src/code/target-hash-table.lisp

   1 ;;;; that part of the implementation of HASH-TABLE which lives solely
   2 ;;;; on the target system, not on the cross-compilation host
   3
   4 ;;;; This software is part of the SBCL system. See the README file for
   5 ;;;; more information.
   6 ;;;;
   7 ;;;; This software is derived from the CMU CL system, which was
   8 ;;;; written at Carnegie Mellon University and released into the
   9 ;;;; public domain. The software is in the public domain and is
  10 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  11 ;;;; files for more information.
  12
  13 (in-package "SB!IMPL")
  14 \f
  15 ;;;; utilities
  16
  17 (eval-when (:compile-toplevel :load-toplevel :execute)
  18   (defconstant max-hash sb!xc:most-positive-fixnum))
  19
  20 (deftype hash ()
  21   `(integer 0 ,max-hash))
  22
  23 ;;; FIXME: Does this always make a nonnegative FIXNUM? If so, then
  24 ;;; explain why. If not (or if the reason it always makes a
  25 ;;; nonnegative FIXNUM is only the accident that pointers in supported
  26 ;;; architectures happen to be in the lower half of the address
  27 ;;; space), then fix it.
  28 #!-sb-fluid (declaim (inline pointer-hash))
  29 (defun pointer-hash (key)
  30   (declare (values hash))
  31   (truly-the hash (%primitive sb!c:make-fixnum key)))
  32
  33 #!-sb-fluid (declaim (inline eq-hash))
  34 (defun eq-hash (key)
  35   (declare (values hash (member t nil)))
  36   (values (pointer-hash key)
  37           (oddp (get-lisp-obj-address key))))
  38
  39 #!-sb-fluid (declaim (inline equal-hash))
  40 (defun equal-hash (key)
  41   (declare (values hash (member t nil)))
  42   (values (sxhash key) nil))
  43
  44 #!-sb-fluid (declaim (inline eql-hash))
  45 (defun eql-hash (key)
  46   (declare (values hash (member t nil)))
  47   (if (numberp key)
  48       (equal-hash key)
  49       (eq-hash key)))
  50
  51 (defun equalp-hash (key)
  52   (declare (values hash (member t nil)))
  53   (values (psxhash key) nil))
  54
  55 (defun almost-primify (num)
  56   (declare (type index num))
  57   #!+sb-doc
  58   "Return an almost prime number greater than or equal to NUM."
  59   (if (= (rem num 2) 0)
  60       (setq num (+ 1 num)))
  61   (if (= (rem num 3) 0)
  62       (setq num (+ 2 num)))
  63   (if (= (rem num 7) 0)
  64       (setq num (+ 4 num)))
  65   num)
  66 \f
  67 ;;;; user-defined hash table tests
  68
  69 (defvar *hash-table-tests* nil)
  70
  71 (defun define-hash-table-test (name test-fun hash-fun)
  72   #!+sb-doc
  73   "Define a new kind of hash table test."
  74   (declare (type symbol name)
  75            (type function test-fun hash-fun))
  76   (setf *hash-table-tests*
  77         (cons (list name test-fun hash-fun)
  78               (remove name *hash-table-tests* :test #'eq :key #'car)))
  79   name)
  80 \f
  81 ;;;; construction and simple accessors
  82
  83 (defconstant +min-hash-table-size+ 16)
  84 (defconstant +min-hash-table-rehash-threshold+ (float 1/16 1.0))
  85 ;; as explained by pmai on openprojects #lisp IRC 2002-07-30: #x80000000
  86 ;; is bigger than any possible nonEQ hash value, and thus indicates an
  87 ;; empty slot; and EQ hash tables don't use HASH-TABLE-HASH-VECTOR
  88 (defconstant +magic-hash-vector-value+ #x80000000)
  89
  90 (defun make-hash-table (&key (test 'eql)
  91                              (size +min-hash-table-size+)
  92                              (rehash-size 1.5)
  93                              (rehash-threshold 1)
  94                              (weak-p nil))
  95   #!+sb-doc
  96   "Create and return a new hash table. The keywords are as follows:
  97      :TEST -- Indicates what kind of test to use.
  98      :SIZE -- A hint as to how many elements will be put in this hash
  99        table.
