML_uva resize(int N, Object X) {
ML_uva VA0 = this;
ML_uva latest;
int size_VA0;
int min;
latest = VA0.latest();
size_VA0 = latest.size();
min = (N <= size_VA0 ? N : size_VA0);
ML_uva VA = new ML_uva();
VA.index = -1;
VA.value = null;
VA.rest = new Object[N];
System.arraycopy(latest.array(), 0, VA.array(), 0, min);
VA0.rewind_into(VA);
java.util.Arrays.fill(VA.array(), min, N, X);
return VA;
}
private boolean is_latest()
{
return index == -1;
}
private ML_uva latest()
{
ML_uva VA = this;
while (!VA.is_latest()) {
VA = VA.next();
}
return VA;
}
private Object[] array()
{
return (Object[]) rest;
}
private ML_uva next()
{
return (ML_uva) rest;
}
public int size()
{
return latest().array().length;
}
public Object get(int I)
throws ArrayIndexOutOfBoundsException
{
ML_uva VA = this;
while (!VA.is_latest()) {
if (I == VA.index) {
return VA.value;
}
VA = VA.next();
}
return VA.array()[I];
}
public ML_uva set(int I, Object X)
{
ML_uva VA0 = this;
ML_uva VA1;
if (VA0.is_latest()) {
VA1 = new ML_uva();
VA1.index = -1;
VA1.value = null;
VA1.rest = VA0.array();
VA0.index = I;
VA0.value = VA0.array()[I];
VA0.rest = VA1;
VA1.array()[I] = X;
} else {
VA1 = VA0.flat_copy();
VA1.array()[I] = X;
}
return VA1;
}
private ML_uva flat_copy()
{
ML_uva VA0 = this;
ML_uva latest;
ML_uva VA;
latest = VA0.latest();
VA = new ML_uva();
VA.index = -1;
VA.value = null;
VA.rest = latest.array().clone();
VA.clone = true;
VA0.rewind_into(VA);
return VA;
}
public boolean isClone() {
return clone;
}
public void resetIsClone() {
this.clone = false;
}
private void rewind_into(ML_uva VA)
{
int I;
Object X;
ML_uva cur;
MercuryBitmap bitmap;
if (this.is_latest()) {
return;
}
// Rewind elements from the oldest to the newest, undoing their
// changes. So that we undo elements in the correct order,
// we use a bitmap to ensure that we never update an array slot twice.
cur = this;
bitmap = new MercuryBitmap(cur.size());
while (!cur.is_latest()) {
I = cur.index;
X = cur.value;
if (I < VA.size() && !bitmap.getBit(I)) {
VA.array()[I] = X;
bitmap.setBit(I);
}
cur = cur.next();
}
}
public ML_uva rewind()
{
int I;
Object X;
ML_uva cur;
MercuryBitmap bitmap;
Object[] array;
if (is_latest()) {
return this;
}
// Rewind elements from the oldest to the newest, undoing their
// changes. So that we undo elements in the correct order,
// we use a bitmap to ensure that we never update an array slot twice.
cur = this;
array = latest().array();
bitmap = new MercuryBitmap(array.length);
while (!cur.is_latest()) {
I = cur.index;
X = cur.value;
if (!bitmap.getBit(I)) {
array[I] = X;
bitmap.setBit(I);
}
cur = cur.next();
}
rest = array;
// This element is no-longer an update element.
index = -1;
value = 0;
return this;
}
}
").
%---------------------------------------------------------------------------%
% Throw an exception indicating an array bounds error.
%
:- pred out_of_bounds_error(int, int, string).
:- mode out_of_bounds_error(in, in, in) is erroneous.
out_of_bounds_error(Index, Max, PredName) :-
% Note: we deliberately do not include the array element type name in the
% error message here, for performance reasons: using the type name could
% prevent the compiler from optimizing away the construction of the
% type_info in the caller, because it would prevent unused argument
% elimination.
string.format("%s: index %d not in range [0, %d]",
[s(PredName), i(Index), i(Max)], Msg),
throw(version_array.index_out_of_bounds(Msg)).
%---------------------------------------------------------------------------%
version_array_to_doc(A) =
indent([str("version_array(["), version_array_to_doc_2(0, A), str("])")]).
:- func version_array_to_doc_2(int, version_array(T)) = doc.
version_array_to_doc_2(I, VA) =
( if I > version_array.max(VA) then
str("")
else
docs([
format_arg(format(lookup(VA, I))),
( if I = version_array.max(VA) then
str("")
else
group([str(", "), nl])
),
format_susp((func) = version_array_to_doc_2(I + 1, VA))
])
).
%---------------------------------------------------------------------------%
:- end_module version_array.
%---------------------------------------------------------------------------%
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