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FUTURE.C
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1989-09-20
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/* -*-C-*-
$Header: future.c,v 9.27 89/09/20 23:08:34 GMT cph Exp $
Copyright (c) 1987, 1988, 1989 Massachusetts Institute of Technology
This material was developed by the Scheme project at the Massachusetts
Institute of Technology, Department of Electrical Engineering and
Computer Science. Permission to copy this software, to redistribute
it, and to use it for any purpose is granted, subject to the following
restrictions and understandings.
1. Any copy made of this software must include this copyright notice
in full.
2. Users of this software agree to make their best efforts (a) to
return to the MIT Scheme project any improvements or extensions that
they make, so that these may be included in future releases; and (b)
to inform MIT of noteworthy uses of this software.
3. All materials developed as a consequence of the use of this
software shall duly acknowledge such use, in accordance with the usual
standards of acknowledging credit in academic research.
4. MIT has made no warrantee or representation that the operation of
this software will be error-free, and MIT is under no obligation to
provide any services, by way of maintenance, update, or otherwise.
5. In conjunction with products arising from the use of this material,
there shall be no use of the name of the Massachusetts Institute of
Technology nor of any adaptation thereof in any advertising,
promotional, or sales literature without prior written consent from
MIT in each case. */
/* Support code for futures */
#include "scheme.h"
#include "prims.h"
#include "locks.h"
#ifndef COMPILE_FUTURES
#include "Error: future.c is useless without COMPILE_FUTURES"
#endif
/* This is how we support future numbering for external metering */
#ifndef New_Future_Number
#define New_Future_Number() SHARP_F
#else
SCHEME_OBJECT Get_New_Future_Number ();
#endif
/*
A future is a VECTOR starting with <determined?>, <locked?> and
<waiting queue / value>,
where <determined?> is #!false if no value is known yet,
#!true if value is known and future can vanish at GC,
otherwise value is known, but keep the slot
and where <locked> is #!true if someone wants slot kept for a time.
*/
DEFINE_PRIMITIVE ("TOUCH", Prim_touch, 1, 1, 0)
{
SCHEME_OBJECT result;
PRIMITIVE_HEADER (1);
TOUCH_IN_PRIMITIVE ((ARG_REF (1)), result);
PRIMITIVE_RETURN (result);
}
DEFINE_PRIMITIVE ("FUTURE?", Prim_future_p, 1, 1, 0)
{
PRIMITIVE_HEADER (1);
PRIMITIVE_RETURN (BOOLEAN_TO_OBJECT (FUTURE_P (ARG_REF (1))));
}
/* Utility setting routine for use by the various test and set if
equal operators.
*/
long
Set_If_Equal(Base, Offset, New, Wanted)
SCHEME_OBJECT Base, Wanted, New;
long Offset;
{
Lock_Handle lock;
SCHEME_OBJECT Old_Value, Desired, Remember_Value;
long success;
TOUCH_IN_PRIMITIVE(Wanted, Desired);
Try_Again:
Remember_Value = MEMORY_REF (Base, Offset);
TOUCH_IN_PRIMITIVE(Remember_Value, Old_Value);
lock = Lock_Cell(MEMORY_LOC (Base, Offset));
if (Remember_Value != FAST_MEMORY_REF (Base, Offset))
{
Unlock_Cell(lock);
goto Try_Again;
}
if (Old_Value == Desired)
{
Do_Store_No_Lock(MEMORY_LOC (Base, Offset), New);
success = true;
}
else
{
success = false;
}
Unlock_Cell(lock);
return success;
}
DEFINE_PRIMITIVE ("SET-CAR-IF-EQ?!", Prim_set_car_if_eq, 3, 3,
"Replace the car of PAIR with NEW-VALUE iff it contains OLD-VALUE.\n\
Return PAIR if so, otherwise return '().")
