09a1f92f61
* guix/build/node-build-system.scm: New file. * guix/build-system/node.scm: New file. * guix/build/json.scm: New file. * doc/guix.texi: Document it. * Makefile.am: Added new files. Co-Authored-By: Julien Lepiller <julien@lepiller.eu>
388 lines
10 KiB
Scheme
388 lines
10 KiB
Scheme
;;;; json.scm --- JSON reader/writer
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;;;; Copyright (C) 2015 Free Software Foundation, Inc.
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;;;;
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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;;;; License as published by the Free Software Foundation; either
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;;;; version 3 of the License, or (at your option) any later version.
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;;;;
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;;;; This library is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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;;;;
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(define-module (guix build json) ;; originally (ice-9 json)
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#:use-module (ice-9 match)
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#:export (read-json write-json))
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;; Snarfed from
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;; https://github.com/cwebber/activitystuff/blob/master/activitystuff/contrib/json.scm
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;;
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;;;
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;;; Reader
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;;;
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(define (json-error port)
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(throw 'json-error port))
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(define (assert-char port char)
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"Read a character from PORT and throw an invalid JSON error if the
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character is not CHAR."
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(unless (eqv? (read-char port) char)
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(json-error port)))
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(define (whitespace? char)
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"Return #t if CHAR is a whitespace character."
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(char-set-contains? char-set:whitespace char))
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(define (consume-whitespace port)
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"Discard characters from PORT until a non-whitespace character is
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encountered.."
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(match (peek-char port)
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((? eof-object?) *unspecified*)
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((? whitespace?)
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(read-char port)
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(consume-whitespace port))
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(_ *unspecified*)))
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(define (make-keyword-reader keyword value)
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"Parse the keyword symbol KEYWORD as VALUE."
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(let ((str (symbol->string keyword)))
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(lambda (port)
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(let loop ((i 0))
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(cond
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((= i (string-length str)) value)
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((eqv? (string-ref str i) (read-char port))
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(loop (1+ i)))
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(else (json-error port)))))))
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(define read-true (make-keyword-reader 'true #t))
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(define read-false (make-keyword-reader 'false #f))
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(define read-null (make-keyword-reader 'null #nil))
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(define (read-hex-digit port)
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"Read a hexadecimal digit from PORT."
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(match (read-char port)
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(#\0 0)
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(#\1 1)
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(#\2 2)
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(#\3 3)
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(#\4 4)
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(#\5 5)
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(#\6 6)
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(#\7 7)
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(#\8 8)
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(#\9 9)
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((or #\A #\a) 10)
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((or #\B #\b) 11)
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((or #\C #\c) 12)
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((or #\D #\d) 13)
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((or #\E #\e) 14)
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((or #\F #\f) 15)
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(_ (json-error port))))
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(define (read-utf16-character port)
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"Read a hexadecimal encoded UTF-16 character from PORT."
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(integer->char
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(+ (* (read-hex-digit port) (expt 16 3))
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(* (read-hex-digit port) (expt 16 2))
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(* (read-hex-digit port) 16)
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(read-hex-digit port))))
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(define (read-escape-character port)
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"Read escape character from PORT."
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(match (read-char port)
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(#\" #\")
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(#\\ #\\)
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(#\/ #\/)
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(#\b #\backspace)
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(#\f #\page)
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(#\n #\newline)
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(#\r #\return)
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(#\t #\tab)
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(#\u (read-utf16-character port))
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(_ (json-error port))))
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(define (read-string port)
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"Read a JSON encoded string from PORT."
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(assert-char port #\")
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(let loop ((result '()))
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(match (read-char port)
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((? eof-object?) (json-error port))
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(#\" (list->string (reverse result)))
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(#\\ (loop (cons (read-escape-character port) result)))
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(char (loop (cons char result))))))
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(define char-set:json-digit
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(char-set #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9))
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(define (digit? char)
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(char-set-contains? char-set:json-digit char))
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(define (read-digit port)
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"Read a digit 0-9 from PORT."
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(match (read-char port)
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(#\0 0)
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(#\1 1)
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(#\2 2)
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(#\3 3)
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(#\4 4)
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(#\5 5)
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(#\6 6)
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(#\7 7)
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(#\8 8)
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(#\9 9)
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(else (json-error port))))
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(define (read-digits port)
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"Read a sequence of digits from PORT."
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(let loop ((result '()))
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(match (peek-char port)
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((? eof-object?)
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(reverse result))
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((? digit?)
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(loop (cons (read-digit port) result)))
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(else (reverse result)))))
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(define (list->integer digits)
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"Convert the list DIGITS to an integer."
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(let loop ((i (1- (length digits)))
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(result 0)
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(digits digits))
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(match digits
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(() result)
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((n . tail)
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(loop (1- i)
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(+ result (* n (expt 10 i)))
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tail)))))
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(define (read-positive-integer port)
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"Read a positive integer with no leading zeroes from PORT."
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(match (read-digits port)
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((0 . _)
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(json-error port)) ; no leading zeroes allowed
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((digits ...)
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(list->integer digits))))
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(define (read-exponent port)
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"Read exponent from PORT."
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(define (read-expt)
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(list->integer (read-digits port)))
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(unless (memv (read-char port) '(#\e #\E))
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(json-error port))
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(match (peek-char port)
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((? eof-object?)