 100      :REHASH-SIZE -- Indicates how to expand the table when it fills up.
 101        If an integer, add space for that many elements. If a floating
 102        point number (which must be greater than 1.0), multiply the size
 103        by that amount.
 104      :REHASH-THRESHOLD -- Indicates how dense the table can become before
 105        forcing a rehash. Can be any positive number <=1, with density
 106        approaching zero as the threshold approaches 0. Density 1 means an
 107        average of one entry per bucket.
 108      :WEAK-P -- (This is an extension from CMU CL, not currently supported
 109        in SBCL 0.6.6, but perhaps supported in a future version.) If T,
 110        don't keep entries if the key would otherwise be garbage."
 111   (declare (type (or function symbol) test))
 112   (declare (type unsigned-byte size))
 113   (when weak-p
 114     (error "stub: unsupported WEAK-P option"))
 115   (multiple-value-bind (test test-fun hash-fun)
 116       (cond ((or (eq test #'eq) (eq test 'eq))
 117              (values 'eq #'eq #'eq-hash))
 118             ((or (eq test #'eql) (eq test 'eql))
 119              (values 'eql #'eql #'eql-hash))
 120             ((or (eq test #'equal) (eq test 'equal))
 121              (values 'equal #'equal #'equal-hash))
 122             ((or (eq test #'equalp) (eq test 'equalp))
 123              (values 'equalp #'equalp #'equalp-hash))
 124             (t
 125              ;; FIXME: I'd like to remove *HASH-TABLE-TESTS* stuff.
 126              ;; Failing that, I'd like to rename it to
 127              ;; *USER-HASH-TABLE-TESTS*.
 128              (dolist (info *hash-table-tests*
 129                            (error "unknown :TEST for MAKE-HASH-TABLE: ~S"
 130                                   test))
 131                (destructuring-bind (test-name test-fun hash-fun) info
 132                  (when (or (eq test test-name) (eq test test-fun))
 133                    (return (values test-name test-fun hash-fun)))))))
 134     (let* ((size (max +min-hash-table-size+
 135                       (min size
 136                            ;; SIZE is just a hint, so if the user asks
 137                            ;; for a SIZE which'd be too big for us to
 138                            ;; easily implement, we bump it down.
 139                            (floor array-dimension-limit 1024))))
 140            (rehash-size (if (integerp rehash-size)
 141                             rehash-size
 142                             (float rehash-size 1.0)))
 143            ;; FIXME: Original REHASH-THRESHOLD default should be 1.0,
 144            ;; not 1, to make it easier for the compiler to avoid
 145            ;; boxing.
 146            (rehash-threshold (max +min-hash-table-rehash-threshold+
 147                                   (float rehash-threshold 1.0)))
 148            (size+1 (1+ size))           ; The first element is not usable.
 149            ;; KLUDGE: The most natural way of expressing the below is
 150            ;; (round (/ (float size+1) rehash-threshold)), and indeed
 151            ;; it was expressed like that until 0.7.0. However,
 152            ;; MAKE-HASH-TABLE is called very early in cold-init, and
 153            ;; the SPARC has no primitive instructions for rounding,
 154            ;; but only for truncating; therefore, we fudge this issue
 155            ;; a little. The other uses of truncate, below, similarly
 156            ;; used to be round. -- CSR, 2002-10-01
 157            ;;
 158            ;; Note that this has not yet been audited for
 159            ;; correctness. It just seems to work. -- CSR, 2002-11-02
 160            (scaled-size (truncate (/ (float size+1) rehash-threshold)))
 161            (length (almost-primify (max scaled-size
 162                                         (1+ +min-hash-table-size+))))
 163            (index-vector (make-array length
 164                                      :element-type
 165                                      '(unsigned-byte #.sb!vm:n-word-bits)
 166                                      :initial-element 0))
 167            ;; needs to be the same length as the KV vector
 168            ;; (FIXME: really?  why doesn't the code agree?)