{
PRIMITIVE_HEADER (3);
CHECK_ARG (1, PAIR_P);
{
fast SCHEME_OBJECT pair = (ARG_REF (1));
if (Set_If_Equal (pair, CONS_CAR, (ARG_REF (2)), (ARG_REF (3))))
PRIMITIVE_RETURN (pair);
}
PRIMITIVE_RETURN (EMPTY_LIST);
}
DEFINE_PRIMITIVE ("SET-CDR-IF-EQ?!", Prim_set_cdr_if_eq, 3, 3,
"Replace the cdr of PAIR with NEW-VALUE iff it contains OLD-VALUE.\n\
Return PAIR if so, otherwise return '().")
{
PRIMITIVE_HEADER (3);
CHECK_ARG (1, PAIR_P);
{
fast SCHEME_OBJECT pair = (ARG_REF (1));
if (Set_If_Equal (pair, CONS_CDR, (ARG_REF (2)), (ARG_REF (3))))
PRIMITIVE_RETURN (pair);
}
PRIMITIVE_RETURN (EMPTY_LIST);
}
/* (VECTOR-SET-IF-EQ?! <Vector> <Offset> <New Value> <Old Value>)
Replaces the <Offset>th element of <Vector> with <New Value> if it used
to contain <Old Value>. The value returned is either <Vector> (if
the modification takes place) or '() if it does not.
*/
DEFINE_PRIMITIVE ("VECTOR-SET-IF-EQ?!", Prim_vector_set_if_eq, 4, 4,
"Replace VECTOR's INDEX'th element with NEW-VALUE iff it contains OLD-VALUE.\n\
Return VECTOR if so, otherwise return '().")
{
PRIMITIVE_HEADER (4);
CHECK_ARG (1, VECTOR_P);
{
fast SCHEME_OBJECT vector = (ARG_REF (1));
if (Set_If_Equal
(vector,
((arg_index_integer (2, (VECTOR_LENGTH (vector)))) + 1),
(ARG_REF (3)),
(ARG_REF (4))))
PRIMITIVE_RETURN (vector);
}
PRIMITIVE_RETURN (EMPTY_LIST);
}
DEFINE_PRIMITIVE ("SET-CXR-IF-EQ?!", Prim_set_cxr_if_eq, 4, 4,
"Replace HUNK3's INDEX'th element with NEW-VALUE iff it contains OLD-VALUE.\n\
Return HUNK3 if so, otherwise return '().")
{
PRIMITIVE_HEADER (4);
CHECK_ARG (1, HUNK3_P);
{
fast SCHEME_OBJECT hunk3 = (ARG_REF (1));
if (Set_If_Equal
(hunk3,
((arg_index_integer (2, 3)) + 1),
(ARG_REF (3)),
(ARG_REF (4))))
PRIMITIVE_RETURN (hunk3);
}
PRIMITIVE_RETURN (EMPTY_LIST);
}
DEFINE_PRIMITIVE ("FUTURE-SIZE", Prim_future_size, 1, 1,
"Return the number of elements in FUTURE.\n\
This is similar to SYSTEM-VECTOR-SIZE,\n\
but works only on futures and doesn't touch them.")
{
PRIMITIVE_HEADER (1)
CHECK_ARG (1, FUTURE_P);
PRIMITIVE_RETURN (LONG_TO_UNSIGNED_FIXNUM (VECTOR_LENGTH (ARG_REF (1))));
}
DEFINE_PRIMITIVE ("FUTURE-REF", Prim_future_ref, 2, 2,
"Return FUTURE's INDEX'th element.\n\
This is similar to SYSTEM-VECTOR-REF,\n\
but works only on futures and doesn't touch them.")
{
PRIMITIVE_HEADER (2);
CHECK_ARG (1, FUTURE_P);
{
fast SCHEME_OBJECT future = (ARG_REF (1));
PRIMITIVE_RETURN
(VECTOR_REF
(future, (arg_index_integer (2, (VECTOR_LENGTH (future))))));
}
}
DEFINE_PRIMITIVE ("FUTURE-SET!", Prim_future_set, 3, 3,
"Modify FUTURE's INDEX'th element to be VALUE.\n\
This is similar to SYSTEM-VECTOR-SET!,\n\
but works only on futures and doesn't touch them.")
