/usr/share/gauche-0.9/0.9.4/lib/rfc/json.scm is in gauche 0.9.4-3.
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;;; json.scm - JSON (RFC4627) Parser
;;;
;;; Copyright (c) 2006 Rui Ueyama (rui314@gmail.com)
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; 2. Redistributions in binary form must reproduce the above copyright
;;; notice, this list of conditions and the following disclaimer in the
;;; documentation and/or other materials provided with the distribution.
;;;
;;; 3. Neither the name of the authors nor the names of its contributors
;;; may be used to endorse or promote products derived from this
;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
;;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
;;; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
;;; PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
;;; LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;;; http://www.ietf.org/rfc/rfc4627.txt
;; NOTE: This module depends on parser.peg, whose API is not officially
;; fixed. Hence do not take this code as an example of parser.peg;
;; this will likely to be rewritten once parser.peg's API is changed.
(define-module rfc.json
(use gauche.parameter)
(use gauche.sequence)
(use gauche.generator)
(use parser.peg)
(use srfi-13)
(use srfi-14)
(use srfi-43)
(use text.unicode)
(export <json-parse-error> <json-construct-error>
parse-json parse-json-string
parse-json*
construct-json construct-json-string
json-array-handler json-object-handler json-special-handler
json-parser ;experimental
))
(select-module rfc.json)
;; NB: We have <json-parse-error> independent from <parse-error> for
;; now, since parser.peg's interface may be changed later.
(define-condition-type <json-parse-error> <error> #f
(position) ;stream position
(objects)) ;offending object(s) or messages
(define-condition-type <json-construct-error> <error> #f
(object)) ;offending object
(define json-array-handler (make-parameter list->vector))
(define json-object-handler (make-parameter identity))
(define json-special-handler (make-parameter identity))
(define (build-array elts) ((json-array-handler) elts))
(define (build-object pairs) ((json-object-handler) pairs))
(define (build-special symbol) ((json-special-handler) symbol))
;;;============================================================
;;; Parser
;;;
(define %ws ($skip-many ($one-of #[ \t\r\n])))
(define %begin-array ($seq ($char #\[) %ws))
(define %begin-object ($seq ($char #\{) %ws))
(define %end-array ($seq ($char #\]) %ws))
(define %end-object ($seq ($char #\}) %ws))
(define %name-separator ($seq ($char #\:) %ws))
(define %value-separator ($seq ($char #\,) %ws))
(define %special
($lift ($ build-special $ string->symbol $ rope-finalize $)
($or ($string "false") ($string "true") ($string "null"))))
(define %value
($lazy
($lift (^[v _] v) ($or %special %object %array %number %string) %ws)))
(define %array
($lift ($ build-array $ rope-finalize $)
($between %begin-array ($sep-by %value %value-separator) %end-array)))
(define %number
(let* ([%sign ($or ($do [($char #\-)] ($return -1))
($do [($char #\+)] ($return 1))
($return 1))]
[%digits ($lift ($ string->number $ list->string $) ($many digit 1))]
[%int %digits]
[%frac ($do [($char #\.)]
[d ($many digit 1)]
($return (string->number (apply string #\0 #\. d))))]
[%exp ($lift (^[_ s d] (* s d)) ($one-of #[eE]) %sign %digits)])
($lift (^[sign int frac exp]
(let1 mantissa (+ int frac)
(* sign (if exp (exact->inexact mantissa) mantissa)
(if exp (expt 10 exp) 1))))
%sign %int ($or %frac ($return 0)) ($or %exp ($return #f)))))
(define %unicode
(let ([%hex4 ($lift (^s (string->number (list->string s) 16))
($many hexdigit 4 4))]
;; NB: If we just $fail, the higher-level parser may conceal the
;; direct cause of the error by backtracking. Unpaired surrogate
;; is an unrecoverable error, so we throw <json-parse-error> directly.
;; There may be a better way to integrate this kind of error in
;; the combinators; let's see.
[err (^c (errorf <json-parse-error>
:position #f :object c
"unpaired surrogate: \\u~4,'0x" c))])
($do [($char #\u)]
[c %hex4]
(cond [(<= #xd800 c #xdbff)
($or ($try ($do [($string "\\u")]
[c2 %hex4]
(receive (cc x)
(utf16->ucs4 `(,c ,c2) 'permissive)
(and (null? x)
($return (ucs->char cc))))))
;; NB: We wrap (err c) with dummy $do to put the call
;; to the err into a parser monad. Simple ($return (err c))
;; or ($fail (err c)) won't do, since (err c) is evaluated
;; at the parser-construction time, not the actual parsing
;; time. We need a dummy ($return #t) clause to ensure
;; (err c) is wrapped; ($do x) is expanded to just x.