 169            (next-vector (make-array size+1
 170                                     :element-type
 171                                     '(unsigned-byte #.sb!vm:n-word-bits)))
 172            (kv-vector (make-array (* 2 size+1)
 173                                   :initial-element +empty-ht-slot+))
 174            (table (%make-hash-table
 175                    :test test
 176                    :test-fun test-fun
 177                    :hash-fun hash-fun
 178                    :rehash-size rehash-size
 179                    :rehash-threshold rehash-threshold
 180                    :rehash-trigger size
 181                    :table kv-vector
 182                    :weak-p weak-p
 183                    :index-vector index-vector
 184                    :next-vector next-vector
 185                    :hash-vector (unless (eq test 'eq)
 186                                   (make-array size+1
 187                                               :element-type '(unsigned-byte #.sb!vm:n-word-bits)
 188                                               :initial-element +magic-hash-vector-value+)))))
 189       (declare (type index size+1 scaled-size length))
 190       ;; Set up the free list, all free. These lists are 0 terminated.
 191       (do ((i 1 (1+ i)))
 192           ((>= i size))
 193         (setf (aref next-vector i) (1+ i)))
 194       (setf (aref next-vector size) 0)
 195       (setf (hash-table-next-free-kv table) 1)
 196       (setf (hash-table-needing-rehash table) 0)
 197       (setf (aref kv-vector 0) table)
 198       table)))
 199
 200 (defun hash-table-count (hash-table)
 201   #!+sb-doc
 202   "Return the number of entries in the given HASH-TABLE."
 203   (declare (type hash-table hash-table)
 204            (values index))
 205   (hash-table-number-entries hash-table))
 206
 207 #!+sb-doc
 208 (setf (fdocumentation 'hash-table-rehash-size 'function)
 209       "Return the rehash-size HASH-TABLE was created with.")
 210
 211 #!+sb-doc
 212 (setf (fdocumentation 'hash-table-rehash-threshold 'function)
 213       "Return the rehash-threshold HASH-TABLE was created with.")
 214
 215 (defun hash-table-size (hash-table)
 216   #!+sb-doc
 217   "Return a size that can be used with MAKE-HASH-TABLE to create a hash
 218    table that can hold however many entries HASH-TABLE can hold without
 219    having to be grown."
 220   (hash-table-rehash-trigger hash-table))
 221
 222 #!+sb-doc
 223 (setf (fdocumentation 'hash-table-test 'function)
 224       "Return the test HASH-TABLE was created with.")
 225
 226 #!+sb-doc
 227 (setf (fdocumentation 'hash-table-weak-p 'function)
 228       "Return T if HASH-TABLE will not keep entries for keys that would
 229    otherwise be garbage, and NIL if it will.")
 230 \f
 231 ;;;; accessing functions
 232
 233 ;;; Make new vectors for the table, extending the table based on the
 234 ;;; rehash-size.
 235 (defun rehash (table)
 236   (declare (type hash-table table))
 237   (let* ((old-kv-vector (hash-table-table table))
 238          (old-next-vector (hash-table-next-vector table))
 239          (old-hash-vector (hash-table-hash-vector table))
 240          (old-size (length old-next-vector))
 241          (new-size
 242           (let ((rehash-size (hash-table-rehash-size table)))
 243             (etypecase rehash-size
 244               (fixnum
 245                (+ rehash-size old-size))
 246               (float
 247                (the index (truncate (* rehash-size old-size)))))))
 248          (new-kv-vector (make-array (* 2 new-size)
 249                                     :initial-element +empty-ht-slot+))
 250          (new-next-vector (make-array new-size
 251                                       :element-type '(unsigned-byte #.sb!vm:n-word-bits)
 252                                       :initial-element 0))
 253          (new-hash-vector (when old-hash-vector
 254                             (make-array new-size
 255                                         :element-type '(unsigned-byte #.sb!vm:n-word-bits)
 256                                         :initial-element +magic-hash-vector-value+)))
 257          (old-index-vector (hash-table-index-vector table))
 258          (new-length (almost-primify
 259                       (truncate (/ (float new-size)
 260                                 (hash-table-rehash-threshold table)))))
 261          (new-index-vector (make-array new-length
 262                                        :element-type '(unsigned-byte #.sb!vm:n-word-bits)
 263                                        :initial-element 0)))
 264     (declare (type index new-size new-length old-size))
 265
 266     ;; Disable GC tricks on the OLD-KV-VECTOR.
 267     (set-header-data old-kv-vector sb!vm:vector-normal-subtype)
 268
 269     ;; FIXME: here and in several other places in the hash table code,
 270     ;; loops like this one are used when FILL or REPLACE would be
 271     ;; appropriate.  why are standard CL functions not used?
