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| | ;;; json.el --- JavaScript Object Notation parser / generator
;; Copyright (C) 2006-2015 Free Software Foundation, Inc.
;; Author: Edward O'Connor <ted@oconnor.cx>
;; Version: 1.4
;; Keywords: convenience
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs 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 General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; This is a library for parsing and generating JSON (JavaScript Object
;; Notation).
;; Learn all about JSON here: <URL:http://json.org/>.
;; The user-serviceable entry points for the parser are the functions
;; `json-read' and `json-read-from-string'. The encoder has a single
;; entry point, `json-encode'.
;; Since there are several natural representations of key-value pair
;; mappings in elisp (alist, plist, hash-table), `json-read' allows you
;; to specify which you'd prefer (see `json-object-type' and
;; `json-array-type').
;; Similarly, since `false' and `null' are distinct in JSON, you can
;; distinguish them by binding `json-false' and `json-null' as desired.
;;; History:
;; 2006-03-11 - Initial version.
;; 2006-03-13 - Added JSON generation in addition to parsing. Various
;; other cleanups, bugfixes, and improvements.
;; 2006-12-29 - XEmacs support, from Aidan Kehoe <kehoea@parhasard.net>.
;; 2008-02-21 - Installed in GNU Emacs.
;; 2011-10-17 - Patch `json-alist-p' and `json-plist-p' to avoid recursion -tzz
;; 2012-10-25 - Added pretty-printed reformatting -Ryan Crum (ryan@ryancrum.org)
;;; Code:
;; Parameters
(defvar json-object-type 'alist
"Type to convert JSON objects to.
Must be one of `alist', `plist', or `hash-table'. Consider let-binding
this around your call to `json-read' instead of `setq'ing it. Ordering
is maintained only for `alist'.")
(defvar json-array-type 'vector
"Type to convert JSON arrays to.
Must be one of `vector' or `list'. Consider let-binding this around
your call to `json-read' instead of `setq'ing it.")
(defvar json-key-type nil
"Type to convert JSON keys to.
Must be one of `string', `symbol', `keyword', or nil.
If nil, `json-read' will guess the type based on the value of
`json-object-type':
If `json-object-type' is: nil will be interpreted as:
`hash-table' `string'
`alist' `symbol'
`plist' `keyword'
Note that values other than `string' might behave strangely for
Sufficiently Weird keys. Consider let-binding this around your call to
`json-read' instead of `setq'ing it.")
(defvar json-false :json-false
"Value to use when reading JSON `false'.
If this has the same value as `json-null', you might not be able to tell
the difference between `false' and `null'. Consider let-binding this
around your call to `json-read' instead of `setq'ing it.")
(defvar json-null nil
"Value to use when reading JSON `null'.
If this has the same value as `json-false', you might not be able to
tell the difference between `false' and `null'. Consider let-binding
this around your call to `json-read' instead of `setq'ing it.")
(defvar json-encoding-separator ","
"Value to use as an element separator when encoding.")
(defvar json-encoding-default-indentation " "
"The default indentation level for encoding.
Used only when `json-encoding-pretty-print' is non-nil.")
(defvar json--encoding-current-indentation "\n"
"Internally used to keep track of the current indentation level of encoding.
Used only when `json-encoding-pretty-print' is non-nil.")
(defvar json-encoding-pretty-print nil
"If non-nil, then the output of `json-encode' will be pretty-printed.")
(defvar json-encoding-lisp-style-closings nil
"If non-nil, ] and } closings will be formatted lisp-style,
without indentation.")
\f
;;; Utilities
(defun json-join (strings separator)
"Join STRINGS with SEPARATOR."
(mapconcat 'identity strings separator))
(defun json-alist-p (list)
"Non-null if and only if LIST is an alist with simple keys."
(while (consp list)
(setq list (if (and (consp (car list))
(atom (caar list)))
(cdr list)
'not-alist)))
(null list))
(defun json-plist-p (list)
"Non-null if and only if LIST is a plist."
(while (consp list)
(setq list (if (and (keywordp (car list))
(consp (cdr list)))
(cddr list)
'not-plist)))
(null list))
(defmacro json--with-indentation (body)
`(let ((json--encoding-current-indentation
(if json-encoding-pretty-print
(concat json--encoding-current-indentation
json-encoding-default-indentation)
"")))
,body))
;; Reader utilities
(defsubst json-advance (&optional n)
"Skip past the following N characters."
