/* Part of SWI-Prolog
Author: Kuniaki Mukai Wielemaker
E-mail: mukai@sfc.keio.ac.jp
WWW: http://www.swi-prolog.org
Copyright (c) 2011-2016, Kuniaki Mukai
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.
*/
/*#define O_DEBUG 1*/
#include "pl-incl.h"
/********************************
* VARIANT *
*********************************/
#define consVar(w) (((intptr_t)(w)<<LMASK_BITS) | TAG_VAR | FIRST_MASK)
#define valVar(w) ((intptr_t)(w) >> LMASK_BITS)
#define TAG_COMPOUND_x (STG_STATIC|TAG_COMPOUND)
#define isCompound_x(w) \
(( (intptr_t)(w) & (STG_MASK|TAG_MASK) ) == TAG_COMPOUND_x )
#define valCompound_x(w) ((intptr_t)(w) >> LMASK_BITS)
#define consCompound_x(i) (((i)<<LMASK_BITS) | TAG_COMPOUND_x)
#define node_bp(p) ((p)->bp)
#define node_orig(p) ((p)->orig)
#define node_variant(p) ((p)->a)
#define node_isom(p) ((p)->b)
typedef struct aWork
{ word * left; /* left term arguments */
word * right; /* right term arguments */
int arg;
int arity;
} aWork;
typedef struct argPairs
{ aWork work; /* current work */
segstack stack;
aWork first_chunk[16];
} argPairs;
typedef struct node
{ Word bp; /* pointer to the original term */
word orig; /* saved word */
int a; /* variant at left */
int b; /* link to isomophic node */
} node;
static void
init_agenda(argPairs *a)
{ initSegStack(&a->stack, sizeof(aWork),
sizeof(a->first_chunk), a->first_chunk);
}
static inline bool
push_start_args(argPairs *a, Word left, Word right, int arity) /* plural */
{ a->work.left = left;
a->work.right = right;
a->work.arg = 0;
a->work.arity = arity;
return TRUE;
}
static inline bool
push_args(argPairs *a, Word left, Word right, int arity) /* plural */
{ if ( !pushSegStack(&a->stack, a->work, aWork) )
return FALSE;
return push_start_args(a, left, right, arity);
}
static inline bool
next_arg(argPairs *a, Word *lp, Word *rp) /* singular (not plural !) */
{ while( a->work.arg >= a->work.arity)
{ if ( !popSegStack(&a->stack, &a->work, aWork) )
return FALSE;
}
*lp = a->work.left;
*rp = a->work.right;
a->work.arg++;
a->work.left++;
a->work.right++;
return TRUE;
}
static inline node *
Node(int i, Buffer buf)
{ return &fetchBuffer(buf, i, node);
}
static inline bool
add_node_buffer(Buffer b, node *obj)
{ if ( ((b->top) + sizeof(node)) > (b->max) )
{ if ( !growBuffer(b, sizeof(node)) )
return FALSE;
}
*((node *)(b)->top) = *obj;
b->top += sizeof(node);
return TRUE;
}
static inline int
var_id(Word p, Buffer buf)
{ word w = *p;
if ( w )
{ return (int)valVar(w); /* node id truncated to int: */
} else /* < 2^31 nodes */
{ int n = (int)entriesBuffer(buf, node);
node new = {p, w, 0, 0};
if ( !add_node_buffer((Buffer)buf, &new) )
return MEMORY_OVERFLOW;
*p = (word)consVar(n);
return n;
}
}
static inline int
term_id(Word p, Buffer buf)
{ word w = *p;
if ( isCompound_x(w) )
{ return (int)valCompound_x(w);
} else