;; Definitely we need something better to do this kind of
;; operation.
($do [($return #t)] (err c)))]
[(<= #xdc00 c #xdfff) (err c)]
[else ($return (ucs->char c))]))))
(define %string
(let* ([%dquote ($char #\")]
[%escape ($char #\\)]
[%special-char
($do %escape
($or ($char #\")
($char #\\)
($char #\/)
($do [($char #\b)] ($return #\x08))
($do [($char #\f)] ($return #\page))
($do [($char #\n)] ($return #\newline))
($do [($char #\r)] ($return #\return))
($do [($char #\t)] ($return #\tab))
%unicode))]
[%unescaped ($none-of #[\"])]
[%body-char ($or %special-char %unescaped)]
[%string-body ($->rope ($many %body-char))])
($between %dquote %string-body %dquote)))
(define %object
(let1 %member ($do [k %string] %ws
%name-separator
[v %value]
($return (cons k v)))
($between %begin-object
($lift ($ build-object $ rope-finalize $)
($sep-by %member %value-separator))
%end-object)))
(define json-parser ($seq %ws ($or eof %object %array)))
;; entry point
(define (parse-json :optional (port (current-input-port)))
(guard (e [(<parse-error> e)
;; not to expose parser.peg's <parse-error>.
(error <json-parse-error>
:position (~ e'position) :objects (~ e'objects)
:message (~ e'message))])
(peg-parse-port json-parser port)))
(define (parse-json-string str)
(call-with-input-string str (cut parse-json <>)))
(define (parse-json* :optional (port (current-input-port)))
(guard (e [(<parse-error> e)
;; not to expose parser.peg's <parse-error>.
(error <json-parse-error>
:position (~ e'position) :objects (~ e'objects)
:message (~ e'message))])
(generator->list (peg-parser->generator json-parser port))))
;;;============================================================
;;; Writer
;;;
(define (print-value obj)
(cond [(or (eq? obj 'false) (eq? obj #f)) (display "false")]
[(or (eq? obj 'true) (eq? obj #t)) (display "true")]
[(eq? obj 'null) (display "null")]
[(list? obj) (print-object obj)]
[(string? obj) (print-string obj)]
[(number? obj) (print-number obj)]
[(is-a? obj <dictionary>) (print-object obj)]
[(is-a? obj <sequence>) (print-array obj)]
[else (error <json-construct-error> :object obj
"can't convert Scheme object to json:" obj)]))
(define (print-object obj)
(display "{")
(fold (^[attr comma]
(unless (pair? attr)
(error <json-construct-error> :object obj
"construct-json needs an assoc list or dictionary, \
but got:" obj))
(display comma)
(print-string (x->string (car attr)))
(display ":")
(print-value (cdr attr))
",")
"" obj)
(display "}"))
(define (print-array obj)
(display "[")
(for-each-with-index (^[i val]
(unless (zero? i) (display ","))
(print-value val))
obj)
(display "]"))
(define (print-number num)
(cond [(or (not (real? num)) (not (finite? num)))
(error <json-construct-error> :object num
"json cannot represent a number" num)]
[(and (rational? num) (not (integer? num)))
(write (exact->inexact num))]
[else (write num)]))
(define (print-string str)
(define specials
'((#\" . #\") (#\\ . #\\) (#\x08 . #\b) (#\page . #\f)
(#\newline . #\n) (#\return . #\r) (#\tab . #\t)))
(define (hexescape code) (format #t "\\u~4,'0x" code))
(define (print-char c)
(cond [(assv c specials) => (^p (write-char #\\) (write-char (cdr p)))]
[(and (char-set-contains? char-set:ascii c)
(not (eq? (char-general-category c) 'Cc)))
(write-char c)]
[else
(let1 code (char->ucs c)
(if (>= code #x10000)
(for-each hexescape (ucs4->utf16 code))
(hexescape code)))]))
(display "\"")
(string-for-each print-char str)
(display "\""))
(define (construct-json x :optional (oport (current-output-port)))
(with-output-to-port oport
(^()
(cond [(or (list? x) (is-a? x <dictionary>)) (print-object x)]
[(and (is-a? x <sequence>) (not (string? x))) (print-array x)]
[else (error <json-construct-error> :object x
"construct-json expects a list or a vector, \
but got" x)]))))
(define (construct-json-string x)
(call-with-output-string (cut construct-json x <>)))
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