mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-23 10:34:07 +00:00
530 lines
16 KiB
EmacsLisp
530 lines
16 KiB
EmacsLisp
;;; json.el --- JavaScript Object Notation parser / generator
|
||
|
||
;; Copyright (C) 2006-2011 Free Software Foundation, Inc.
|
||
|
||
;; Author: Edward O'Connor <ted@oconnor.cx>
|
||
;; Version: 1.2
|
||
;; 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.
|
||
|
||
;;; Code:
|
||
|
||
(eval-when-compile (require 'cl))
|
||
|
||
;; Compatibility code
|
||
|
||
(defalias 'json-encode-char0 'encode-char)
|
||
(defalias 'json-decode-char0 'decode-char)
|
||
|
||
|
||
;; 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.")
|
||
|
||
(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.")
|
||
|
||
|
||
|
||
;;; 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."
|
||
(or (null list)
|
||
(and (consp (car list))
|
||
(json-alist-p (cdr list)))))
|
||
|
||
(defun json-plist-p (list)
|
||
"Non-null if and only if LIST is a plist."
|
||
(or (null list)
|
||
(and (keywordp (car list))
|
||
(consp (cdr list))
|
||
(json-plist-p (cddr list)))))
|
||
|
||
;; 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 '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 "))
|
||
|
||
|
||
|
||
;; Error conditions
|
||
|
||
(put 'json-error 'error-message "Unknown JSON error")
|
||
(put 'json-error 'error-conditions '(json-error error))
|
||
|
||
(put 'json-readtable-error 'error-message "JSON readtable error")
|
||
(put 'json-readtable-error 'error-conditions
|
||
'(json-readtable-error json-error error))
|
||
|
||
(put 'json-unknown-keyword 'error-message "Unrecognized keyword")
|
||
(put 'json-unknown-keyword 'error-conditions
|
||
'(json-unknown-keyword json-error error))
|
||
|
||
(put 'json-number-format 'error-message "Invalid number format")
|
||
(put 'json-number-format 'error-conditions
|
||
'(json-number-format json-error error))
|
||
|
||
(put 'json-string-escape 'error-message "Bad unicode escape")
|
||
(put 'json-string-escape 'error-conditions
|
||
'(json-string-escape json-error error))
|
||
|
||
(put 'json-string-format 'error-message "Bad string format")
|
||
(put 'json-string-format 'error-conditions
|
||
'(json-string-format json-error error))
|
||
|
||
(put 'json-object-format 'error-message "Bad JSON object")
|
||
(put 'json-object-format 'error-conditions
|
||
'(json-object-format json-error error))
|
||
|
||
|
||
|
||
;;; 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)
|
||
(json-decode-char0 'ucs (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-char (char)
|
||
"Encode CHAR as a JSON string."
|
||
(setq char (json-encode-char0 char 'ucs))
|
||
(let ((control-char (car (rassoc char json-special-chars))))
|
||
(cond
|
||
;; Special JSON character (\n, \r, etc.)
|
||
(control-char
|
||
(format "\\%c" control-char))
|
||
;; ASCIIish printable character
|
||
((and (> char 31) (< char 161))
|
||
(format "%c" char))
|
||
;; Fallback: UCS code point in \uNNNN form
|
||
(t
|
||
(format "\\u%04x" char)))))
|
||
|
||
(defun json-encode-string (string)
|
||
"Return a JSON representation of STRING."
|
||
(format "\"%s\"" (mapconcat 'json-encode-char string "")))
|
||
|
||
;;; 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)
|
||
elements))
|
||
|
||
;; Hash table encoding
|
||
|
||
(defun json-encode-hash-table (hash-table)
|
||
"Return a JSON representation of HASH-TABLE."
|
||
(format "{%s}"
|
||
(json-join
|
||
(let (r)
|
||
(maphash
|
||
(lambda (k v)
|
||
(push (format "%s:%s"
|
||
(json-encode k)
|
||
(json-encode v))
|
||
r))
|
||
hash-table)
|
||
r)
|
||
", ")))
|
||
|
||
;; List encoding (including alists and plists)
|
||
|
||
(defun json-encode-alist (alist)
|
||
"Return a JSON representation of ALIST."
|
||
(format "{%s}"
|
||
(json-join (mapcar (lambda (cons)
|
||
(format "%s:%s"
|
||
(json-encode (car cons))
|
||
(json-encode (cdr cons))))
|
||
alist)
|
||
", ")))
|
||
|
||
(defun json-encode-plist (plist)
|
||
"Return a JSON representation of PLIST."
|
||
(let (result)
|
||
(while plist
|
||
(push (concat (json-encode (car plist))
|
||
":"
|
||
(json-encode (cadr plist)))
|
||
result)
|
||
(setq plist (cddr plist)))
|
||
(concat "{" (json-join (nreverse result) ", ") "}")))
|
||
|
||
(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."
|
||
(concat "[" (mapconcat 'json-encode array ", ") "]"))
|
||
|
||
|
||
|
||
;;; 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 '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)))
|
||
|
||
|
||
|
||
;;; 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)))))
|
||
|
||
(provide 'json)
|
||
|
||
;;; json.el ends here
|