 272     ;; Performance issues?  General laziness?  -- NJF, 2004-03-10
 273
 274     ;; Copy over the kv-vector. The element positions should not move
 275     ;; in case there are active scans.
 276     (dotimes (i (* old-size 2))
 277       (declare (type index i))
 278       (setf (aref new-kv-vector i) (aref old-kv-vector i)))
 279
 280     ;; Copy over the hash-vector.
 281     (when old-hash-vector
 282       (dotimes (i old-size)
 283         (setf (aref new-hash-vector i) (aref old-hash-vector i))))
 284
 285     (setf (hash-table-next-free-kv table) 0)
 286     (setf (hash-table-needing-rehash table) 0)
 287     ;; Rehash all the entries; last to first so that after the pushes
 288     ;; the chains are first to last.
 289     (do ((i (1- new-size) (1- i)))
 290         ((zerop i))
 291       (let ((key (aref new-kv-vector (* 2 i)))
 292             (value (aref new-kv-vector (1+ (* 2 i)))))
 293         (cond ((and (eq key +empty-ht-slot+)
 294                     (eq value +empty-ht-slot+))
 295                ;; Slot is empty, push it onto the free list.
 296                (setf (aref new-next-vector i)
 297                      (hash-table-next-free-kv table))
 298                (setf (hash-table-next-free-kv table) i))
 299               ((and new-hash-vector
 300                     (not (= (aref new-hash-vector i) +magic-hash-vector-value+)))
 301                ;; Can use the existing hash value (not EQ based)
 302                (let* ((hashing (aref new-hash-vector i))
 303                       (index (rem hashing new-length))
 304                       (next (aref new-index-vector index)))
 305                  (declare (type index index)
 306                           (type hash hashing))
 307                  ;; Push this slot into the next chain.
 308                  (setf (aref new-next-vector i) next)
 309                  (setf (aref new-index-vector index) i)))
 310               (t
 311                ;; EQ base hash.
 312                ;; Enable GC tricks.
 313                (set-header-data new-kv-vector
 314                                 sb!vm:vector-valid-hashing-subtype)
 315                (let* ((hashing (pointer-hash key))
 316                       (index (rem hashing new-length))
 317                       (next (aref new-index-vector index)))
 318                  (declare (type index index)
 319                           (type hash hashing))
 320                  ;; Push this slot onto the next chain.
 321                  (setf (aref new-next-vector i) next)
 322                  (setf (aref new-index-vector index) i))))))
 323     (setf (hash-table-table table) new-kv-vector)
 324     (setf (hash-table-index-vector table) new-index-vector)
 325     (setf (hash-table-next-vector table) new-next-vector)
 326     (setf (hash-table-hash-vector table) new-hash-vector)
 327     ;; Shrink the old vectors to 0 size to help the conservative GC.
 328     (shrink-vector old-kv-vector 0)
 329     (shrink-vector old-index-vector 0)
 330     (shrink-vector old-next-vector 0)
 331     (when old-hash-vector
 332       (shrink-vector old-hash-vector 0))
 333     (setf (hash-table-rehash-trigger table) new-size))
 334   (values))
 335
 336 ;;; Use the same size as before, re-using the vectors.
 337 (defun rehash-without-growing (table)
 338   (declare (type hash-table table))
 339   (let* ((kv-vector (hash-table-table table))
 340          (next-vector (hash-table-next-vector table))
 341          (hash-vector (hash-table-hash-vector table))
 342          (size (length next-vector))
 343          (index-vector (hash-table-index-vector table))
 344          (length (length index-vector)))
 345     (declare (type index size length))
 346
 347     ;; Disable GC tricks, they will be re-enabled during the re-hash
 348     ;; if necesary.
 349     (set-header-data kv-vector sb!vm:vector-normal-subtype)
 350
 351     ;; Rehash all the entries.
 352     (setf (hash-table-next-free-kv table) 0)
 353     (setf (hash-table-needing-rehash table) 0)
 354     (dotimes (i size)
 355       (setf (aref next-vector i) 0))
 356     (dotimes (i length)
 357       (setf (aref index-vector i) 0))
 358     (do ((i (1- size) (1- i)))
 359         ((zerop i))
 360       (let ((key (aref kv-vector (* 2 i)))
 361             (value (aref kv-vector (1+ (* 2 i)))))
 362         (cond ((and (eq key +empty-ht-slot+)
 363                     (eq value +empty-ht-slot+))
 364                ;; Slot is empty, push it onto free list.