{
PRIMITIVE_HEADER (3);
CHECK_ARG (1, FUTURE_P);
{
fast SCHEME_OBJECT future = (ARG_REF (1));
fast long index = (arg_index_integer (2, (VECTOR_LENGTH (future))));
fast SCHEME_OBJECT result = (VECTOR_REF (future, index));
VECTOR_SET (future, index, (ARG_REF (3)));
PRIMITIVE_RETURN (result);
}
}
DEFINE_PRIMITIVE ("LOCK-FUTURE!", Prim_lock_future, 1, 1,
"Set the lock flag on FUTURE.\n\
This flag prevents FUTURE from being spliced out by the garbage collector.\n\
If FUTURE is not a future, return #F immediately,\n\
otherwise return #T after the lock has been set.\n\
Will wait as long as necessary for the lock to be set.")
{
PRIMITIVE_HEADER (1);
{
fast SCHEME_OBJECT future = (ARG_REF (1));
if (! (FUTURE_P (future)))
PRIMITIVE_RETURN (SHARP_F);
while (1)
{
if (INTERRUPT_PENDING_P (INT_Mask))
signal_interrupt_from_primitive ();
{
fast SCHEME_OBJECT lock;
SWAP_POINTERS ((MEMORY_LOC (future, FUTURE_LOCK)), SHARP_T, lock);
if (lock == SHARP_F)
PRIMITIVE_RETURN (SHARP_T);
}
Sleep (CONTENTION_DELAY);
}
}
}
DEFINE_PRIMITIVE ("UNLOCK-FUTURE!", Prim_unlock_future, 1, 1,
"Clear the lock flag on FUTURE.\n\
If FUTURE is not a future, return #F immediately,\n\
otherwise return #T after the lock has been cleared.")
{
PRIMITIVE_HEADER (1);
{
fast SCHEME_OBJECT future = (ARG_REF (1));
if (! (FUTURE_P (future)))
PRIMITIVE_RETURN (SHARP_F);
if (! (Future_Is_Locked (future)))
error_wrong_type_arg (1);
MEMORY_SET (future, FUTURE_LOCK, SHARP_F);
PRIMITIVE_RETURN (SHARP_T);
}
}
DEFINE_PRIMITIVE ("FUTURE->VECTOR", Prim_future_to_vector, 1, 1,
"Return a newly-allocated vector containing FUTURE's elements.
If FUTURE is not a future, return #F instead.")
{
PRIMITIVE_HEADER (1);
{
SCHEME_OBJECT future = (ARG_REF (1));
if (! (FUTURE_P (future)))
PRIMITIVE_RETURN (SHARP_F);
{
long length = (VECTOR_LENGTH (future));
fast SCHEME_OBJECT * scan_source = (MEMORY_LOC (future, 1));
fast SCHEME_OBJECT * end_source = (scan_source + length);
SCHEME_OBJECT result =
(allocate_marked_vector (TC_VECTOR, length, true));
fast SCHEME_OBJECT * scan_result = (MEMORY_LOC (result, 1));
while (scan_source < end_source)
(*scan_result++) = (MEMORY_FETCH (*scan_source++));
PRIMITIVE_RETURN (result);
}
}
}
DEFINE_PRIMITIVE ("NON-TOUCHING-EQ?", Prim_future_eq, 2, 2, 0)
{
PRIMITIVE_HEADER (2);
PRIMITIVE_RETURN (BOOLEAN_TO_OBJECT ((ARG_REF (1)) == (ARG_REF (2))));
}
/* MAKE-INITIAL-PROCESS is called to create a small stacklet which
* will just call the specified thunk and then end the computation
*/
DEFINE_PRIMITIVE ("MAKE-INITIAL-PROCESS", Prim_make_initial_process, 1, 1, 0)
{
SCHEME_OBJECT Result;
long Useful_Length;
PRIMITIVE_HEADER (1);
Result = MAKE_POINTER_OBJECT (TC_CONTROL_POINT, Free);
