108 lines
3.3 KiB
Scheme
108 lines
3.3 KiB
Scheme
; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
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; Different ways to call the GC, depending on how many temporaries need to
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; be traced.
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; ENSURE-SPACE and friends make sure that there is at least SPACE remaining
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; in the heap, triggering a GC if necessary. A key to the pre-allocated space
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; is returned (keys and pre-allocation are described in heap.scm). If SPACE
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; is not available, even after a GC, we kill the process.
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(define (ensure-space space)
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(receive (key temp)
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(ensure-space-saving-temp space false)
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key))
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(define (ensure-space-saving-temp space temp)
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(receive (okay? key temp ignore)
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(maybe-ensure-space-saving-temps space temp false)
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(if (not okay?)
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(error "Scheme48 heap overflow"))
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(values key temp)))
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(define (ensure-space-saving-temps space temp0 temp1)
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(receive (okay? key temp0 temp1)
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(maybe-ensure-space-saving-temps space temp0 temp1)
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(if (not okay?)
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(error "Scheme48 heap overflow"))
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(values key temp0 temp1)))
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; Same thing, except that we return a flag instead of dying if the space is
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; not available.
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(define (maybe-ensure-space space)
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(receive (okay? key ignore0 ignore1)
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(maybe-ensure-space-saving-temps space false false)
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(values okay? key)))
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(define (maybe-ensure-space-saving-temp space temp)
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(receive (okay? key temp ignore0)
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(maybe-ensure-space-saving-temps space temp false)
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(values okay? key temp)))
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(define (maybe-ensure-space-saving-temps space temp0 temp1)
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(if (s48-available? space)
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(values #t (s48-preallocate-space space) temp0 temp1)
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(receive (temp0 temp1)
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(collect-saving-temps temp0 temp1)
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(if (s48-available? space)
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(values #t (s48-preallocate-space space) temp0 temp1)
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(values #f 0 temp0 temp1)))))
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;----------------
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; The GC itself, with versions that handle one or two temporaries.
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(define (collect)
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(receive (ignore0 ignore1)
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(collect-saving-temps (enter-fixnum 0) (enter-fixnum 0))
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0)) ; type checker rejected (values) here; why?
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(define (collect-saving-temp value)
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(receive (value ignore1)
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(collect-saving-temps value (enter-fixnum 0))
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value))
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; This is a front for the real GC, which is a separate program. All that the
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; interpreter contributes is the root set and some post-gc cleanup code.
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(define (collect-saving-temps value0 value1)
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(s48-begin-collection)
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(gc-root)
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(let ((value0 (s48-trace-value value0))
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(value1 (s48-trace-value value1)))
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(s48-do-gc)
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(post-gc-cleanup)
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(s48-end-collection)
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(values value0 value1)))
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;----------------
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; GC-ROOT and POST-GC-CLEANUP are defined incrementally.
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;
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; (ADD-GC-ROOT! <thunk>) ; call <thunk> when tracing the GC roots
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; (ADD-POST-GC-CLEANUP! <thunk>) ; call <thunk> when a GC has finished
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;
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; (GC-ROOT) ; call all the root thunks
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; (POST-GC-CLEANUP) ; call all the cleanup thunks
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(define-syntax define-extensible-proc
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(syntax-rules ()
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((define-extensible-proc proc extender temp)
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(begin
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(define temp unspecific)
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(define (proc) (temp))
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(define (extender more)
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(let ((old temp))
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(set! temp (lambda ()
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(more)
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(old)))))))))
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(define-extensible-proc gc-root
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add-gc-root!
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*gc-root-proc*)
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(define-extensible-proc post-gc-cleanup
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add-post-gc-cleanup!
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*post-gc-cleanup*)
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