1 ;;;; the needed-on-the-cross-compilation-host part of HASH-TABLE
4 ;;;; This software is part of the SBCL system. See the README file for
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.
13 (in-package "SB!IMPL")
15 ;;; HASH-TABLE is implemented as a STRUCTURE-OBJECT.
16 (sb!xc
:defstruct
(hash-table (:constructor %make-hash-table
29 ;; The type of hash table this is. Only used for printing and as
30 ;; part of the exported interface.
31 (test nil
:type symbol
:read-only t
)
32 ;; The function used to compare two keys. Returns T if they are the
33 ;; same and NIL if not.
34 (test-fun nil
:type function
:read-only t
)
35 ;; The function used to compute the hashing of a key. Returns two
36 ;; values: the index hashing and T if that might change with the
38 (hash-fun nil
:type function
:read-only t
)
39 ;; How much to grow the hash table by when it fills up. If an index,
40 ;; then add that amount. If a floating point number, then multiply
42 (rehash-size nil
:type
(or index
(single-float (1.0
)))
44 ;; How full the hash table has to get before we rehash
45 (rehash-threshold nil
:type
(single-float (0.0
) 1.0) :read-only t
)
46 ;; The number of entries before a rehash, just one less than the
47 ;; size of the next-vector, hash-vector, and half the size of the
49 (rehash-trigger nil
:type index
)
50 ;; The current number of entries in the table.
51 (number-entries 0 :type index
)
52 ;; The Key-Value pair vector.
53 (table nil
:type simple-vector
)
54 ;; This slot is used to link weak hash tables during GC. When the GC
55 ;; isn't running it is always NIL.
56 (next-weak-hash-table nil
:type null
)
57 ;; Non-NIL if this is some kind of weak hash table. For details see
58 ;; the docstring of MAKE-HASH-TABLE.
59 (weakness nil
:type
(member nil
:key
:value
:key-or-value
:key-and-value
)
61 ;; Index into the Next vector chaining together free slots in the KV
63 (next-free-kv 0 :type index
)
64 ;; A cache that is either nil or is an index into the hash table
65 ;; that should be checked first
66 (cache nil
:type
(or null index
))
67 ;; The index vector. This may be larger than the hash size to help
69 (index-vector nil
:type
(simple-array sb
!vm
:word
(*)))
70 ;; This table parallels the KV vector, and is used to chain together
71 ;; the hash buckets and the free list. A slot will only ever be in
72 ;; one of these lists.
73 (next-vector nil
:type
(simple-array sb
!vm
:word
(*)))
74 ;; This table parallels the KV table, and can be used to store the
75 ;; hash associated with the key, saving recalculation. Could be
76 ;; useful for EQL, and EQUAL hash tables. This table is not needed
77 ;; for EQ hash tables, and when present the value of
78 ;; +MAGIC-HASH-VECTOR-VALUE+ represents EQ-based hashing on the
80 (hash-vector nil
:type
(or null
(simple-array sb
!vm
:word
(*))))
81 ;; Used for locking GETHASH/(SETF GETHASH)/REMHASH
82 (lock (sb!thread
:make-mutex
:name
"hash-table lock")
83 :type sb
!thread
:mutex
:read-only t
)
84 ;; The GC will set this to T if it moves an EQ-based key. This used
85 ;; to be signaled by a bit in the header of the kv vector, but that
86 ;; implementation caused some concurrency issues when we stopped
87 ;; inhibiting GC during hash-table lookup.
88 (needs-rehash-p nil
:type
(member nil t
))
89 ;; Has user requested synchronization?
90 (synchronized-p nil
:type
(member nil t
) :read-only t
)
91 ;; For detecting concurrent accesses.
92 #!+sb-hash-table-debug
93 (signal-concurrent-access t
:type
(member nil t
))
94 #!+sb-hash-table-debug
96 #!+sb-hash-table-debug
99 ;; as explained by pmai on openprojects #lisp IRC 2002-07-30: #x80000000
100 ;; is bigger than any possible nonEQ hash value, and thus indicates an
101 ;; empty slot; and EQ hash tables don't use HASH-TABLE-HASH-VECTOR.
102 ;; The previous sentence was written when SBCL was 32-bit only. The value
103 ;; now depends on the word size. It is propagated to C in genesis because
104 ;; the generational garbage collector needs to know it.
105 (defconstant +magic-hash-vector-value
+ (ash 1 (1- sb
!vm
:n-word-bits
)))
107 (defmacro-mundanely with-hash-table-iterator
((name hash-table
) &body body
)
109 "WITH-HASH-TABLE-ITERATOR ((name hash-table) &body body)
111 Provides a method of manually looping over the elements of a hash-table. NAME
112 is bound to a generator-macro that, within the scope of the invocation,
113 returns one or three values. The first value tells whether any objects remain
114 in the hash table. When the first value is non-NIL, the second and third
115 values are the key and the value of the next object.
117 Consequences are undefined if HASH-TABLE is mutated during execution of BODY,
118 except for changing or removing elements corresponding to the current key. The
119 applies to all threads, not just the current one -- even for synchronized
120 hash-tables. If the table may be mutated by another thread during iteration,
121 use eg. SB-EXT:WITH-LOCKED-HASH-TABLE to protect the WITH-HASH-TABLE-ITERATOR
123 ;; This essentially duplicates MAPHASH, so any changes here should
124 ;; be reflected there as well.
125 (let ((function (make-symbol (concatenate 'string
(symbol-name name
) "-FUN"))))
127 (let* ((table ,hash-table
)
128 (length (length (hash-table-next-vector table
)))
130 (declare (type index
/2 index
))
133 ;; (We grab the table again on each iteration just in
134 ;; case it was rehashed by a PUTHASH.)
135 (let ((kv-vector (hash-table-table table
)))
137 ((>= index length
) (values nil
))
138 (let ((key (aref kv-vector
(* 2 index
)))
139 (value (aref kv-vector
(1+ (* 2 index
)))))
141 (unless (or (eq key
+empty-ht-slot
+)
142 (eq value
+empty-ht-slot
+))
143 (return (values t key value
))))))))
145 (macrolet ((,name
() '(funcall ,function
)))
148 (defmacro-mundanely with-locked-hash-table
((hash-table) &body body
)
150 "Limits concurrent accesses to HASH-TABLE for the duration of BODY.
151 If HASH-TABLE is synchronized, BODY will execute with exclusive
152 ownership of the table. If HASH-TABLE is not synchronized, BODY will
153 execute with other WITH-LOCKED-HASH-TABLE bodies excluded -- exclusion
154 of hash-table accesses not surrounded by WITH-LOCKED-HASH-TABLE is
156 ;; Needless to say, this also excludes some internal bits, but
157 ;; getting there is too much detail when "unspecified" says what
158 ;; is important -- unpredictable, but harmless.
159 `(sb!thread
::with-recursive-lock
((hash-table-lock ,hash-table
))
162 (defmacro-mundanely with-locked-system-table
((hash-table) &body body
)
163 `(sb!thread
::with-recursive-system-lock
164 ((hash-table-lock ,hash-table
))
167 ;;; Return an association list representing the same data as HASH-TABLE.
168 (defun %hash-table-alist
(hash-table)
170 (maphash (lambda (key value
)
171 (push (cons key value
) result
))