;;; strip.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 ()
  ; per file
  (define-threaded fasl-who)
  (define-threaded fasl-count)

  (define-datatype fasl
    (entry situation fasl)
    (header version machine dependencies)
    (pair vfasl)
    (tuple ty vfasl)
    (string ty string)
    (gensym pname uname)
    (vector ty vfasl)
    (fxvector ty viptr)
    (bytevector ty bv)
    (record maybe-uid size nflds rtd pad-ty* fld*) ; maybe-uid => rtd
    (closure offset c)
    (flonum high low)
    (small-integer iptr)
    (large-integer sign vuptr)
    (eq-hashtable mutable? subtype minlen veclen vpfasl)
    (symbol-hashtable mutable? minlen equiv veclen vpfasl)
    (code flags free name arity-mask info pinfo* bytes m vreloc)
    (atom ty uptr)
    (reloc type-etc code-offset item-offset fasl)
    (indirect g i))

  (define-datatype field
    (ptr fasl)
    (byte n)
    (iptr n)
    (single n)
    (double high low))

  (define follow-indirect
    (lambda (x)
      (fasl-case x
        [indirect (g i) (follow-indirect (vector-ref g i))]
        [else x])))

  (define-syntax bogus
    (lambda (x)
      (syntax-case x ()
        [(_ msg arg ...)
         (string? (datum msg))
         #`($oops fasl-who #,(string-append (datum msg) " within fasl entry ~d") arg ... fasl-count)])))

  (define-syntax sorry!
    (syntax-rules ()
      [(_ str arg ...) ($oops 'fasl-internal str arg ...)]))

