scsh-0.6/scheme/big/external.scm

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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
; Code for keeping external pointers in a table similar to the symbol table.
;
; The entry points for this code are:
;
; (GET-EXTERNAL string) returns an external pointer
; (LOOKUP-ALL-EXTERNALS) looks up new values for all external pointers;
; ideally this should be called automatically
; on startup
;
; (DYNAMIC-LOAD filename) loads the file into the current image
;
; The following used to be in the PRIMITIVES interface when externals were
; a primitive data type.
;
; external?
; external-name
; external-value
; (external-lookup external)
; (call-external external . args)
; New, non-primitive data type.
(define-record-type external :external
(make-external name value)
external?
(name external-name)
(value external-value))
; Table of externals.
(define *the-external-table* #f)
(define (flush-the-external-table!)
(set! *the-external-table* #f))
(define (restore-the-external-table!)
(set! *the-external-table* (make-string-table))
(vector-for-each (lambda (external)
(table-set! *the-external-table*
(external-name external)
external))
(find-all-records :external)))
(define (gc-externals)
(flush-the-external-table!)
(collect)
(restore-the-external-table!))
(define (vector-for-each proc vector)
(do ((i 0 (+ i 1)))
((>= i (vector-length vector))
(unspecific))
(proc (vector-ref vector i))))
(restore-the-external-table!)
;----------------
; Making new externals.
(define (get-external name)
(cond ((table-ref *the-external-table* name)
=> (lambda (x) x))
(else
(let* ((value (make-code-vector 4 0))
(new (make-external name value)))
(table-set! *the-external-table* name new)
(if (not (external-lookup name value))
(warn "External not found" name))
new))))
(import-lambda-definition external-lookup (name value) "s48_external_lookup")
; No longer necessary, as all strings now end with nulls.
(define (null-terminate str)
str)
;----------------
; Re-lookup all externals. This needs to be done whenever we resume an image.
(define (lookup-all-externals)
(cond ((null? (really-lookup-all-externals))
#t)
(else
(display "GCing to try to remove unbound externals")
(newline)
(gc-externals)
(let ((losers (really-lookup-all-externals)))
(if (null? losers)
#t
(let ((out (current-error-port)))
(display "Unbound external(s):" out)
(for-each (lambda (name)
(write-char #\space out)
(display name out))
losers)
#f))))))
; Re-lookup one external.
(define (lookup-external external)
(external-lookup (external-name external)
(external-value external)))
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; Quietly look up all externals, returning #F if unsuccessful
(define (try-to-lookup-all-externals)
(null? (really-lookup-all-externals)))
; Look up all externals, returning a list of the names of those that cannot
; be found.
(define (really-lookup-all-externals)
(let ((losers '()))
(table-walk (lambda (name external)
(if (not (external-lookup name (external-value external)))
(set! losers (cons name losers))))
*the-external-table*)
losers))
;----------------
(define (call-external external . args)
(apply call-external-value (external-value external)
(external-name external)
args))
;----------------
(import-lambda-definition dynamic-load (filename) "s48_dynamic_load")