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1/*
2** $Id: ltable.c,v 2.32 2006/01/18 11:49:02 roberto Exp $
3** Lua tables (hash)
4** See Copyright Notice in lua.h
5*/
6
7
8/*
9** Implementation of tables (aka arrays, objects, or hash tables).
10** Tables keep its elements in two parts: an array part and a hash part.
11** Non-negative integer keys are all candidates to be kept in the array
12** part. The actual size of the array is the largest `n' such that at
13** least half the slots between 0 and n are in use.
14** Hash uses a mix of chained scatter table with Brent's variation.
15** A main invariant of these tables is that, if an element is not
16** in its main position (i.e. the `original' position that its hash gives
17** to it), then the colliding element is in its own main position.
18** Hence even when the load factor reaches 100%, performance remains good.
19*/
20
21#include <math.h>
22#include <string.h>
23
24#define ltable_c
25#define LUA_CORE
26
27#include "lua.h"
28
29#include "ldebug.h"
30#include "ldo.h"
31#include "lgc.h"
32#include "lmem.h"
33#include "lobject.h"
34#include "lstate.h"
35#include "ltable.h"
36
37
38/*
39** max size of array part is 2^MAXBITS
40*/
41#if LUAI_BITSINT > 26
42#define MAXBITS26
43#else
44#define MAXBITS(LUAI_BITSINT-2)
45#endif
46
47#define MAXASIZE(1 << MAXBITS)
48
49
50#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
51
52#define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
53#define hashboolean(t,p) hashpow2(t, p)
54
55
56/*
57** for some types, it is better to avoid modulus by power of 2, as
58** they tend to have many 2 factors.
59*/
60#define hashmod(t,n)(gnode(t, ((n) % ((sizenode(t)-1)|1))))
61
62
63#define hashpointer(t,p)hashmod(t, IntPoint(p))
64
65
66/*
67** number of ints inside a lua_Number
68*/
69#define numintscast_int(sizeof(lua_Number)/sizeof(int))
70
71
72
73#define dummynode(&dummynode_)
74
75static const Node dummynode_ = {
76 {{NULL}, LUA_TNIL}, /* value */
77 {{{NULL}, LUA_TNIL, NULL}} /* key */
78};
79
80
81/*
82** hash for lua_Numbers
83*/
84static Node *hashnum (const Table *t, lua_Number n) {
85 unsigned int a[numints];
86 int i;
87 n += 1; /* normalize number (avoid -0) */
88 lua_assert(sizeof(a) <= sizeof(n));
89 memcpy(a, &n, sizeof(a));
90 for (i = 1; i < numints; i++) a[0] += a[i];
91 return hashmod(t, a[0]);
92}
93
94
95
96/*
97** returns the `main' position of an element in a table (that is, the index
98** of its hash value)
99*/
100static Node *mainposition (const Table *t, const TValue *key) {
101 switch (ttype(key)) {
102 case LUA_TNUMBER:
103 return hashnum(t, nvalue(key));
104 case LUA_TSTRING:
105 return hashstr(t, rawtsvalue(key));
106 case LUA_TBOOLEAN:
107 return hashboolean(t, bvalue(key));
108 case LUA_TLIGHTUSERDATA:
109 return hashpointer(t, pvalue(key));
110 default:
111 return hashpointer(t, gcvalue(key));
112 }
113}
114
115
116/*
117** returns the index for `key' if `key' is an appropriate key to live in
118** the array part of the table, -1 otherwise.
119*/
120static int arrayindex (const TValue *key) {
121 if (ttisnumber(key)) {
122 lua_Number n = nvalue(key);
123 int k;
124 lua_number2int(k, n);
125 if (luai_numeq(cast_num(k), n))
126 return k;
127 }
128 return -1; /* `key' did not match some condition */
129}
130
131
132/*
133** returns the index of a `key' for table traversals. First goes all
134** elements in the array part, then elements in the hash part. The
135** beginning of a traversal is signalled by -1.
