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Scheme

;;; trace.ss
;;; Copyright 1984-2017 Cisco Systems, Inc.
;;;
;;; Licensed under the Apache License, Version 2.0 (the "License");
;;; you may not use this file except in compliance with the License.
;;; You may obtain a copy of the License at
;;;
;;; http://www.apache.org/licenses/LICENSE-2.0
;;;
;;; Unless required by applicable law or agreed to in writing, software
;;; distributed under the License is distributed on an "AS IS" BASIS,
;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;;; See the License for the specific language governing permissions and
;;; limitations under the License.
(let ()
(define tracer-list '())
(define-threaded trace-level 0)
(define-threaded trace-continuation #f)
(define-record-type tracer
(fields (mutable id) (mutable old) (mutable new))
(nongenerative)
(sealed #t))
(define bars
(lambda (i p)
(letrec ([bars1
(lambda (i p)
(unless (fx<= i 0)
(write-char #\space p)
(bars2 (fx- i 1) p)))]
[bars2
(lambda (i p)
(unless (fx<= i 0)
(write-char #\| p)
(bars1 (fx- i 1) p)))])
(bars2 i p))))
(define trace-display
(let ([last-trace-level 0])
(lambda (print x)
(let ([p (trace-output-port)])
(if (> trace-level 10)
(let ([s (number->string (- trace-level 1))])
(bars (fx- 9 (string-length s)) p)
(write-char #\[ p)
(display s p)
(write-char #\] p))
(bars trace-level p))
(set! last-trace-level trace-level)
(parameterize ([pretty-initial-indent (fxmin trace-level 11)]
[pretty-line-length 80]
[pretty-one-line-limit 80])
(print x p))))))
(define pretty-print-multiple
(lambda (ls p)
(let ([indent (pretty-initial-indent)])
(let f ([x (car ls)] [ls (cdr ls)])
((trace-print) x p)
(unless (null? ls)
(let f ([n indent])
(write-char #\space p)
(unless (fx= n 1) (f (fx- n 1))))
(f (car ls) (cdr ls)))))))
(define prune-tracer-list
(lambda ()
(set! tracer-list
(let prune ([ls tracer-list])
(if (null? ls)
'()
(let ((t (car ls)))
(if (and (top-level-bound? (tracer-id t))
(eq? (tracer-new t)
(top-level-value (tracer-id t))))
(cons t (prune (cdr ls)))
(prune (cdr ls)))))))))
(set! $trace
(lambda ids
(prune-tracer-list)
(for-each (lambda (id)
(unless (symbol? id)
($oops 'trace "~s is not a symbol" id))
(unless (top-level-bound? id)
($oops 'trace "~:s is not bound" id))
(unless (procedure? (top-level-value id))
($oops 'trace
"the top-level value of ~s is not a procedure"
id)))
ids)
(if (null? ids)
(map tracer-id tracer-list)
(map (lambda (id)
(unless (memq id (map tracer-id tracer-list))
(let ([old (top-level-value id)])
(let ([new ($trace-closure id old)])
(if (top-level-mutable? id)
(set-top-level-value! id new)
(begin
(define-top-level-value id new)
(warningf 'trace "redefining ~s; existing references will not be traced" id)))
(set! tracer-list
(cons (make-tracer id old new)
tracer-list)))))
id)
ids))))
(set! $untrace
(lambda ids
(prune-tracer-list)
(let f ([ls tracer-list] [gone '()] [keep '()])
(if (null? ls)
(begin (set! tracer-list keep)
gone)
(let* ([x (car ls)] [id (tracer-id x)])
(if (or (null? ids) (memq id ids))
(begin (set-top-level-value! id (tracer-old x))
(f (cdr ls) (cons id gone) keep))
(f (cdr ls) gone (cons x keep))))))))
(set! $trace-closure
(lambda (name closure)
(unless (procedure? closure)
($oops 'trace "~s is not a procedure" closure))
(lambda args
(call/1cc
(lambda (k)
(if (eq? k trace-continuation)
(begin (trace-display (trace-print) (cons name args))
(apply closure args))
(fluid-let ([trace-level (+ 1 trace-level)]
[trace-continuation trace-continuation])
(trace-display (trace-print) (cons name args))
(call-with-values
(lambda ()
(call/1cc
(lambda (k)
(set! trace-continuation k)
(apply closure args))))
(case-lambda
[(x) (trace-display (trace-print) x) x]
[() (trace-display
(lambda (x p) (display x p) (newline p))
"*** no values ***")
(values)]
[args (trace-display pretty-print-multiple args)
(apply values args)])))))))))
) ;let