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source: code/trunk/src/lua/ltable.c @ 2256

Last change on this file since 2256 was 1810, checked in by rgrieder, 16 years ago

merged ceguilua branch back to trunk

  • Property svn:eol-style set to native
File size: 15.9 KB
Line 
1/*
2** $Id: ltable.c,v 2.32.1.2 2007/12/28 15:32:23 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 MAXBITS         26
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 numints         cast_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  if (luai_numeq(n, 0))  /* avoid problems with -0 */
88    return gnode(t, 0);
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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