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| -rw-r--r-- | Makefile.am | 1 | ||||
| -rw-r--r-- | chickadee/json.scm | 308 |
2 files changed, 309 insertions, 0 deletions
diff --git a/Makefile.am b/Makefile.am index abbdba0..b8e6f19 100644 --- a/Makefile.am +++ b/Makefile.am @@ -41,6 +41,7 @@ godir=$(libdir)/guile/$(GUILE_EFFECTIVE_VERSION)/ccache SOURCES = \ chickadee/config.scm \ chickadee/utils.scm \ + chickadee/json.scm \ chickadee/heap.scm \ chickadee/array-list.scm \ chickadee/queue.scm \ diff --git a/chickadee/json.scm b/chickadee/json.scm new file mode 100644 index 0000000..7440f3b --- /dev/null +++ b/chickadee/json.scm @@ -0,0 +1,308 @@ +;;;; json.scm --- JSON reader/writer +;;;; Copyright © 2015, 2017 David Thompson <davet@gnu.org> +;;;; Copyright © 2017 Christopher Allan Webber <cwebber@dustycloud.org> +;;;; +;;;; This library is free software; you can redistribute it and/or +;;;; modify it under the terms of the GNU Lesser General Public +;;;; License as published by the Free Software Foundation; either +;;;; version 3 of the License, or (at your option) any later version. +;;;; +;;;; This library is distributed in the hope that it will be useful, +;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +;;;; Lesser General Public License for more details. +;;;; +;;;; You should have received a copy of the GNU Lesser General Public +;;;; License along with this library; if not, write to the Free Software +;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +;;;; 02110-1301 USA + +(define-module (chickadee json) + #:use-module (ice-9 match) + #:export (read-json)) + +(define (json-error port) + (throw 'json-error port)) + +(define (assert-char port char) + "Read a character from PORT and throw an invalid JSON error if the +character is not CHAR." + (unless (eqv? (read-char port) char) + (json-error port))) + +(define (whitespace? char) + "Return #t if CHAR is a whitespace character." + (char-set-contains? char-set:whitespace char)) + +(define (consume-whitespace port) + "Discard characters from PORT until a non-whitespace character is +encountered.." + (match (peek-char port) + ((? eof-object?) *unspecified*) + ((? whitespace?) + (read-char port) + (consume-whitespace port)) + (_ *unspecified*))) + +(define (make-keyword-reader keyword value) + "Parse the keyword symbol KEYWORD as VALUE." + (let ((str (symbol->string keyword))) + (lambda (port) + (let loop ((i 0)) + (cond + ((= i (string-length str)) value) + ((eqv? (string-ref str i) (read-char port)) + (loop (1+ i))) + (else (json-error port))))))) + +(define read-true (make-keyword-reader 'true #t)) +(define read-false (make-keyword-reader 'false #f)) +(define read-null (make-keyword-reader 'null 'null)) + +(define (read-hex-digit port) + "Read a hexadecimal digit from PORT." + (match (read-char port) + (#\0 0) + (#\1 1) + (#\2 2) + (#\3 3) + (#\4 4) + (#\5 5) + (#\6 6) + (#\7 7) + (#\8 8) + (#\9 9) + ((or #\A #\a) 10) + ((or #\B #\b) 11) + ((or #\C #\c) 12) + ((or #\D #\d) 13) + ((or #\E #\e) 14) + ((or #\F #\f) 15) + (_ (json-error port)))) + +(define (read-utf16-character port) + "Read a hexadecimal encoded UTF-16 character from PORT." + (integer->char + (+ (* (read-hex-digit port) (expt 16 3)) + (* (read-hex-digit port) (expt 16 2)) + (* (read-hex-digit port) 16) + (read-hex-digit port)))) + +(define (read-escape-character port) + "Read escape character from PORT." + (match (read-char port) + (#\" #\") + (#\\ #\\) + (#\/ #\/) + (#\b #\backspace) + (#\f #\page) + (#\n #\newline) + (#\r #\return) + (#\t #\tab) + (#\u (read-utf16-character port)) + (_ (json-error port)))) + +(define (read-string port) + "Read a JSON encoded string from PORT." + (assert-char port #\") + (let loop ((result '())) + (match (read-char port) + ((? eof-object?) (json-error port)) + (#\" (list->string (reverse result))) + (#\\ (loop (cons (read-escape-character port) result))) + (char (loop (cons char result)))))) + +(define char-set:json-digit + (char-set #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9)) + +(define (digit? char) + (char-set-contains? char-set:json-digit char)) + +(define (read-digit port) + "Read a digit 0-9 from PORT." + (match (read-char port) + (#\0 0) + (#\1 1) + (#\2 