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(json-error port))
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(#\-
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(read-char port)
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(- (read-expt)))
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(#\+
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(read-char port)
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(read-expt))
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((? digit?)
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(read-expt))
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(_ (json-error port))))
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(define (read-fraction port)
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"Read fractional number part from PORT as an inexact number."
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(let* ((digits (read-digits port))
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(numerator (list->integer digits))
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(denomenator (expt 10 (length digits))))
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(/ numerator denomenator)))
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(define (read-positive-number port)
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"Read a positive number from PORT."
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(let* ((integer (match (peek-char port)
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((? eof-object?)
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(json-error port))
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(#\0
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(read-char port)
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0)
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((? digit?)
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(read-positive-integer port))
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(_ (json-error port))))
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(fraction (match (peek-char port)
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(#\.
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(read-char port)
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(read-fraction port))
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(_ 0)))
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(exponent (match (peek-char port)
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((or #\e #\E)
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(read-exponent port))
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(_ 0)))
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(n (* (+ integer fraction) (expt 10 exponent))))
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;; Keep integers as exact numbers, but convert numbers encoded as
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;; floating point numbers to an inexact representation.
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(if (zero? fraction)
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n
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(exact->inexact n))))
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(define (read-number port)
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"Read a number from PORT"
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(match (peek-char port)
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((? eof-object?)
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(json-error port))
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(#\-
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(read-char port)
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(- (read-positive-number port)))
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((? digit?)
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(read-positive-number port))
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(_ (json-error port))))
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(define (read-object port)
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"Read key/value map from PORT."
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(define (read-key+value-pair)
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(let ((key (read-string port)))
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(consume-whitespace port)
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(assert-char port #\:)
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(consume-whitespace port)
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(let ((value (read-value port)))
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(cons key value))))
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(assert-char port #\{)
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(consume-whitespace port)
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(if (eqv? #\} (peek-char port))
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(begin
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(read-char port)
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'(@)) ; empty object
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(let loop ((result (list (read-key+value-pair))))
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(consume-whitespace port)
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(match (peek-char port)
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(#\, ; read another value
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(read-char port)
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(consume-whitespace port)
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(loop (cons (read-key+value-pair) result)))
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(#\} ; end of object
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(read-char port)
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(cons '@ (reverse result)))
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(_ (json-error port))))))
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(define (read-array port)
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"Read array from PORT."
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(assert-char port #\[)
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(consume-whitespace port)
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(if (eqv? #\] (peek-char port))
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(begin
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(read-char port)
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'()) ; empty array
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(let loop ((result (list (read-value port))))
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(consume-whitespace port)
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(match (peek-char port)
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(#\, ; read another value
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(read-char port)
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(consume-whitespace port)
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(loop (cons (read-value port) result)))
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(#\] ; end of array
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(read-char port)
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(reverse result))
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(_ (json-error port))))))
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(define (read-value port)
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"Read a JSON value from PORT."
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(consume-whitespace port)
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(match (peek-char port)
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((? eof-object?) (json-error port))
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(#\" (read-string port))
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(#\{ (read-object port))
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(#\[ (read-array port))
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(#\t (read-true port))
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(#\f (read-false port))
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(#\n (read-null port))
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((or #\- (? digit?))
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(read-number port))
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(_ (json-error port))))
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(define (read-json port)
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"Read JSON text from port and return an s-expression representation."
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(let ((result (read-value port)))
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(consume-whitespace port)
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(unless (eof-object? (peek-char port))
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(json-error port))
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result))
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;;;
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;;; Writer
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;;;
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(define (write-string str port)
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"Write STR to PORT in JSON string format."
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(define (escape-char char)
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(display (match char
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(#\" "\\\"")
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(#\\ "\\\\")
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(#\/ "\\/")
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(#\backspace "\\b")
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(#\page "\\f")
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(#\newline "\\n")
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(#\return "\\r")
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(#\tab "\\t")
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(_ char))
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port))
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(display "\"" port)
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(string-for-each escape-char str)
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(display "\"" port))
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(define (write-object alist port)
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"Write ALIST to PORT in JSON object format."
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;; Keys may be strings or symbols.
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(define key->string
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(match-lambda
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((? string? key) key)
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((? symbol? key) (symbol->string key))))
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(define (write-pair pair)
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(match pair
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((key . value)
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(write-string (key->string key) port)
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(display ":" port)
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(write-json value port))))
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(display "{" port)
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(match alist
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(() #f)
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((front ... end)
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(for-each (lambda (pair)
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(write-pair pair)
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(display "," port))
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front)
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(write-pair end)))
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(display "}" port))
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(define (write-array lst port)
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"Write LST to PORT in JSON array format."
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(display "[" port)
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(match lst
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(() #f)
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((front ... end)
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(for-each (lambda (val)
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(write-json val port)
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(display "," port))
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front)
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(write-json end port)))
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(display "]" port))
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(define (write-json exp port)
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"Write EXP to PORT in JSON format."
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(match exp
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(#t (display "true" port))
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(#f (display "false" port))
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;; Differentiate #nil from '().
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((and (? boolean? ) #nil) (display "null" port))
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((? string? s) (write-string s port))
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((? real? n) (display n port))
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(('@ . alist) (write-object alist port))
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((vals ...) (write-array vals port))))
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