 365                (setf (aref next-vector i) (hash-table-next-free-kv table))
 366                (setf (hash-table-next-free-kv table) i))
 367               ((and hash-vector (not (= (aref hash-vector i) +magic-hash-vector-value+)))
 368                ;; Can use the existing hash value (not EQ based)
 369                (let* ((hashing (aref hash-vector i))
 370                       (index (rem hashing length))
 371                       (next (aref index-vector index)))
 372                  (declare (type index index))
 373                  ;; Push this slot into the next chain.
 374                  (setf (aref next-vector i) next)
 375                  (setf (aref index-vector index) i)))
 376               (t
 377                ;; EQ base hash.
 378                ;; Enable GC tricks.
 379                (set-header-data kv-vector sb!vm:vector-valid-hashing-subtype)
 380                (let* ((hashing (pointer-hash key))
 381                       (index (rem hashing length))
 382                       (next (aref index-vector index)))
 383                  (declare (type index index)
 384                           (type hash hashing))
 385                  ;; Push this slot into the next chain.
 386                  (setf (aref next-vector i) next)
 387                  (setf (aref index-vector index) i)))))))
 388   (values))
 389
 390 (defun flush-needing-rehash (table)
 391   (let* ((kv-vector (hash-table-table table))
 392          (index-vector (hash-table-index-vector table))
 393          (next-vector (hash-table-next-vector table))
 394          (length (length index-vector)))
 395     (do ((next (hash-table-needing-rehash table)))
 396         ((zerop next))
 397       (declare (type index next))
 398       (let* ((key (aref kv-vector (* 2 next)))
 399              (hashing (pointer-hash key))
 400              (index (rem hashing length))
 401              (temp (aref next-vector next)))
 402         (setf (aref next-vector next) (aref index-vector index))
 403         (setf (aref index-vector index) next)
 404         (setf next temp))))
 405   (setf (hash-table-needing-rehash table) 0)
 406   (values))
 407
 408 (defun gethash (key hash-table &optional default)
 409   #!+sb-doc
 410   "Finds the entry in HASH-TABLE whose key is KEY and returns the associated
 411    value and T as multiple values, or returns DEFAULT and NIL if there is no
 412    such entry. Entries can be added using SETF."
 413   (declare (type hash-table hash-table)
 414            (values t (member t nil)))
 415   (without-gcing
 416    (cond ((= (get-header-data (hash-table-table hash-table))
 417              sb!vm:vector-must-rehash-subtype)
 418           (rehash-without-growing hash-table))
 419          ((not (zerop (hash-table-needing-rehash hash-table)))
 420           (flush-needing-rehash hash-table)))
 421    ;; Search for key in the hash table.
 422    (multiple-value-bind (hashing eq-based)
 423        (funcall (hash-table-hash-fun hash-table) key)
 424      (declare (type hash hashing))
 425      (let* ((index-vector (hash-table-index-vector hash-table))
 426             (length (length index-vector))
 427             (index (rem hashing length))
 428             (next (aref index-vector index))
 429             (table (hash-table-table hash-table))
 430             (next-vector (hash-table-next-vector hash-table))
 431             (hash-vector (hash-table-hash-vector hash-table))
 432             (test-fun (hash-table-test-fun hash-table)))
 433        (declare (type index index))
 434        ;; Search next-vector chain for a matching key.
 435        (if (or eq-based (not hash-vector))
 436            (do ((next next (aref next-vector next)))
 437                ((zerop next) (values default nil))
 438              (declare (type index next))
 439              (when (eq key (aref table (* 2 next)))
 440                (return (values (aref table (1+ (* 2 next))) t))))
 441            (do ((next next (aref next-vector next)))
 442                ((zerop next) (values default nil))
 443              (declare (type index next))
 444              (when (and (= hashing (aref hash-vector next))
 445                         (funcall test-fun key (aref table (* 2 next))))
 446                ;; Found.
