303 lines
9.3 KiB
Scheme
303 lines
9.3 KiB
Scheme
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; Allocation
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; *hp* is the heap pointer and *limit* is the limit beyond which no
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; storage should be allocated. Both of these are addresses (not
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; descriptors).
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(define check-preallocation? #f)
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(define *hp* 0)
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(define *limit* 0)
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; These are all in address units
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(define *newspace-begin* (unassigned))
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(define *newspace-end* (unassigned))
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(define *oldspace-begin* (unassigned))
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(define *oldspace-end* (unassigned))
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(define (initialize-heap start size)
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(let ((semisize (cells->a-units (quotient size 2))))
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(set! *newspace-begin* start)
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(set! *newspace-end* (addr+ *newspace-begin* semisize))
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(set! *oldspace-begin* *newspace-end*)
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(set! *oldspace-end* (addr+ *oldspace-begin* semisize))
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(set! *hp* *newspace-begin*)
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(set! *limit* *newspace-end*)))
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(define (available? cells)
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(addr< (addr+ *hp* (cells->a-units cells)) *limit*))
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(define (available)
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(a-units->cells (addr- *limit* *hp*)))
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(define (heap-size)
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(- *newspace-end* *newspace-begin*))
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(define *heap-key* 0)
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(define universal-key 0)
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(define *okayed-space* 0)
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(define (preallocate-space cells)
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(cond (check-preallocation?
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(assert (available? cells))
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(set! *heap-key* (+ *heap-key* 1))
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(set! *okayed-space* cells)
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*heap-key*)
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(else
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universal-key)))
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(define (make-stob type len key) ;len is in bytes
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(if check-preallocation?
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(let ((cells (+ (bytes->cells len) 1)))
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(assert (available? cells))
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(cond ((not (= key universal-key))
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(if (not (and (= key *heap-key*)
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(>= *okayed-space* cells)))
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(error "invalid heap key" key cells))
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(set! *okayed-space* (- *okayed-space* cells))))))
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(store! *hp* (make-header type len))
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(set! *hp* (addr1+ *hp*))
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(let ((new (address->stob-descriptor *hp*)))
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(set! *hp* (addr+ *hp* (bytes->a-units len)))
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(if (> len 0) ; for B-VECTORs that don't want to use all of the
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(store! (addr+ *hp* (cells->bytes -1)) 0)) ; last descriptor
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new))
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(define *pure-areas* (unassigned))
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(define *impure-areas* (unassigned))
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(define *pure-sizes* (unassigned))
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(define *impure-sizes* (unassigned))
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(define *pure-area-count* 0)
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(define *impure-area-count* 0)
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(define (register-static-areas pure-count pure-areas pure-sizes
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impure-count impure-areas impure-sizes)
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(set! *pure-area-count* pure-count)
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(set! *pure-areas* pure-areas)
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(set! *pure-sizes* pure-sizes)
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(set! *impure-area-count* impure-count)
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(set! *impure-areas* impure-areas)
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(set! *impure-sizes* impure-sizes))
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(define (walk-areas proc areas sizes count)
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(let loop ((i 0))
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(cond ((>= i count)
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#t)
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((proc (vector-ref areas i)
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(+ (vector-ref areas i)
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(vector-ref sizes i)))
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(loop (+ i 1)))
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(else
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#f))))
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(define (walk-pure-areas proc)
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(walk-areas proc *pure-areas* *pure-sizes* *pure-area-count*))
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(define (walk-impure-areas proc)
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(walk-areas proc *impure-areas* *impure-sizes* *impure-area-count*))
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; Used to find end of an object
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(define (header-a-units h)
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(bytes->a-units (header-length-in-bytes h)))
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(define (walk-over-type-in-area type proc)
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(lambda (start end)
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(let loop ((addr start))
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(cond ((addr< addr end)
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(let ((d (fetch addr)))
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(cond ((not (header? d))
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(write-string "heap is in an inconsistent state."
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(current-output-port))
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#f)
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((or (not (= type (header-type d)))
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(proc (address->stob-descriptor (addr1+ addr))))
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(loop (addr1+ (addr+ addr (header-a-units d)))))
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(else
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#f))))
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(else
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#t)))))
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(define (walk-over-symbols proc)
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(let ((proc (walk-over-type-in-area (enum stob symbol) proc))
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(start-hp *hp*))
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(cond ((and (proc *newspace-begin* *hp*)
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(walk-pure-areas proc))
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#t)
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(else
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(set! *hp* start-hp) ; out of space, so undo and give up
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#f))))
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(define (find-all-xs type)
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(let ((proc (walk-over-type-in-area type maybe-push-obj))
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(start-hp *hp*))
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(store-next! 0) ; reserve space for header
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(cond ((and (proc *newspace-begin* start-hp)
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(walk-impure-areas proc)
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(walk-pure-areas proc))
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(let ((size (addr- *hp* (addr1+ start-hp))))
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(store! start-hp (make-header (enum stob vector) size) )
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(address->stob-descriptor (addr1+ start-hp))))
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(else
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(set! *hp* start-hp) ; out of space, so undo and give up
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false))))
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(define (maybe-push-obj thing)
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(cond ((available? (cells->a-units 1))
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(store-next! thing)
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#t)
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(else #f)))
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;;;; Write-image and read-image
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(define level 15)
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(define (image-writing-okay?)