(forward-char n))
(defsubst json-peek ()
"Return the character at point."
(let ((char (char-after (point))))
(or char :json-eof)))
(defsubst json-pop ()
"Advance past the character at point, returning it."
(let ((char (json-peek)))
(if (eq char :json-eof)
(signal 'json-end-of-file nil)
(json-advance)
char)))
(defun json-skip-whitespace ()
"Skip past the whitespace at point."
(skip-chars-forward "\t\r\n\f\b "))
\f
;; Error conditions
(define-error 'json-error "Unknown JSON error")
(define-error 'json-readtable-error "JSON readtable error" 'json-error)
(define-error 'json-unknown-keyword "Unrecognized keyword" 'json-error)
(define-error 'json-number-format "Invalid number format" 'json-error)
(define-error 'json-string-escape "Bad Unicode escape" 'json-error)
(define-error 'json-string-format "Bad string format" 'json-error)
(define-error 'json-key-format "Bad JSON object key" 'json-error)
(define-error 'json-object-format "Bad JSON object" 'json-error)
(define-error 'json-end-of-file "End of file while parsing JSON"
'(end-of-file json-error))
\f
;;; Keywords
(defvar json-keywords '("true" "false" "null")
"List of JSON keywords.")
;; Keyword parsing
(defun json-read-keyword (keyword)
"Read a JSON keyword at point.
KEYWORD is the keyword expected."
(unless (member keyword json-keywords)
(signal 'json-unknown-keyword (list keyword)))
(mapc (lambda (char)
(unless (char-equal char (json-peek))
(signal 'json-unknown-keyword
(list (save-excursion
(backward-word 1)
(thing-at-point 'word)))))
(json-advance))
keyword)
(unless (looking-at "\\(\\s-\\|[],}]\\|$\\)")
(signal 'json-unknown-keyword
(list (save-excursion
(backward-word 1)
(thing-at-point 'word)))))
(cond ((string-equal keyword "true") t)
((string-equal keyword "false") json-false)
((string-equal keyword "null") json-null)))
;; Keyword encoding
(defun json-encode-keyword (keyword)
"Encode KEYWORD as a JSON value."
(cond ((eq keyword t) "true")
((eq keyword json-false) "false")
((eq keyword json-null) "null")))
;;; Numbers
;; Number parsing
(defun json-read-number (&optional sign)
"Read the JSON number following point.
The optional SIGN argument is for internal use.
N.B.: Only numbers which can fit in Emacs Lisp's native number
representation will be parsed correctly."
;; If SIGN is non-nil, the number is explicitly signed.
(let ((number-regexp
"\\([0-9]+\\)?\\(\\.[0-9]+\\)?\\([Ee][+-]?[0-9]+\\)?"))
(cond ((and (null sign) (char-equal (json-peek) ?-))
(json-advance)
(- (json-read-number t)))
((and (null sign) (char-equal (json-peek) ?+))
(json-advance)
(json-read-number t))
((and (looking-at number-regexp)
(or (match-beginning 1)
(match-beginning 2)))
(goto-char (match-end 0))
(string-to-number (match-string 0)))
(t (signal 'json-number-format (list (point)))))))
;; Number encoding
(defun json-encode-number (number)
"Return a JSON representation of NUMBER."
(format "%s" number))
;;; Strings
(defvar json-special-chars
'((?\" . ?\")
(?\\ . ?\\)
(?b . ?\b)
(?f . ?\f)
(?n . ?\n)
(?r . ?\r)
(?t . ?\t))
"Characters which are escaped in JSON, with their elisp counterparts.")
;; String parsing
(defun json-read-escaped-char ()
"Read the JSON string escaped character at point."
;; Skip over the '\'
(json-advance)
(let* ((char (json-pop))
(special (assq char json-special-chars)))
(cond
(special (cdr special))
((not (eq char ?u)) char)
((looking-at "[0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f]")
(let ((hex (match-string 0)))
(json-advance 4)
(string-to-number hex 16)))
(t
(signal 'json-string-escape (list (point)))))))
(defun json-read-string ()
"Read the JSON string at point."
(unless (char-equal (json-peek) ?\")
(signal 'json-string-format (list "doesn't start with `\"'!")))
;; Skip over the '"'
(json-advance)
(let ((characters '())
(char (json-peek)))
(while (not (char-equal char ?\"))
(push (if (char-equal char ?\\)
(json-read-escaped-char)
(json-pop))
characters)
(setq char (json-peek)))
;; Skip over the '"'
(json-advance)
(if characters
(apply 'string (nreverse characters))
"")))
;; String encoding
(defun json-encode-string (string)
"Return a JSON representation of STRING."