  (module (read-entry)
    (define-syntax fasl-type-case
      (syntax-rules (else)
        [(_ e0 [(k ...) e1 e2 ...] ... [else ee1 ee2 ...])
         (let ([x e0])
           (cond
             [(memv x (list (constant k) ...)) e1 e2 ...]
             ...
             [else ee1 ee2 ...]))]))
    (define read-iptr
      (lambda (p)
        (let ([k0 (read-byte p)])
          (let f ([k k0] [n (fxsrl (fxlogand k0 #x7f) 1)])
            (if (fxlogbit? 0 k)
                (let ([k (read-byte p)])
                  (f k (logor (ash n 7) (fxsrl k 1))))
                (if (fxlogbit? 7 k0) (- n) n))))))
    (define read-uptr
      (lambda (p)
        (let ([k (read-byte p)])
          (let f ([k k] [n (fxsrl k 1)])
            (if (fxlogbit? 0 k)
                (let ([k (read-byte p)])
                  (f k (logor (ash n 7) (fxsrl k 1))))
                n)))))
    (define read-uptr/bytes
      (lambda (p)
        (let ([k (read-byte p)])
          (let f ([k k] [n (fxsrl k 1)] [bytes 1])
            (if (fxlogbit? 0 k)
                (let ([k (read-byte p)])
                  (f k (logor (ash n 7) (fxsrl k 1)) (fx+ bytes 1)))
                (values n bytes))))))
    (define read-byte-or-eof
      (lambda (p)
        (get-u8 p)))
    (define read-byte
      (lambda (p)
        (let ([b (get-u8 p)])
          (when (eof-object? b) (bogus "unexpected eof in ~a" (port-name p)))
          b)))
    (define (read-byte! x p)
      (let ([y (read-byte p)])
        (unless (eqv? y x)
          (bogus "expected byte ~s, got ~s from ~a" x y (port-name p)))))
    (define read-bytevector
      (lambda (p n)
        (let ([bv (make-bytevector n)])
          (do ([i 0 (fx+ i 1)])
              ((fx= i n) bv)
            (bytevector-u8-set! bv i (read-byte p))))))
    (define read-string
      (lambda (p)
        (let ([n (read-uptr p)])
          (let ([s (make-string n)])
            (do ([i 0 (+ i 1)])
                ((= i n))
              (string-set! s i (integer->char (read-uptr p))))
            s))))
    (define (read-entry p)
      (let ([ty (read-byte-or-eof p)])
        (if (eof-object? ty)
            ty
            (fasl-type-case ty
              [(fasl-type-header) (read-header p)]
              [(fasl-type-visit fasl-type-revisit fasl-type-visit-revisit)
               (let* ([situation ty]
                      [size (read-uptr p)]
                      [compressed-flag (read-byte p)])
                 (fasl-type-case compressed-flag
                   [(fasl-type-gzip fasl-type-lz4)
                    (let-values ([(dest-size dest-size-bytes) (read-uptr/bytes p)])
                      (let* ([src-size (- size 1 dest-size-bytes)]
                             [bv (read-bytevector p src-size)]
                             [bv ($bytevector-uncompress bv dest-size
                                   (if (eqv? compressed-flag (constant fasl-type-gzip))
                                       (constant COMPRESS-GZIP)
                                       (constant COMPRESS-LZ4)))])
                        (fasl-entry situation (read-fasl (open-bytevector-input-port bv) #f))))]
                   [(fasl-type-uncompressed) (fasl-entry situation (read-fasl p #f))]
                   [else (bogus "expected compression flag in ~a" (port-name p))]))]
              [else (bogus "expected header or situation in ~a" (port-name p))]))))
    (define (read-header p)
      (let* ([bv (constant fasl-header)] [n (bytevector-length bv)])
        (do ([i 1 (fx+ i 1)])
            ((fx= i n))
          (read-byte! (bytevector-u8-ref bv i) p)))
      (let* ([version (read-uptr p)]
             [machine (read-uptr p)])
        (unless (eqv? version (constant scheme-version))
          (bogus "expected version ~a, but found ~a in ~a"
            ($format-scheme-version (constant scheme-version))
            ($format-scheme-version version)
            (port-name p)))
        (read-byte! (char->integer #\() p) ;)
        (fasl-header version machine
          (let f () ;(
            (let ([c (read-byte p)])
              (if (eqv? c (char->integer #\)))
                  '()
                  (cons c (f))))))))
    (define (read-fld p g ty)
      (define (read-double p)
        (let* ([high (read-uptr p)]
               [low (read-uptr p)])
          (field-double high low)))
      (fasl-type-case ty
        [(fasl-fld-ptr) (field-ptr (read-fasl p g))]
        [(fasl-fld-u8) (field-byte (read-byte p))]
        [(fasl-fld-i16) (field-iptr (read-iptr p))]
        [(fasl-fld-i24) (field-iptr (read-iptr p))]
        [(fasl-fld-i32) (field-iptr (read-iptr p))]
        [(fasl-fld-i40) (field-iptr (read-iptr p))]
        [(fasl-fld-i48) (field-iptr (read-iptr p))]
        [(fasl-fld-i56) (field-iptr (read-iptr p))]
        [(fasl-fld-i64) (field-iptr (read-iptr p))]
        [(fasl-fld-single) (field-single (read-uptr p))]
        [(fasl-fld-double) (read-double p)]
        [else (bogus "unexpected record fld type ~s in ~a" ty (port-name p))]))
    (define (read-vfasl p g n)
      (let ([v (make-vector n)])
        (do ([i 0 (fx+ i 1)])
          ((fx= i n) v)
          (vector-set! v i (read-fasl p g)))))
    (define (read-vpfasl p g)
      (let ([n (read-uptr p)])
        (let ([v (make-vector n)])
          (do ([i 0 (fx+ i 1)])
            ((fx= i n) v)