 447                (return (values (aref table (1+ (* 2 next))) t)))))))))
 448
 449 ;;; so people can call #'(SETF GETHASH)
 450 (defun (setf gethash) (new-value key table &optional default)
 451   (declare (ignore default))
 452   (%puthash key table new-value))
 453
 454 (defun %puthash (key hash-table value)
 455   (declare (type hash-table hash-table))
 456   (aver (hash-table-index-vector hash-table))
 457   (without-gcing
 458    ;; We need to rehash here so that a current key can be found if it
 459    ;; exists. Check that there is room for one more entry. May not be
 460    ;; needed if the key is already present.
 461    (cond ((zerop (hash-table-next-free-kv hash-table))
 462           (rehash hash-table))
 463          ((= (get-header-data (hash-table-table hash-table))
 464              sb!vm:vector-must-rehash-subtype)
 465           (rehash-without-growing hash-table))
 466          ((not (zerop (hash-table-needing-rehash hash-table)))
 467           (flush-needing-rehash hash-table)))
 468
 469    ;; Search for key in the hash table.
 470    (multiple-value-bind (hashing eq-based)
 471        (funcall (hash-table-hash-fun hash-table) key)
 472      (declare (type hash hashing))
 473      (let* ((index-vector (hash-table-index-vector hash-table))
 474             (length (length index-vector))
 475             (index (rem hashing length))
 476             (next (aref index-vector index))
 477             (kv-vector (hash-table-table hash-table))
 478             (next-vector (hash-table-next-vector hash-table))
 479             (hash-vector (hash-table-hash-vector hash-table))
 480             (test-fun (hash-table-test-fun hash-table)))
 481        (declare (type index index))
 482
 483        (cond ((or eq-based (not hash-vector))
 484               (when eq-based
 485                 (set-header-data kv-vector sb!vm:vector-valid-hashing-subtype))
 486
 487               ;; Search next-vector chain for a matching key.
 488               (do ((next next (aref next-vector next)))
 489                   ((zerop next))
 490                 (declare (type index next))
 491                 (when (eq key (aref kv-vector (* 2 next)))
 492                   ;; Found, just replace the value.
 493                   (setf (aref kv-vector (1+ (* 2 next))) value)
 494                   (return-from %puthash value))))
 495              (t
 496               ;; Search next-vector chain for a matching key.
 497               (do ((next next (aref next-vector next)))
 498                   ((zerop next))
 499                 (declare (type index next))
 500                 (when (and (= hashing (aref hash-vector next))
 501                            (funcall test-fun key
 502                                     (aref kv-vector (* 2 next))))
 503                   ;; Found, just replace the value.
 504                   (setf (aref kv-vector (1+ (* 2 next))) value)
 505                   (return-from %puthash value)))))
 506
 507        ;; Pop a KV slot off the free list
 508        (let ((free-kv-slot (hash-table-next-free-kv hash-table)))
 509          ;; Double-check for overflow.
 510          (aver (not (zerop free-kv-slot)))
 511          (setf (hash-table-next-free-kv hash-table)
 512                (aref next-vector free-kv-slot))
 513          (incf (hash-table-number-entries hash-table))
 514
 515          (setf (aref kv-vector (* 2 free-kv-slot)) key)
 516          (setf (aref kv-vector (1+ (* 2 free-kv-slot))) value)
 517
 518          ;; Setup the hash-vector if necessary.
 519          (when hash-vector
 520            (if (not eq-based)
 521                (setf (aref hash-vector free-kv-slot) hashing)
 522                (aver (= (aref hash-vector free-kv-slot) +magic-hash-vector-value+))))
 523
 524          ;; Push this slot into the next chain.
 525          (setf (aref next-vector free-kv-slot) next)
 526          (setf (aref index-vector index) free-kv-slot)))))
 527   value)
 528
 529 (defun remhash (key hash-table)
 530   #!+sb-doc
 531   "Remove the entry in HASH-TABLE associated with KEY. Return T if there
 532    was such an entry, or NIL if not."
 533   (declare (type hash-table hash-table)
 534            (values (member t nil)))
 535   (without-gcing
 536    ;; We need to rehash here so that a current key can be found if it
 537    ;; exists.
