\f
;;;; level and length abbreviations
-(defvar *current-level* 0
- #!+sb-doc
- "The current level we are printing at, to be compared against *PRINT-LEVEL*.
- See the macro DESCEND-INTO for a handy interface to depth abbreviation.")
+;;; The current level we are printing at, to be compared against
+;;; *PRINT-LEVEL*. See the macro DESCEND-INTO for a handy interface to
+;;; depth abbreviation.
+(defvar *current-level-in-print* 0)
+;;; Automatically handle *PRINT-LEVEL* abbreviation. If we are too
+;;; deep, then a #\# is printed to STREAM and BODY is ignored.
(defmacro descend-into ((stream) &body body)
- #!+sb-doc
- "Automatically handle *PRINT-LEVEL* abbreviation. If we are too deep, then
- a # is printed to STREAM and BODY is ignored."
(let ((flet-name (gensym)))
`(flet ((,flet-name ()
,@body))
(cond ((and (null *print-readably*)
*print-level*
- (>= *current-level* *print-level*))
+ (>= *current-level-in-print* *print-level*))
(write-char #\# ,stream))
(t
- (let ((*current-level* (1+ *current-level*)))
+ (let ((*current-level-in-print* (1+ *current-level-in-print*)))
(,flet-name)))))))
+;;; Punt if INDEX is equal or larger then *PRINT-LENGTH* (and
+;;; *PRINT-READABLY* is NIL) by outputting \"...\" and returning from
+;;; the block named NIL.
(defmacro punt-print-if-too-long (index stream)
- #!+sb-doc
- "Punt if INDEX is equal or larger then *PRINT-LENGTH* (and *PRINT-READABLY*
- is NIL) by outputting \"...\" and returning from the block named NIL."
`(when (and (not *print-readably*)
*print-length*
(>= ,index *print-length*))
(write-string "..." ,stream)
(return)))
+
+\f
+;;;; circularity detection stuff
+
+;;; When *PRINT-CIRCLE* is T, this gets bound to a hash table that
+;;; (eventually) ends up with entries for every object printed. When
+;;; we are initially looking for circularities, we enter a T when we
+;;; find an object for the first time, and a 0 when we encounter an
+;;; object a second time around. When we are actually printing, the 0
+;;; entries get changed to the actual marker value when they are first
+;;; printed.
+(defvar *circularity-hash-table* nil)
+
+;;; When NIL, we are just looking for circularities. After we have
+;;; found them all, this gets bound to 0. Then whenever we need a new
+;;; marker, it is incremented.
+(defvar *circularity-counter* nil)
+
+;;; Check to see whether OBJECT is a circular reference, and return
+;;; something non-NIL if it is. If ASSIGN is true, reference
+;;; bookkeeping will only be done for existing entries, no new
+;;; references will be recorded. If ASSIGN is true, then the number to
+;;; use in the #n= and #n# noise is assigned at this time.
+;;;
+;;; Note: CHECK-FOR-CIRCULARITY must be called *exactly* once with
+;;; ASSIGN true, or the circularity detection noise will get confused
+;;; about when to use #n= and when to use #n#. If this returns non-NIL
+;;; when ASSIGN is true, then you must call HANDLE-CIRCULARITY on it.
+;;; If CHECK-FOR-CIRCULARITY returns :INITIATE as the second value,
+;;; you need to initiate the circularity detection noise, e.g. bind
+;;; *CIRCULARITY-HASH-TABLE* and *CIRCULARITY-COUNTER* to suitable values
+;;; (see #'OUTPUT-OBJECT for an example).
+;;;
+;;; Circularity detection is done in two places, OUTPUT-OBJECT and
+;;; WITH-CIRCULARITY-DETECTION (which is used from PPRINT-LOGICAL-BLOCK).
+;;; These checks aren't really redundant (at least I can't really see
+;;; a clean way of getting by with the checks in only one of the places).
+;;; This causes problems when mixed with pprint-dispatching; an object is
+;;; marked as visited in OUTPUT-OBJECT, dispatched to a pretty printer
+;;; that uses PPRINT-LOGICAL-BLOCK (directly or indirectly), leading to
+;;; output like #1=#1#. The MODE parameter is used for detecting and
+;;; correcting this problem.
+(defun check-for-circularity (object &optional assign (mode t))
+ (cond ((null *print-circle*)
+ ;; Don't bother, nobody cares.
+ nil)
+ ((null *circularity-hash-table*)
+ (values nil :initiate))
+ ((null *circularity-counter*)
+ (ecase (gethash object *circularity-hash-table*)
+ ((nil)
+ ;; first encounter
+ (setf (gethash object *circularity-hash-table*) mode)
+ ;; We need to keep looking.