Useful_Length = (3 * CONTINUATION_SIZE) + STACK_ENV_EXTRA_SLOTS + 1;
#ifdef USE_STACKLETS
{
long Allocated_Length, Waste_Length;
Allocated_Length = (Useful_Length + STACKLET_SLACK + STACKLET_HEADER_SIZE);
if (Allocated_Length < Default_Stacklet_Size)
{
Allocated_Length = Default_Stacklet_Size;
Waste_Length = ((Allocated_Length + 1) -
(Useful_Length + STACKLET_HEADER_SIZE));
}
else
{
Waste_Length = (STACKLET_SLACK + 1);
}
Primitive_GC_If_Needed(Allocated_Length + 1);
Free[STACKLET_LENGTH] =
MAKE_POINTER_OBJECT (TC_MANIFEST_VECTOR, Allocated_Length);
Free[STACKLET_REUSE_FLAG] = SHARP_T;
Free[STACKLET_UNUSED_LENGTH] =
MAKE_OBJECT (TC_MANIFEST_NM_VECTOR, Waste_Length);
Free += (Allocated_Length + 1) - Useful_Length;
}
#else /* not USE_STACKLETS */
Free[STACKLET_LENGTH] =
MAKE_OBJECT (TC_MANIFEST_VECTOR, Useful_Length + STACKLET_HEADER_SIZE - 1);
Free[STACKLET_REUSE_FLAG] = SHARP_F;
Free[STACKLET_UNUSED_LENGTH] = MAKE_OBJECT (TC_MANIFEST_NM_VECTOR, 0);
Free += STACKLET_HEADER_SIZE;
#endif /* USE_STACKLETS */
Free[CONTINUATION_EXPRESSION] = LONG_TO_FIXNUM(FETCH_INTERRUPT_MASK());
Free[CONTINUATION_RETURN_CODE] =
MAKE_OBJECT (TC_RETURN_CODE, RC_RESTORE_INT_MASK);
Free += CONTINUATION_SIZE;
Free[CONTINUATION_EXPRESSION] = SHARP_F;
Free[CONTINUATION_RETURN_CODE] =
MAKE_OBJECT (TC_RETURN_CODE, RC_INTERNAL_APPLY);
Free += CONTINUATION_SIZE;
*Free++ = STACK_FRAME_HEADER;
*Free++ = (ARG_REF (1));
Free[CONTINUATION_EXPRESSION] = (ARG_REF (1)); /* For testing & debugging */
Free[CONTINUATION_RETURN_CODE] =
MAKE_OBJECT (TC_RETURN_CODE, RC_END_OF_COMPUTATION);
Free += CONTINUATION_SIZE;
PRIMITIVE_RETURN (Result);
}
/*
Absolutely the cheapest future we can make. This includes
the I/O stuff and whatnot. Notice that the name is required.
(make-cheap-future orig-code user-proc name)
*/
DEFINE_PRIMITIVE ("MAKE-CHEAP-FUTURE", Prim_make_cheap_future, 3, 3, 0)
{
PRIMITIVE_HEADER (3);
{
fast SCHEME_OBJECT future = (allocate_marked_vector (TC_FUTURE, 10, true));
FAST_MEMORY_SET (future, FUTURE_IS_DETERMINED, SHARP_F);
FAST_MEMORY_SET (future, FUTURE_LOCK, SHARP_F);
FAST_MEMORY_SET (future, FUTURE_QUEUE, (cons (EMPTY_LIST, EMPTY_LIST)));
FAST_MEMORY_SET (future, FUTURE_PROCESS, (ARG_REF (1)));
FAST_MEMORY_SET (future, FUTURE_STATUS, SHARP_T);
FAST_MEMORY_SET (future, FUTURE_ORIG_CODE, (ARG_REF (2)));
/* Put the I/O system stuff here. */
FAST_MEMORY_SET
(future,
FUTURE_PRIVATE,
(make_vector
(1,
(hunk3_cons
(SHARP_F,
(ARG_REF (3)),
(cons ((LONG_TO_UNSIGNED_FIXNUM (0)),
(char_pointer_to_string ("")))))),
true)));
FAST_MEMORY_SET (future, FUTURE_WAITING_ON, EMPTY_LIST);
FAST_MEMORY_SET (future, FUTURE_METERING, (New_Future_Number ()));
FAST_MEMORY_SET (future, FUTURE_USER, SHARP_F);
PRIMITIVE_RETURN (future);
}
}