{ int n = (int)entriesBuffer(buf, node);
node new = {p, w, 0, 0};
if ( !add_node_buffer((Buffer)buf, &new) )
return MEMORY_OVERFLOW;
*p = (word)consCompound_x(n);
return n;
}
}
static inline int
Root(int i, node **r, Buffer buf)
{ int k;
node * n;
do
{ k = i;
n = Node(i, buf);
DEBUG(CHK_SECURE, assert(n != NULL));
i = node_isom(n);
} while ( i != 0 );
*r = n;
return k;
}
static inline void
univ(word t, Word d, Word *a ARG_LD)
{ Functor f;
f = valueTerm(t);
while ( isRef(f->definition) )
f = (Functor)unRef(f->definition);
*d = f->definition;
*a = f->arguments;
}
static inline void
reset_terms(node * r)
{ *(r->bp) = r->orig;
}
/* isomorphic (==) */
static int
isomorphic(argPairs *a, int i, int j, Buffer buf ARG_LD)
{ Word l = NULL, r = NULL, lm, ln;
word dm, dn;
Word dummy = NULL;
if ( i == j )
return TRUE;
if ( !push_args(a, dummy, dummy, 1) )
return MEMORY_OVERFLOW;
univ(node_orig(Node(i, buf)), &dm, &lm PASS_LD);
univ(node_orig(Node(j, buf)), &dn, &ln PASS_LD);
if ( dm != dn )
return FALSE;
if ( !push_args(a, lm, ln, arityFunctor(dm)) )
return MEMORY_OVERFLOW;
while( next_arg(a, &l, &r) )
{ word wl, wr;
if ( l == NULL )
return TRUE;
attvar:
deRef(l);
deRef(r);
wl = *l;
wr = *r;
if ( tag(wl) != tag(wr) )
return FALSE;
if ( tag(wl) == TAG_VAR )
{ if ( l != r ) /* identity test on variables */
return FALSE;
continue;
}
if ( tag(wl) == TAG_ATTVAR )
{ l = valPAttVar(wl);
r = valPAttVar(wr);
goto attvar;
}
if ( wl == wr && !isTerm(wl) )
continue;
switch(tag(wl))
{ case TAG_ATOM:
return FALSE;
case TAG_INTEGER:
if ( storage(wl) == STG_INLINE ||
storage(wr) == STG_INLINE )
return FALSE;
case TAG_STRING:
case TAG_FLOAT:
if ( equalIndirect(wl, wr) )
continue;
return FALSE;
case TAG_COMPOUND:
{ Word lm, ln;
word dm, dn;
int i, j;
node *m, *n;
if ( (i = term_id(l, buf)) < 0 )
return MEMORY_OVERFLOW;
i = Root(i, &m, buf);
if ( (j = term_id(r, buf)) < 0 )
return MEMORY_OVERFLOW;
j = Root(j, &n, buf);
if ( i==j )
continue;
univ(node_orig(m), &dm, &lm PASS_LD);
univ(node_orig(n), &dn, &ln PASS_LD);
if ( dm != dn )
return FALSE;
if ( i <= j )
node_isom(m) = j; /* union */
else
node_isom(n) = i;
if ( !push_args(a, lm, ln, arityFunctor(dm)) )
return MEMORY_OVERFLOW;
continue;
}
default:
assert(0);
}
}
return TRUE;
}
/* t =@= u */
static int
variant(argPairs *agenda, Buffer buf ARG_LD)
{ Word l = NULL, r =NULL;
while( next_arg(agenda, &l, &r) )
{ word wl, wr;
attvar:
deRef(l);
deRef(r);
wl = *l;
wr = *r;
if ( tag(wl) != tag(wr) )
return FALSE;
if ( tag(wl) == TAG_VAR )
{ int i, j, m, n;
node *vl, *vr;
if ((i = var_id(l, buf)) < 0)
return MEMORY_OVERFLOW;
if ((j = var_id(r, buf)) < 0)
return MEMORY_OVERFLOW;
vl = Node(i, buf);
vr = Node(j, buf);
m = vl->a;
n = vr->b;
if ( (m==0) && (n==0) )
{ vl->a = j;
vr->b = i;
continue;
}
if ( (m != 0) && (n != 0) )
{ if ( (m == j) && (n == i) )
continue;
}
