ikarus/lib/libfasl.ss

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;;; FASL
;;;
;;; A fasl object is a header followed by one or more objects followed by an
;;; end-of-fasl marker
;;;
;;; The header is the string "#@IK01"
;;; The end of fasl marker is "@"
;;;
;;; An object is either:
;;; "N" : denoting the empty list
;;; "T" : denoting #t
;;; "F" : denoting #f
;;; "E" : denoting the end of file object
;;; "U" : denoting the unspecified value
;;; "I" + 4-bytes : denoting a fixnum (in host byte order)
;;; "C" + 1-byte : denoting a character
;;; "P" + object1 + object2 : a pair
;;; "V" + 4-bytes(n) + object ... : a vector of length n followed by n
;;; objects
;;; "S" + 4-bytes(n) + char ... : a string
;;; "M" + symbol-name : a symbol
;;; "G" + pretty-name + unique-name : a gensym
;;; "R" + rtd-name + rtd-symbol + field-count + field-names
;;; "{" + field-count + rtd + fields
;;; ">" + 4-bytes(i) : mark the next object with index i
;;; "<" + 4-bytes(i) : dereference the object marked with index i
;;; "x" : denotes code
;;; "T" : Thunk; followed by code.
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(let ()
(define write-fixnum
(lambda (x p)
(unless (fixnum? x) (error 'write-fixnum "not a fixnum ~s" x))
(write-char (integer->char (fxsll (fxlogand x #x3F) 2)) p)
(write-char (integer->char (fxlogand (fxsra x 6) #xFF)) p)
(write-char (integer->char (fxlogand (fxsra x 14) #xFF)) p)
(write-char (integer->char (fxlogand (fxsra x 22) #xFF)) p)))
(define write-int
(lambda (x p)
(unless (fixnum? x) (error 'write-int "not a fixnum ~s" x))
(write-char (integer->char (fxlogand x #xFF)) p)
(write-char (integer->char (fxlogand (fxsra x 8) #xFF)) p)
(write-char (integer->char (fxlogand (fxsra x 16) #xFF)) p)
(write-char (integer->char (fxlogand (fxsra x 24) #xFF)) p)))
(define fasl-write-immediate
(lambda (x p)
(cond
[(null? x) (write-char #\N p)]
[(fixnum? x)
(write-char #\I p)
(write-fixnum x p)]
[(char? x)
(write-char #\C p)
(write-char x p)]
[(boolean? x)
(write-char (if x #\T #\F) p)]
[(eof-object? x) (write-char #\E p)]
[(eq? x (void)) (write-char #\U p)]
[else (error 'fasl-write "~s is not a fasl-writable immediate" x)])))
(define do-write
(lambda (x p h m)
(cond
[(pair? x)
(write-char #\P p)
(fasl-write (cdr x) p h
(fasl-write (car x) p h m))]
[(vector? x)
(write-char #\V p)
(write-int (vector-length x) p)
(let f ([x x] [i 0] [n (vector-length x)] [m m])
(cond
[(fx= i n) m]
[else
(f x (fxadd1 i) n
(fasl-write (vector-ref x i) p h m))]))]
[(string? x)
(write-char #\S p)
(write-int (string-length x) p)
(let f ([x x] [i 0] [n (string-length x)])
(cond
[(fx= i n) m]
[else
(write-char (string-ref x i) p)
(f x (fxadd1 i) n)]))]
[(gensym? x)
(write-char #\G p)
(fasl-write (gensym->unique-string x) p h
(fasl-write (symbol->string x) p h m))]
[(symbol? x)
(write-char #\M p)
(fasl-write (symbol->string x) p h m)]
[(code? x)
(write-char #\x p)
(write-int (code-size x) p)
(write-fixnum (code-freevars x) p)
(let f ([i 0] [n (code-size x)])
(unless (fx= i n)
(write-char (integer->char (code-ref x i)) p)
(f (fxadd1 i) n)))
(fasl-write (code-reloc-vector x) p h m)]
[(record? x)