            (vector-set! v i
              (let ([key (read-fasl p g)])
                (cons key (read-fasl p g))))))))
    (define (read-record p g maybe-uid)
      (let* ([size (read-uptr p)] [nflds (read-uptr p)] [rtd (read-fasl p g)])
        (let loop ([n nflds] [rpad-ty* '()] [rfld* '()])
          (if (fx= n 0)
              (fasl-record maybe-uid size nflds rtd (reverse rpad-ty*) (reverse rfld*))
              (let* ([pad-ty (read-byte p)] [fld (read-fld p g (fxlogand pad-ty #x0f))])
                (loop (fx- n 1) (cons pad-ty rpad-ty*) (cons fld rfld*)))))))
    (define (read-fasl p g)
      (let ([ty (read-byte p)])
        (fasl-type-case ty
          [(fasl-type-pair) (fasl-pair (read-vfasl p g (+ (read-uptr p) 1)))]
          [(fasl-type-box fasl-type-immutable-box) (fasl-tuple ty (vector (read-fasl p g)))]
          [(fasl-type-symbol) (fasl-string ty (read-string p))]
          [(fasl-type-gensym)
           (let* ([pname (read-string p)] [uname (read-string p)])
             (fasl-gensym pname uname))]
          [(fasl-type-ratnum fasl-type-exactnum fasl-type-inexactnum fasl-type-weak-pair)
           (let ([first (read-fasl p g)])
             (fasl-tuple ty (vector first (read-fasl p g))))]
          [(fasl-type-vector fasl-type-immutable-vector) (fasl-vector ty (read-vfasl p g (read-uptr p)))]
          [(fasl-type-fxvector fasl-type-immutable-fxvector)
           (fasl-fxvector
             ty
             (let ([n (read-uptr p)])
               (let ([v (make-vector n)])
                 (do ([i 0 (fx+ i 1)])
                     ((fx= i n) v)
                   (vector-set! v i (read-iptr p))))))]
          [(fasl-type-bytevector fasl-type-immutable-bytevector)
           (fasl-bytevector ty (read-bytevector p (read-uptr p)))]
          [(fasl-type-base-rtd) (fasl-tuple ty '#())]
          [(fasl-type-rtd) (read-record p g (read-fasl p g))]
          [(fasl-type-record) (read-record p g #f)]
          [(fasl-type-closure)
           (let* ([offset (read-uptr p)]
                  [c (read-fasl p g)])
             (fasl-closure offset c))]
          [(fasl-type-flonum)
           (let* ([high (read-uptr p)]
                  [low (read-uptr p)])
             (fasl-flonum high low))]
          [(fasl-type-string fasl-type-immutable-string) (fasl-string ty (read-string p))]
          [(fasl-type-small-integer) (fasl-small-integer (read-iptr p))]
          [(fasl-type-large-integer)
           (let* ([sign (read-byte p)]
                  [n (read-uptr p)])
             (fasl-large-integer sign
               (let ([v (make-vector n)])
                 (do ([i 0 (fx+ i 1)])
                     ((fx= i n) v)
                   (vector-set! v i (read-uptr p))))))]
          [(fasl-type-eq-hashtable)
           (let* ([mutable? (read-byte p)]
                  [subtype (read-byte p)]
                  [minlen (read-uptr p)]
                  [veclen (read-uptr p)]
                  [v (read-vpfasl p g)])
             (fasl-eq-hashtable mutable? subtype minlen veclen v))]
          [(fasl-type-symbol-hashtable)
           (let* ([mutable? (read-byte p)]
                  [minlen (read-uptr p)]
                  [equiv (read-byte p)]
                  [veclen (read-uptr p)]
                  [v (read-vpfasl p g)])
             (fasl-symbol-hashtable mutable? minlen equiv veclen v))]
          [(fasl-type-code)
           (let* ([flags (read-byte p)]
                  [free (read-uptr p)]
                  [nbytes (read-uptr p)]
                  [name (read-fasl p g)]
                  [arity-mask (read-fasl p g)]
                  [info (read-fasl p g)]
                  [pinfo* (read-fasl p g)]
                  [bytes (let ([bv (make-bytevector nbytes)])
                           (do ([i 0 (fx+ i 1)])
                             ((fx= i nbytes) bv)
                             (bytevector-u8-set! bv i (read-byte p))))]
                  [m (read-uptr p)]
                  [vreloc (let loop ([n 0] [rls '()])
                            (if (fx= n m)
                                (list->vector (reverse rls))
                                (let* ([type-etc (read-byte p)]
                                       [code-offset (read-uptr p)]
                                       [item-offset (if (fxlogtest type-etc 2) (read-uptr p) 0)])
                                  (loop
                                    (fx+ n (if (fxlogtest type-etc 1) 3 1))
                                    (cons (fasl-reloc type-etc code-offset item-offset (read-fasl p g)) rls)))))])
             (fasl-code flags free name arity-mask info pinfo* bytes m vreloc))]
          [(fasl-type-immediate fasl-type-entry fasl-type-library fasl-type-library-code)
           (fasl-atom ty (read-uptr p))]
          [(fasl-type-graph) (read-fasl p (make-vector (read-uptr p) #f))]
          [(fasl-type-graph-def)
           (let ([n (read-uptr p)])
             (let ([x (read-fasl p g)])
               (when (vector-ref g n) (bogus "duplicate definition for graph element ~s in ~a" n (port-name p)))
               (vector-set! g n x)
               x))]
          [(fasl-type-graph-ref)
           (let ([n (read-uptr p)])
             (or (vector-ref g n)
                 (fasl-indirect g n)))]
          [else (bogus "unexpected fasl code ~s in ~a" ty (port-name p))]))))