+ nil)
+ ((:logical-block)
+ (setf (gethash object *circularity-hash-table*)
+ :logical-block-circular)
+ t)
+ ((t)
+ (cond ((eq mode :logical-block)
+ ;; We've seen the object before in output-object, and now
+ ;; a second time in a PPRINT-LOGICAL-BLOCK (for example
+ ;; via pprint-dispatch). Don't mark it as circular yet.
+ (setf (gethash object *circularity-hash-table*)
+ :logical-block)
+ nil)
+ (t
+ ;; second encounter
+ (setf (gethash object *circularity-hash-table*) 0)
+ ;; It's a circular reference.
+ t)))
+ ((0 :logical-block-circular)
+ ;; It's a circular reference.
+ t)))
+ (t
+ (let ((value (gethash object *circularity-hash-table*)))
+ (case value
+ ((nil t :logical-block)
+ ;; If NIL, we found an object that wasn't there the
+ ;; first time around. If T or :LOGICAL-BLOCK, this
+ ;; object appears exactly once. Either way, just print
+ ;; the thing without any special processing. Note: you
+ ;; might argue that finding a new object means that
+ ;; something is broken, but this can happen. If someone
+ ;; uses the ~@<...~:> format directive, it conses a new
+ ;; list each time though format (i.e. the &REST list),
+ ;; so we will have different cdrs.
+ nil)
+ ;; A circular reference to something that will be printed
+ ;; as a logical block. Wait until we're called from
+ ;; PPRINT-LOGICAL-BLOCK with ASSIGN true before assigning the
+ ;; number.
+ ;;
+ ;; If mode is :LOGICAL-BLOCK and assign is false, return true
+ ;; to indicate that this object is circular, but don't assign
+ ;; it a number yet. This is neccessary for cases like
+ ;; #1=(#2=(#2# . #3=(#1# . #3#))))).
+ (:logical-block-circular
+ (cond ((and (not assign)
+ (eq mode :logical-block))
+ t)
+ ((and assign
+ (eq mode :logical-block))
+ (let ((value (incf *circularity-counter*)))
+ ;; first occurrence of this object: Set the counter.
+ (setf (gethash object *circularity-hash-table*) value)
+ value))
+ (t
+ nil)))
+ (0
+ (if (eq assign t)
+ (let ((value (incf *circularity-counter*)))
+ ;; first occurrence of this object: Set the counter.
+ (setf (gethash object *circularity-hash-table*) value)
+ value)
+ t))
+ (t
+ ;; second or later occurrence
+ (- value)))))))
+
+;;; Handle the results of CHECK-FOR-CIRCULARITY. If this returns T then
+;;; you should go ahead and print the object. If it returns NIL, then
+;;; you should blow it off.
+(defun handle-circularity (marker stream)
+ (case marker
+ (:initiate
+ ;; Someone forgot to initiate circularity detection.
+ (let ((*print-circle* nil))
+ (error "trying to use CHECK-FOR-CIRCULARITY when ~
+ circularity checking isn't initiated")))
+ ((t :logical-block)
+ ;; It's a second (or later) reference to the object while we are
+ ;; just looking. So don't bother groveling it again.
+ nil)
+ (t
+ (write-char #\# stream)
+ (let ((*print-base* 10) (*print-radix* nil))
+ (cond ((minusp marker)
+ (output-integer (- marker) stream)
+ (write-char #\# stream)
+ nil)
+ (t
+ (output-integer marker stream)
+ (write-char #\= stream)
+ t))))))
+
+(defmacro with-circularity-detection ((object stream) &body body)
+ (let ((marker (gensym "WITH-CIRCULARITY-DETECTION-"))
+ (body-name (gensym "WITH-CIRCULARITY-DETECTION-BODY-")))
+ `(labels ((,body-name ()
+ ,@body))
+ (cond ((not *print-circle*)
+ (,body-name))
+ (*circularity-hash-table*
+ (let ((,marker (check-for-circularity ,object t :logical-block)))
+ (if ,marker
+ (when (handle-circularity ,marker ,stream)
+ (,body-name))
+ (,body-name))))
+ (t
+ (let ((*circularity-hash-table* (make-hash-table :test 'eq)))
+ (output-object ,object (make-broadcast-stream))
+ (let ((*circularity-counter* 0))
+ (let ((,marker (check-for-circularity ,object t
+ :logical-block)))
+ (when ,marker
+ (handle-circularity ,marker ,stream)))
+ (,body-name))))))))
+
projects / sbcl.git / blobdiff