return FALSE;
}
if ( tag(wl) == TAG_ATTVAR )
{ l = valPAttVar(wl);
r = valPAttVar(wr);
goto attvar;
}
if ( wl == wr && !isTerm(wl) )
continue;
switch(tag(wl))
{ case TAG_ATOM:
return FALSE;
case TAG_INTEGER:
if ( storage(wl) == STG_INLINE ||
storage(wr) == STG_INLINE )
return FALSE;
case TAG_STRING:
case TAG_FLOAT:
if ( equalIndirect(wl, wr) )
continue;
return FALSE;
case TAG_COMPOUND:
{ int i, j, k, h;
node *m;
word dm, dn; /* definition (= functor/arity) */
Word lm, ln; /* arguments list */
if ( (i = term_id(l, buf)) < 0 )
return MEMORY_OVERFLOW;
if ( (j = term_id(r, buf)) < 0 )
return MEMORY_OVERFLOW;
m = Node(i, buf);
k = node_variant(m);
if ( 0 != k )
{ if ( ( h = isomorphic(agenda, k, j, buf PASS_LD) ) <= 0 )
return h;
continue;
}
univ(node_orig(m), &dm, &lm PASS_LD);
univ(node_orig(Node(j,buf)), &dn, &ln PASS_LD);
if ( dm != dn )
return FALSE;
node_variant(m) = j;
if ( !push_args(agenda, lm, ln, arityFunctor(dm)) )
return MEMORY_OVERFLOW;
continue;
}
}
}
return TRUE;
}
int
is_variant_ptr(Word p1, Word p2 ARG_LD)
{ argPairs agenda;
tmp_buffer buf;
Buffer VARIANT_BUFFER = (Buffer)&buf;
bool rval;
node *r;
node new = {NULL, 0, 0, 0}; /* dummy node as 0-th element*/
deRef(p1);
deRef(p2);
if ( *p1 == *p2 ) /* same term */
return TRUE;
if ( tag(*p1) != tag(*p2) ) /* different type */
return FALSE;
again:
switch(tag(*p1)) /* quick tests */
{ case TAG_VAR:
return TRUE;
case TAG_ATTVAR:
p1 = valPAttVar(*p1);
p2 = valPAttVar(*p2);
goto again;
case TAG_ATOM:
return FALSE;
case TAG_INTEGER:
if ( !(isIndirect(*p1) && isIndirect(*p2)) )
return FALSE;
/*FALLTHROUGH*/
case TAG_FLOAT:
case TAG_STRING:
return equalIndirect(*p1, *p2);
case TAG_COMPOUND:
{ Functor t1 = valueTerm(*p1);
Functor t2 = valueTerm(*p2);
if ( t1->definition != t2->definition )
return FALSE;
break;
}
default:
assert(0);
return FALSE;
}
startCritical;
initBuffer(&buf); /* can be faster! */
init_agenda(&agenda);
if ( (add_node_buffer(VARIANT_BUFFER, &new) >= 0) &&
(push_start_args(&agenda, p1, p2, 1) >=0) )
rval = variant(&agenda, VARIANT_BUFFER PASS_LD);
else
rval = MEMORY_OVERFLOW;
for(r = baseBuffer(VARIANT_BUFFER, node) + 1;
r < topBuffer(VARIANT_BUFFER, node); r++ )
reset_terms(r);
discardBuffer(VARIANT_BUFFER);
clearSegStack(&agenda.stack);
DEBUG(CHK_SECURE, checkStacks(NULL));
if ( !endCritical )
return FALSE;
if ( rval >= 0 )
return rval;
return PL_error(NULL, 0, NULL, ERR_NOMEM);
}
static
PRED_IMPL("=@=", 2, variant, 0)
{ PRED_LD
return is_variant_ptr(valTermRef(A1), valTermRef(A2) PASS_LD);
}
static
PRED_IMPL("\\=@=", 2, not_variant, 0)
{ PRED_LD
return !is_variant_ptr(valTermRef(A1), valTermRef(A2) PASS_LD);
}
/*******************************
* PUBLISH PREDICATES *
*******************************/
BeginPredDefs(variant)
PRED_DEF("=@=", 2, variant, 0)
PRED_DEF("\\=@=", 2, not_variant, 0)
EndPredDefs