  (define read-script-header
    (lambda (ip)
      (let-values ([(bvop extract) (open-bytevector-output-port)])
        (define get
          (lambda ()
            (let ([b (get-u8 ip)])
              (put-u8 bvop b)
              b)))
        (if (and (eqv? (get) (char->integer #\#))
                 (eqv? (get) (char->integer #\!))
                 (let ([b (get)])
                   (or (eqv? b (char->integer #\/))
                       (eqv? b (char->integer #\space)))))
            (let f ()
              (let ([b (get)])
                (if (eof-object? b)
                    (bogus "unexpected eof reading #! line in ~a" (port-name ip))
                    (if (eqv? b (char->integer #\newline))
                        (extract)
                        (f)))))
            (begin (set-port-position! ip 0) #f)))))

  (let ()
    (define-threaded strip-inspector-information?)
    (define-threaded strip-profile-information?)
    (define-threaded strip-source-annotations?)
    (define-threaded strip-compile-time-information?)

    (module (fasl-record-predicate fasl-record-accessor)
      (define field-index
        (lambda (rtd field-name)
          (let ([v (record-type-field-names rtd)])
            (let loop ([i 0] [index #f])
              (if (fx= i (vector-length v))
                  (or index (sorry! "field ~s not found for ~s" field-name rtd))
                  (if (eq? (vector-ref v i) field-name)
                      (if index
                          (sorry! "duplicate field ~s found for ~s" field-name rtd)
                          (loop (fx+ i 1) i))
                      (loop (fx+ i 1) index)))))))
      (define uid-index (field-index #!base-rtd 'uid))
      (define fasl-record?
        (lambda (uname x)
          (fasl-case (follow-indirect x)
            [record (maybe-uid size nflds rtd pad-ty* fld*)
              (fasl-case (follow-indirect rtd)
                [record (rtd-uid rtd-size rtd-nflds rtd-rtd rtd-pad-ty* rtd-fld*)
                  (and (> (length rtd-fld*) uid-index)
                       (field-case (list-ref rtd-fld* uid-index)
                         [ptr (fasl)
                          (fasl-case (follow-indirect fasl)
                            [gensym (pname2 uname2) (string=? uname2 uname)]
                            [else #f])]
                         [else #f]))]
                [else #f])]
            [else #f])))
      (define fasl-record-predicate
        (lambda (rtd)
          (let ([uname (gensym->unique-string (record-type-uid rtd))])
            (lambda (x)
              (fasl-record? uname x)))))
      (define fasl-record-accessor
        (lambda (rtd field-name)
          (let ([uname (gensym->unique-string (record-type-uid rtd))]
                [index (field-index rtd field-name)])
            (lambda (x)
              (unless (fasl-record? uname x)
                (sorry! "unexpected type of object ~s" x))
              (fasl-case (follow-indirect x)
                [record (maybe-uid size nflds rtd pad-ty* fld*)
                  (unless (> (length fld*) index)
                    (sorry! "fewer fields than expected for ~s" x))
                  (let ([fld (list-ref fld* index)])
                    (field-case fld
                      [ptr (fasl) fasl]
                      [else (sorry! "unexpected type of field ~s" fld)]))]
                [else (sorry! "~s should have been a fasl record" x)]))))))

    (module (fasl-annotation? fasl-annotation-stripped)
      (include "types.ss")
      (define fasl-annotation? (fasl-record-predicate (record-type-descriptor annotation)))
      (define fasl-annotation-stripped (fasl-record-accessor (record-type-descriptor annotation) 'stripped)))

    (define-record-type table
      (nongenerative)
      (sealed #t)
      (fields (mutable count) (immutable ht))
      (protocol
        (lambda (new)
          (lambda ()
            (new 0 (make-eq-hashtable))))))

    (define build-graph!
      (lambda (x t th)
        (let ([a (eq-hashtable-cell (table-ht t) x 'first)])
          (let ([p (cdr a)])
            (cond
              [(eq? p 'first) (set-cdr! a #f) (th)]
              [(not p)
               (let ([n (table-count t)])
                 (set-cdr! a (cons n #t))
                 (table-count-set! t (fx+ n 1)))])))))

    (define build!
      (lambda (x t)
        (define build-vfasl!
          (lambda (vfasl)
            (lambda ()
              (vector-for-each (lambda (fasl) (build! fasl t)) vfasl))))
        (fasl-case x
          [entry (situation fasl) (sorry! "unexpected fasl-record-type entry")]
          [header (version machine dependencies) (sorry! "unexpected fasl-record-type header")]
          [pair (vfasl) (build-graph! x t (build-vfasl! vfasl))]
          [tuple (ty vfasl) (build-graph! x t (build-vfasl! vfasl))]
          [string (ty string) (build-graph! x t void)]
          [gensym (pname uname) (build-graph! x t void)]
          [vector (ty vfasl) (build-graph! x t (build-vfasl! vfasl))]
          [fxvector (ty viptr) (build-graph! x t void)]
          [bytevector (ty viptr) (build-graph! x t void)]
          [record (maybe-uid size nflds rtd pad-ty* fld*)
           (if (and strip-source-annotations? (fasl-annotation? x))
               (build! (fasl-annotation-stripped x) t)
               (build-graph! x t
                 (lambda ()
                   (when maybe-uid (build! maybe-uid t))
                   (build! rtd t)
                   (for-each (lambda (fld)
                               (field-case fld
                                 [ptr (fasl) (build! fasl t)]
                                 [else (void)]))
                     fld*))))]
          [closure (offset c) (build-graph! x t (lambda () (build! c t)))]
          [flonum (high low) (build-graph! x t void)]
          [small-integer (iptr) (void)]
          [large-integer (sign vuptr) (build-graph! x t void)]
          [eq-hashtable (mutable? subtype minlen veclen vpfasl)
           (build-graph! x t
             (lambda ()
               (vector-for-each
                 (lambda (pfasl)
                   (build! (car pfasl) t)
                   (build! (cdr pfasl) t))
                 vpfasl)))]
          [symbol-hashtable (mutable? minlen equiv veclen vpfasl)
           (build-graph! x t
             (lambda ()
               (vector-for-each
                 (lambda (pfasl)
                   (build! (car pfasl) t)
                   (build! (cdr pfasl) t))
                 vpfasl)))]
          [code (flags free name arity-mask info pinfo* bytes m vreloc)
           (build-graph! x t
             (lambda ()
               (build! name t)
               (build! arity-mask t)
               (unless strip-inspector-information? (build! info t))
               (unless strip-profile-information? (build! pinfo* t))
               (vector-for-each (lambda (reloc) (build! reloc t)) vreloc)))]
          [atom (ty uptr) (void)]
          [reloc (type-etc code-offset item-offset fasl) (build! fasl t)]
          [indirect (g i) (build! (vector-ref g i) t)])))