136*/
137static int findindex (lua_State *L, Table *t, StkId key) {
138 int i;
139 if (ttisnil(key)) return -1; /* first iteration */
140 i = arrayindex(key);
141 if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
142 return i-1; /* yes; that's the index (corrected to C) */
143 else {
144 Node *n = mainposition(t, key);
145 do { /* check whether `key' is somewhere in the chain */
146 /* key may be dead already, but it is ok to use it in `next' */
147 if (luaO_rawequalObj(key2tval(n), key) ||
148 (ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
149 gcvalue(gkey(n)) == gcvalue(key))) {
150 i = cast_int(n - gnode(t, 0)); /* key index in hash table */
151 /* hash elements are numbered after array ones */
152 return i + t->sizearray;
153 }
154 else n = gnext(n);
155 } while (n);
156 luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
157 return 0; /* to avoid warnings */
158 }
159}
160
161
162int luaH_next (lua_State *L, Table *t, StkId key) {
163 int i = findindex(L, t, key); /* find original element */
164 for (i++; i < t->sizearray; i++) { /* try first array part */
165 if (!ttisnil(&t->array[i])) { /* a non-nil value? */
166 setnvalue(key, cast_num(i+1));
167 setobj2s(L, key+1, &t->array[i]);
168 return 1;
169 }
170 }
171 for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
172 if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
173 setobj2s(L, key, key2tval(gnode(t, i)));
174 setobj2s(L, key+1, gval(gnode(t, i)));
175 return 1;
176 }
177 }
178 return 0; /* no more elements */
179}
180
181
182/*
183** {=============================================================
184** Rehash
185** ==============================================================
186*/
187
188
189static int computesizes (int nums[], int *narray) {
190 int i;
191 int twotoi; /* 2^i */
192 int a = 0; /* number of elements smaller than 2^i */
193 int na = 0; /* number of elements to go to array part */
194 int n = 0; /* optimal size for array part */
195 for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
196 if (nums[i] > 0) {
197 a += nums[i];
198 if (a > twotoi/2) { /* more than half elements present? */
199 n = twotoi; /* optimal size (till now) */
200 na = a; /* all elements smaller than n will go to array part */
201 }
202 }
203 if (a == *narray) break; /* all elements already counted */
204 }
205 *narray = n;
206 lua_assert(*narray/2 <= na && na <= *narray);
207 return na;
208}
209
210
211static int countint (const TValue *key, int *nums) {
212 int k = arrayindex(key);
213 if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
214 nums[ceillog2(k)]++; /* count as such */
215 return 1;
216 }
217 else
218 return 0;
219}
220
221
222static int numusearray (const Table *t, int *nums) {
223 int lg;
224 int ttlg; /* 2^lg */
225 int ause = 0; /* summation of `nums' */
226 int i = 1; /* count to traverse all array keys */
227 for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
228 int lc = 0; /* counter */
229 int lim = ttlg;
230 if (lim > t->sizearray) {
231 lim = t->sizearray; /* adjust upper limit */
232 if (i > lim)
233 break; /* no more elements to count */
234 }
235 /* count elements in range (2^(lg-1), 2^lg] */
236 for (; i <= lim; i++) {
237 if (!ttisnil(&t->array[i-1]))
238 lc++;
239 }
240 nums[lg] += lc;
241 ause += lc;
242 }
243 return ause;
244}
245
246
247static int numusehash (const Table *t, int *nums, int *pnasize) {
248 int totaluse = 0; /* total number of elements */
249 int ause = 0; /* summation of `nums' */
250 int i = sizenode(t);
251 while (i--) {
252 Node *n = &t->node[i];
253 if (!ttisnil(gval(n))) {
254 ause += countint(key2tval(n), nums);
255 totaluse++;
256 }
257 }
258 *pnasize += ause;
259 return totaluse;
260}
261
262
263static void setarrayvector (lua_State *L, Table *t, int size) {
264 int i;
265 luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
266 for (i=t->sizearray; i<size; i++)
267 setnilvalue(&t->array[i]);
268 t->sizearray = size;
269}
270
271
272static void setnodevector (lua_State *L, Table *t, int size) {
273 int lsize;
274 if (size == 0) { /* no elements to hash part? */
275 t->node = cast(Node *, dummynode); /* use common `dummynode' */
276 lsize = 0;
277 }
278 else {
279 int i;
280 lsize = ceillog2(size);
281 if (lsize > MAXBITS)
282 luaG_runerror(L, "table overflow");
283 size = twoto(lsize);
284 t->node = luaM_newvector(L, size, Node);
285 for (i=0; i<size; i++) {
286 Node *n = gnode(t, i);
287 gnext(n) = NULL;
