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/*-----------------------------------------------------------------*-C-*---
* File: handc/runtime/dequeue.c
*
* Copyright (C)1997 Donovan Kolbly <d.kolbly@rscheme.org>
* as part of the RScheme project, licensed for free use.
* See <http://www.rscheme.org/> for the latest information.
*
* File version: 1.8
* File mod date: 1997.11.29 23:10:50
* System build: v0.7.2, 97.12.21
*
*------------------------------------------------------------------------*/
#include <rscheme/scheme.h>
#include <rscheme/smemory.h>
#include <rscheme/allocns.h>
/*
* example state:
*
* 0 1 2 3 4 5 6
* +-----+-----+-----+-----+-----+-----+-----+
* | | | a | b | c | | |
* +-----+-----+-----+-----+-----+-----+-----+
* ^ ^
* front back
* =2 =5
* pop-front => a
* pop-back => c
*/
#define DEQ_STATE(deq) gvec_ref((deq),SLOT(0))
#define DEQ_FRONT(deq) gvec_ref((deq),SLOT(1))
#define DEQ_BACK(deq) gvec_ref((deq),SLOT(2))
#define SET_DEQ_STATE(deq,s) gvec_set((deq),SLOT(0),(s))
#define SET_DEQ_FRONT(deq,f) gvec_write_non_ptr((deq),SLOT(1),(f))
#define SET_DEQ_BACK(deq,b) gvec_write_non_ptr((deq),SLOT(2),(b))
obj make_dequeue( void )
{
return make3( dequeue_class,
make_gvec( vector_class, SLOT(5), FALSE_OBJ ),
ZERO,
ZERO );
}
rs_bool dequeue_empty( obj deq )
{
return EQ(DEQ_FRONT(deq),DEQ_BACK(deq));
}
obj dequeue_count( obj deq )
{
obj len;
len = FX_SUB( DEQ_BACK(deq), DEQ_FRONT(deq) );
if (FX_LT(len,ZERO))
return FX_ADD( len, RIBYTES_TO_FXWORDS(SIZEOF_PTR(DEQ_STATE(deq))) );
else
return len;
}
static obj expanded_state( obj deq, UINT_32 expand_bytes )
{
obj state, len = dequeue_count(deq);
UINT_32 i, j, end, lim;
obj result;
result = alloc( expand_bytes + FXWORDS_TO_RIBYTES(len), vector_class );
state = DEQ_STATE(deq);
j = 0;
i = FXWORDS_TO_RIBYTES(DEQ_FRONT(deq));
end = FXWORDS_TO_RIBYTES(DEQ_BACK(deq));
lim = SIZEOF_PTR(state);
while (i != end)
{
gvec_write_init( result, j, gvec_ref( state, i ) );
j += SLOT(1);
i += SLOT(1);
if (i >= lim)
i = 0;
}
while (expand_bytes > 0)
{
gvec_write_init_non_ptr( result, j, FALSE_OBJ );
j += SLOT(1);
expand_bytes -= SLOT(1);
}
return result;
}
obj dequeue_state( obj deq )
{
return expanded_state( deq, 0 );
}
static void expand( obj deq )
{
obj len = dequeue_count(deq);
SET_DEQ_STATE( deq, expanded_state( deq, SLOT(10) ) );
SET_DEQ_FRONT( deq, ZERO );
SET_DEQ_BACK( deq, len );
}
static obj succ( obj deq, obj i )
{
i = ADD1(i);
if (EQ(i,RIBYTES_TO_FXWORDS(SIZEOF_PTR(DEQ_STATE(deq)))))
return ZERO;
else
return i;
}
static obj pred( obj deq, obj i )
{
if (EQ(i,ZERO))
i = RIBYTES_TO_FXWORDS(SIZEOF_PTR(DEQ_STATE(deq)));
return SUB1(i);
}
static void dequeue_is_empty( char *op )
{
scheme_error( "~a: <dequeue> is empty", 1, make_string(op) );
}
#define assert_ne(deq,op) if (dequeue_empty(deq)) dequeue_is_empty( op )
void dequeue_push_back( obj deq, obj item )
{
obj oldb = DEQ_BACK(deq);
obj newb;
newb = succ( deq, oldb );
if (EQ(newb,DEQ_FRONT(deq)))
{
expand(deq);
dequeue_push_back( deq, item );
}
else
{
gvec_set( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(oldb), item );
SET_DEQ_BACK( deq, newb );
}
}
void dequeue_push_front( obj deq, obj item )
{
obj oldf = DEQ_FRONT(deq);
obj newf;
newf = pred( deq, oldf );
if (EQ(newf, DEQ_BACK(deq)))
{
expand(deq);
dequeue_push_front( deq, item );
}
else
{
gvec_set( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(newf), item );
SET_DEQ_FRONT( deq, newf );
}
}
obj dequeue_pop_back( obj deq )
{
obj item, newb, oldb = DEQ_BACK(deq);
assert_ne(deq, "dequeue-pop-back!");
newb = pred( deq, oldb );
SET_DEQ_BACK( deq, newb );
item = gvec_ref( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(newb) );
/* clear the now-unused position in case there is a GC liveness issue
* (ie, I was seeing annoying latencies finalizing threads in the
* new threads system)
*/
gvec_write_non_ptr( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(newb), FALSE_OBJ );
return item;
}
obj dequeue_pop_front( obj deq )
{
obj item, newf, oldf = DEQ_FRONT(deq);
assert_ne(deq, "dequeue-pop-front!");
newf = succ( deq, oldf );
SET_DEQ_FRONT( deq, newf );
item = gvec_ref( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(oldf) );
gvec_write_non_ptr( DEQ_STATE(deq), FXWORDS_TO_RIBYTES(oldf), FALSE_OBJ );
return item;
}
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