    (include "fasl-helpers.ss")

    (define write-entry
      (lambda (p x)
        (define (append-bvs bv*)
          (let f ([bv* bv*] [n 0])
            (if (null? bv*)
                (if (fixnum? n)
                    (make-bytevector n)
                    ($oops 'fasl-write "fasl output is too large to compress"))
                (let ([bv1 (car bv*)])
                  (let ([m (bytevector-length bv1)])
                    (let ([bv2 (f (cdr bv*) (+ n m))])
                      (bytevector-copy! bv1 0 bv2 n m)
                      bv2))))))
        (fasl-case x
          [header (version machine dependencies)
           (emit-header p version machine dependencies)]
          [entry (situation fasl)
           (let ([t (make-table)])
             (build! fasl t)
             ($fasl-start p t situation
               (lambda (p) (write-fasl p t fasl))))]
          [else (sorry! "unrecognized top-level fasl-record-type ~s" x)])))

    (define write-graph
      (lambda (p t x th)
        (let ([a (eq-hashtable-ref (table-ht t) x #f)])
          (cond
            [(not a) (th)]
            [(cdr a)
             (put-u8 p (constant fasl-type-graph-def))
             (put-uptr p (car a))
             (set-cdr! a #f)
             (th)]
            [else
             (put-u8 p (constant fasl-type-graph-ref))
             (put-uptr p (car a))]))))

    (define write-fasl
      (lambda (p t x)
        (fasl-case x
          [entry (situation fasl) (sorry! "unexpected fasl-record-type entry")]
          [header (version machine dependencies) (sorry! "unexpected fasl-record-type header")]
          [pair (vfasl)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-pair))
               (put-uptr p (fx- (vector-length vfasl) 1))
               (vector-for-each (lambda (fasl) (write-fasl p t fasl)) vfasl)))]
          [tuple (ty vfasl)
           (write-graph p t x
             (lambda ()
               (put-u8 p ty)
               (vector-for-each (lambda (fasl) (write-fasl p t fasl)) vfasl)))]
          [string (ty string)
           (write-graph p t x
             (lambda ()
               (put-u8 p ty)
               (write-string p string)))]
          [gensym (pname uname)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-gensym))
               (write-string p pname)
               (write-string p uname)))]
          [vector (ty vfasl)
           (write-graph p t x
             (lambda ()
               (put-u8 p ty)
               (put-uptr p (vector-length vfasl))
               (vector-for-each (lambda (fasl) (write-fasl p t fasl)) vfasl)))]
          [fxvector (ty viptr)
           (write-graph p t x
             (lambda ()
               (put-u8 p ty)
               (put-uptr p (vector-length viptr))
               (vector-for-each (lambda (iptr) (put-iptr p iptr)) viptr)))]
          [bytevector (ty bv)
           (write-graph p t x
             (lambda ()
               (put-u8 p ty)
               (put-uptr p (bytevector-length bv))
               (put-bytevector p bv)))]
          [record (maybe-uid size nflds rtd pad-ty* fld*)
           (if (and strip-source-annotations? (fasl-annotation? x))
               (write-fasl p t (fasl-annotation-stripped x))
               (write-graph p t x
                 (lambda ()
                   (if maybe-uid
                       (begin
                         (put-u8 p (constant fasl-type-rtd))
                         (write-fasl p t maybe-uid))
                       (put-u8 p (constant fasl-type-record)))
                   (put-uptr p size)
                   (put-uptr p nflds)
                   (write-fasl p t rtd)
                   (for-each (lambda (pad-ty fld)
                               (put-u8 p pad-ty)
                               (field-case fld
                                 [ptr (fasl) (write-fasl p t fasl)]
                                 [byte (n) (put-u8 p n)]
                                 [iptr (n) (put-iptr p n)]
                                 [single (n) (put-uptr p n)]
                                 [double (high low)
                                  (put-uptr p high)
                                  (put-uptr p low)]))
                     pad-ty* fld*))))]
          [closure (offset c)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-closure))
               (put-uptr p offset)
               (write-fasl p t c)))]
          [flonum (high low)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-flonum))
               (put-uptr p high)
               (put-uptr p low)))]
          [large-integer (sign vuptr)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-large-integer))
               (put-u8 p sign)
               (put-uptr p (vector-length vuptr))
               (vector-for-each (lambda (uptr) (put-uptr p uptr)) vuptr)))]
          [eq-hashtable (mutable? subtype minlen veclen vpfasl)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-eq-hashtable))
               (put-u8 p mutable?)
               (put-u8 p subtype)
               (put-uptr p minlen)
               (put-uptr p veclen)
               (put-uptr p (vector-length vpfasl))
               (vector-for-each
                 (lambda (pfasl)
                   (write-fasl p t (car pfasl))
                   (write-fasl p t (cdr pfasl)))
                 vpfasl)))]
          [symbol-hashtable (mutable? minlen equiv veclen vpfasl)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-symbol-hashtable))
               (put-u8 p mutable?)
               (put-uptr p minlen)
               (put-u8 p equiv)
               (put-uptr p veclen)
               (put-uptr p (vector-length vpfasl))
               (vector-for-each
                 (lambda (pfasl)
                   (write-fasl p t (car pfasl))
                   (write-fasl p t (cdr pfasl)))
                 vpfasl)))]
          [code (flags free name arity-mask info pinfo* bytes m vreloc)
           (write-graph p t x
             (lambda ()
               (put-u8 p (constant fasl-type-code))
               (put-u8 p flags)
               (put-uptr p free)
               (put-uptr p (bytevector-length bytes))
               (write-fasl p t name)
               (write-fasl p t arity-mask)
               (if strip-inspector-information?
                   (write-fasl p t (fasl-atom (constant fasl-type-immediate) (constant sfalse)))
                   (write-fasl p t info))
               (if strip-profile-information?
                   (write-fasl p t (fasl-atom (constant fasl-type-immediate) (constant snil)))
                   (write-fasl p t pinfo*))
               (put-bytevector p bytes)
               (put-uptr p m)
               (vector-for-each (lambda (reloc) (write-fasl p t reloc)) vreloc)))]
          [small-integer (iptr)
           (put-u8 p (constant fasl-type-small-integer))
           (put-iptr p iptr)]
          [atom (ty uptr)
           (put-u8 p ty)
           (put-uptr p uptr)]
          [reloc (type-etc code-offset item-offset fasl)
           (put-u8 p type-etc)
           (put-uptr p code-offset)
           (when (fxlogtest type-etc 2) (put-uptr p item-offset))
           (write-fasl p t fasl)]
          [indirect (g i) (write-fasl p t (vector-ref g i))])))