288 setnilvalue(gkey(n));
289 setnilvalue(gval(n));
290 }
291 }
292 t->lsizenode = cast_byte(lsize);
293 t->lastfree = gnode(t, size); /* all positions are free */
294}
295
296
297static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
298 int i;
299 int oldasize = t->sizearray;
300 int oldhsize = t->lsizenode;
301 Node *nold = t->node; /* save old hash ... */
302 if (nasize > oldasize) /* array part must grow? */
303 setarrayvector(L, t, nasize);
304 /* create new hash part with appropriate size */
305 setnodevector(L, t, nhsize);
306 if (nasize < oldasize) { /* array part must shrink? */
307 t->sizearray = nasize;
308 /* re-insert elements from vanishing slice */
309 for (i=nasize; i<oldasize; i++) {
310 if (!ttisnil(&t->array[i]))
311 setobjt2t(L, luaH_setnum(L, t, i+1), &t->array[i]);
312 }
313 /* shrink array */
314 luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
315 }
316 /* re-insert elements from hash part */
317 for (i = twoto(oldhsize) - 1; i >= 0; i--) {
318 Node *old = nold+i;
319 if (!ttisnil(gval(old)))
320 setobjt2t(L, luaH_set(L, t, key2tval(old)), gval(old));
321 }
322 if (nold != dummynode)
323 luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
324}
325
326
327void luaH_resizearray (lua_State *L, Table *t, int nasize) {
328 int nsize = (t->node == dummynode) ? 0 : sizenode(t);
329 resize(L, t, nasize, nsize);
330}
331
332
333static void rehash (lua_State *L, Table *t, const TValue *ek) {
334 int nasize, na;
335 int nums[MAXBITS+1]; /* nums[i] = number of keys between 2^(i-1) and 2^i */
336 int i;
337 int totaluse;
338 for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
339 nasize = numusearray(t, nums); /* count keys in array part */
340 totaluse = nasize; /* all those keys are integer keys */
341 totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
342 /* count extra key */
343 nasize += countint(ek, nums);
344 totaluse++;
345 /* compute new size for array part */
346 na = computesizes(nums, &nasize);
347 /* resize the table to new computed sizes */
348 resize(L, t, nasize, totaluse - na);
349}
350
351
352
353/*
354** }=============================================================
355*/
356
357
358Table *luaH_new (lua_State *L, int narray, int nhash) {
359 Table *t = luaM_new(L, Table);
360 luaC_link(L, obj2gco(t), LUA_TTABLE);
361 t->metatable = NULL;
362 t->flags = cast_byte(~0);
363 /* temporary values (kept only if some malloc fails) */
364 t->array = NULL;
365 t->sizearray = 0;
366 t->lsizenode = 0;
367 t->node = cast(Node *, dummynode);
368 setarrayvector(L, t, narray);
369 setnodevector(L, t, nhash);
370 return t;
371}
372
373
374void luaH_free (lua_State *L, Table *t) {
375 if (t->node != dummynode)
376 luaM_freearray(L, t->node, sizenode(t), Node);
377 luaM_freearray(L, t->array, t->sizearray, TValue);
378 luaM_free(L, t);
379}
380
381
382static Node *getfreepos (Table *t) {
383 while (t->lastfree-- > t->node) {
384 if (ttisnil(gkey(t->lastfree)))
385 return t->lastfree;
386 }
387 return NULL; /* could not find a free place */
388}
389
390
391
392/*
393** inserts a new key into a hash table; first, check whether key's main
394** position is free. If not, check whether colliding node is in its main
395** position or not: if it is not, move colliding node to an empty place and
396** put new key in its main position; otherwise (colliding node is in its main
397** position), new key goes to an empty position.
398*/
399static TValue *newkey (lua_State *L, Table *t, const TValue *key) {
400 Node *mp = mainposition(t, key);
401 if (!ttisnil(gval(mp)) || mp == dummynode) {
402 Node *othern;
403 Node *n = getfreepos(t); /* get a free place */
404 if (n == NULL) { /* cannot find a free place? */
405 rehash(L, t, key); /* grow table */
406 return luaH_set(L, t, key); /* re-insert key into grown table */
407 }
408 lua_assert(n != dummynode);
409 othern = mainposition(t, key2tval(mp));
410 if (othern != mp) { /* is colliding node out of its main position? */
411 /* yes; move colliding node into free position */
412 while (gnext(othern) != mp) othern = gnext(othern); /* find previous */
413 gnext(othern) = n; /* redo the chain with `n' in place of `mp' */
414 *n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
415 gnext(mp) = NULL; /* now `mp' is free */
416 setnilvalue(gval(mp));
417 }
418 else { /* colliding node is in its own main position */
419 /* new node will go into free position */
420 gnext(n) = gnext(mp); /* chain new position */