;; Reimplement the meat of `replace-regexp-in-string', for
;; performance (bug#20154).
(let ((l (length string))
(start 0)
res mb)
;; Only escape quotation mark, backslash and the control
;; characters U+0000 to U+001F (RFC 4627, ECMA-404).
(while (setq mb (string-match "[\"\\[:cntrl:]]" string start))
(let* ((c (aref string mb))
(special (rassq c json-special-chars)))
(push (substring string start mb) res)
(push (if special
;; Special JSON character (\n, \r, etc.).
(string ?\\ (car special))
;; Fallback: UCS code point in \uNNNN form.
(format "\\u%04x" c))
res)
(setq start (1+ mb))))
(push (substring string start l) res)
(push "\"" res)
(apply #'concat "\"" (nreverse res))))
(defun json-encode-key (object)
"Return a JSON representation of OBJECT.
If the resulting JSON object isn't a valid JSON object key,
this signals `json-key-format'."
(let ((encoded (json-encode object)))
(unless (stringp (json-read-from-string encoded))
(signal 'json-key-format (list object)))
encoded))
;;; JSON Objects
(defun json-new-object ()
"Create a new Elisp object corresponding to a JSON object.
Please see the documentation of `json-object-type'."
(cond ((eq json-object-type 'hash-table)
(make-hash-table :test 'equal))
(t
(list))))
(defun json-add-to-object (object key value)
"Add a new KEY -> VALUE association to OBJECT.
Returns the updated object, which you should save, e.g.:
(setq obj (json-add-to-object obj \"foo\" \"bar\"))
Please see the documentation of `json-object-type' and `json-key-type'."
(let ((json-key-type
(if (eq json-key-type nil)
(cdr (assq json-object-type '((hash-table . string)
(alist . symbol)
(plist . keyword))))
json-key-type)))
(setq key
(cond ((eq json-key-type 'string)
key)
((eq json-key-type 'symbol)
(intern key))
((eq json-key-type 'keyword)
(intern (concat ":" key)))))
(cond ((eq json-object-type 'hash-table)
(puthash key value object)
object)
((eq json-object-type 'alist)
(cons (cons key value) object))
((eq json-object-type 'plist)
(cons key (cons value object))))))
;; JSON object parsing
(defun json-read-object ()
"Read the JSON object at point."
;; Skip over the "{"
(json-advance)
(json-skip-whitespace)
;; read key/value pairs until "}"
(let ((elements (json-new-object))
key value)
(while (not (char-equal (json-peek) ?}))
(json-skip-whitespace)
(setq key (json-read-string))
(json-skip-whitespace)
(if (char-equal (json-peek) ?:)
(json-advance)
(signal 'json-object-format (list ":" (json-peek))))
(setq value (json-read))
(setq elements (json-add-to-object elements key value))
(json-skip-whitespace)
(unless (char-equal (json-peek) ?})
(if (char-equal (json-peek) ?,)
(json-advance)
(signal 'json-object-format (list "," (json-peek))))))
;; Skip over the "}"
(json-advance)
(if (eq json-object-type 'alist)
(nreverse elements)
elements)))
;; Hash table encoding
(defun json-encode-hash-table (hash-table)
"Return a JSON representation of HASH-TABLE."
(format "{%s%s}"
(json-join
(let (r)
(json--with-indentation
(maphash
(lambda (k v)
(push (format
(if json-encoding-pretty-print
"%s%s: %s"
"%s%s:%s")
json--encoding-current-indentation
(json-encode-key k)
(json-encode v))
r))
hash-table))
r)
json-encoding-separator)
(if (or (not json-encoding-pretty-print)
json-encoding-lisp-style-closings)
""
json--encoding-current-indentation)))
;; List encoding (including alists and plists)
(defun json-encode-alist (alist)
"Return a JSON representation of ALIST."
(format "{%s%s}"
(json-join
(json--with-indentation
(mapcar (lambda (cons)
(format (if json-encoding-pretty-print
"%s%s: %s"
"%s%s:%s")
json--encoding-current-indentation
(json-encode-key (car cons))
(json-encode (cdr cons))))
alist))
json-encoding-separator)
(if (or (not json-encoding-pretty-print)
json-encoding-lisp-style-closings)
""
json--encoding-current-indentation)))
(defun json-encode-plist (plist)
"Return a JSON representation of PLIST."
