;;; json.el --- JavaScript Object Notation parser / generator ;; Copyright (C) 2006-2014 Free Software Foundation, Inc. ;; Author: Edward O'Connor ;; 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 . ;;; Commentary: ;; This is a library for parsing and generating JSON (JavaScript Object ;; Notation). ;; Learn all about JSON here: . ;; 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 . ;; 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: ;; 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.") (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.") ;;; 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 '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 (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) ;;; 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 127)) (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 ""))) (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) 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) "]"))) ;;; 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))))) ;; 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) (txt (delete-and-extract-region begin end))) (insert (json-encode (json-read-from-string txt)))))) (provide 'json) ;;; json.el ends here