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(and (= 0 *pure-area-count*)
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(= 0 *impure-area-count*)))
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(define (write-image port restart-proc)
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(write-string "This is a Scheme48 heap image file." port)
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(newline port)
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(write-page port)
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(newline port)
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(write-number level port)
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(write-number bytes-per-cell port)
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(write-number (a-units->cells *newspace-begin*) port)
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(write-number (a-units->cells *hp*) port)
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(write-number restart-proc port)
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(write-page port)
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(store! *hp* 1) ; used to detect endianess of image
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(write-bytes *hp* (- (addr1+ *hp*) *hp*) port)
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(write-bytes *newspace-begin* (- *hp* *newspace-begin*) port)
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(- *hp* *newspace-begin*))
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; Make sure the image file is okay and return the size of the heap it
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; contains.
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(define (check-image-header filename)
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(call-with-input-file filename
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(lambda (port)
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(let ((lose (lambda (message)
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(let ((out (current-output-port)))
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(write-string message out)
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(newline out)
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-1))))
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(cond ((null-port? port)
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(lose "Can't open heap image file"))
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(else
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(read-page port) ; read past any user cruft at the beginning of the file
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(let* ((old-level (read-number port))
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(old-bytes-per-cell (read-number port))
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(old-begin (cells->a-units (read-number port)))
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(old-hp (cells->a-units (read-number port))))
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(cond ((not (= old-level level))
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(lose "format of image is incompatible with this version of system"))
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((not (= old-bytes-per-cell bytes-per-cell))
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(lose "incompatible bytes-per-cell in image"))
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(else
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(- old-hp old-begin))))))))))
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(define (read-image filename startup-space)
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(call-with-input-file filename
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(lambda (port)
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(if (null-port? port)
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(error "Can't open heap image file"))
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(read-page port) ; read past any user cruft at the beginning of the file
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(let* ((old-level (read-number port))
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(old-bytes-per-cell (read-number port))
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(old-begin (cells->a-units (read-number port)))
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(old-hp (cells->a-units (read-number port)))
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(startup-proc (read-number port)))
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(read-page port)
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(if (not (= old-level level))
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(error "format of image is incompatible with this version of system"
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old-level level))
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(if (not (= old-bytes-per-cell bytes-per-cell))
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(error "incompatible bytes-per-cell"
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old-bytes-per-cell bytes-per-cell))
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(let* ((delta (- *hp* old-begin))
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(new-hp (+ old-hp delta))
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(new-limit *newspace-end*)
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(start *hp*))
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(if (addr>= (+ startup-space new-hp) new-limit)
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(error "heap not big enough to restore this image"
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new-hp new-limit))
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(let ((reverse? (check-image-byte-order port)))
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(read-bytes *hp* (- old-hp old-begin) port)
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(if reverse?
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(reverse-byte-order start new-hp))
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(if (not (= delta 0))
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(relocate-image delta start new-hp))
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(set! *hp* new-hp)
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(adjust startup-proc delta)))))))
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(define (check-image-byte-order port)
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(read-bytes *hp* (cells->a-units 1) port)
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(cond ((= (fetch *hp*) 1)
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#f)
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(else
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(reverse-descriptor-byte-order! *hp*)
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(if (= (fetch *hp*) 1)
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#t
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(begin (error "unable to correct byte order" (fetch *hp*))
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#f))))) ; to keep from confusing the type checker
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; ABCD => DCBA
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; memory intensive, but independent of Scheme's integer size
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(define (reverse-descriptor-byte-order! addr)
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(let ((x (fetch-byte addr)))
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(store-byte! addr (fetch-byte (addr+ addr 3)))
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(store-byte! (addr+ addr 3) x))
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(let ((x (fetch-byte (addr+ addr 1))))
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(store-byte! (addr+ addr 1) (fetch-byte (addr+ addr 2)))
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(store-byte! (addr+ addr 2) x)))
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(define (reverse-byte-order start end)
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(write-string "Correcting byte order of resumed image."
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(current-output-port))
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(newline (current-output-port))
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(let loop ((ptr start))
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(reverse-descriptor-byte-order! ptr)
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(let ((value (fetch ptr)))
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(if (addr< ptr end)
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(loop (if (b-vector-header? value)
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(addr+ (addr1+ ptr) (header-a-units value))
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(addr1+ ptr)))))))
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(define (adjust descriptor delta)
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(if (stob? descriptor)
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(address->stob-descriptor (addr+ (address-after-header descriptor) delta))
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descriptor))
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(define (relocate-image delta start end)
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(let loop ((ptr start))
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(if (addr< ptr end)
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(let ((d (adjust (fetch ptr) delta)))
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(store! ptr d)
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(loop (if (b-vector-header? d)
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(addr+ (addr1+ ptr) (header-a-units d))
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(addr1+ ptr)))))))
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; The page character is used to mark the ends of the user and prelude sections
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; of image files.
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(define page-character (ascii->char 12))
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(define (write-page port)
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(write-char page-character port))
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(define (read-page port)
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(let loop ()
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(ps-read-char port
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(lambda (ch)
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(if (not (char=? ch page-character))
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(loop)))
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(lambda ()
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(error "end of file while looking for page break")))))
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