    (define write-string
      (lambda (p x)
        (let ([n (string-length x)])
          (put-uptr p n)
          (do ([i 0 (fx+ i 1)])
            ((fx= i n))
            (put-uptr p (char->integer (string-ref x i)))))))

    (module (fasl-program-info? fasl-library/rt-info? fasl-recompile-info?)
      (import (nanopass))
      (include "base-lang.ss")
      (include "expand-lang.ss")
      (define fasl-program-info? (fasl-record-predicate (record-type-descriptor program-info)))
      (define fasl-library/rt-info? (fasl-record-predicate (record-type-descriptor library/rt-info)))
      (define fasl-recompile-info? (fasl-record-predicate (record-type-descriptor recompile-info))))

    (define keep-revisit-info
      (lambda (x)
        (fasl-case x
          [entry (situation fasl)
           (and (or (eqv? situation (constant fasl-type-revisit))
                    (eqv? situation (constant fasl-type-visit-revisit)))
                x)]
          [header (version machine dependencies) x]
          [else (sorry! "expected entry or header, got ~s" x)])))

    (set-who! $fasl-strip-options (make-enumeration '(inspector-source profile-source source-annotations compile-time-information)))
    (set-who! $make-fasl-strip-options (enum-set-constructor $fasl-strip-options))

    (let ()
      (define read-and-strip-file
        (lambda (ifn)
          (let ([ip ($open-file-input-port fasl-who ifn)])
            (on-reset (close-port ip)
              (let* ([script-header (read-script-header ip)]
                     [mode (and script-header (unless-feature windows (get-mode ifn)))])
                (let loop ([rentry* '()])
                  (set! fasl-count (fx+ fasl-count 1))
                  (let ([entry (read-entry ip)])
                    (if (eof-object? entry)
                        (begin
                          (close-port ip)
                          (values script-header mode (reverse rentry*)))
                        (let ([entry (if strip-compile-time-information? (keep-revisit-info entry) entry)])
                          (loop (if entry (cons entry rentry*) rentry*)))))))))))
      (set-who! strip-fasl-file
        (rec strip-fasl-file
          (lambda (ifn ofn options)
            (unless (string? ifn) ($oops who "~s is not a string" ifn))
            (unless (string? ofn) ($oops who "~s is not a string" ofn))
            (unless (and (enum-set? options) (enum-set-subset? options $fasl-strip-options))
              ($oops who "~s is not a fasl-strip-options object" options))
            (fluid-let ([strip-inspector-information? (enum-set-subset? (fasl-strip-options inspector-source) options)]
                        [strip-profile-information? (enum-set-subset? (fasl-strip-options profile-source) options)]
                        [strip-source-annotations? (enum-set-subset? (fasl-strip-options source-annotations) options)]
                        [strip-compile-time-information? (enum-set-subset? (fasl-strip-options compile-time-information) options)]
                        [fasl-who who]
                        [fasl-count 0])
              (let-values ([(script-header mode entry*) (read-and-strip-file ifn)])
                (let ([op ($open-file-output-port who ofn (file-options replace))])
                  (on-reset (delete-file ofn #f)
                    (on-reset (close-port op)
                      (when script-header (put-bytevector op script-header))
                      (for-each (lambda (entry) (write-entry op entry)) entry*)
                      (close-port op)
                      (unless-feature windows (when mode (chmod ofn mode)))))))))))))