421 gnext(mp) = n;
422 mp = n;
423 }
424 }
425 gkey(mp)->value = key->value; gkey(mp)->tt = key->tt;
426 luaC_barriert(L, t, key);
427 lua_assert(ttisnil(gval(mp)));
428 return gval(mp);
429}
430
431
432/*
433** search function for integers
434*/
435const TValue *luaH_getnum (Table *t, int key) {
436 /* (1 <= key && key <= t->sizearray) */
437 if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
438 return &t->array[key-1];
439 else {
440 lua_Number nk = cast_num(key);
441 Node *n = hashnum(t, nk);
442 do { /* check whether `key' is somewhere in the chain */
443 if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
444 return gval(n); /* that's it */
445 else n = gnext(n);
446 } while (n);
447 return luaO_nilobject;
448 }
449}
450
451
452/*
453** search function for strings
454*/
455const TValue *luaH_getstr (Table *t, TString *key) {
456 Node *n = hashstr(t, key);
457 do { /* check whether `key' is somewhere in the chain */
458 if (ttisstring(gkey(n)) && rawtsvalue(gkey(n)) == key)
459 return gval(n); /* that's it */
460 else n = gnext(n);
461 } while (n);
462 return luaO_nilobject;
463}
464
465
466/*
467** main search function
468*/
469const TValue *luaH_get (Table *t, const TValue *key) {
470 switch (ttype(key)) {
471 case LUA_TNIL: return luaO_nilobject;
472 case LUA_TSTRING: return luaH_getstr(t, rawtsvalue(key));
473 case LUA_TNUMBER: {
474 int k;
475 lua_Number n = nvalue(key);
476 lua_number2int(k, n);
477 if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
478 return luaH_getnum(t, k); /* use specialized version */
479 /* else go through */
480 }
481 default: {
482 Node *n = mainposition(t, key);
483 do { /* check whether `key' is somewhere in the chain */
484 if (luaO_rawequalObj(key2tval(n), key))
485 return gval(n); /* that's it */
486 else n = gnext(n);
487 } while (n);
488 return luaO_nilobject;
489 }
490 }
491}
492
493
494TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
495 const TValue *p = luaH_get(t, key);
496 t->flags = 0;
497 if (p != luaO_nilobject)
498 return cast(TValue *, p);
499 else {
500 if (ttisnil(key)) luaG_runerror(L, "table index is nil");
501 else if (ttisnumber(key) && luai_numisnan(nvalue(key)))
502 luaG_runerror(L, "table index is NaN");
503 return newkey(L, t, key);
504 }
505}
506
507
508TValue *luaH_setnum (lua_State *L, Table *t, int key) {
509 const TValue *p = luaH_getnum(t, key);
510 if (p != luaO_nilobject)
511 return cast(TValue *, p);
512 else {
513 TValue k;
514 setnvalue(&k, cast_num(key));
515 return newkey(L, t, &k);
516 }
517}
518
519
520TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {
521 const TValue *p = luaH_getstr(t, key);
522 if (p != luaO_nilobject)
523 return cast(TValue *, p);
524 else {
525 TValue k;
526 setsvalue(L, &k, key);
527 return newkey(L, t, &k);
528 }
529}
530
531
532static int unbound_search (Table *t, unsigned int j) {
533 unsigned int i = j; /* i is zero or a present index */
534 j++;
535 /* find `i' and `j' such that i is present and j is not */
536 while (!ttisnil(luaH_getnum(t, j))) {
537 i = j;
538 j *= 2;
539 if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
540 /* table was built with bad purposes: resort to linear search */
541 i = 1;
542 while (!ttisnil(luaH_getnum(t, i))) i++;
543 return i - 1;
544 }
545 }
546 /* now do a binary search between them */
547 while (j - i > 1) {
548 unsigned int m = (i+j)/2;
549 if (ttisnil(luaH_getnum(t, m))) j = m;
550 else i = m;
551 }
552 return i;
553}
554
555
556/*
557** Try to find a boundary in table `t'. A `boundary' is an integer index
558** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
559*/
560int luaH_getn (Table *t) {
561 unsigned int j = t->sizearray;
562 if (j > 0 && ttisnil(&t->array[j - 1])) {
563 /* there is a boundary in the array part: (binary) search for it */
564 unsigned int i = 0;
565 while (j - i > 1) {
566 unsigned int m = (i+j)/2;
567 if (ttisnil(&t->array[m - 1])) j = m;
568 else i = m;
569 }
570 return i;
571 }
572 /* else must find a boundary in hash part */
573 else if (t->node == dummynode) /* hash part is empty? */
574 return j; /* that is easy... */
575 else return unbound_search(t, j);
576}
577
578
579
580#if defined(LUA_DEBUG)
581
582Node *luaH_mainposition (const Table *t, const TValue *key) {
583 return mainposition(t, key);
584}
585
586int luaH_isdummy (Node *n) { return n == dummynode; }
587
588#endif

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