+ ;; for EQ hash tables, and when present the value of
+ ;; +MAGIC-HASH-VECTOR-VALUE+ represents EQ-based hashing on the
+ ;; respective key.
+ (hash-vector nil :type (or null (simple-array sb!vm:word (*))))
+ ;; Used for locking GETHASH/(SETF GETHASH)/REMHASH
+ (spinlock (sb!thread::make-spinlock :name "hash-table lock")
+ :type sb!thread::spinlock :read-only t)
+ ;; The GC will set this to T if it moves an EQ-based key. This used
+ ;; to be signaled by a bit in the header of the kv vector, but that
+ ;; implementation caused some concurrency issues when we stopped
+ ;; inhibiting GC during hash-table lookup.
+ (needs-rehash-p nil :type (member nil t))
+ ;; Has user requested synchronization?
+ (synchronized-p nil :type (member nil t) :read-only t)
+ ;; For detecting concurrent accesses.
+ #!+sb-hash-table-debug
+ (signal-concurrent-access t :type (member nil t))
+ #!+sb-hash-table-debug
+ (reading-thread nil)
+ #!+sb-hash-table-debug
+ (writing-thread nil))
+
+;; as explained by pmai on openprojects #lisp IRC 2002-07-30: #x80000000
+;; is bigger than any possible nonEQ hash value, and thus indicates an
+;; empty slot; and EQ hash tables don't use HASH-TABLE-HASH-VECTOR.
+;; The previous sentence was written when SBCL was 32-bit only. The value
+;; now depends on the word size. It is propagated to C in genesis because
+;; the generational garbage collector needs to know it.
+(defconstant +magic-hash-vector-value+ (ash 1 (1- sb!vm:n-word-bits)))
+
+(defmacro-mundanely with-hash-table-iterator ((name hash-table) &body body)
+ #!+sb-doc
+ "WITH-HASH-TABLE-ITERATOR ((name hash-table) &body body)
+
+Provides a method of manually looping over the elements of a hash-table. NAME
+is bound to a generator-macro that, within the scope of the invocation,
+returns one or three values. The first value tells whether any objects remain
+in the hash table. When the first value is non-NIL, the second and third
+values are the key and the value of the next object.
+
+Consequences are undefined if HASH-TABLE is mutated during execution of BODY,
+except for changing or removing elements corresponding to the current key. The
+applies to all threads, not just the curren one -- even for synchronized
+hash-tables. If the table may be mutated by another thread during iteration,
+use eg. SB-EXT:WITH-LOCKED-HASH-TABLE to protect the WITH-HASH-TABLE-ITERATOR
+for."
+ ;; This essentially duplicates MAPHASH, so any changes here should
+ ;; be reflected there as well.
+ (let ((function (make-symbol (concatenate 'string (symbol-name name) "-FUN"))))
+ `(let ((,function
+ (let* ((table ,hash-table)
+ (length (length (hash-table-next-vector table)))
+ (index 1))
+ (declare (type index/2 index))
+ (labels
+ ((,name ()
+ ;; (We grab the table again on each iteration just in
+ ;; case it was rehashed by a PUTHASH.)
+ (let ((kv-vector (hash-table-table table)))
+ (do ()
+ ((>= index length) (values nil))
+ (let ((key (aref kv-vector (* 2 index)))
+ (value (aref kv-vector (1+ (* 2 index)))))
+ (incf index)
+ (unless (or (eq key +empty-ht-slot+)
+ (eq value +empty-ht-slot+))
+ (return (values t key value))))))))
+ #',name))))
+ (macrolet ((,name () '(funcall ,function)))
+ ,@body))))
+
+(defmacro-mundanely with-locked-hash-table ((hash-table) &body body)