  (let ()
    ; per file
    (define-threaded fail)
    (define-threaded eq-hashtable-warning-issued?)
    ; per entry
    (define-threaded cmp-ht)
    (define-threaded gensym-table)

    (define-syntax cmp-case
      (lambda (x)
        (define (make-clause t x-case)
          (lambda (variant arg* e)
            (with-syntax ([(arg1 ...) (map (lambda (x) (construct-name x x "1")) arg*)]
                          [(arg2 ...) (map (lambda (x) (construct-name x x "2")) arg*)]
                          [variant variant]
                          [e e]
                          [t t]
                          [x-case x-case])
              #'[variant (arg1 ...)
                 (or (x-case t
                       [variant (arg2 ...) e]
                       [else #f])
                     (fail 'variant))])))
        (syntax-case x ()
          [(_ x-case e1 e2 [variant (arg ...) e] ...)
           #`(let ([t2 e2])
               (x-case e1
                 #,@(map (make-clause #'t2 #'x-case) #'(variant ...) #'((arg ...) ...) #'(e ...))))])))

    (define-who vandmap
      (lambda (p v1 v2)
        (let ([n (vector-length v1)])
          (and (fx= (vector-length v2) n)
               (let f ([i 0])
                 (or (fx= i n)
                     (and (p (vector-ref v1 i) (vector-ref v2 i))
                          (f (fx+ i 1)))))))))

    (define fld=?
      (lambda (fld1 fld2)
        (cmp-case field-case fld1 fld2
          [ptr (fasl) (fasl=? fasl1 fasl2)]
          [byte (n) (eqv? n1 n2)]
          [iptr (n) (eqv? n1 n2)]
          [single (n) (eqv? n1 n2)]
          [double (high low)
           (and (eqv? high1 high2)
                (eqv? low1 low2))])))