2) + (#\3 3) + (#\4 4) + (#\5 5) + (#\6 6) + (#\7 7) + (#\8 8) + (#\9 9) + (else (json-error port)))) + +(define (read-digits port) + "Read a sequence of digits from PORT." + (let loop ((result '())) + (match (peek-char port) + ((? eof-object?) + (reverse result)) + ((? digit?) + (loop (cons (read-digit port) result))) + (else (reverse result))))) + +(define (list->integer digits) + "Convert the list DIGITS to an integer." + (let loop ((i (1- (length digits))) + (result 0) + (digits digits)) + (match digits + (() result) + ((n . tail) + (loop (1- i) + (+ result (* n (expt 10 i))) + tail))))) + +(define (read-positive-integer port) + "Read a positive integer with no leading zeroes from PORT." + (match (read-digits port) + ((0 . _) + (json-error port)) ; no leading zeroes allowed + ((digits ...) + (list->integer digits)))) + +(define (read-exponent port) + "Read exponent from PORT." + (define (read-expt) + (list->integer (read-digits port))) + + (unless (memv (read-char port) '(#\e #\E)) + (json-error port)) + + (match (peek-char port) + ((? eof-object?) + (json-error port)) + (#\- + (read-char port) + (- (read-expt))) + (#\+ + (read-char port) + (read-expt)) + ((? digit?) + (read-expt)) + (_ (json-error port)))) + +(define (read-fraction port) + "Read fractional number part from PORT as an inexact number." + (let* ((digits (read-digits port)) + (numerator (list->integer digits)) + (denomenator (expt 10 (length digits)))) + (/ numerator denomenator))) + +(define (read-positive-number port) + "Read a positive number from PORT." + (let* ((integer (match (peek-char port) + ((? eof-object?) + (json-error port)) + (#\0 + (read-char port) + 0) + ((? digit?) + (read-positive-integer port)) + (_ (json-error port)))) + (fraction (match (peek-char port) + (#\. + (read-char port) + (read-fraction port)) + (_ 0))) + (exponent (match (peek-char port) + ((or #\e #\E) + (read-exponent port)) + (_ 0))) + (n (* (+ integer fraction) (expt 10 exponent)))) + + ;; Keep integers as exact numbers, but convert numbers encoded as + ;; floating point numbers to an inexact representation. + (if (zero? fraction) + n + (exact->inexact n)))) + +(define (read-number port) + "Read a number from PORT" + (match (peek-char port) + ((? eof-object?) + (json-error port)) + (#\- + (read-char port) + (- (read-positive-number port))) + ((? digit?) + (read-positive-number port)) + (_ (json-error port)))) + +(define (read-object port) + "Read key/value map from PORT." + (define (read-key+value-pair) + (let ((key (read-string port))) + (consume-whitespace port) + (assert-char port #\:) + (consume-whitespace port) + (let ((value (read-value port))) + (cons key value)))) + + (assert-char port #\{) + (consume-whitespace port) + + (if (eqv? #\} (peek-char port)) + (begin + (read-char port) + '()) ; empty object + (cons (read-key+value-pair) + (let loop () + (consume-whitespace port) + (match (peek-char port) + (#\, ; read another value + (read-char port) + (consume-whitespace port) + (cons (read-key+value-pair) (loop))) + (#\} ; end of object + (read-char port) + '()) + (_ (json-error port))))))) + +(define (read-array port) + "Read array from PORT." + (assert-char port #\[) + (consume-whitespace port) + + (list->vector + (if (eqv? #\] (peek-char port)) + (begin + (read-char port) + '() ); empty array + (cons (read-value port) + (let loop () + (consume-whitespace port) + (match (peek-char port) + (#\, ; read another value + (read-char port) + (consume-whitespace port) + (cons (read-value port) (loop))) + (#\] ; end of array + (read-char port) + '()) + (_ (json-error port)))))))) + +(define (read-value port) + "Read a JSON value from PORT." + (consume-whitespace port) + (match (peek-char port) + ((? eof-object?) (json-error port)) + (#\" (read-string port)) + (#\{ (read-object port)) + (#\[ (read-array port)) + (#\t (read-true port)) + (#\f (read-false port)) + (#\n (read-null port)) + ((or #\- (? digit?)) + (read-number port)) + (_ (json-error port)))) + +(define (read-json port) + "Read JSON text from port and return an s-expression representation." + (let ((result (read-value port))) + (consume-whitespace port) + (unless (eof-object? (peek-char port)) + (json-error port)) + result)) |