(let ([rtd (record-type-descriptor x)])
(cond
[(eq? rtd #%$base-rtd)
;;; rtd record
(write-char #\R p)
(let ([names (record-type-field-names x)]
[m
(fasl-write (record-type-symbol x) p h
(fasl-write (record-type-name x) p h m))])
(write-int (length names) p)
(let f ([names names] [m m])
(cond
[(null? names) m]
[else
(f (cdr names)
(fasl-write (car names) p h m))])))]
[else
;;; non-rtd record
(write-char #\{ p)
(write-int (length (record-type-field-names rtd)) p)
(let f ([names (record-type-field-names rtd)]
[m (fasl-write rtd p h m)])
(cond
[(null? names) m]
[else
(f (cdr names)
(fasl-write
((record-field-accessor rtd (car names)) x)
p h m))]))]))]
[(procedure? x)
(write-char #\Q p)
(fasl-write ($closure-code x) p h m)]
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[else (error 'fasl-write "~s is not fasl-writable" x)])))
(define fasl-write
(lambda (x p h m)
(cond
[(immediate? x) (fasl-write-immediate x p) m]
[(get-hash-table h x #f) =>
(lambda (mark)
(unless (fixnum? mark)
(error 'fasl-write "BUG: invalid mark ~s" mark))
(cond
[(fx= mark 0) ; singly referenced
(do-write x p h m)]
[(fx> mark 0) ; marked but not written
(put-hash-table! h x (fx- 0 m))
(write-char #\> p)
(write-int m p)
(do-write x p h (fxadd1 m))]
[else
(write-char #\< p)
(write-int (fx- 0 mark) p)
m]))]
[else (error 'fasl-write "BUG: not in hash table ~s" x)])))
(define make-graph
(lambda (x h)
(unless (immediate? x)
(cond
[(get-hash-table h x #f) =>
(lambda (i)
(put-hash-table! h x (fxadd1 i)))]
[else
(put-hash-table! h x 0)
(cond
[(pair? x)
(make-graph (car x) h)
(make-graph (cdr x) h)]
[(vector? x)
(let f ([x x] [i 0] [n (vector-length x)])
(unless (fx= i n)
(make-graph (vector-ref x i) h)
(f x (fxadd1 i) n)))]
[(symbol? x)
(make-graph (symbol->string x) h)
(when (gensym? x) (make-graph (gensym->unique-string x) h))]
[(string? x) (void)]
[(code? x)
(make-graph (code-reloc-vector x) h)]
[(record? x)
(when (eq? x #%$base-rtd)
(error 'fasl-write "$base-rtd is not writable"))
(let ([rtd (record-type-descriptor x)])
(cond
[(eq? rtd #%$base-rtd)
;;; this is an rtd
(make-graph (record-type-name x) h)
(make-graph (record-type-symbol x) h)
(for-each (lambda (x) (make-graph x h))
(record-type-field-names x))]
[else
;;; this is a record
(make-graph rtd h)
(for-each
(lambda (name)
(make-graph ((record-field-accessor rtd name) x) h))
(record-type-field-names rtd))]))]
[(procedure? x)
(let ([code ($closure-code x)])
(unless (fxzero? ($code-freevars code))
(error 'fasl-write
"Cannot write a non-thunk procedure; the one given has ~s free vars"
($code-freevars code)))
(make-graph code h))]
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[else (error 'fasl-write "~s is not fasl-writable" x)])]))))
(define do-fasl-write
(lambda (x port)
(let ([h (make-hash-table)])
(make-graph x h)
(write-char #\# port)
(write-char #\@ port)
(write-char #\I port)
(write-char #\K port)
(write-char #\0 port)
(write-char #\1 port)
(fasl-write x port h 1))))
(primitive-set! 'fasl-write
(case-lambda
[(x) (do-fasl-write x (current-output-port))]
[(x port)
(unless (output-port? port)
(error 'fasl-write "~s is not an output port" port))
(do-fasl-write x port)])))