(let (result)
(json--with-indentation
(while plist
(push (concat
json--encoding-current-indentation
(json-encode-key (car plist))
(if json-encoding-pretty-print
": "
":")
(json-encode (cadr plist)))
result)
(setq plist (cddr plist))))
(concat "{"
(json-join (nreverse result) json-encoding-separator)
(if (and json-encoding-pretty-print
(not json-encoding-lisp-style-closings))
json--encoding-current-indentation
"")
"}")))
(defun json-encode-list (list)
"Return a JSON representation of LIST.
Tries to DWIM: simple lists become JSON arrays, while alists and plists
become JSON objects."
(cond ((null list) "null")
((json-alist-p list) (json-encode-alist list))
((json-plist-p list) (json-encode-plist list))
((listp list) (json-encode-array list))
(t
(signal 'json-error (list list)))))
;;; Arrays
;; Array parsing
(defun json-read-array ()
"Read the JSON array at point."
;; Skip over the "["
(json-advance)
(json-skip-whitespace)
;; read values until "]"
(let (elements)
(while (not (char-equal (json-peek) ?\]))
(push (json-read) elements)
(json-skip-whitespace)
(unless (char-equal (json-peek) ?\])
(if (char-equal (json-peek) ?,)
(json-advance)
(signal 'json-error (list 'bleah)))))
;; Skip over the "]"
(json-advance)
(apply json-array-type (nreverse elements))))
;; Array encoding
(defun json-encode-array (array)
"Return a JSON representation of ARRAY."
(if (and json-encoding-pretty-print
(> (length array) 0))
(concat
(json--with-indentation
(concat (format "[%s" json--encoding-current-indentation)
(json-join (mapcar 'json-encode array)
(format "%s%s"
json-encoding-separator
json--encoding-current-indentation))))
(format "%s]"
(if json-encoding-lisp-style-closings
""
json--encoding-current-indentation)))
(concat "["
(mapconcat 'json-encode array json-encoding-separator)
"]")))
\f
;;; JSON reader.
(defvar json-readtable
(let ((table
'((?t json-read-keyword "true")
(?f json-read-keyword "false")
(?n json-read-keyword "null")
(?{ json-read-object)
(?\[ json-read-array)
(?\" json-read-string))))
(mapc (lambda (char)
(push (list char 'json-read-number) table))
'(?- ?+ ?. ?0 ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9))
table)
"Readtable for JSON reader.")
(defun json-read ()
"Parse and return the JSON object following point.
Advances point just past JSON object."
(json-skip-whitespace)
(let ((char (json-peek)))
(if (not (eq char :json-eof))
(let ((record (cdr (assq char json-readtable))))
(if (functionp (car record))
(apply (car record) (cdr record))
(signal 'json-readtable-error record)))
(signal 'json-end-of-file nil))))
;; Syntactic sugar for the reader
(defun json-read-from-string (string)
"Read the JSON object contained in STRING and return it."
(with-temp-buffer
(insert string)
(goto-char (point-min))
(json-read)))
(defun json-read-file (file)
"Read the first JSON object contained in FILE and return it."
(with-temp-buffer
(insert-file-contents file)
(goto-char (point-min))
(json-read)))
\f
;;; JSON encoder
(defun json-encode (object)
"Return a JSON representation of OBJECT as a string."
(cond ((memq object (list t json-null json-false))
(json-encode-keyword object))
((stringp object) (json-encode-string object))
((keywordp object) (json-encode-string
(substring (symbol-name object) 1)))
((symbolp object) (json-encode-string
(symbol-name object)))
((numberp object) (json-encode-number object))
((arrayp object) (json-encode-array object))
((hash-table-p object) (json-encode-hash-table object))
((listp object) (json-encode-list object))
(t (signal 'json-error (list object)))))
;; Pretty printing
(defun json-pretty-print-buffer ()
"Pretty-print current buffer."
(interactive)
(json-pretty-print (point-min) (point-max)))
(defun json-pretty-print (begin end)
"Pretty-print selected region."
(interactive "r")
(atomic-change-group
(let ((json-encoding-pretty-print t)
;; Ensure that ordering is maintained
(json-object-type 'alist)
(txt (delete-and-extract-region begin end)))
(insert (json-encode (json-read-from-string txt))))))
(provide 'json)
;;; json.el ends here
|