 538    (cond ((= (get-header-data (hash-table-table hash-table))
 539              sb!vm:vector-must-rehash-subtype)
 540           (rehash-without-growing hash-table))
 541          ((not (zerop (hash-table-needing-rehash hash-table)))
 542           (flush-needing-rehash hash-table)))
 543
 544    ;; Search for key in the hash table.
 545    (multiple-value-bind (hashing eq-based)
 546        (funcall (hash-table-hash-fun hash-table) key)
 547      (declare (type hash hashing))
 548      (let* ((index-vector (hash-table-index-vector hash-table))
 549             (length (length index-vector))
 550             (index (rem hashing length))
 551             (next (aref index-vector index))
 552             (table (hash-table-table hash-table))
 553             (next-vector (hash-table-next-vector hash-table))
 554             (hash-vector (hash-table-hash-vector hash-table))
 555             (test-fun (hash-table-test-fun hash-table)))
 556        (declare (type index index next))
 557        (flet ((clear-slot (chain-vector prior-slot-location slot-location)
 558                 ;; Mark slot as empty.
 559                 (setf (aref table (* 2 slot-location)) +empty-ht-slot+
 560                       (aref table (1+ (* 2 slot-location))) +empty-ht-slot+)
 561                 ;; Update the prior pointer in the chain to skip this.
 562                 (setf (aref chain-vector prior-slot-location)
 563                       (aref next-vector slot-location))
 564                 ;; Push KV slot onto free chain.
 565                 (setf (aref next-vector slot-location)
 566                       (hash-table-next-free-kv hash-table))
 567                 (setf (hash-table-next-free-kv hash-table) slot-location)
 568                 (when hash-vector
 569                   (setf (aref hash-vector slot-location) +magic-hash-vector-value+))
 570                 (decf (hash-table-number-entries hash-table))
 571                 t))
 572          (cond ((zerop next)
 573                 nil)
 574                ((if (or eq-based (not hash-vector))
 575                     (eq key (aref table (* 2 next)))
 576                     (and (= hashing (aref hash-vector next))
 577                          (funcall test-fun key (aref table (* 2 next)))))
 578                 (clear-slot index-vector index next))
 579                ;; Search next-vector chain for a matching key.
 580                ((or eq-based (not hash-vector))
 581                 ;; EQ based
 582                 (do ((prior next next)
 583                      (next (aref next-vector next) (aref next-vector next)))
 584                     ((zerop next) nil)
 585                   (declare (type index next))
 586                   (when (eq key (aref table (* 2 next)))
 587                     (return-from remhash (clear-slot next-vector prior next)))))
 588                (t
 589                 ;; not EQ based
 590                 (do ((prior next next)
 591                      (next (aref next-vector next) (aref next-vector next)))
 592                     ((zerop next) nil)
 593                   (declare (type index next))
 594                   (when (and (= hashing (aref hash-vector next))
 595                              (funcall test-fun key (aref table (* 2 next))))
 596                     (return-from remhash (clear-slot next-vector prior next)))))))))))
 597
 598 (defun clrhash (hash-table)
 599   #!+sb-doc
 600   "This removes all the entries from HASH-TABLE and returns the hash table
 601    itself."
 602   (declare (optimize speed))
 603   (let* ((kv-vector (hash-table-table hash-table))
 604          (next-vector (hash-table-next-vector hash-table))
 605          (hash-vector (hash-table-hash-vector hash-table))
 606          (size (length next-vector))
 607          (index-vector (hash-table-index-vector hash-table)))
 608     ;; Disable GC tricks.
 609     (set-header-data kv-vector sb!vm:vector-normal-subtype)
 610     ;; Mark all slots as empty by setting all keys and values to magic
 611     ;; tag.
 612     (aver (eq (aref kv-vector 0) hash-table))
 613     (fill kv-vector +empty-ht-slot+ :start 2)
 614     ;; Set up the free list, all free.
 615     (do ((i 1 (1+ i)))
 616         ((>= i (1- size)))
 617       (setf (aref next-vector i) (1+ i)))
 618     (setf (aref next-vector (1- size)) 0)
 619     (setf (hash-table-next-free-kv hash-table) 1)
 620     (setf (hash-table-needing-rehash hash-table) 0)
 621     ;; Clear the index-vector.
 622     (fill index-vector 0)
 623     ;; Clear the hash-vector.
