(in-package "SB!IMPL")
-;;; an internal tag for marking empty slots
-;;;
-;;; CMU CL 18b used :EMPTY for this purpose, which was somewhat nasty
-;;; since it's easily accessible to the user, so that e.g.
-;;; (DEFVAR *HT* (MAKE-HASH-TABLE))
-;;; (SETF (GETHASH :EMPTY *HT*) :EMPTY)
-;;; (MAPHASH (LAMBDA (K V) (FORMAT T "~&~S ~S~%" K V)))
-;;; gives no output -- oops!
-;;;
-;;; Note that as of version 0.6.6 there's a dependence in the gencgc.c
-;;; code on this value being a symbol. (This is only one of many nasty
-;;; dependencies between that code and this, alas.)
-(defconstant +empty-ht-slot+ '%empty-ht-slot%)
-;;; KLUDGE: Using a private symbol still leaves us vulnerable to users
-;;; getting nonconforming behavior by messing around with
-;;; DO-ALL-SYMBOLS. That seems like a fairly obscure problem, so for
-;;; now we just don't worry about it. If for some reason it becomes
-;;; worrisome and the magic value needs replacement:
-;;; * The replacement value needs to be LOADable with EQL preserved,
-;;; so that macroexpansion for WITH-HASH-TABLE-ITERATOR will work
-;;; when compiled into a file and loaded back into SBCL.
-;;; (Thus, just uninterning %EMPTY-HT-SLOT% doesn't work.)
-;;; * The replacement value needs to be acceptable to the
-;;; low-level gencgc.lisp hash table scavenging code.
-;;; * The change will break binary compatibility, since comparisons
-;;; against the value used at the time of compilation are wired
-;;; into FASL files.
-;;; -- WHN 20000622
-
;;; HASH-TABLE is implemented as a STRUCTURE-OBJECT.
(sb!xc:defstruct (hash-table (:constructor %make-hash-table))
- ;; The type of hash table this is. Only used for printing and as part of
- ;; the exported interface.
- (test (required-argument) :type symbol :read-only t)
- ;; The function used to compare two keys. Returns T if they are the same
- ;; and NIL if not.
- (test-fun (required-argument) :type function :read-only t)
- ;; The function used to compute the hashing of a key. Returns two values:
- ;; the index hashing and T if that might change with the next GC.
- (hash-fun (required-argument) :type function :read-only t)
- ;; How much to grow the hash table by when it fills up. If an index, then
- ;; add that amount. If a floating point number, then multiple it by that.
- (rehash-size (required-argument) :type (or index (single-float (1.0)))
- :read-only t)
- ;; How full the hash table has to get before we rehash.
- (rehash-threshold (required-argument) :type (single-float (0.0) 1.0)
- :read-only t)
- ;; The number of entries before a rehash, just the one less than the
+ ;; The type of hash table this is. Only used for printing and as
+ ;; part of the exported interface.
+ (test (missing-arg) :type symbol :read-only t)
+ ;; The function used to compare two keys. Returns T if they are the
+ ;; same and NIL if not.
+ (test-fun (missing-arg) :type function :read-only t)
+ ;; The function used to compute the hashing of a key. Returns two
+ ;; values: the index hashing and T if that might change with the
+ ;; next GC.
+ (hash-fun (missing-arg) :type function :read-only t)
+ ;; how much to grow the hash table by when it fills up. If an index,
+ ;; then add that amount. If a floating point number, then multiply
+ ;; it by that.
+ (rehash-size (missing-arg) :type (or index (single-float (1.0)))
+ :read-only t)
+ ;; how full the hash table has to get before we rehash
+ (rehash-threshold (missing-arg) :type (single-float (0.0) 1.0) :read-only t)
+ ;; The number of entries before a rehash, just one less than the
;; size of the next-vector, hash-vector, and half the size of the
;; kv-vector.
- (rehash-trigger (required-argument) :type index)
+ (rehash-trigger (missing-arg) :type index)
;; The current number of entries in the table.
(number-entries 0 :type index)
;; The Key-Value pair vector.
- (table (required-argument) :type simple-vector)
- ;; True if this is a weak hash table, meaning that key->value mappings will
- ;; disappear if there are no other references to the key. Note: this only
- ;; matters if the hash function indicates that the hashing is EQ based.
+ (table (missing-arg) :type simple-vector)
+ ;; True if this is a weak hash table, meaning that key->value
+ ;; mappings will disappear if there are no other references to the
+ ;; key. Note: this only matters if the hash function indicates that
+ ;; the hashing is EQ based.
(weak-p nil :type (member t nil))
;; Index into the next-vector, chaining together buckets that need
;; to be rehashed because their hashing is EQ based and the key has
;; Index into the Next vector chaining together free slots in the KV
;; vector.
(next-free-kv 0 :type index)
+ ;; A cache that is either nil or is an index into the hash table
+ ;; that should be checked first
+ (cache nil :type (or null index))
;; The index vector. This may be larger than the hash size to help
;; reduce collisions.
- (index-vector (required-argument)
- :type (simple-array (unsigned-byte 32) (*)))
+ (index-vector (missing-arg)
+ :type (simple-array (unsigned-byte #.sb!vm:n-word-bits) (*)))
;; This table parallels the KV vector, and is used to chain together
;; the hash buckets, the free list, and the values needing rehash, a
;; slot will only ever be in one of these lists.
- (next-vector (required-argument) :type (simple-array (unsigned-byte 32) (*)))
+ (next-vector (missing-arg)
+ :type (simple-array (unsigned-byte #.sb!vm:n-word-bits) (*)))
;; This table parallels the KV table, and can be used to store the
;; hash associated with the key, saving recalculation. Could be
;; useful for EQL, and EQUAL hash tables. This table is not needed
- ;; for EQ hash tables, and when present the value of #x8000000
- ;; represents EQ-based hashing on the respective Key.
- (hash-vector nil :type (or null (simple-array (unsigned-byte 32) (*)))))
+ ;; 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 (unsigned-byte
+ #.sb!vm:n-word-bits) (*)))))
+
+;; 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)))
+
\f
(defmacro-mundanely with-hash-table-iterator ((function hash-table) &body body)
#!+sb-doc
the second and third values are the key and the value of the next object."
(let ((n-function (gensym "WITH-HASH-TABLE-ITERATOR-")))
`(let ((,n-function
- (let* ((table ,hash-table)
- (length (length (hash-table-next-vector table)))
- (index 1))
- (declare (type (mod #.(floor most-positive-fixnum 2)) index))
- (labels
- ((,function ()
- ;; (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 (and (eq key '#.+empty-ht-slot+)
- (eq value '#.+empty-ht-slot+))
- (return (values t key value))))))))
- #',function))))
+ (let* ((table ,hash-table)
+ (length (length (hash-table-next-vector table)))
+ (index 1))
+ (declare (type (mod #.(floor most-positive-fixnum 2)) index))
+ (labels
+ ((,function ()
+ ;; (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 (and (eq key +empty-ht-slot+)
+ (eq value +empty-ht-slot+))
+ (return (values t key value))))))))
+ #',function))))
(macrolet ((,function () '(funcall ,n-function)))
- ,@body))))
+ ,@body))))