elisp: implement stdio-read-json

elisp/json-test

@@ -0,0 +1,22 @@
+"hello world"
+2
+{ "a": 1,
+  "b": 2,
+  "c": 3
+  }
+
+1
+
+true
+
+false
+
+null
+
+"hello"
+
+[ 1, 2,
+
+3,
+
+4]

elisp/jx.el

@@ -11,5 +11,14 @@
     (while-let ((line (stdio-read-line process)))
       (message (format "jx-test: %s" line)))))
 
+(defun jx-text-json ()
+  "test the jx json input."
+  (interactive)
+  (let ((process (stdio-call (list "cat" "json-test"))))
+    (while-let ((object (stdio-read-json process
+                                         :object-type 'plist
+                                         :array-type 'list)))
+      (message (format "jx-json-object: %s" object)))))
+
 (provide 'jx)
 ;;; jx.el ends here

elisp/stdio.el

@@ -9,13 +9,14 @@
   emacs-process buffer)
 
 (defun stdio-make-filter (process)
-  "Return a filter function for PROCESS."
+  "Return a input filter function for PROCESS."
   (lambda (_ input)
     (setf (stdio-process-buffer process)
           (concat (stdio-process-buffer process)
                   input))))
 
 (defvar stdio--process-counter 0)
+
 (defun stdio--make-process-name ()
   "Generate a new uniqe process name."
   (let* ((num stdio--process-counter)
@@ -54,5 +55,25 @@
         (progn (setf (stdio-process-buffer process) "")
                stdin-buf)))))
 
+(defun stdio-read-json (process &rest JSON-ARGS)
+  "Read next json element from PROCESS.
+
+The arguments JSON-ARGS are directly passed to `json-parse-string'
+and control how json elements are represented as Lisp constructs.
+
+Json elements need to be seperated by newlines."
+  (let (next-line input-string json-object done)
+    (while (not done)
+      (setq next-line (stdio-read-line process)
+            input-string (concat input-string next-line)
+            json-object (condition-case err
+                            (apply #'json-parse-string input-string JSON-ARGS)
+                          (json-trailing-content (signal (car err) (cdr err)))
+                          (json-end-of-file nil)
+                          (json-parse-error nil))
+            done (or (not next-line)
+                     json-object)))
+    json-object))
+
 (provide 'stdio)
 ;;; stdio.el ends here