 624     (when hash-vector
 625       (fill hash-vector +magic-hash-vector-value+)))
 626   (setf (hash-table-number-entries hash-table) 0)
 627   hash-table)
 628 \f
 629 ;;;; MAPHASH
 630
 631 ;;; FIXME: This should be made into a compiler transform for two reasons:
 632 ;;;   1. It would then be available for compiling the entire system,
 633 ;;;      not only parts of the system which are defined after DEFUN MAPHASH.
 634 ;;;   2. It could be conditional on compilation policy, so that
 635 ;;;      it could be compiled as a full call instead of an inline
 636 ;;;      expansion when SPACE>SPEED.
 637 (declaim (inline maphash))
 638 (defun maphash (function-designator hash-table)
 639   #!+sb-doc
 640   "For each entry in HASH-TABLE, call the designated two-argument function
 641    on the key and value of the entry. Return NIL."
 642   (let ((fun (%coerce-callable-to-fun function-designator))
 643         (size (length (hash-table-next-vector hash-table))))
 644     (declare (type function fun))
 645     (do ((i 1 (1+ i)))
 646         ((>= i size))
 647       (declare (type index i))
 648       (let* ((kv-vector (hash-table-table hash-table))
 649              (key (aref kv-vector (* 2 i)))
 650              (value (aref kv-vector (1+ (* 2 i)))))
 651         (unless (and (eq key +empty-ht-slot+)
 652                      (eq value +empty-ht-slot+))
 653           (funcall fun key value))))))
 654 \f
 655 ;;;; methods on HASH-TABLE
 656
 657 ;;; Return a list of keyword args and values to use for MAKE-HASH-TABLE
 658 ;;; when reconstructing HASH-TABLE.
 659 (defun %hash-table-ctor-args (hash-table)
 660   (when (hash-table-weak-p hash-table)
 661     ;; FIXME: This might actually work with no trouble, but as of
 662     ;; sbcl-0.6.12.10 when this code was written, weak hash tables
 663     ;; weren't working yet, so I couldn't test it. When weak hash
 664     ;; tables are supported again, this should be fixed.
 665     (error "can't dump weak hash tables readably")) ; defensive programming..
 666   `(:test             ',(hash-table-test             hash-table)
 667     :size             ',(hash-table-size             hash-table)
 668     :rehash-size      ',(hash-table-rehash-size      hash-table)
 669     :rehash-threshold ',(hash-table-rehash-threshold hash-table)))
 670
 671 ;;; Return an association list representing the same data as HASH-TABLE.
 672 (defun %hash-table-alist (hash-table)
 673   (let ((result nil))
 674     (maphash (lambda (key value)
 675                (push (cons key value) result))
 676              hash-table)
 677     result))
 678
 679 ;;; Stuff an association list into HASH-TABLE. Return the hash table,
 680 ;;; so that we can use this for the *PRINT-READABLY* case in
 681 ;;; PRINT-OBJECT (HASH-TABLE T) without having to worry about LET
 682 ;;; forms and readable gensyms and stuff.
 683 (defun %stuff-hash-table (hash-table alist)
 684   (dolist (x alist)
 685     (setf (gethash (car x) hash-table) (cdr x)))
 686   hash-table)
 687
 688 (def!method print-object ((hash-table hash-table) stream)
 689   (declare (type stream stream))
 690   (cond ((not *print-readably*)
 691          (print-unreadable-object (hash-table stream :type t :identity t)
 692            (format stream
 693                    ":TEST ~S :COUNT ~S"
 694                    (hash-table-test hash-table)
 695                    (hash-table-count hash-table))))
 696         ((not *read-eval*)
 697          (error "can't print hash tables readably without *READ-EVAL*"))
 698         (t
 699          (with-standard-io-syntax
 700           (format stream
 701                   "#.~W"
 702                   `(%stuff-hash-table (make-hash-table ,@(%hash-table-ctor-args
 703                                                           hash-table))
 704                                      ',(%hash-table-alist hash-table)))))))
 705
 706 (def!method make-load-form ((hash-table hash-table) &optional environment)
 707   (declare (ignore environment))
 708   (values `(make-hash-table ,@(%hash-table-ctor-args hash-table))
 709           `(%stuff-hash-table ,hash-table ',(%hash-table-alist hash-table))))