    (define (fasl=? entry1 entry2)
      (let ([entry1 (follow-indirect entry1)] [entry2 (follow-indirect entry2)])
        (let ([a (eq-hashtable-cell cmp-ht entry1 #f)])
          (or (eq? entry2 (cdr a))
              (and (not (cdr a))
                   (begin
                     (set-cdr! a entry2)
                     (cmp-case fasl-case entry1 entry2
                       [entry (situation fasl) (and (= situation1 situation2) (fasl=? fasl1 fasl2))]
                       [header (version machine dependencies)
                        (and (equal? version1 version2)
                             (equal? machine1 machine2)
                             (equal? dependencies1 dependencies2))]
                       [pair (vfasl) (vandmap fasl=? vfasl1 vfasl2)]
                       [tuple (ty vfasl) (and (eqv? ty1 ty2) (vandmap fasl=? vfasl1 vfasl2))]
                       [string (ty string) (and (eqv? ty1 ty2) (string=? string1 string2))]
                       [gensym (pname uname)
                        (and (string=? pname1 pname2)
                             (let ([x (hashtable-ref gensym-table uname1 #f)])
                               (if (not x)
                                   (hashtable-set! gensym-table uname1 uname2)
                                   (string=? x uname2))))]
                       [vector (ty vfasl) (and (eqv? ty1 ty2) (vandmap fasl=? vfasl1 vfasl2))]
                       [fxvector (ty viptr) (and (eqv? ty1 ty2) (vandmap = viptr1 viptr2))]
                       [bytevector (ty bv) (and (eqv? ty1 ty2) (bytevector=? bv1 bv2))]
                       [record (maybe-uid size nflds rtd pad-ty* fld*)
                        (and (if maybe-uid1
                                 (and maybe-uid2 (fasl=? maybe-uid1 maybe-uid2))
                                 (not maybe-uid2))
                             (eqv? size1 size2)
                             (eqv? nflds1 nflds2)
                             (fasl=? rtd1 rtd2)
                             (andmap eqv? pad-ty*1 pad-ty*2)
                             (andmap fld=? fld*1 fld*2))]
                       [closure (offset c) (and (eqv? offset1 offset2) (fasl=? c1 c2))]
                       [flonum (high low)
                        (and (eqv? high1 high2)
                             (eqv? low1 low2))]
                       [large-integer (sign vuptr) (and (eqv? sign1 sign2) (vandmap = vuptr1 vuptr2))]
                       [eq-hashtable (mutable? subtype minlen veclen vpfasl)
                        (and (eqv? mutable?1 mutable?2)
                             (eqv? subtype1 subtype2)
                             (eqv? minlen1 minlen2)
                             ; don't care if veclens differ
                             #;(eqv? veclen1 veclen2)
                             ; making gross assumption that equal-length hashtables are equal.
                             ; actual eq-hashtable equivalence is hard.
                             (fx= (vector-length vpfasl1) (vector-length vpfasl2))
                             (begin
                               (unless (or (fx= (vector-length vpfasl1) 0) eq-hashtable-warning-issued?)
                                 (set! eq-hashtable-warning-issued? #t)
                                 (warning fasl-who "punting on comparison of eq-hashtable entries"))
                               #t))]
                       [symbol-hashtable (mutable? minlen equiv veclen vpfasl)
                        (let ()
                          (define keyval?
                            (lambda (x1 x2)
                              (fasl-case (car x1)
                                [gensym (pname1 uname1)
                                  (fasl-case (car x2)
                                    [gensym (pname2 uname2) (string<? uname1 uname2)]
                                    [string (ty2 string2) #t]
                                    [else (sorry! "unexpected key ~s" x2)])]
                                [string (ty1 string1)
                                  (fasl-case (car x2)
                                    [gensym (pname2 uname2) #f]
                                    [string (ty2 string2) (string<? string1 string2)]
                                    [else (sorry! "unexpected key ~s" x2)])]
                                [else (sorry! "unexpected key ~s" x1)])))
                          (and (eqv? mutable?1 mutable?2)
                               (eqv? minlen1 minlen2)
                               (eqv? equiv1 equiv2)
                               ; don't care if veclens differ
                               #;(eqv? veclen1 veclen2)
                               (vandmap (lambda (x y) (and (fasl=? (car x) (car y)) (fasl=? (cdr x) (cdr y))))
                                 (vector-sort keyval? vpfasl1)
                                 (vector-sort keyval? vpfasl2))))]
                       [code (flags free name arity-mask info pinfo* bytes m reloc)
                        (and (eqv? flags1 flags2)
                             (eqv? free1 free2)
                             (fasl=? name1 name2)
                             (fasl=? arity-mask1 arity-mask2)
                             (fasl=? info1 info2)
                             (fasl=? pinfo*1 pinfo*2)
                             (bytevector=? bytes1 bytes2)
                             (eqv? m1 m2)
                             (vandmap fasl=? reloc1 reloc2))]
                       [small-integer (iptr) (eqv? iptr1 iptr2)]
                       [atom (ty uptr) (and (eqv? ty1 ty2) (eqv? uptr1 uptr2))]
                       [reloc (type-etc code-offset item-offset fasl)
                        (and (eqv? type-etc1 type-etc2)
                             (eqv? code-offset1 code-offset2)
                             (eqv? item-offset1 item-offset2)
                             (fasl=? fasl1 fasl2))]
                       [indirect (g i) (sorry! "unexpected indirect")])))))))

    (set-who! $fasl-file-equal?
      (rec fasl-file-equal?
        (case-lambda
          [(ifn1 ifn2) (fasl-file-equal? ifn1 ifn2 #f)]
          [(ifn1 ifn2 error?)
           (unless (string? ifn1) ($oops who "~s is not a string" ifn1))
           (unless (string? ifn2) ($oops who "~s is not a string" ifn2))
           (fluid-let ([fasl-who who]
                       [fasl-count 0]
                       [fail (if error? (lambda (what) (bogus "~s comparison failed while comparing ~a and ~a" what ifn1 ifn2)) (lambda (what) #f))]
                       [eq-hashtable-warning-issued? #f])
             (call-with-port ($open-file-input-port who ifn1)
               (lambda (ip1)
                 (on-reset (close-port ip1)
                   (call-with-port ($open-file-input-port who ifn2)
                     (lambda (ip2)
                       (on-reset (close-port ip2)
                         (let ([script-header1 (read-script-header ip1)]
                               [script-header2 (read-script-header ip2)])
                           (if (equal? script-header1 script-header2)
                               (let loop ()
                                 (set! fasl-count (fx+ fasl-count 1))
                                 (let ([entry1 (read-entry ip1)] [entry2 (read-entry ip2)])
                                   (if (eof-object? entry1)
                                       (or (eof-object? entry2)
                                           (and error? (bogus "~a has fewer fasl entries than ~a" ifn1 ifn2)))
                                       (if (eof-object? entry2)
                                           (and error? (bogus "~a has fewer fasl entries than ~a" ifn2 ifn1))
                                           (and (fluid-let ([cmp-ht (make-eq-hashtable)]
                                                            [gensym-table (make-hashtable string-hash string=?)])
                                                  (fasl=? entry1 entry2))
                                                (loop))))))
                               (and error? (bogus "script headers ~s and ~s differ" script-header1 script-header2)))))))))))])))))